CCNP Practical Studies: Routing
Copyright About the Author About the Technical Reviewers Acknowledgments Introduction Goals of This Book Audience Chapter Organization How Best to Use This Book Getting Equipment How to Use The Book if You Cannot Get Equipment Command Syntax Conventions Conclusion Chapter 1. Internet Protocol Basic Internet Protocol Variable-Length Subnet Masks (VLSM) Summarization and How to Configure Summarization IP Helper Address Scenarios Scenario 1-1: Configuring a Cisco Router for IP Scenario 1-2: Efficiently Configuring a Network for IP Scenario 1-3: Configuring IP VLSM for a Large Network Scenario 1-4: Summarization with EIGRP and OSPF Scenario 1-5: Configuring IP Helper Address Practical Exercise: IP Review Questions Summary Chapter 2. Routing Principles Routing IP on Cisco Routers Distance Vector and Link-State Routing Protocols Scenarios Scenario 2-1: Routing IP on Cisco Routers Scenario 2-2: Basic OSPF Scenario 2-3: Basic IGRP Scenario 2-4: Basic EIGRP Scenario 2-5: Using the show, ping, trace, and debug Commands Practical Exercise: RIP Version 2 Review Questions Summary Chapter 3. Basic Open Shortest Path First Basic OSPF Configuring OSPF in a Single Area OSPF and Nonbroadcast Multiaccess Environments Scenarios Scenario 3-1: Configuring OSPF in a Single Area Scenario 3-2: Configuring OSPF in Multiple Areas

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CCNP Practical Studies: Routing
Scenario 3-3: How OSPF Monitors, Manages, and Maintains Routes Scenario 3-4: OSPF over Frame Relay in an NBMA Environment Scenario 3-5: Verifying OSPF Routing Practical Exercise: Routing OSPF Review Questions Summary Chapter 4. Advanced OSPF and Integrated Intermediate System-to-Intermediate System Advanced OSPF Integrated Intermediate System-to-Intermediate System Scenarios Scenario 4-1: Configuring OSPF with Multiple Areas Scenario 4-2: Configuring OSPF Summarization Scenario 4-3: Configuring Integrated IS-IS Scenario 4-4: OSPF and Integrated IS-IS Redistribution Scenario 4-5: Recommendations for Designing OSPF Networks Practical Exercise: OSPF and RIP Redistribution Review Questions Summary Chapter 5. Enhanced Interior Gateway Routing Protocol Introduction to Enhanced Interior Gateway Routing Protocol (EIGRP) Discovering and Maintaining Routes in EIGRP EIGRP in NBMA Environments EIGRP Route Summarization and Large IP Network Support Scenarios Scenario 5-1: Configuring EIGRP Scenario 5-2: Summarization with EIGRP Scenario 5-3: EIGRP and VLSM Scenario 5-4: Configuring Advanced EIGRP and Redistribution Scenario 5-5: Verifying EIGRP Configuration Practical Exercise: EIGRP Review Questions Summary Chapter 6. Basic Border Gateway Protocol Basic Border Gateway Protocol (BGP4) Defined BGP Attributes Configuring BGP Scenarios Scenario 6-1: EBGP and IBGP Scenario 6-2: BGP and Static Routes Scenario 6-3: BGP with Policy-Based Routing Scenario 6-4: BGP with Communities and Peer Groups Scenario 6-5: Verifying BGP Operation Practical Exercise: EBGP and Attributes Review Questions Summary Chapter 7. Advanced BGP Scalability with Border Gateway Protocol (BGP4)

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CCNP Practical Studies: Routing
Configuring Route Reflectors Multihoming Connections to the Internet Scenarios Scenario 7-1: Configuring Route Reflectors Scenario 7-2: Configuring Advanced BGP Route Reflectors Scenario 7-3: Configuring Dual-Homing ISP Connections Scenario 7-4: Configuring Prefix Lists Scenario 7-5: Monitoring BGP and Verifying Correct Operation Practical Exercise: Advanced BGP Review Questions Summary Chapter 8. Route Redistribution and Optimization Controlling Routing Updates Redistribution Defined Redistributing from Classless to Classful Protocols Cisco IOS Command Syntax for Redistribution Scenarios Scenario 8-1: Redistributing Between RIP and IGRP Scenario 8-2: Migrating from RIP to OSPF in the Core Scenario 8-3: Redistributing Between EIGRP and OSPF Scenario 8-4: Route Summarization Using Static Routes Scenario 8-5: Route Summarization Without Using Static Routes Practical Exercise: Redistribution Review Questions Summary Chapter 9. CCNP Routing Self-Study Lab How to Best Use This Chapter The Goal of the Lab Physical Connectivity (1 Hour) Catalyst Switch Setup 6509 (0.25 Hours) IP Address Configuration (0.5 Hours) IGP Routing (7 Hours) BGP Routing Configuration (5 Hours) Self-Study Lab Solution Summary Appendix A. Study Tips Strategies for Cisco Exam Preparation Hands-On Experience Strategies for the Exam Cisco Certification Status Appendix B. What to Do After CCNP? Steps Required to Achieve CCIE Certification CCIE Qualification Exam Test Format CCIE Lab Exam Test Format Appendix C. Answers to Review Questions Chapter 1

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CCNP Practical Studies: Routing
Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Appendix D. CCIE Preparation—Sample Multiprotocol Lab Basic Setup (1 Hour) IP Configuration and IP Addressing (No Time) Frame Relay Setup (0.5 Hours) IGP Routing (3 Hours) IPX Configuration (1 Hour) Basic ISDN Configuration (0.5 Hours) DLSw+ Configuration (0.75 Hours) Flash Configuration (0.20 Hours) VTY Changes (0.20 Hours) HTTP Server (0.20 Hours) Catalyst 6509 Password Recovery (0.20 Hours) Private Address Space Allocation (0.20 Hours) BGP Routing Configuration (0.75 Hours) Index

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CCNP Practical Studies: Routing

About the Author

Henry Benjamin is a dual Cisco Certified Internet Expert (CCIE #4695), having been certified in Routing and Switching in May 1999 and ISP Dial in June 2001. His other Cisco certifications include CCNA and CCDA. He has more than 10 years experience in Cisco networks, including planning, designing, and implementing large IP networks running IGRP, EIGRP, BGP, and OSPF. Recently, Henry worked for Cisco Systems, Inc. in the internal IT department as a key network designer, designing and implementing networks all over Australia and Asia.

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CCNP Practical Studies: Routing
In the past two years, Henry has been a key member of the CCIE global team based in Sydney, Australia. As a senior and core member of the team, his tasks include writing new laboratory examinations and written questions for the coveted CCIE R/S certification, recertification examinations, and ISP laboratory examinations. Proctoring candidates from all parts of the world is a favorite pastime of his. Henry has authored another book, CCIE Routing and Switching Exam Cram: Exam: 350-001, for the CCIE qualification examination and helped edit many other titles. Henry holds a bachelor of aeronautical engineering degree from Sydney University in Australia.

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he attained his CCIE in Routing and Switching and has also proctored CCIE R/S exams. With his extensive knowledge in the networking field. and support work for companies. reading. Currently. and CNA. Eddie has a diploma in aviation studies and a commercial pilot license. such as EDS. and a Graduate Certificate in Internetworking. wireless. design. Frank has done consulting. He is currently working with the WAN team. in Sydney. and PDVSA.com. and high-speed networks. During this period. The University of New South Wales. and flying. helping customer deployments and troubleshooting day-today network connectivity. vii . CCNA. He can be contacted at echami@cisco. Inc. Qantas. Frank has 11 years of experience in the computer industry and is also a CCNP. a Graduate Diploma in Information Systems. DSL. Eddie found great satisfaction in not only learning from others but also teaching others. He holds a bachelor of engineering in telecommunications degree as well as a masters degree in multichannel communications. he also has great interests in GMPLS. where he joined the Technical Assistance Center (TAC) at Cisco Systems in Australia. Prior to working at Cisco. Eddie's other interests are in the areas of optical. Australia. Eddie Chami has three years of networking experience. CNE. Eddie is broadening his knowledge in the optical space field. His hobbies are sports.CCNP Practical Studies: Routing About the Technical Reviewers Frank Arteaga works as a support engineer for Cisco Systems. Eddie entered Cisco Systems two years ago. Schindler Lifts.

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Thank you Mum. and all three showed they have the technical expertise and keen eye for detail to become accomplished authors themselves. Inc. Thank you Tammi Ross for being such a great help. for all of their expert work on this book. In particular. Frank. I love you to the sun and keep going around forever and ever. If I ever write another book. It has been a true pleasure to be invited to write this book. and my one and only son. This book would have never been written if my mum and dad had never told me to study. Davin and Eddie are CCIEs that I had the pleasure of passing. The technical editors. Eddie. I'd also like to thank San Dee Phillips. Any aspiring author in this field should seriously consider working with Cisco Press. at Cisco Press. Thank you Dad. The team at Cisco Press includes an amazing family of hard-working people. Simon. I treasure my time with my family and my growing little boy who makes me proud to be his dad. ix . who turned eight years old while I was completing this book. Sharon. Sydney Jones. provided valuable technical expertise. I'd like to thank Michelle Stroup for introducing me to this project and Andrew Cupp for the tireless work on this book and complete trust in me. I was always grateful to them both for their understanding and knowing when I needed time to complete this project. I would also like to thank my wife. Tim Wright.CCNP Practical Studies: Routing Acknowledgments Cisco Press was wonderful to work with—no bones about it. and I eagerly await Frank's attempt in the near future. Simon. and Davin. and Octal Publishing. it will be only with the fine folks at Cisco Press.

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Having read many books. through the examinations required. "CCNP Routing Self-Study Lab. and list-in-order style questions. open the door to many career opportunities. Chapter 9. Each chapter starts by briefly describing the technology that is covered in the practical portion of the chapter.0 exam is a computer-based exam with multiple-choice. You should check with Sylvan Prometric for the exact length of the exam. You can assess your mastery of the subjects by looking over the Practical Exercise solution. all this book's features. demonstrate a large knowledge base that can be built upon with almost any company running any technology. each chapter ends with a series of review questions designed to allow you to further assess your knowledge of the technology covered. This technology background is brief and assumes the reader has a strong technical background and now desires a practical environment to apply this knowledge. which are outlined in this introduction. By demonstrating the determination to prepare for and pass the extensive CCNP exam process. Finally. Goals of This Book The primary goal of this book is to ensure that a CCNP candidate has all the practical skills and knowledge required to pass the Routing 2. which provide you with an opportunity to apply the material at hand practically with the aid of complete explanations. CCNPs also demonstrate a strong desire to succeed. www. CCNP Practical Studies: Routing is intended to help you move concepts and theories into practical experience on Cisco routers. You should have CCNA-level knowledge to use this book to its full extent.0 exam means that you have mastered the concepts and implementation skills necessary to build a complex IP network of Cisco routers. The exam takes approximately 75 minutes and has approximately 60 questions. This book provides you with a practical way to prepare for the Routing examination and enables you to obtain some practical skills required to fully appreciate the power of routing in any environment. and routing protocols from start to finish.CCNP Practical Studies: Routing Introduction The Cisco Certified Network Professional (CCNP) certification on the Routing and Switching career track is becoming increasingly popular. xi - . This book is designed to allow a reader. Professional-level certifications.0 exam-related topics. I know that technical content alone will probably not allow you to attain the skills necessary to pass a Cisco examination. fill-in-the-blank. and the only way to provide you with those skills is to demonstrate them in a working environment that uses common Cisco-defined techniques. Therefore. The bulk of each chapter contains five scenarios. A Practical Exercise. without too much coverage of topics not on the exam. so be sure to check the latest updates from Cisco at www. are geared toward helping you discover the IP routing challenges and configuration scenarios that are on the Routing exam. Ultimately.0 exam.0 exam is one of the exams that you must pass to become a CCNP. The second goal of this book is to provide you with comprehensive coverage of Routing 2.com).0 examination.2test. who desire a hands-on approach to applying their knowledge. in a structured manner. NOTE The Routing 2. The best method to accomplish this is to demonstrate these topics and provide a step-by-step practical studies guide. The exam can be taken at any Sylvan Prometric testing center (1-800-829-NETS. By working through these various elements. you will not only gain more confidence navigating within the Cisco IOS but also an understanding of how these various networking concepts relate. Passing the Routing 2. to configure an entire network consisting of various topologies. such as CCNP.cisco.com/warp/public/10/wwtraining/. The exam is constantly under review. familiar with networking concepts and the principles of routing theory. based on the fact that a company can hire many CCNPs who are technically very sound and can provide quality technical skills without the burden of paying large amounts for a single individual who may have more expertise but whose vast expertise isn't necessary for that company's needs. technologies. This is a great skill and demonstrates to any employer that you are ready for any challenges that might be asked of you." is designed to assist you in your final preparation for the Routing exam by providing you a lab scenario that incorporates many technologies and concepts. Various help tools and author experience are included to ensure that you are fully aware of any problematic configurations and challenges that face network designers in today's large networks. Most Cisco certifications require practical skills. Detailed solutions and tips are provided to guide you through the configurations. where you have a knowledge deficiency in these topics. The Routing 2. CCNP certification builds on your foundation established from the Cisco Certified Network Associate (CCNA) certification. Audience CCNP Practical Studies: Routing is targeted to networking professionals. CCNPs today are valuable compared to even CCIEs. at the end of each chapter. CCNPs. lets you test yourself by applying your knowledge without the benefit of the inline explanations that are provided in the scenarios. the goal of this book is to get you from where you are today to the point that you can confidently pass the Routing 2. and what you need to know to master those topics. The final chapter in the book is a special chapter that reinforces all the concepts and technologies covered in this guide into one complex scenario.

so most Cisco certifications. namely Enhanced Interior Gateway Routing Protocol (EIGRP). this book was written assuming you have CCNA-level experience and knowledge concerning Cisco routers and routing protocols. "Enhanced Interior Gateway Routing Protocol" Chapter 5 focuses on a protocol developed by Cisco Systems and used on Cisco IOS routers only. Chapter 3. The chapter briefly explains why OSPF is considered an improved routing protocol over RIP by explaining how OSPF discovers. and review questions. IS-IS. The following subsections briefly describe the subject of each chapter and appendix. and the chapter explains how OSPF is used in large IP routing environments and how OSPF can be configured to reduce IP routing tables and CPU usage. variable-length subnet masks. "Routing Principles" Chapter 2 covers the basic information required on Cisco routers to route IP data across an IP network. IP routing tables are covered in more detail using common IP routing algorithms. Topics include what a distancevector protocol is and how to configure one on Cisco routers. heavily test on OSPF. Border Gateway Protocol (BGP). and subnetting topics. CCNP Practical Studies: Routing is for individuals studying for the CCNP Routing 2. The issues and challenges facing network designers when configuring OSPF in larger networks are demonstrated with the practical scenarios. "Basic Open Shortest Path First" Chapter 3 covers basic OSPF routing principles and how OSPF routing is fundamental for any small or large network. IP concepts are reviewed and explained. such as RIP and IGRP. The solution contains the full configuration. Chapter 6. Link-state routing protocols are described and configured. followed by an explanation of the IP routing table on Cisco routers and instructions about how to minimize the IP routing table using summarization. Nonbroadcast multiaccess (NBMA) is demonstrated using a common network topology. Chapter 2. Chapter Organization This book has nine chapters.CCNP Practical Studies: Routing The end result is that you will become a more complete network engineer ready to tackle and design any IP routing solution. Finally. Basic OSPF terminology is described and configured. so readers without network equipment can still follow the configuration requirements. Chapter 4. OSPF is a popular IP routing protocol.0 exam who would like to apply their knowledge while preparing themselves for the exam. You discover how EIGRP learns about new neighbors and how EIGRP operates in NMBA networks. following the scenarios. OSPF is explained in more detail. one practical lab requires you to configure the network on your own. Chapter 1. and lower the memory requirements of access or edge routers. five scenarios with detailed explanations and full Cisco IOS configurations. Chapter 5. This book also contains four appendixes. EIGRP is explained and configured on Cisco routers. "Advanced OSPF and Integrated Intermediate System-to-Intermediate System" Chapter 4 covers the more advanced topics in OSPF and another link-state routing protocol. xii - . a Practical Exercise with solutions. Each chapter (except Chapter 9) contains brief background information. including CCNP and CCIE. This is followed by some common techniques used to ensure IP data is routing as correctly and efficiently as possible. "Basic Border Gateway Protocol" Chapter 6 covers the most important routing protocol in use today. and maintains routing tables. Again. "Internet Protocol" Chapter 1 covers basic IP addressing. A Review Questions section follows each Practical Exercise to ensure that you digest the fundamental terms and concepts presented in each chapter. In each chapter. chooses.

so full working solutions and sample displays are presented to ensure that you understand and fully appreciate all concepts. The exercises presented are a combination of all the most critical topics found in this book into one scenario. There are five practical scenarios to complete your understanding of BGP to help you appreciate its complexity. For more details on CIM. NOTE xiii - . Having your own equipment or access to the equipment is the ideal way to use this book but is not required. and some great tips are provided in the explanations to show you how to ensure network connectivity.ciscopress. contact Cisco Systems for second-hand or used routers at very competitive prices. numerous places exist on the Internet. in particular. and ways to overcome large BGP networks are covered and configured on Cisco routers.com. "Study Tips" Appendix A describes some useful study tips for CCNP candidates. This chapter also covers how information can be controlled to ensure that the network is routing IP as correctly and efficiently as possible. the chapter covers how BGP deals with large networks. If you want to purchase equipment. Chapter 8. visit www.0 exam by providing you a lab scenario that incorporates many of the technologies and concepts covered in this book. Appendix B. offers a product called Cisco Interactive Mentor (CIM) that enables candidates to simulate real-life networks. "Advanced BGP" Chapter 7 describes BGP in greater detail. Full working configurations and sample displays are presented. "Route Redistribution and Optimization" Chapter 8 covers the issues and challenges facing networks when information from one routing algorithm is redistributed into another. Cisco. most readers will appreciate that Cisco routers are not easy to come by. search Cisco partners or auction sites for cheap devices to help you. this may be your first option. Chapter 9. Chapter 7.CCNP Practical Studies: Routing The basics terms and configuration options are described to help you appreciate the powerful nature of BGP. Of course. "CCIE Preparation—Sample Multiprotocol Lab" Appendix D is a bonus aid designed to assist you in your final preparation for the most widely sought after certification in the world today. If your place of employment has spare equipment that you can use. Scalability issues are presented. Alternatively. "CCNP Routing Self-Study Lab" Chapter 9 is designed to assist you in your final preparation for the Routing 2. "What to Do After CCNP?" Appendix B describes what a CCNP can achieve after becoming CCNP certified. There are also simulators that offer a cheap solution to purchasing equipment. "Answers to Review Questions" Appendix C provides answers to all of the review questions. Getting Equipment You can obtain reasonably priced equipment from various places. Appendix A. How Best to Use This Book This book provides a practical approach to learning networking concepts. namely CCIE (Routing and Switching). This gives you the opportunity to gain the hands-on experience of configuring each router according to the lab objectives without the need to have any physical equipment. Appendix C. for example. Sample displays are provided to demonstrate the working solutions. Appendix D. Common exam techniques and the best study practices are provided to ensure that you are fully prepared on the day of the examination.

ciscopress. Building Cisco Multilayer Switched Networks by Karen Webb (Cisco Press). Command Syntax Conventions The conventions used to present command syntax in this book are the same conventions used in the Cisco IOS Command Reference. Square brackets [ and ] indicate optional elements. As a future CCNP. as follows: • • • • • Boldface indicates commands and keywords that are entered literally as shown. In examples (not syntax). a show command). Because each scenario includes thorough explanations. Italics indicates arguments for which you supply values. Thomas II (Cisco Press). Second Edition. you can still profit from this book. Braces { and } contain a choice of required keywords. I recommend the companion book to this guide from Cisco Press. For more quality resources visit www. xiv - . you might run into concepts about which you want additional information. boldface indicates user input (for example.cisco. CCNP Routing Exam Certification Guide by Clare Gough. Building Scalable Cisco Networks by Catherine Paquet and Diane Teare (Cisco Press). It is a CCNP certification book from the only Cisco-authorized publisher. meeting those challenges will drive you to acquire skills you never thought you could master. Because some experience and knowledge level has been assumed of the reader. There are always challenges facing network engineers. If you do not have the equipment. pay closer attention to the figures and examples within the chapter and observe the changes that are made to the network.com) to be invaluable.CCNP Practical Studies: Routing Visit the following web site for a number of quality tools and Internet links: www. even if you can't work along with the scenarios. The book is structured to walk you through each configuration task step by step. do not despair. Vertical bars (|) separate alternative. the joy and success I have achieved has significantly changed my life and that of my family.net How to Use The Book if You Cannot Get Equipment If you are unable to get equipment. You might find it handy to keep notes as you work through this book. Having many Cisco certifications myself. Internet Routing Architectures. I recommend using the following resources as reference material while reading the book: • • • • • • • Routing TCP/IP. Conclusion The CCNP certification has great value in the networking environment. you will also find Cisco Connection Online (www. CCNP Practical Studies: Routing is designed to help you attain CCNP certification. Routing in the Internet by Christian Huitema (Prentice Hall PTR). by Sam Halabi (Cisco Press). In particular. It proves your competence and dedication. you should always strive to build upon your knowledge beyond a studying perspective so that you can proceed to a technical level far beyond the minimum required for Cisco-based certifications. As always. OSPF Network Design Solutions by Thomas M. The author and editors at Cisco Press believe that this book will help you achieve CCNP certification. and it is a huge step in distinguishing yourself as someone who has proven knowledge of Cisco products and technology. Volumes I and II by Jeff Doyle and Jennifer DeHaven Carroll (Volume II only) (Cisco Press). after you are a qualified Cisco professional. so be on the lookout for Practical Studies books that will help you prepare for the other exams besides the Routing exam that you must pass to achieve CCNP status. Thomas II (The Coriolis Group). mutually exclusive elements. It is required for several other certifications. and no doubt.iponeverything. you will begin to understand how configuration tasks are applied and impact the network. Cisco Press has plans to expand its line of Practical Studies books.com and follow the links guiding you to certification materials. The dedication required to achieve any success is up to you. CCIE Routing and Switching Exam Cram: Exam: 350-001 by Henry Benjamin and Thomas M.

have the perfect companion through your journey to becoming a CCNP. xv - . please feel free to e-mail me at benjamin@cisco.com. it took months and long nights to complete to ensure that you. And when you succeed in attaining your certification. so I too can enjoy your success and joy as well. as the reader.CCNP Practical Studies: Routing I sincerely hope you enjoy your time spent with this book.

determine how many hosts are available on a particular subnet. segment to allow a hierarchical routing topology.0-192.168.16. and what the broadcast address is.255 192. Next. The host address is a logical unique address that resides on a subnet. defined five classes of addresses and the appropriate address ranges.255.255 Soon after these ranges were defined and the Internet's popularity extended beyond the Department of Defense in the United States.0.255.255 172. IP.255.0. To best illustrate an IP address and subnet portion. You can deduce the subnet for any IP address by performing a logical AND operation along with the subnet mask.CCNP Practical Studies: Routing Chapter 1. how many hosts can reside on this subnet. 127[*] 128–191 192–223 224–239 240–255 Default Subnet Mask 255. it became clear that to ensure that a larger community could connect to the World Wide Web there had to be a way to extend IP address space by using subnetting. Basic Internet Protocol IP is a term widely used in today's networking world to describe a Network layer protocol that logically defines a distinct host or end systems such as a PC or router with an IP address. Other reserved addresses for private use as defined by RFC 1918 are 10. This example helps you determine what the subnet is.0.0-10.0. You are given the IP address 131. -1- . An IP address is configured on end systems to allow communication between hosts that are geographically dispersed. Understanding basic Internet Protocol (IP) networking not only applies to the CCNP certification but all Cisco-based certification. Internet Protocol This chapter focuses on a number of objectives falling under the CCNP routing principles. C. Subnetting allows an administrator to extend the boundary for any given subnet.255. The Internet Engineering Task Force (IETF) standards body.0 is reserved for loopbacks purposes.255. Five practical scenarios complete your understanding of these topics and ensure you have all the basic IP networking knowledge to complement your knowledge of today's most widely used networking protocol. This chapter starts by covering basic IP concepts.255. or even how to best utilize an IP address space.255.255.0-172.0.240 Reserved 127.255. B. A subnet is a network that you.1.108.0.0 255. It then briefly explains how to efficiently configure IP to ensure full use of address space. consider the following example.16. Routing allows communication between these subnets.255.168. this chapter covers when and how IP routing tables can be minimized using summarization techniques with various routing protocols.0.0.0. as network administrator. Table 1-1.56 and the subnet mask is 255.255.0 255. which is a task force consisting of over 80 working groups responsible for developing Internet standards. An IP address is 32 bits in length with the network mask or subnet mask (also 32 bits in length) defining the host and subnet portion. D. Class A. A concrete understanding of how IP is used in today's networking environments is one of the most important tools to have before taking on the more advanced chapters in this guide.0 255.0. and E Ranges Class of Address Class A Class B Class C Class D Class E [*] Starting Bit Pattern 0 10 110 1110 1111 Range 1–126. Table 1-1 displays the five ranges.

224 (or 11100000. you must examine the subnet mask in binary.1. the number of hosts that can reside are 28 .64.1. in binary (positive is 1 and negative is 0).1. and so forth.224.255. Figure 1-1 displays the logical AND operation used to determine the subnet address.255. a broadcast address consists of all binary 1s.0. To determine the number of borrowed bits.224. The number of hosts that can reside on this network with a subnet mask of 255.2 = 254 hosts.108. Given the host address 171. This is best explained with examples. this example shows you how to determine the subnet and the number of hosts that can reside on this network.) Now consider another example. Figure 1-2.255. the last eight bits represent the borrowed bits.) In IP. So. 1 AND 1 is 1. you simply apply the formula 2n . 0 AND 0 is 0. To determine the subnet. (You subtract two host addresses for the subnet address and the broadcast address.255.2 = 256 . The subnet address is reserved and cannot be assigned to end devices.255.10. and applying a subnet mask that is not the default or classful kind enables you to extend IP address space and allow a larger number of devices to connect to the IP network. or C address. To determine the number of hosts available in any given subnet. So. You can apply the technique used in this simple example to any Class A. Figure 1-1. One is that positive and positive equal positive. perform a logical AND. B.108. Figure 1-2 displays the operation.10.2 where n is the number of borrowed bits.2 = 30 hosts.255. and the second is that negative and positive or negative is negative. 0 AND 1 is 0.255.67 and the subnet mask of 255. For a default Class C network mask of 255. the broadcast address for the subnet 131.2 = 32 . which are not permitted to be used by host devices.0 is 131. Logical AND Operation The subnet is 171. for a Class C network.224. -2- . 5 borrow bits) is 25 .0. AND Logic Operation The result of the logical AND operation reveals the subnet address is 131. 1 AND 0 is 0.108.CCNP Practical Studies: Routing NOTE A logical AND operation follows two basic rules. so for this example. (255 in binary is 11111111.

Remember that you must subtract two host addresses for the subnet address and broadcast address. Table 1-2. 252 addresses in fact. To allow a greater number of devices to connect to the Internet and intranets. Only two devices host systems are needed. a Class C network with 255 hosts among 255 different routers and conserves valuable IP address space. for example. and the broadcast address is 11. The subnet mask is 30 bits in length or 255. the second is 10.255. OSPF. you get 2n . To use any IP address space effectively. consider the example of connecting two Cisco routers through a wide-area link. it would be wise to use the lowest possible number of subnet bits and lowest possible number of host bits. or n = 2 borrowed bits.CCNP Practical Studies: Routing Table 1-2 displays some common subnets used in today's network and the number of hosts available on those subnets. To demonstrate the use of VLSM. Apply the formula to determine the best subnet to use to cater to two hosts on any given subnet and class of address. -3- .11111111.11111111. or 2n = 4.255. the first host address is 01. summarization is important for limiting or reducing IP routing tables. You could use a Class C mask or a mask that allows for 254 hosts. require memory.111111100. most importantly. put simply. Common Subnets in Today's Networks Decimal 252 (1111 1100) 248 (1111 1000) 240 (1111 0000) 224 (1110 0000) 192 (1100 0000) 128 (1000 0000) 64 (0100 0000) [*] Subnets 64 subnets 32 subnets 16 subnets 8 subnets 4 subnets 2 subnets 2 hosts[*] 6 hosts 14 hosts 30 hosts 62 hosts 126 hosts Hosts Used commonly for WAN circuits when no more than 2 hosts reside. and BGP4. NOTE The following routing algorithms support VLSM: RIP Version 2. which allows. the subnet is 00. IP routing entries consume bandwidth of expensive links between different geographic locations. Variable-Length Subnet Masks (VLSM) A variable-length subnet mask (VLSM) is designed to allow more efficient use of IP address space by borrowing bits from the subnet mask and allocating them to host devices. the standards body of various routing protocols designed an IP routing algorithm to cater to IP networks with a different subnet mask than the default used in classful networks. take CPU cycles on routers. which is represented as 11111111.252 in binary. The most important consideration to make when summarizing any IP address space is to ensure a hierarchical design. this wastes a vast amount of space. and. enables a given routing protocol to minimize IP routing tables by taking steps to advertise a smaller or lesser IP route destination for a large set of subnets or networks. IS-IS. You need to borrow only two bits from the subnet mask to allow for two host addresses. EIGRP. NOTE Loopback interfaces configured on Cisco routers are typically configured with a host address using a 32-bit subnet mask. Summarization and How to Configure Summarization Summarization. Applying the formula. For a link that never uses more than two hosts. To give network designers the ability to manage large networks.2 = 2. The last two bits (00) are available for host addresses.

you must disable automatic summarization to allow the more specific routes to be advertised.108.255. you must first disable automatic summarization with the following command: router eigrp 1 no auto-summary Then.7. Class B with 16-bit mask. and this includes renumbering an IP network or using secondary addressing on Cisco routers. Because the first five bits are the same.108. you apply the manual summarization on the interface to which you want to send the advertised summary.10. automatic summarization occurs.0/24 131. and a Class C mask with a 24-bit mask. from 131.0/24 131. Because the high-order bits are common in Table 1-3 (0000 0) and all seven routes are contiguous (binary 001 to 111).5. The best practice is to assign a group of addresses to a geographic area so that the distribution layer of any network enables summarization to be relatively easy to complete.CCNP Practical Studies: Routing In a hierarchical design.0/24 131. The following example shows you how to summarize the networks in Table 1-3 using EIGRP. To configure summarization with EIGRP. In other words.108.0. Also. as seven different IP route entries.0/24 and 131.1. The binary examination of the subnets 1 to 7 in Table 1-3 displays that the first five bits (shaded) are unchanged.255.107. 255. it is important to understand that if a range of addresses is not contiguous (that is. the following is a list of benefits when using summarization: • • • • Reduces routing table sizes Allows for network growth Simplifies routing algorithm recalculation when changes occur Reduces requirements for memory and CPU usage on routers significantly The alternatives to network summarization are not easy to accomplish.0. IP address space is configured across any given router so that it can be easily summarized. You could still summarize the first seven networks. To disable automatic summaries with RIPv2. Depending on the routing protocols in use. Before looking at how to complete this summarization using RIP.0.6.108.0/24). EIGRP. otherwise a default mask is assumed.1.0.0/24 0000 0001 0000 0010 0000 0011 0000 0100 0000 0101 0000 0110 0000 0111 Binary Last Third Octet A router would normally advertise each of the seven IP address ranges. summarization may be enabled by default.2. The most important fact is that these seven networks are contiguous or in a range that you can easily summarize. or OSPF.108. 255. summarization is impossible.0/24 131. but they might reside in other parts of your network and cause IP routing problems.1–7. With RIPv2.4.108.0/24 131. for example. Table 1-3. Example 1-1 displays the command you use to summarize the seven networks in Table 1-3. EIGRP also applies automatic summaries but it also enables the manual configuration of summary addresses. you can apply the mask 248 (11111 000) on the third octet and send an advertisement encompassing all seven routes. Automatic summarization simply announces a Class A network with an 8-bit mask. they do not start from a range that can be easily summarized.0/24 131. such as the range of addresses 131. use the following command: router rip version 2 no auto-summary The command no auto-summary disables automatic summaries and allows subnets to be advertised. you can perform summarization.108. which is not an ideal solution for management purposes and also provides extra overhead on a router. -4- .3.108. To illustrate the capabilities of summarization consider the following IP address ranges in Table 1-3. IP Address Range IP Subnet 131.108.

you use the IP helper address to change a broadcast into a more specific destination address so not all devices must view the IP data.108.CCNP Practical Studies: Routing Example 1-1 Summary with EIGRP interface serial 0 ip summary-address eigrp 1 131. An ABR resides in more than one OSPF area. "Basic Border Gateway Protocol" and 7.0 Example 1-1 applies a summary on the serial interface. So to allow the ability to forward packets wisely.108. Assume the area-id for now is 1. The actual summary is 131.108. You use the following command in OSPF to summarize internal OSPF routes: area area-id range address mask Example 1-2 displays the configuration required to summarize the seven networks in Table 1-3. "Advanced BGP. To save on bandwidth.0. The IP helper address forwards packets that are normally discarded by default to the following services: • • • • • • Trivial File Transfer Protocol (TFTP) Domain Name System (DNS) BOOTP server BOOTP client NetBIOS Name Server Dynamic Host Configuration Protocol (DHCP) -5- . NOTE With OSPF. which conserves bandwidth. Also note that the EIGRP autonomous system number is 1." 6.108. you use broadcasts to find an end system's MAC address. Example 1-2 OSPF summary router ospf 1 area 1 range 131. In a Layer 2 environment.255.1-7. IP also uses broadcasts for such services as sending IP datagrams to all hosts on a particular network.248.0 NOTE OSPF also enables you to summarize external OSPF routes redistributed from such protocols as IGRP or RIP. Broadcasts on any network consume CPU and bandwidth to reduce this even more. assume the Cisco router is an ABR.255.1. IP Helper Address As in any network. The command to enable an IP help address is as follows: ip helper-address address You can configure more than one helper address per interface on a Cisco router.1." also provide complex summarization techniques. which replaces the seven individual routers numbered 131. matching the configuration on the router because you can have more than one EIGRP process running.0/24 with one simple route. OSPF allows summarization manually under the OSPF process ID. you can use the IP helper address command to convert a broadcast into a more specific destination address.248. Layer 3 of the TCP/IP model. all Cisco routers installed with Cisco Internet Operating System (IOS) software by default have an algorithm that dictates that not all broadcast packets be forwarded.248.255. broadcasts are used to find and discover end systems. Now look at how to configure the seven networks in Table 1-3 with an OSPF summary. BGP and IS-IS. In an IP network. covered in Chapters 4.0 255.1.0 255. you can correctly configure summarization only on area border routers (ABRs).0 255. For this example. "Advanced OSPF and Integrated Intermediate System-to-Intermediate System.

IP Routing on Cisco Routers Example 1-3 displays the IP configuration performed on R1's Ethernet interface. The five scenarios presented in this chapter are based on simple IP technologies to introduce you to the configuration of IP on Cisco routers and give you the basic foundation required to complete the more advanced topics and scenarios found later in this book.CCNP Practical Studies: Routing NOTE The most common use for the helper address is for clients running DHCP. and using good practice and defining your end goal are important in any real-life design or solution.0 R1(config-if)#no shutdown 4w1d: %LINK-3-UPDOWN: Interface Ethernet0/0.255. changed state to up 4w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0. -6- .108. which remote servers assign IP addresses and subnet masks usually performed locally through a broadcast to be served remotely with a unicast (one) packet.1 255.255. There is no one right way to accomplish many of the tasks presented. Figure 1-3. Also." Scenario 1-1: Configuring a Cisco Router for IP In this scenario. the IOS message tells you the Ethernet interface and the line protocol are up.0 or /24 mask). named R1.255. changed state to up NOTE When you enable the Ethernet interface with the command [no] shutdown. You can disable IP routing with the command [no] ip routing. with one Ethernet interface.1.255. "Routing Principles. Readers who are familiar with these basics may want to skip this chapter and move on to Chapter 2. all Cisco routers are enabled for IP routing with the command ip routing. To see these messages remotely. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs.1. you see how to configure one Cisco router for IP routing using a Class B (/16) network 161. Figure 1-3 displays the one router.108.0 with a Class C subnet mask (255. enable terminal monitor on any VTY lines. Example 1-3 IP Configuration on R1 R1(config)#int e 0/0 R1(config-if)#ip address 161. by default.

1. input queue 0/75. 0 drops 5 minute input rate 0 bits/sec.108. 45 interface resets 0 babbles.255.1. 0 packets/sec 5 minute output rate 0 bits/sec. address is 0001. 0 drops. Example 1-4 show interface ethernet e0/0 on R1 R1#show interfaces ethernet 0/0 Ethernet0/0 is up. keepalive set (10 sec) ARP type: ARPA. line protocol is up Hardware is AmdP2.ff40) Internet address is 161.9645. Confirm the IP address assignment by displaying the interface statistics with the command show interfaces Ethernet 0/0. ARP Timeout 04:00:00 Last input 00:00:21. 0 throttles 0 input errors.0 secondary ip address 161. 3 collisions. Example 1-7 displays the full working configuration on R1 along with the secondary IP address.1/24.1/24 and 131. BW 10000 Kbit. rely 255/255. and the only way to view any secondary addressing is to view the configuration.9645.1/24 MTU 1500 bytes. the Cisco IOS does not display IP secondary addressing.108.1.255.255. line protocol is up Interface is up and active Hardware is AmdP2..9645. 22 deferred 0 lost carrier. Example 1-6 show interfaces ethernet 0/0 R1#show interfaces ethernet 0/0 Ethernet0/0 is up.ff40) Internet address is 161.1/24 configure IP address MTU 1500 bytes. output 00:00:02.108. load 1/255 Encapsulation ARPA. Unfortunately.108. 0 output buffers swapped out Next.1.255.ff40 (bia 0001. loopback not set.108. DLY 1000 usec.1/24.truncated Example 1-6 does not show the secondary addressing on R1. Example 1-5 Secondary Address Configuration on R1 R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131. 0 runts. 0 overrun. you see how to configure a secondary address on R1 using the IP address 131. Example 1-5 displays the secondary IP address assignment.9645.255.1.ff40 (bia 0001. 0 late collision. load 1/255 Encapsulation ARPA. BW 10000 Kbit.1. keepalive set (10 sec) .0 ! interface Serial0/0 shutdown -7- . 0 giants..1 255. 0 frame. address is 0001. 0 underruns 0 output errors. 0 ignored. 30894958 bytes.1.108. loopback not set. output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40. 0 CRC.1. 131.1 255. DLY 1000 usec.1 255.1. 0 no buffer Received 315628 broadcasts.0 secondary R1 now has two IP address assignments: 161. 0 abort 0 input packets with dribble condition detected 470705 packets output. Example 1-7 Full working configuration on R1 hostname R1 ! interface Ethernet0/0 ip address 131. 0 packets/sec 315871 packets input.108.255.CCNP Practical Studies: Routing Example 1-4 displays the active Ethernet interface up and the current IP address configuration. 43588385 bytes.108. Example 1-6 displays the Ethernet statistics on R1 and is truncated for clarity.1.108. 0 no carrier 0 output buffer failures. rely 255/255.

The first subnet starts from 131.0/24 into four equal subnets that can be used to allow at most 62 hosts per subnet. so count from binary 0 to all 1s. The host devices use the last six bits. So to allow at most 62 hosts.0/24 for all wide-area network (WAN) connections that use no more than two hosts per subnet. so by default you have 254 IP address available. you must use the subnet mask of 255. n.1.108. This is only half the job. In addition to this.CCNP Practical Studies: Routing ! interface Serial0/1 shutdown ! line con 0 line aux 0 line vty 0 4 ! end Scenario 1-2: Efficiently Configuring a Network for IP Suppose you have been asked by a network architect to break up the Class B address 131.192. where 192 in binary is 11000000. The last eight bits are used for host addresses. Table 1-4 displays the binary calculation. -8- . you use the formula 2n . becomes six bits.108. which becomes 2n = 64.108. IP Address Configuration Requirements Start by breaking up the subnet 131.108. you must use the address space 131. You know the broadcast address ends in all 1s.0/24 into four equal subnets.255.1.2 = 62. To do this. which is the borrowed amount of bits.2. To allow at most 62 hosts. The network architect has also asked you to document all WAN addresses for future use. To determine the four subnets you must count in binary.0. Figure 1-4. Count only from the last octet. you must also configure the four different subnets on R1 in Figure 1-4.255.1. examine the subnet in binary. Figure 1-4 displays the network topology graphically.

so the first subnet ranges from 131. which in binary is 001111111.128.63. Binary Addition Subnet 2 Decimal 64 65 66 … 126 127 1000000 1000001 1000010 1111110 1111111 Binary Subnet all zeros First host address Second host address Last host address Host address Comment Table 1-5 displays the second subnet with all zeros as 131.1.0.127. Table 1-5 performs the same calculation in binary without the intermediate steps to demonstrate the broadcast address for the second subnet. which indicates the broadcast address.191. and the broadcast address as 131.108.108.108.1. Binary Addition 1 Decimal 0 1 2 3 … 62 63 000000 000001 000010 000011 111110 111111 Binary Subnet (all zeros) First host address Second host address Third host address Last host address Broadcast address (all 1s) Comment Table 1-4 counts in binary from 0 to 3 and so forth until 63.1.63.1. Binary Addition Subnet 3 Decimal 128 129 130 131 … 190 191 10000000 10000001 10000010 10000011 10111110 10111111 Binary Subnet (all zero's) First host address Second host address Third host address Last host address Broadcast address (all 1s) Comment Table 1-6 displays the subnet as 131.108.CCNP Practical Studies: Routing Table 1-4.1.64 and the broadcast of 131.108. -9- . The subnet is 131. Table 1-5.1.108. Notice that the last six bits are all 1s. and the broadcast address is 131.108. Table 1-6.0 to 131.1.1. Table 1-6 displays the third subnet calculation starting from the next available decimal number of 128.108.

.108. Example 1-8 IP Configuration on R1 with Four Subnets R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131. so you can quickly break up any type of subnet in various design situations or examination scenarios.108.255.0/24 into 30-bit sized subnets so that they can be used on WAN circuits that contain no more than two hosts. simply use a Windows-based calculator to perform the calculation to assist in your first few calculations.1.65 255.1.255. Binary Addition Subnet 4 Decimal 192 193 194 195 … 253 255 NOTE If you are confused about how to convert binary from decimal. configure the Router R1 in Figure 1-4 for IP routing.1. where n = 2.255.2 = 2.129 255.255.1 255.108.108.255.255.1. To complete this scenario. So.108. you need two bits per subnet.255. you can deduce the last subnet available in exactly the same way.192 R1(config)#interface ethernet 0/1 R1(config-if)#ip address 131.252.255.255.1.192 R1(config)#interface ethernet 0/2 R1(config-if)#ip address 131. Example 1-8 displays the IP configuration on the four interfaces on R1.255.192 and the broadcast address for the final subnet as 131. Now that you have the four broken subnets.255. or 2n = 4.2. use the simple formula 2n .CCNP Practical Studies: Routing Finally. It is vital that you can perform these steps without much thought. Table 1-7.0.108.192 in Example 1-8. you have to break up the network 131.1. The mask or subnet mask is derived from the six bits you borrowed to extend the Class B address 131.193 255. 11000000 11000001 11000010 11000011 11111110 11111111 Binary Subnet (all zeros) First host address Second host address Third host address Last host address Broadcast address (all 1s) Comment Table 1-7 displays the subnet as 131. Table 1-7 displays the final binary addition.10 - .192 The mask is 255.192 R1(config)#interface ethernet 0/3 R1(config-if)#ip address 131.108. and you have already discovered that the mask is 255.255.255.1. Once more. Binary 1100000 is 192.108.

CCNP Practical Studies: Routing
Table 1-8 displays the first four subnets available along with the subnet, broadcast address, and binary equivalent.

Table 1-8. WAN Host Assignment Decimal 131.108.2.0 131.108.2.1 131.108.2.2 131.108.2.3 131.108.2.4 131.108.2.5 131.108.2.6 131.108.2.7 131.108.2.8 131.108.2.9 131.108.2.10 131.108.2.11 131.108.2.12 131.108.2.13 131.108.2.14 131.108.2.15 Binary 00000000 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 00001001 00001010 00001011 00001100 00001101 00001110 00001111 Comment First subnet, last two bits all zeros First host Second host Broadcast address, last two bits all 1s Second subnet, last two bits all zeros First host Second Host Broadcast address, last two bits all 1s First subnet, last two bits all zeros First host Second host Broadcast address, last two bits all 1s Second subnet, last two bits all zeros First host Second host Broadcast address, last two bits all 1s

As an exercise, you can try to complete the table on your own. Simply count in binary and the next available subnet is clearly evident to you. Notice that the subnets in decimal count in fours, so the first subnet is 131.108.2.0/30, then 131.108.2.4/30, 131.108.2.8/30, 131.108.2.12/30, and so forth.

Scenario 1-3: Configuring IP VLSM for a Large Network
This scenario is slightly more complex. Figure 1-5 displays a network requiring a core network with a large number of routers (assume around 20), a distribution network with three routers, and an access network initially containing only six routers. The access network should have a potential for at most 25 routers (commonly known as access-level routers) to be connected through the distribution routers. Figure 1-5 displays the core network surrounded by three distribution routers and the six access-level routers. Figure 1-5. VLSM in a Large Network

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The Class B address 141.108.0.0 has been assigned to you for this task. You should ensure this address space is designed so that company growth allows you to use IP address space wisely to conserve it. Ensure summarization is possible with the three distribution routers. It is important that the IP addressing scheme is correctly laid out in a hierarchical fashion so that you can use summarization IP routing tables to keep them to a minimum. Start with the core of the network with a possible 20 routers. The core network of any large organization typically grows at a slower pace than access routers, so assume that allowing for over 1500 hosts should suffice. Assign seven Class C networks for the core, and reserve another eight for future use. Using 15 subnets allows for easy summarization as well. Assign the range 141.108.1.0–141.108.15.255 to the core network. In binary, this is the range 00000001 to 00001111, so the first four bits are common. The distribution routers generally perform all the summarization, so you can assign another seven subnets and reserve another eight Class C networks for future use. So now the distribution routers use the range 141.108.16.0–141.108.31.255. The access-level routers, where the users generally reside, typically grow at a fast rate, and in this scenario, each site has over 100 users; it is also possible that over 30 (90 in total) remote sites will be added in the future. It is vital that the subnets used here are contiguous so that summarization can take place on the distribution Routers R1, R2, and R3. The following describes a sample solution:

• • • •

For access Routers R4 and R5 and possible new routers, use the range 141.108.32.0 to 141.100.63.255; in binary that ranges from 100000 (32) to 63(11111). For access Routers R6 and R7 and possible new routers, use the range 141.108.64.0 to 141.100.95.255; in binary that ranges from 1000000(64) to 1011111(95). For access Routers R8 and R9 and possible new routers, use the range 141.108.96.0 to 141.108.127.255; in binary that ranges from 1100000(96) to 1111111(127). You can reserve the remaining 128 subnets for future use.

This is by no means the only way you can accomplish the tasks in this scenario, but you need to apply these principles in any IP subnet addressing design. NOTE Cisco IOS gives you even more IP address space by allowing the use of subnet zero with the IOS command ip subnet-zero. Of course nonCisco devices may not understand subnet zero. A good use for subnet zero would be for WAN links or loopback interfaces and conserving IP address space for real hosts, such as UNIX devices and user PCs. Subnet zero, for example, when using the Class B address 141.108.0.0 is 141.108.0.0, so a host address on a Cisco router could be 141.108.0.1/24.

When designing any IP network, you must answer the following core questions:

• • • • • • • • • • •

How many subnets are available? What IP ranges will be used; will private address space be applied to conserve public addresses? How many hosts reside on the edge of the network? What are the expansion possibilities for the network? What are the geographic locations of remote sites? Is there a connection to the Internet or WWW? Is an IP address space currently being used? What are the current sizes of exiting IP routing tables? Are any non-IP protocols already in use? If so, can you tunnel these non-IP protocols? What routing protocols enable the use of VLSM? These are just some of the major questions that you need to look at carefully. Cisco Systems provides a comprehensive guide to subnets at the following URL: www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2003.htm

NOTE Great resources for information on IP addressing and subnet calculators are also available on the Internet.

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Scenario 1-4: Summarization with EIGRP and OSPF
In this scenario, given the address ranges in Table 1-9, you see how to configure summarization with EIGRP and OSPF. Table 1-9 displays the IP address ranges to be summarized, as well as the binary representation of the third octet or the subnet port of the IP address space.

Table 1-9. IP Address Ranges IP Subnet 151.100.1.0 151.100.2.0 151.100.3.0 151.100.4.0 151.100.5.0 151.100.6.0 151.100.7.0 151.100.8.0 151.100.9.0 151.100.10.0 151.100.11.0 151.100.12.0 151.100.13.0 151.100.14.0 151.100.15.0 151.100.16.0 Subnet Mask 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 Binary Representation of Third Octet 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 00001001 00001010 00001011 00001100 00001101 00001110 00001111 00010000

Before configuring EIGRP or OSPF summarization, you first need to decide whether summarization is possible at all. Table 1-9 displays 16 subnets, numbered from 1-16. The first 15 subnets all have one thing in common when viewed in binary: The first four bits or highorder bits are always 0. Therefore, you can summarize the first 15 networks using the subnet mask 255.255.255.240. (240 in binary is 1111000 where the first four bits are common.) The last four bits contains the networks 1 to 15 or in binary encompass all networks from 0000 to 1111. The last remaining subnet 151.100.16.0 is the odd network out. Although it is contiguous, you cannot summarize it along with the first 15 network, because any summary address range encompasses networks beyond 151.100.16.0, which may reside in other parts of the network. Configure EIGRP to summarize these routes out of a serial port (serial 0/0 in this example). Example 1-9 displays the configuration required to disable automatic summarization and the two required summary address commands on the serial 0/0 on a router named R1. Example 1-9 EIGRP Summary

R1(config)#router eigrp 1 R1(config-router)#no auto-summary R1(config)#interface serial 0/0 R1(config-if)#ip summary-address eigrp 1 151.100.1.0 255.255.255.240 R1(config-if)#ip summary-address eigrp 1 151.100.16.0 255.255.255.0
In Example 1-9, the router R1 sends only two updates: one for the networks ranging from 151.100.1.0 to 151.100.15.0 and another for 151.100.16.0. These two are instead of 16 separate IP route entries. Even in a small scenario like this, you saved 14 IP route entries. Reducing IP routing tables means when a router performs a routing table search, the time it takes to determine the outbound interface is reduced allowing end-user data to be sent faster over a given medium. With OSPF, you do not need to disable automatic summarization, because OSPF does not automatically summarize IP subnets. Hence, to summarize the same block of addresses of a router (OSPF ABR), you apply two commands under the OSPF process. Example 1-10 displays the summary commands required.

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Example 1-10 OSPF Summary

R1(config)#router ospf 1 R1(config-router)#no area 1 range 151.100.16.0 255.255.255.240 R1(config-router)#area 1 range 151.100.16.0 255.255.255.0

Scenario 1-5: Configuring IP Helper Address
The following scenario demonstrates the powerful use of the helper command and how broadcast traffic, which is dropped by default on Cisco routers, can be forwarded in a manageable fashion and enable IP connectivity across a WAN. In this scenario, you have a group of users on one segment requiring IP address assignment. No local servers reside on the segment with this group of users. Figure 1-6 displays the network topology. Figure 1-6. IP Helper Requirement

Now, when the users on the local-area network (LAN) segment attached to R1 send out a request for an IP address, this IP packet is sent to the broadcast address, which is dropped by default. Unless a local Dynamic Host Configuration Protocol (DHCP) server exists on this segment, the users' requests for an IP address aren't responded to. To alleviate this problem, you configure a helper address on R1 pointing to the remote file server(s)' address. In this case, two servers are available for redundancy, so you can configure two helper addresses on R1's Ethernet port. NOTE Remember, a helper address can forward many UDP-based protocols such as DNS and BOOTP requests. You can further restrict which protocols are sent by using the IOS command ip forward-protocol {udp [port]} or you can forward a packet based on a particular port number used by a certain application. Example 1-11 displays the helper address configuration on R1.

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CCNP Practical Studies: Routing
Example 1-11 IP Helper Address Configuration on R1

R1(config)#interface ethernet 0/0 R1(config-if)#ip helper-address 131.108.1.99 R1(config-if)#ip helper-address 131.108.1.100
The five basic scenarios in this first chapter are aimed at addressing your basic knowledge or re-enforcing what you already know. The Practical Exercise that follows gives you an opportunity to test yourself on these concepts.

Practical Exercise: IP
NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. The solution can be found at the end. Given the IP address ranges in Table 1-10 and using EIGRP as your routing algorithm, ensure that the least number of IP routing entries are sent out the Ethernet 0/0 port on a Cisco IOS-based router. Table 1-10 displays the IP subnet ranges.

Table 1-10. IP Subnet Ranges IP Subnet 171.100.1.0 171.100.2.0 171.100.3.0 171.100.4.0 171.100.5.0 171.100.6.0 171.100.7.0 Subnet Mask 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 255.255.255.0 Binary Value of Third Octet 00000001 00000010 00000011 00000100 00000101 00000110 00000111

Practical Exercise Solution
You should notice that the first five bits are the same and the last three encompass the range 1-7, so you can apply the following summary command:

ip summary address eigrp 1 171.100.1.0 255.255.255.248
Example 1-12 displays the configuration required to summarize the networks from Table 1-10 on an Ethernet 0/0 port using the ? tool to demonstrate the available options required by Cisco IOS. Example 1-12 Sample Configuration

R1(config)#interface ethernet 0/0 R1(config-if)#ip summary-address ? eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) R1(config-if)#ip summary-address eigrp 1 171.100.1.0 255.255.255.248 R1(config-if)#ip summary-address ? eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) R1(config-if)#ip summary-address eigrp ? <1-65535> Autonomous system number R1(config-if)#ip summary-address eigrp 1 ? A.B.C.D IP address R1(config-if)#ip summary-address eigrp 1 171.100.1.0 255.255.255.248
NOTE

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CCNP Practical Studies: Routing
Example 1-12 displays the Cisco IOS prompts that appear when the user enters the question mark (?) to display the options or parameters the Cisco IOS requires next. They are illustrated here for your reference.

Review Questions
You can find the answers to these questions in Appendix C, "Answers to Review Questions."

1:

Given the following host address and subnet mask combinations, determine the subnet address and broadcast addresses:

• • • •

131.108.1.24 255.255.255.0 151.108.100.67 255.255.255.128 171.199.100.10 255.255.255.224 161.88.40.54 255.255.255.192

2: 3: 4: 5: 6: 7: 8: 9: 10:

Given the network 141.56.80.0 and a subnet mask of 255.255.254.0, how many hosts are available on this subnet? What is the broadcast address for the subnet 131.45.1.0/24? What is the purpose of the broadcast address in any given subnet? Given the subnet in binary notation 1111111.11111111.00000000.00000000, what is the decimal equivalent? Which routing protocols support VLSM and why? Which routing protocols do not support VLSM? Which subnet mask provides approximately 1022 hosts? What is the equivalent subnet mask for the notation 131.108.1.0/24? Identify the private address ranges defined in RFC 1918.

Summary
You have successfully worked through five scenarios using common techniques in today's large IP networks. You can now begin to apply this knowledge to the chapters ahead and work through more complex scenarios. The basic information described in this chapter can be applied to any networking scenario you come across when designing and implementing a Cisco-powered network or any network for that matter. Table 1-11 summarizes the commands used in this chapter.

Table 1-11. Summary of IOS Commands Used in This Chapter Command area area-id range network mask router ospf process id router eigrp autonomous domain ID no auto-summary show interfaces ethernet 0/0 version 2 [no] shutdown Purpose Summarizes OSPF network ranges between area border routers. Enables OSPF routing. The process ID is local to the router. You can have more than one OSPF running. Enables EIGRP routing under a common administrative control known as the autonomous domain or AD. Disables automatic summarization. Displays Ethernet statistics on port 0/0. Enables RIPv2. Enables or disables an interface. All hardware interfaces are shut down by default.

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CCNP Practical Studies: Routing

Chapter 2. Routing Principles
This chapter describes how to configure a Cisco Internet Operating System (IOS) router for IP routing and explains common troubleshooting techniques by covering the following:

• • • •

Internet Protocol (IP) routing tables Dynamic routing protocols Classful and classless routing Using show, debug, ping, and trace commands

This chapter focuses on a number of objectives relating to the CCNP routing principles. Understanding basic routing principles not only applies to the CCNP certification but to all Cisco-based certification. A concrete understanding of how to route traffic across the network is fundamental for the more advanced topics covered later in this book. This chapter starts by covering the basic information a Cisco router requires to route traffic and then describes classful and classless routing protocols. The chapter then briefly covers distance vector and link-state protocols and examines IP routing tables and common testing techniques used to troubleshoot IP networks. Five practical scenarios complete your understanding and ensure you have all the basic IP routing skills to complement your understanding of IP routing on Cisco IOS routers.

Routing IP on Cisco Routers
Routing is defined as a process whereby a path to a destination host is selected by either a dynamic routing protocol or static (manual) definition by a network administrator. A routing protocol is an algorithm that routes traffic or data across the network. Each router makes routing decisions from source to destination based on specific metrics used by the routing protocol in use. For example, Routing Information Protocol (RIP) uses hop count (commonly known as the network diameter) to determine which interface on a router sends the data. A lower hop count is always preferred. On the other hand, Open Shortest Path First (OSPF) uses a cost metric; the lower the cost of the path is the more preferred path to a destination. NOTE The method by which a routing algorithm, such as RIP/OSPF, determines that one route is better than another is based upon a metric. The metric value is stored in routing tables. Metrics can include bandwidth, communication cost, delay, hop count, load, MTU, path cost, and reliability.

For routing IP across a network, Cisco routers require IP address allocation to interfaces and then statically or dynamically advertise these networks to local or remote routers. After these networks are advertised, IP data can flow across the network. Routing occurs at Layer 3, or the network layer, of the Open System Interconnection (OSI) model. By default, IP routing is enabled on Cisco routers. The command you use to start or disable it is [no] ip routing. However, because IP routing is enabled, you do not see this command by viewing the running configuration as displayed with the IOS command, show runningconfig. Consider a one-router network with two directly connected Ethernet interfaces as an introductory example, shown in Figure 2-1. Figure 2-1. Routing IP with Directly Connected Networks

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CCNP Practical Studies: Routing
In Figure 2-1 router R1 has two interfaces: E0 (IP address 172.108.1.1/24) and E1 (172.108.2.1/24). Assume there are users on E0 and E1 with PCs labeled PC 1 and PC 2. By default, an IP packet from PC 1 to PC 2 is routed by R1 because both IP networks connect directly to R1. No routing algorithm is required on a single Cisco router (not attached to any other routers) when all interfaces are directly connected as described in this example. Example 2-1 displays R1's routing table. Example 2-1 show ip route Command on R1

R1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is not set C C R1# 172.108.0.0/24 is subnetted, 2 subnets 172.108.1.0 is directly connected, Ethernet0 172.108.2.0 is directly connected, Ethernet1

In Example 2-1, the C on the left side of the IP routing table denotes the two directly connected networks. Cisco IOS routers support many dynamic routing protocols as well as static (denoted by S) routes. Later chapters in this book cover the main dynamic routing protocols, such as the Open shortest Path First (OSPF) Protocol, RIP, Interior Gateway Routing Protocol (IGRP), and EIGRP. Scenario 2-1 covers all the fields used in an IP routing table. NOTE The IP address source and destination in an IP datagram does not change, but the Layer 2 Media Access Control (MAC) source and destination do. For example, when PC 1 sends a packet to PC 2, and because PC 2 resides on a different subnet, PC 1 automatically sends the IP packet to the default router using the destination MAC address of Router R1 (or E0 burnt in address) or the default gateway address of 172.108.1.1/24 (assuming a default gateway has been configured on PC 1 and PC 2). The router then strips the Layer 2 header and installs its own Layer 2 header when the packet enters the network where PC 2 resides. The Layer 2 header contains the source address of R1 E1 and the destination address of the PC 2 MAC address. The Layer 3 IP source and destination address do not change. Some exceptions exist, of course, and many new emerging technologies, because of IP address depletion, change the Layer 3 addressing to allow more hosts to connect to the Internet. Example technologies include Network Address Translation (NAT) or the implementation of Web proxies. Cisco routers require only IP addressing and routing to allow hosts on different segments to communicate. This chapter covers dynamic and static routing in the section "Classful and Classless Routing Protocols."

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if a router has two paths to a destination and one is listed as OSPF (AD is 110) and another as IGRP (AD is 100). EIGRP. and RIP are dynamic routing protocols and are all covered in this book. the router selects the IGRP path because of the lower AD. The higher the value (between 0–255). Example 2-2 shows a full list of the protocols that Cisco IOS-based routers support.CCNP Practical Studies: Routing Cisco IOS-Based Routers All Cisco routers support IP routing. Intermediate System-to-Intermediate System (IS-IS) Protocol. Cisco IOS enables the network designer to change the AD with the distance command. Using AD ensures that the Cisco routers can compare the remote destinations they learn through various routing algorithms. Cisco AD Default Values Routing Method Connected interface Static route Enhanced IGRP summary route External BGP Internal Enhanced IGRP IGRP OSPF IS-IS RIP EGP External Enhanced IGRP Internal BGP Unknown 0 1 5 20 90 100 110 115 120 140 170 200 255 Administrative Distance For example. To overcome this problem. You can use static routing to minimize large routing tables and can manually configure it to override dynamic information. OSPF. Table 2-1 displays the default AD values on a Cisco router. whether dynamic or static. IGRP. deciding which path to take is vital. Distance Vector and Link-State Routing Protocols Now that you are aware of the routing methods available. AD is defined as the trustworthiness of a routing information source. RIP's metric to OSPF's metric because hop count means nothing in OSPF and cost means nothing in a RIP domain. Example 2-2 Routing Protocols You Can Enable on a Cisco Router R1(config)#router ? bgp egp eigrp igrp isis iso-igrp mobile odr ospf rip static traffic-engineering Border Gateway Protocol (BGP) Exterior Gateway Protocol (EGP) Enhanced Interior Gateway Routing Protocol (EIGRP) Interior Gateway Routing Protocol (IGRP) ISO IS-IS IGRP for OSI networks Mobile routes On Demand stub Routes Open Shortest Path First (OSPF) Routing Information Protocol (RIP) Static routes Traffic engineered routes Border Gateway Protocol (BGP). for example.19 - . When you configure multiple routing algorithms on a Cisco router. AD is important because routers cannot compare. this section looks at the two main types of routing methods that routers use to detect remote destinations dynamically. the less trusted the source. you assign each routing method. . an administrative distance (AD). Table 2-1.

Examples RIP and IGRP are examples of distance vector protocols. determine the path to remote networks using hop count as the metric. This saves on bandwidth as well. Therefore.0.255.6 for all DRs and BDRs. Count to infinity This is the maximum hop count. which is the highest IP address configured on the local router.5 for all OSPF routers and 224.0. two reserved multicast addresses are vital for maintaining OSPF adjacencies across any broadcast media. the maximum hop is 15. also known as Dijkstra's Algorithm) to determine the path to a remote destination.0.) NOTE Hello packets are used to discover neighboring routers. also sends all summary information every 30 minutes by default. the loopback interface with (numerically) the highest IP address is the router ID. Updates are not sent out an outgoing interface from which the source network was received. it is 255.0 through 239. One of the drawbacks of protocols. Examples OSPF and IS-IS. Hello packets are used to establish and maintain neighbors. Linkstate protocols implement an algorithm called the shortest path first (SPF. such as Ethernet or Token Ring. such as RIP and IGRP. updates Database A database contains all topological information from which an IP routing table is assembled. When an update is sent. Any new OSPF-enabled routers immediately transmit a multicast Hello packet by using the OSPF routers multicast address of 224. so when changes occur updates can be sent immediately. it is 15 and for IGRP. For IP RIP.0. the maximum time to live ensures that loops are avoided. Typically.0. such as OSPF and IS-IS. OSPF administrators configure loopback interfaces to ensure that the OSPF process is not prone to failures. Also known as Flash updates.5. IGRP is another example of a distance vector protocol with a higher hop count of 255 hops. Algorithm Dijkstra Algorithm for OSPF. A hop count is defined as the number of times a packet needs to pass through a router to reach a remote destination. Table 2-2. Algorithm One algorithm example is Bellman-Ford for RIP. (For an IP datagram. the entire routing table is sent. You use this method to stop routing loops.255. Distance Vector Protocol Summary Characteristic Periodic updates Broadcast updates Full table updates Triggered updates Split horizon Description Periodic updates are sent at a set interval.20 - . Convergence Updates are faster and convergence times are reduced.255.0.0. A higher hop counts allows your network to scale larger. Link-State Protocol Summary Characteristic Explanation Periodic updates Only when changes occur. such as cost and the advertising router or the router ID. Updates are sent to a multicast address. Table 2-3 displays the characteristics of link-state protocols. this interval is 30 seconds.CCNP Practical Studies: Routing Distance vector protocols (a vector contains both distance and direction). these are sent when a change occurs outside the update interval. For RIP. is convergence time. Updates are sent to the broadcast address 255. such as RIP. There is no hop count limit. (Loopback interfaces never fail unless you shut them down or manually delete them. DRs use the multicast address 224. which is the time it takes for routing information changes to propagate through all your topology. A hop count of 16 indicates an unreachable network. OSPF uses the Class D multicast addresses in the range 224. OSPF. . Table 2-3. For IP RIP.0.255.255.) In the event that more than one loopback interface is configured on a Cisco router. The OSPF database is populated with link-state advertisements (LSAs) from neighboring routers. CPU/memory Higher CPU and memory requirements to maintain link-state databases. The LSA packets contain information. for example. Only devices running routing algorithms listen to these updates. Broadcast Only devices running routing algorithms listen to these updates. The two most important reserved addresses are 224. Link-state routing protocols. create a topology of the network and place themselves at the root of the tree.6 to send updates to all other OSPF routers.0.0. Two versions of RIP exist: version 1 and version 2. Table 2-2 describes the characteristics of distance vector protocols.255.

and when designing networks.0. 0 1.255. D.0. 1 Address Range 1.0.0. you can use a Class B network. 0 1. (Class D is reserved for multicasts.0 is applied and so forth. A Class B network uses the mask 255.254.0 224.16.0.31. the ability to apply summarization techniques enables you to reduce the size of a routing table.0.0.0. and apply a Class C mask (255. At last count (October 2001). B.0. there are over 80.255. Table 2-4. For example.0. classless routing better utilizes address space. 1. .255 Maximum Hosts 16.0 192.0.255.0.1. Classful and Classless Routing Protocols Routing protocols can also be described as classful and classless.255. 1. This method of routing does not scale well.0.0–172.255. With classless routing.255. For example.0–223.0. Reducing the IP routing table size allows for faster delivery of IP packets and lower memory requirements.0. BGP is considered a path vector protocol because autonomous system numbers are carried in all updates. If a router is configured with a Class A address 10.255.0.000 IP routing table entries on the Internet. Classful routing protocols apply the same rules. and BGP.0.168. and Class C uses 255.0. 1. or /24. IP Address Ranges IP Address Class A B C D E Typically Used By: Few large organizations Medium-sized organizations Relatively small organizations Multicast groups (RFC 1112) Experimental High-Order Bit(s) 0 1.0–192. Examples of classless routing protocols are OSPF.168.777.0. and E network.0. Also note distance vector protocols are simpler to implement.255.0–254.0–239. and the vector indicates the direction and path to a remote network. EIGRP.) Class A.0–191.255. mask).255. 1. BGP is considered the most complex routing protocol to configure.1.255. Classful addressing is the use of Class A. 0 1.0. whereas RIP is considered the easiest. such as 131. and link-state protocols are more complex. B.255 192.254.255.255 Table 2-4 summarizes the addressing ranges in Class A.0.21 - . NOTE The following three blocks of IP address space for private networks have been reserved according to RFC 1597: • • • 10. 1.255. and Class C addresses.0.255.CCNP Practical Studies: Routing NOTE EIGRP is considered an advanced distance vector protocol because EIGRP sends out only incremental updates. and C addresses define a set number of binary bits for the subnet portion. and Class E is reserved for future use. C.108. the default mask of 255.0.1. IS-IS.0–126.0 128.543 254 N/A N/A Examples of classful routing protocols are RIPv1 and IGRP.0–10.214 65.255 240.0. Class B.0.1.0.255 172. a Class A network ranges from 1–127 and uses a subnet mask of 255.

0. configure router R1 for IP routing. and you can use it as a tool to populate routing tables. NOTE A loopback interface is a software interface. Scenario 2-1: Routing IP on Cisco Routers In this scenario. As with any wide-area network (WAN) connection. or /24). Ethernet. clocking is required to enable the two routers to communicate. You learn how to build a small network up from the physical layer and build an IP routing table using one serial link between the two routers. Typically. Figure 2-2.CCNP Practical Studies: Routing Scenarios The following scenarios and questions are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs.0. Refer to Figure 2-2 for IP address assignments.22 - . There is not always one right way to accomplish the tasks presented here. this is a modem. with a Class C subnet mask (255. You need to start by configuring the loopbacks. A loopback interface is a software interface that can be numbered from 0-2147483647. Loopbacks are handy when you don't have access to a large number of routers and are vital tools when you are configuring IOS on Cisco routers. You can ping it and communicate with it. Routing IP with Directly Connected Networks Routing IP with Cisco Routers First. and the serial interface.108. .255. Example 2-3 displays the hardware information on R1. 131. use the show controller command to determine which end of the network is the data circuit-terminating equipment (DCE).0. and using good practice and defining your end goal are important in any real-life design or solution. Most importantly. R1 is directly connected to R2 with back-to-back serial cables. Figure 2-2 shows the network for this scenario. NOTE To determine which router requires a clock to enable communication at Layer 2 of the OSI model. R1 and R2. you configure two Cisco routers for IP routing using a Class B (/16) network address. it never goes down.255. You also configure a number of loopback interfaces to populate the IP routing table.

buffer size 1524. Example 2-4 show controllers s0/1 on R2 R2#show controllers s1/0 CD2430 Slot 1. To configure the three loopbacks for this scenario.4. no clock .0 R1(config-if)#interface loopback 1 2w1d: %LINK-3-UPDOWN: Interface Loopback1.108. Port 0.255. type the commands on R1 as displayed in Example 2-5. so R2 requires a clocking source. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback2.CCNP Practical Studies: Routing Example 2-3 show controllers s0/1 on R1 R1#show controllers s0/1 Interface Serial0/1 Hardware is PowerQUICC MPC860 DCE V. changed state to up R1(config-if)#ip address 131. changed state to up R1(config-if)#ip address 131. Example 2-4 displays the hardware information on R2.35. Example 2-5 IP Address Configuration on R1 R1(config)#interface loopback 0 R1(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Loopback0. To configure the loopbacks with an IP address.108. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0..35 DTE cable output omitted NOTE The output in Example 2-4 is different from that of Example 2-3 because this scenario uses different model routers for R1 (2600) and R2 (3600). changed state to up R1(config-if)#ip address 131. In this case.255. Revision 15 Channel mode is synchronous serial idb 0x61209474. Controller 0.35. Channel 0.0 R1(config-if)#interface loopback 2 2w1d: %LINK-3-UPDOWN: Interface Loopback2.255.255. R1. simply use the following command syntax: interface loopback number The value for number is a number within the range of 0-2147483647.23 - .255. supplies the clock. and the cable types used on the routers are V.5.108. V.1 255.255.6.1 255.. The Cisco IOS automatically enables the loopback interface if you have not previously created it. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1.output omitted Notice that R1 has the DCE connection so you need to configure a clock rate with the clock rate speed command.0 .1 255. the DCE. Router R2 has the data terminal equipment (DTE).

Example 2-8 Enabling E0/0 and S1/1 on R2 R2(config)#interface e0/0 R2(config-if)#ip address 131. and the link to R1 is active because R1 is enabled and supplying a clock source.0 R1(config-if)#interface s 0/1 R1(config-if)#ip address 131. You now simply configure the IP addresses for the Ethernet and serial link to R2. NOTE If you do not have access to any form of switch or hub. but you still have no active connection on R1 serial link because R1 S0/1 connects to R2. and you have yet to enable R2 serial interface to R1.0 R2(config-if)#no shutdown R2(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Ethernet0/0. no users can attach to your network. changed state to up On this occasion.1.255.3.255.0 R2(config-if)#no shut R2(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Serial1/1.1 255. The lack of such a message is because that all physical interfaces are shut down by default when you first configure a router from the default state. you can enable the Ethernet interface with the command keepalive 0. You need to enable the interfaces.255. in which case hardware is unnecessary. notice both the Ethernet and serial connections are immediately active because R2 is connected to an Ethernet switch. .108.255.108.255.255. Similarly. Example 2-7 displays the Ethernet interface and serial interface on R1 being enabled.1 255. You have now configured two routers with IP addressing.0 R1(config-if)#clock rate 128000 This time you did not get any messages to indicate the link is active.2 255. this happens for loopbacks 1 and 2. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0. as demonstrated in Example 2-6. Example 2-7 no shutdown Command on R1 R1(config-if)#interface e0/0 R1(config-if)#no shutdown R1(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Ethernet0/0. Example 2-6 IP Address Configuration on R1 R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131. Of course. you get a message that indicates Loopback 0 is active.108. Example 2-8 displays IP address configuration and the enabling of the hardware interfaces on R2. but for training purposes it is a great command to use. The Cisco IOS considers the interface active and includes the network in the IP routing table. changed state to up R2(config-if)#int s 1/1 R2(config-if)#ip address 131.255. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0.2.255.CCNP Practical Studies: Routing In Example 2-5 when the first interface Loopback 0 is created.3.108.1 255. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/1.24 - . You can assume that the Ethernet on R1 is connected to a Catalyst switch. changed state to up R1(config-if)#int s 0/1 R1(config-if)#no shutdown The Ethernet interfaces is running.

candidate default U .8. The first half of the display summarizes the abbreviations the Cisco IOS uses to denote how it learns or discovers routing entries. B .IS-IS.0.OSPF external type 1.0/24 is directly connected.7.candidate default U .IGRP.0/16 is variably subnetted.108. In particular. That the gateway of last resort is not set in this case means that if the router receives an IP packet. 5 subnets directly connected.CCNP Practical Studies: Routing Viewing IP Routing Tables Now view the routing tables on R1 and R2 in Scenario 2-1 to see what exactly is described in an IP routing table. Ethernet0/0 R2# Both of these cases show routing entries for only directly connected interfaces. L1 . Loopback2 directly connected. and so forth. Loopback1 C 131.4.static.25 - .5. R . Serial1/1 C 131.OSPF NSSA external type 2 E1 . M .108. namely the three loopbacks. o .EIGRP external. E2 .108.0/25 is directly connected. 5 subnets .0/24 is subnetted.BGP D . EX .108. I .mobile. * .ODR Gateway of last resort is not set C C C C C R1# 131. S . E2 . Now.EIGRP.1.IS-IS. L2 . S .BGP D . E . the Ethernet.IGRP. O .108.108.OSPF NSSA external type 2 E1 . L1 .IS-IS level-1.OSPF inter area N1 . IA . I .0 131.108. by default if the router doesn't know the destination. Loopback0 directly connected. If the router knows the gateway of last resort. Serial0/1 directly connected. which are denoted by the C on the left side of each routing table.2.108. M .OSPF external type 2.9.RIP.3. the router forwards the IP packets to that destination or next hop address.0 subnetted with five individual networks. N2 . R .OSPF NSSA external type 1. look at the shaded portions in Example 2-9. Loopback2 C 131. o .108.OSPF external type 2.EGP i .EIGRP external. O .108.6.connected.OSPF.ODR Gateway of last resort is not set 131. B .108.3.0/24 131.0. EX . entries denoted by D are discovered by EIGRP.IS-IS level-1.0/24 is directly connected. Example 2-10 show ip route on R2 R2#show ip route Codes: C . L2 . which is typically represented by a next hop address.IS-IS level-2. you take the R1 routing table and look at it in depth. For example. Example 2-9 displays R1's routing table. E .108. Loopback1 directly connected. * . Example 2-9 show ip route Command on R1 R1#show ip route Codes: C . and the serial link to R2: 131. Loopback0 C 131.OSPF external type 1.108.EIGRP. N2 . IA . 9 subnets.0/24 is directly connected.per-user static route.0.OSPF.0 131.0/30 is directly connected. Ethernet0/0 Example 2-10 displays R2's IP routing table. The following entry describes the fact that R1 has the Class B network 131.connected.EGP i . entries that display C are directly connected networks.IS-IS level-2.static.OSPF NSSA external type 1.RIP.OSPF inter area N1 .0 131. 3 masks C 131.0 is is is is is is subnetted. it drops the IP packet.mobile.per-user static route.0 131.108.0.

metric 1 .1) 2w1d: subnet 131. In this example.108.255.0.0. metric 1 2w1d: subnet 131.0.0.1) 2w1d: subnet 131.3.108.0. Step 2.5.108.2. Specify the networks on which RIP will run.6.1.108. Example 2-13 displays the debug commands enabled on R1. To start.0 Example 2-12 Enable IP RIP on R2 R2(config)#router rip R2(config-router)#network 131.0.0 in 1 hops 2w1d: RIP: Update contains 1 routes 2w1d: RIP: sending v1 update to 255.6.2.0.255.0.0.4. Example 2-13 debug ip rip Output on R1 R1#debug ip rip RIP protocol debugging is on R1#debug ip rip events RIP event debugging is on 2w1d: RIP: received v1 update from 131.255. metric 1 2w1d: subnet 131.255.108. you need to specify only the major network because RIP is a classful protocol.1.0.108. metric 1 2w1d: subnet 131.108. metric 1 2w1d: subnet 131. metric 1 2w1d: subnet 131.0.108.0.5.1. Example 2-11 and Example 2-12 display the configurations required on R1 and R2.0. metric 1 2w1d: RIP: Update sent via Ethernet0/0 2w1d: RIP: Update contains 4 routes 2w1d: RIP: Update queued 2w1d: RIP: sending v1 update to 255. metric 1 2w1d: subnet 131.108.0 Now enable debugging on R1 to view the routing updates on R1. metric 1 2w1d: subnet 131.0.255. IP RIP is one of the easiest routing protocols to configure.0.255 via Loopback0 (131. metric 1 2w1d: subnet 131.2. configure R1/R2 with RIP and then OSPF.108.3.108.108.108.255. To enable IP RIP.1) 2w1d: subnet 131.255 via Serial0/1 (131. Enable the routing protocol with the command router rip.108. metric 1 2w1d: RIP: Update sent via Serial0/1 2w1d: RIP: Update contains 5 routes 2w1d: RIP: Update queued 2w1d: RIP: sending v1 update to 255. metric 1 2w1d: subnet 131.255.26 - . the Class B network is 131.108.6. Example 2-11 Enable IP RIP on R1 R1(config)#router rip R1(config-router)#network 131.108.108.6.0.CCNP Practical Studies: Routing To make the routing table a little more interesting.4.108. R1 is not aware of any IP networks on R2 and vice versa. metric 1 2w1d: subnet 131.108. metric 2 2w1d: RIP: Update contains 5 routes 2w1d: RIP: Update queued 2w1d: RIP: sending v1 update to 255.0.255 via Ethernet0/0 (131.108. respectively.0.3.1) 2w1d: subnet 131. metric 1 2w1d: subnet 131. With RIP.0.0. to enable IP RIP.108.108.108.255 via Loopback1 (131. metric 2 2w1d: subnet 131.255.5.4.4. configure RIP on both R1 and R2.108. you need to perform the following steps: Step 1. At this stage.5.108.2 on Serial0/1 2w1d: 131.3.

108.108.108. metric 1 Update sent via Loopback0 Update contains 5 routes Update queued sending v1 update to 255.108.0.3.9.0 [120/1] via 131.0 131. is directly connected.0.2.1. Example 2-14 R1's Ip Routing Table R1#show ip route R R R C C C C R C R1# 131.0.108.0/24 131. metric 1 Update sent via Loopback1 Update contains 5 routes Update queued Update sent via Loopback2 RIP: RIP: RIP: RIP: RIP: RIP: RIP: RIP: Example 2-13 displays routing updates sent (by default version 1 of RIP is sent and both versions 1 and 2 are accepted) and received by R1. it sends updates to R1. 9 subnets R 131.0.2.108.7.108. 131. metric 1 subnet 131.0 [120/1] via 131.2. and most importantly to R2 through the serial link S0/1.3.108. you typically use a subnet that allows only two hosts.2. R 131.108.6. 9 subnets [120/1] via 131.0 [120/1] via 131. To ensure the efficient use of IP address space when designing networks.108.0 131.0/24.0 131.108. 00:00:20.255. 1.0 131.3.255.1.0. 131.2. that is.1.4.108. R 131. R2 is advertising the Class B subnetted networks 131.108.3. R1# 00:00:20.2.9. 00:00:08.108.2.0. the administrative distance is 120 and the metric is hop count.3. R 131.108.108.108. metric 2 subnet 131.108. Example 2-14 displays the IP routing table on R1.0 131.4. you must use the subnet mask 255.0.108. 00:00:20.108.108. metric 2 subnet 131.0 131.5. metric 1 subnet 131.0.0 [120/1] via 131.3. The hop count to all the remote networks in Example 2-15 is 1.0 131. In the case of IP RIP. 00:00:08.0.108.2.2.0 131.108.108.108.0/24 is subnetted.2. Now change the IP address on the serial link to the most commonly used subnet. Ethernet 0/0.252.2.2.108.108.7.108.3. 00:00:08. Serial0/1 [120/1] via 131.8. 00:00:20.3. R2 performs the same routing function.6.108.108.0/24 through the next hop address 131.108.255.108. R1 sends information about the local interfaces so that R2 can dynamically insert these entries into its own routing table.108. metric 1 subnet 131.3.255 via Loopback2 (131. is directly connected. RIP works in this environment because all the networks are Class C.5.3. Then R1 sends updates to loopbacks 0.255. Loopback1 is directly connected.7. metric 1 subnet 131.255.0 is subnetted. [120/1] via 131. Loopback0 is directly connected.255.2.9. .252. [120/1] via 131.108.108. Serial0/1 Serial0/1 Serial0/1 Serial0/1 As you can see in Example 2-15. and 131. 00:00:08.8. and 2.3.2.27 - . Example 2-16 displays the IP address change on R1 and R2 using the new subnet mask of 255. The outgoing interface is serial 0/1.0/24.0/24.1) subnet 131.CCNP Practical Studies: Routing 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: subnet 131.108. Example 2-15 R1's RIP Entries Only R1#show ip route rip 131.3.108. Ethernet0/0 Serial0/1 Serial0/1 Serial0/1 Serial0/1 Example 2-15 shows just IP RIP routes using the command show ip route rip. To allow two hosts.108. Another important field described in the IP routing table is the administrative distance and the metric.8.0. Loopback2 is directly connected.

2. 5 subnets.0. Ethernet0/0 Notice what happens to the IP RIP routes.0/24 131. IP RIP version 1 does not.108.0/16 is 131.0/16 is C 131. 00:00:00. Example 2-19 R1's IP Route Table with RIPv2 Enabled R1#show ip route R R R C C C C R C 131.0/24 C 131.3.9. Example 2-20 and Example 2-21 display the full configurations for R1 and R2 using VLSM and RIPv2. Example 2-18 Enabling RIPv 2 on R1 and R2 R1(config)#router rip R1(config-router)#version 2 R2(config)#router rip R2(config-router)#version 2 IP RIPv2 understands VLSM.6.0/24 R1# variably subnetted.108. To enable version 2.3.255. Loopback0 is directly connected. You can also use static routes to accomplish connectivity.108.108.0/30 C 131. Ethernet0/0 The remote networks are now back in the routing table because RIPv2 understands VLSM. Serial0/1 is directly connected. Serial0/1 [120/1] via 131.3.2 255.0/24 131. Because you use a variable-length subnet mask (VLSM) across this network means you need a routing protocol that understands VLSM.0/24 variably subnetted. Serial0/1 is directly connected.6.2.0/24 131.1.0/24 131. whereas all the other directly connected interfaces are /24. Another routing protocol that understands VLSM is OSPF.108.0 ! ! hostname R1 .108.2. Loopback2 is directly connected. 2 masks is directly connected. a /24 network was used on all interfaces.8.108.2.108.0/24 C 131.4. Example 2-19 displays the new IP routing table on R1.28 - . or whatever mask is applied.255. Example 2-20 R1 Full Configuration version 12. 2 masks [120/1] via 131. 00:00:00.108. Example 2-17 now displays the new IP routing table on R1.1.3.5. Serial0/1 [120/1] via 131. Example 2-18 displays the enabling of RIP version 2.0/24 131. Loopback2 is directly connected. Serial0/1 [120/1] via 131.255.255.108.108. 9 subnets.108.108.3.108. you type the command version 2. Loopback1 is directly connected. Before you learn how to configure OSPF.108.1 255. Loopback0 is directly connected.0. Example 2-17 show ip route on R1 R1#show ip route 131.108.252 Look at the IP routing table on R1.108.0/30 131. to a directly attached interface. Also notice that the serial link to R2 through Serial 0/1 is a /30 subnet.3. 00:00:00.108. 00:00:00.108.2.0/24 131.0/24 131. Remember that RIP is classful so it applies the default subnet mask.252 1/1 address 131.5.4.7.108. Loopback1 is directly connected. Enable version 2 of IP RIP.0/24 C 131.108. In the first RIP example.CCNP Practical Studies: Routing Example 2-16 IP Address Change on R1 and R2 R1(config)#int s R1(config-if)#ip R2(config)#int s R2(config-if)#ip 0/1 address 131. Serial0/1 is directly connected.108.3.3.

255.255.0 no ip directed-broadcast ! interface Loopback1 ip address 131.29 - .108.6.1 255.108.0 ! line con 0 transport input none line aux 0 line vty 0 4 end Example 2-21 R2 Full Configuration version 12.108.7.8.255.255.255.255.5.9.0 no ip directed-broadcast ! interface Ethernet0/0 .108.108.1 255.108.255.0 no ip directed-broadcast ! interface Loopback2 ip address 131.108.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 131.1 255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.0 ! hostname R2 ! enable password cisco no ip domain-lookup ! interface Loopback0 ip address 131.1.1 255.0.0 no ip directed-broadcast ! interface Loopback2 ip address 131.255.255.255.1 255.255.108.CCNP Practical Studies: Routing ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.255.255.4.1 255.255.255.1 255.255.252 no ip directed-broadcast clockrate 128000 ! router rip version 2 network 131.0 no ip directed-broadcast ! interface Loopback1 ip address 131.1 255.108.3.

108. you learn how to change the routing protocol to OSPF on both Routers R1 and R2. the command no ip domain-lookup is configured.3. Basic OSPF .2.108.2 255. Every time you type an unknown command on a router in exec or priv mode. Figure 2-3 shows the network and areas you use for this scenario. the extra serial interfaces are not configured and are in a shutdown state or are not enabled by default. This IOS command is a handy command to disable when you are studying on Cisco IOS routers.0 ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 ! end NOTE In both cases.255.0. the router automatically queries the DNS server.252 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router rip version 2 network 131. On R2.CCNP Practical Studies: Routing ip address 131. which is time consuming and annoying. Leave the Ethernet segments with a Class C network to enable 254 hosts to attach to the router.108. Scenario 2-2: Basic OSPF In this scenario. Use a /30 mask on the serial link and host addressing or a /32 mask on all the loopbacks to conserve address space.255.255.0 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.1 255. Figure 2-3.255. You change the IP addresses as well to learn about VLSM.30 - .

255.0.4.255. configure R1 for OSPF by using the process number 1 and for R2 using process number 2.0 area 2 0. Example 2-23 IP Address Change and Disabling IP RIP on R2 R2(config)#int lo0 R2(config-if)#ip address 131.2 255. To enable OSPF.0.108. The process number is significant to only the local router.3 0.31 - .108.0.108.0.4.255 area 2 0. Example 2-24 and Example 2-25 display the new OSPF configurations on R1 and R2.3.10 0.0.255 R1(config-if)#exit! it is not required to exit interface mode to remove RIP R1(config)#no router rip Example 2-23 displays the IP address changes and the removal of IP RIP on R2. Before you configure OSPF.255.2 0.1.255.0.108.5 255. Area 0 (or area 0. Step 2. 1.0 area 2 0. Example 2-22 displays IP address changes and the removal of IP RIP.4.108.0.CCNP Practical Studies: Routing In this basic scenario.108. Example 2-24 OSPF Configuration on R1 R1(config)#router ospf 1 R1(config-router)#network R1(config-router)#network R1(config-router)#network R1(config-router)#network R1(config-router)#network 131. Specify the networks on which OSPF will run and the area assignments.0.0) is the backbone.4.255 R2(config-if)#int lo1 R2(config-if)#ip address 131.0.0 area 2 0.0 area 0 Example 2-25 OSPF Configuration on R2 R2(config)#router ospf 2 R2(config-router)#network R2(config-router)#network R2(config-router)#network R2(config-router)#network R2(config-router)#network 131.108.4.255.255. As on all good OSPF networks.108.0 area 1 131.108.4 131. The IOS command to enable OSPF per interface is network address wildcard-mask area area-id The wildcard mask defines what networks are assigned.255. you need to perform the following steps: Step 1.0.4.0.255 R1(config-if)#int lo1 R1(config-if)#ip address 131. You can run more than one process.0.0 0. areas 1 and 2 cover the Ethernets on R1 and R2 and their respective loopbacks.4.0.0.255 area 1 131.0.108. Example 2-22 IP Address Changes and Disabling IP RIP on R1 R1(config)#int lo0 R1(config-if)#ip address 131.2.4. Enable the routing protocol with the command router ospf process number. renumber all interfaces and remove IP RIP with the command no router rip.0.0.1 131. a backbone OSPF area 0 is configured.108.2 0.255.255.3.108.0 area 1 131.0 area 0 .108.255.1 0.108.255 R1(config-if)#int lo2 R1(config-if)#ip address 131.6 131.3 255.4 255.0.0.108.1 255.0.4.255.4.5 131.0.255 R2(config-if)#int lo2 R2(config-if)#ip address 131.0.4. you configure three areas: 0.0 area 1 131.108.255.4.6 255.255 R2(config-if)#exit ! it is not required to exit interface mode to remove RIP R2(config)#no router rip Now that RIP is removed and the IP addressing is redone. the area ID defines the OSPF area assignment. and 2.

1/32 O IA 131.0 0.108.1.0.108.254 all match.108.255.1.2.2.3/32 O IA 131.255.255 no ip directed-broadcast ! interface Loopback2 ip address 131.108.32 - .0.3.0.0 indicates an exact match.108.1. Serial0/1 You can see from Example 2-26 that R1 discovers four remote networks (R2's Ethernet and three loopback interfaces) through OSPF.3.3. Serial0/1 [110/74] via 131.1.2 255.1.1 to 131.108.108. Ethernet0/0 [110/65] via 131. Loopback1 is directly connected.255. Example 2-28 28 R1 Full Configuration version 12.255 no ip directed-broadcast ! interface Loopback1 ip address 131.2. Loopback0 is directly connected.2/32 O IA 131.4/32 variably subnetted.0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131. 3 masks is directly connected.3 255. 9 subnets.108.4.4.255 means 131. 00:41:54. Serial1/1 [110/782] via 131.108.0.4. 00:43:09.4.108. Serial1/1 [110/782] via 131.108. Serial0/1 [110/65] via 131. you can configure any IP address in the range 131.255. 00:43:09.108.4. In addition.1 to 131. 00:01:29.108.108.0/24 R2# variably subnetted.108.254 to be in area 1 on R1 E0/0. In this case.108.3.4. Example 2-27 uses the command show ip route ospf on Router R2 to display only the OSPF routes.6/32 131.1.0/30 131.0.3.0. 3 masks [110/782] via 131.108.108. 00:01:29.4.108. Example 2-27 R2 OSPF Routing Table R2#show ip route ospf 131.108.4. Serial1/1 Example 2-28 and Example 2-29 display the complete configurations for R1 and R2 for your reference.108.0. the command network 131. in this case area 2.4.1.0/16 is O IA 131.255.108. 00:01:29. 00:43:09.4.1/32 131.CCNP Practical Studies: Routing The wildcard mask 0.3.0/24 131.108.108. The left side indicates the routing type as O for OSPF. The wildcard mask 0. The IA (inter-area) indicates the remote network is part of another area. Example 2-26 IP Routing Table on R1 C C C C O O O C O IA IA IA IA 131. For example. Serial1/1 [110/791] via 131.2 and the outbound interface Serial 0/1.108.108. In the case of OSPF.1.3/32 131.1. Serial0/1 is directly connected.255.2.108.2/32 131.4.0/16 is 131. 9 subnets.0/24 131. Example 2-26 displays the IP routing table on R1.3.108. 00:01:29.1 255.3. Serial0/1 [110/65] via 131. the administrative distance is 110 (more trusted than RIP at 120) and the metric used by OSPF is cost.3.108.2.108. Notice once again the administrative distance and metric pairing.255 no ip directed-broadcast .1. Loopback2 is directly connected.4. there are also the directly attached links.108.108.0.5/32 131.1.3.255 means the first three octets must match and the last octet does not matter. R1 dynamically learns the remote networks on R2 through the next hop address of 131.

1 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.4.0 area 1 network 131.2 ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown 255.0 area 1 ! router rip version 2 network 131.255.2.255.4.4.252 .4.255.CCNP Practical Studies: Routing ! interface Ethernet0/0 ip address 131.0.252 clockrate 128000 ! router ospf 1 network 131.0 ! ip classless ! line con 0 line aux 0 line vty 0 4 end Example 2-29 R2 Full Configuration ! hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.3 0.0.0.4 ! interface Loopback1 ip address 131.0.255 area 1 network 131.6 ! interface Ethernet0/0 ip address 131.3.255.255.108.1 0.108.255.255 255.0.255.4.1 255.108.33 - .255.4.108.0 0.108.108.0.255 255.3.5 ! interface Loopback2 ip address 131.108.0.108.255 255.0.0.108.0 area 1 network 131.1.108.0 255.255.1 0.1.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 131.255.255.2 0.0.0.3.108.1 255.255.255.255.108.0 area 0 network 131.108.

To enable IGRP.108.0 ! ip classless ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 no login ! end Scenario 2-3: Basic IGRP This scenario is designed to introduce you to the basics of IGRP and EIGRP configurations.0 area 2 ! router rip version 2 network 131. you need to specify only the major class network.0 area 2 network 131.0.255 area 2 network 131. Basic IGRP/EIGRP Network This scenario starts with IGRP and then changes the routing protocol to EIGRP.5 0.108. revisit the two-router scenario.0. you need to perform the following steps: Step 1.0 area 2 network 131. The administrative domain must be the same for routers that are under a common administrative control or the same network.34 - . You then specify the networks on which IGRP runs.4.0. In this scenario. In this basic scenario.0 area 0 network 131.0.108. Figure 2-4. so you have to change the IP addressing back to a nonVLSM network.3. Use the command router igrp administrative domain to enable the routing protocol. you need to configure the same administrative domain. Step 2. you use a different class address as well.108.4.4 0.0 0.0. you configure the two routers R1 and R2 for IGRP using the same administrative domain.0. To share information between routers in IGRP.0.6 0. Once more.108.108.0.0.CCNP Practical Studies: Routing ! router ospf 2 network 131. As with IP RIP.4.0.0. Figure 2-4 displays the network topology and IP addressing scheme.2 0. .2. IGRP is a classful routing protocol.

100.100.4.100.9.0 199.0 199.3. .7.255.1 255.1 255.1 255.100.5.255.8.255.255.100.0 199.100.7.255.0 199.5.1 255.255.100.1 255. you must specify each network in IGRP. Example 2-30 IP Addressing on R1 R1(config)#int e 0/0 R1(config-if)#ip address R1(config-if)#int lo0 R1(config-if)#ip address R1(config-if)#int lo1 R1(config-if)#ip address R1(config-if)#int lo2 R1(config-if)#ip address R1(config-if)#int s0/1 R1(config-if)#ip address 199.255.0 199.255.0 199.1 255.0 Example 2-33 similarly displays the IGRP commands configured on R2.100. NOTE When using a class C network with the default class C mask.2.100.0 199.255. Example 2-31 IP Addressing on R2 R2(config)#int e 0/0 R2(config-if)#ip address R2(config-if)#int lo0 R2(config-if)#ip address R2(config-if)#int lo1 R2(config-if)#ip address R2(config-if)#int lo2 R2(config-if)#ip address R2(config-if)#int s1/1 R2(config-if)#ip address 199.100.0 Example 2-34 now displays the IP routing table on R1.255.4.255.8.100.255.0/24 through to 199.CCNP Practical Studies: Routing Use the Class C network 199.0 199.255.3.255.100.0 Example 2-32 displays the IOS commands required to enable IGRP in AS 1.0 199.9.100.2.2 255.100.255.0 199.100.0 199.0 199.255.100. Example 2-30 displays the IP address changes made to Router R1.1 255.255.1 255.100.1.100.0 199.35 - .6.0 Example 2-31 displays the IP address changes made to router R2.255.100.255.1 255.6.100.255.0/24.1.100.0 199.1.3.3.0 199.9. Example 2-32 IP Addressing on R1 R1(config)#router igrp 1 R1(config-router)#network R1(config-router)#network R1(config-router)#network R1(config-router)#network R1(config-router)#network 199.0 199.100. Example 2-33 IP Addressing on R2 R2(config)#router igrp 1 R2(config-router)#network R2(config-router)#network R2(config-router)#network R2(config-router)#network R2(config-router)#network 199.

CCNP Practical Studies: Routing Example 2-34 R1 IP Routing Table R1#show ip route Gateway of last resort is not set I 199.2.100.8.100.4.4.2. C 199.3.2.100.100.100.100.100.3.load) + K3 x delay The values K1 through K5 are constants. I 199.2 (R1's link to R2) and through the outbound interface Serial 0/1. Loopback2 C 199. Notice the administrative distance and metric pairing. K1 = K3 = 1 is as follows: IGRP composite metric = bandwidth + delay Example 2-35 and Example 2-36 display the full configurations for R1 and R2.2 and the outbound interface Serial 0/1. the administrative distance is 100 (more trusted than RIP at 120 and OSPF at 110) and the metric IGRP uses is called a composite metric.0/24 [100/8976] via 199.3. 00:00:47.108.255.3.0/24 is directly connected. If the defaults are used. R1 dynamically learns the remote networks on R2 through the next hop address of 131.100.9.3.3. Loopback0 Serial0/1 Serial0/1 Serial0/1 Serial0/1 On R1.1 255. C 199.100. the formula with K2 = K4 = K5 = 0.36 - .100. If K5 is not zero. The left side indicates the routing type as I for IGRP.0/24 [100/8976] via 199. Serial0/1 I 199.100.100.2.5. Loopback1 C 199. In the case of IGRP.255. NOTE The calculation for a composite metric is as follows: Composite metric = K1 x bandwidth + (K2 x bandwidth) / (256 .3. Example 2-35 Full Configuration for R1 hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 199.255. where type of service must be zero. Ethernet0/0 I 199.0 . 00:00:46. Typically.100. you can see four remote IGRP networks learned through the next hop address 199.0/24 is directly connected. C 199. 00:00:46.100.0/24 [100/8576] via 199.0 no ip directed-broadcast ! interface Loopback1 ip address 199. respectively.1.0/24 is directly connected.7.100. K1 = K3 = 1 and K2 = K4 = K5 = 0.5.255.6.0/24 [100/8976] via 199.100.0/24 is directly connected. the formula is as follows: IGRPmetric = Metric x [K5 / (reliability + K4)].2. 00:00:46.0/24 is directly connected.1 255. Values K1 through K5 can be configured with nondefaults with the IOS command metric weights tos k1 k2 k3 k4 k5.

0 no ip directed-broadcast ! interface Loopback1 ip address 199.255.100.0 ! ip classless ! line con 0 transport input none line aux 0 line vty 0 4 no login ! end Example 2-36 Full Configuration for R2 Current configuration: ! version 12.255.100.0 network 199.100.1.100.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 199.1 255.1.255.0 clockrate 128000 ! router igrp 1 network 199.100.100.100.9.100.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 199.255.1 255.255.3.0 no ip directed-broadcast ! interface Loopback2 ip address 199.255.6.1 255.255.0 .255.8.0 ! service timestamps log uptime no service password-encryption ! hostname R2 ! enable password c ! ip subnet-zero no ip domain-lookup frame-relay switching ! interface Loopback0 ip address 199.4.37 - .CCNP Practical Studies: Routing no ip directed-broadcast ! interface Loopback2 ip address 199.255.3.1 255.255.0 network 199.100.6.255.0 network 199.1 255.7.100.0 network 199.5.255.1 255.100.

or a classful network is assumed.3.3.100.2.0 network 199.0 network 199. .0 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router igrp 1 network 199.0 no ip directed-broadcast no cdp enable ! interface TokenRing0/0 no ip address no ip directed-broadcast shutdown ring-speed 16 no cdp enable ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 199.100. Figure 2-5 shows the sample network for this EIGRP example.8. EIGRP also supports VLSM. EIGRP enables network summarization by default. Also.2 255. you simply enable the routing protocol and define the networks.255.0 ! no ip classless ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 end Now remove IGRP and use EIGRP instead.100.1 255. but it is multiplied by 256.0 network 199.100. the default mask is assumed. the metric EIGRP uses is the same as the metric IGRP uses. To configure EIGRP.255.255. That is.100.100. You can use the command no auto-summary to disable automatic summarization.38 - .9.CCNP Practical Studies: Routing no ip directed-broadcast ! interface Ethernet0/0 ip address 199.100.7.2.255.0 network 199.

5.128/25.0 R2(config-router)#network 199.0 R2(config-router)#network 131. .1.1.3.0 R2(config-router)#network 131.0 !define network in eigrp R1(config-router)#network 199.0 R1(config-router)#network 199.100.100.1.6.0 Notice IGRP is removed first and the AS number is the same in R1 and R2 so that both routers can share information.255.1. Now view R1's EIGRP routing table.129 255.108. EIGRP Configuration Modify the Ethernet segments on R1 and R2 to use a different class address of 131.108.255.128 R2(config-if)#router eigrp 1 R2(config-router)#network 199.108.7.100. Example 2-38 Configuring EIGRP on R2 R2(config)#no router igrp 1 R2(config)#router eigrp 1 R2(config-router)#exit R2(config)#int e 0/0 R2(config-if)#ip address 131.108.1 255.108.1.8.0 R1(config-router)#network 199.100.0 R1(config-router)#network 199.108. Example 2-37 displays the removal of IGRP and the enabling of EIGRP in AS 1 on Router R1.100.255.CCNP Practical Studies: Routing Figure 2-5.39 - . You have not disabled automatic summarization yet.9.0 R1(config-router)#int e 0/0 ! change IP address on R1 e0/0 R1(config-if)#ip address 131.1.0/25 and 131. Example 2-37 Configuring EIGRP on R1 R1(config)#no router igrp 1 !remove igrp 1 R1(config)#router eigrp 1 !enable EIGRP in AS 1 R1(config-router)#network 131.3.108.1.9.255.100.0 R2(config-router)#network 199. as displayed in Example 2-39.128 Example 2-38 displays the removal of IGRP and the enabling of EIGRP in AS 1 on Router R2.0 R2(config-router)#network 199.9. respectively.4.

0/16 is a summary. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24 [90/2297856] via 199. 00:00:01. 2 masks D 131. Sending 5.108. 100-byte ICMP Echos to 131. 00:00:55.3. 2 subnets. short for the bit bucket.108. The left side indicates the routing type as D for EIGRP. Sending 5. 00:00:01.40 - .2.0/24 [90/2297856] via 199. R1 dynamically learns the remote networks on R2 through the next hop address of 199.1. Packets sent to null0 are discarded.100. Null0 D 199.108.0.1.1.100. and IGRP at 100).100.129 Type escape sequence to abort. Serial0/1 R1#ping 131.100.100. which means redistributed into an EIGRP domain.3.1. Example 2-40 displays a sample ping from Router R1.1. Serial0/1 R1# On R1..108.108. 2 subnets D 131. Serial0/1 131. 00:00:55.0/16 is variably subnetted.108.108.100.1.100. One of these routes is to null0.1.100. Configure R1 and R2 to disable automatic summarization as in Example 2-41. The remote network 131.108.2..0.2 (R1's link to R2) and through the outbound interface Serial 0/1.0/25 is subnetted.3.129.100.108.0/24 [90/2297856] via 199.2 and the outbound interface Serial 0/1..100. you can see four remote EIGRP networks learned through the next hop address 199.0/16 are sent to null0.129.2.2. in this case. To solve the problem of packets being discarded.) or. Notice the administrative distance and metric pairing.100. 00:00:01.. round-trip min/avg/max = 16/16/16 ms R1# .128/25 has no entry because R1 has a locally connected subnet 131. Serial0/1 D 199. Example 2-41 Disabling Automatic Summarization on R1 and R2 R1(config)#router eigrp 1 R1(config-router)#no auto-summary R2(config)#router eigrp 1 R2(config-router)#no auto-summary Example 2-42 now displays R1's EIGRP routing table and a sample ping request to the remote network 131. You'll also see D EX.129/25 from R1.100. Success rate is 0 percent (0/5) R1# The response from the router in Example 2-40 is no reply (….1.3.0/25.3.100.7. Serial0/1 D 199. timeout is 2 seconds: .108.129 Type escape sequence to abort.7. Now.3.130. OSPF at 110.100.8.100. the administrative distance is 90 (more trusted than RIP at 120. 00:00:01.3.0. Serial0/1 131.0/24 [90/2297856] via 199.2.108.108.1. 00:00:55. Example 2-40 Ping Request from R1 R1#ping 131.128 [90/2195456] via 199.9.108.3. the packets are sent to null0.2. you need to disable automatic summarization.0/24 [90/2297856] via 199. ping the remote network 131.2.CCNP Practical Studies: Routing Example 2-39 R1's IP Routing Table R1#show ip route eigrp D 199. In the case of EIGRP.9.0/24 [90/2297856] via 199. You can also see that all routes for 131. Example 2-42 show ip route eigrp on R1 R1#show ip route eigrp D 199. 100-byte ICMP Echos to 131. or discarded. 00:00:55.3. and the metric EIGRP uses is 256 times that of IGRP.0. Serial0/1 D 199.8.

1 255.0 no ip directed-broadcast clockrate 128000 ! router eigrp 1 network 131.128 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 199.5.255. Example 2-43 and Example 2-44 display the full configurations for R1 and R2.100.100.41 - .128/25 is inserted and there is a successful ping from R1 to R2 Ethernet interface.100.0 network 199.255.0 no ip directed-broadcast ! interface Loopback1 ip address 199.100. using EIGRP.1 255.108.4.1 255.100.5.6.0 network 199.CCNP Practical Studies: Routing Notice that the 131.1.255. Example 2-43 R1 Full Configuration version 12.1 255.4.108. It is vital you understand these simple topics.255. fixed-length variable subnet masks (FLSMs) and VLSM.3.108.0 network 199. such as classful and classless.255.255.6.3.1 255.0 ! service timestamps log uptime no service password-encryption ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 199.255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.100.100.255.0 no ip directed-broadcast ! interface Loopback2 ip address 199.255.1. respectively.0 network 199.0.0 no auto-summary ! ip classless ! line con 0 transport input none line aux 0 line vty 0 4 no login ! end .255.100.

129 255.CCNP Practical Studies: Routing Example 2-44 R2 Full Configuration version 12.7.108.255.7.2 255.0 network 199.42 - .8.0.0 no ip directed-broadcast ! interface Loopback1 ip address 199.255.255.100.0 no auto-summary ! no ip classless ! line con 0 line aux 0 line vty 0 4 ! end .0 network 199.255.100.1.3.0 network 199.1 255.255.0 no ip directed-broadcast ! interface Loopback2 ip address 199.1 255.100.100.100.0 network 199.100.8.1 255.100.9.3.255.255.0 ! service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 199.255.100.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.255.9.0 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router eigrp 1 network 131.128 no ip directed-broadcast no cdp enable ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 199.108.255.

43 - .255.128 131. Figure 2-6 displays the OSPF/IGRP topology and the IP addressing scheme in place between R1 and R2.1 255.255.9.255.0 131.255. .0 131.255. hence redistribution is required. Figure 2-6.2 255.255.3.255.3.255.224 131.255.255. configure IGRP.0.255.108. so you need to enable IGRP only in AS 1.5.CCNP Practical Studies: Routing Scenario 2-4: Basic EIGRP This scenario covers another simple example of routing between classless and classful networks.255.255 131.108.8.128 131.255.1 255.255. R2 runs both IGRP and OSPF.0.7.0 On R1. IGRP/OSPF Topology Example 2-45 and Example 2-46 display the IP addressing changes to R1 and R2.6.0 131.108.108.108. Example 2-45 R1 IP Address Changes R1(config)#int lo0 R1(config-if)#ip address R1(config-if)#int lo1 R1(config-if)#ip address R1(config-if)#int lo2 R1(config-if)#ip address R1(config-if)#int e 0/0 R1(config-if)#ip address R1(config-if)#int s 0/1 R1(config-if)#ip address 131. This simple two-router example uses the same class network and IGRP and OSPF.255.108.255.8.1 255. again IGRP is classful.1 255.1 255.1 255.1 255.108.255.255.1.4.108. you need to perform redistribution from one routing protocol to another. It is easier to understand this scenario if you use the same Class B address 131.255.0 Example 2-46 R2 IP Address Changes R2(config)#int lo0 R2(config-if)#ip address R2(config-if)#int lo1 R2(config-if)#ip address R2(config-if)#int lo2 R2(config-if)#ip address R2(config-if)#int e 0/0 R2(config-if)#ip address R2(config-if)#int s 0/0 R2(config-if)#ip address 131. respectively.1 255.0 131. Here.255.108. Example 2-47 enables IGRP in AS 1 on R1.108.108.129 255.

Example 2-50 IP Routing Table on R1 R1#show ip route 131.0.8. as in Example 2-49.0 C 131. IGRP does not use OSPF cost but uses a composite metric.0. Loopback2 directly connected. Serial0/1 directly connected.108.3. you need to define values so that IGRP has a valid metric. 5 subnets directly connected.108.6. in 10 microsecond units R2(config-router)#redistribute ospf 1 metric 128 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R2(config-router)#redistribute ospf 1 metric 128 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R2(config-router)#redistribute ospf 1 metric 128 20000 255 1 ? <1-4294967295> IGRP MTU of the path R2(config-router)#redistribute ospf 1 metric 128 20000 255 1 150 Look on R1 and R2 to find which IP networks have been discovered.1. Ethernet0/0 Example 2-51 displays R2's IP routing table. Example 2-48 Enabling IGRP on R1 R2(config)#router igrp 1 R2(config-router)#network 131.0 C 131.0.0.0 0. using the ? character to discover which metric IGRP requires.108.) On R2.0.1 0.0. configure IGRP and OSPF.108.0 On R2. You need to advise R1 of the bandwidth (128 kbps). configure IGRP to redistribute the OSPF interfaces into IGRP.7. 255 being 100 percent loaded). Example 2-49 displays the redistribution and also displays the various options the Cisco IOS Software requires.0 area 0 R2(config-router)#network 131.0/24 C 131.108.5. 255 is 100 percent loaded).0.108.0.9.0 R2(config)#router ospf 1 R2(config-router)#network 131. As with any form of redistribution.44 - . and finally the MTU (1500 bytes).0.108.0 area 0 R2(config-router)#network 131.1 0.8.0 0.0.108.108.129 0. Therefore. Example 2-48 enables IGRP in AS 1 and OSPF with a process ID of 1. Example 2-50 displays R1's IP routing table.108.4. delay (20000 ms).8. loading (1 out of 255. you must use the metric that the routing protocol you are redistributing into uses. Example 2-49 Enabling Redistribution on R2 R2(config-router)#router igrp 1 R2(config-router)#redistribute ospf 1 metric ? <1-4294967295> Bandwidth metric in Kbits per second R2(config-router)#redistribute ospf 1 metric 128 ? <0-4294967295> IGRP delay metric.0 area 0 You also need to configure redistribution on R2 so that R1 discovers the OSPF interfaces through IGRP. .0 C 131. Loopback0 directly connected.8.0 area 0 R2(config-router)#no network 131.0. reliability (1 is low.0 is is is is is is subnetted. (R1 is running only IGRP.0.0 C 131.0.1 0.CCNP Practical Studies: Routing Example 2-47 Enabling IGRP on R1 R1(config)#router igrp 1 R1(config-router)#network 131. Loopback1 directly connected.108.108.108.255 area 0 R2(config-router)#network 131.0. Follow the prompts.0.108.255 area 0 R2(config-router)#network 131.

CCNP Practical Studies: Routing
Example 2-51 IP Routing Table on R2

R2#show ip route C C C I C I I C I R2# 199.100.8.0/24 is directly connected, Loopback1 131.108.0.0/16 is variably subnetted, 8 subnets, 4 masks 131.108.8.128/25 is directly connected, Ethernet0/0 131.108.8.0/27 is directly connected, Loopback2 131.108.6.0/24 [100/80625] via 131.108.3.1, 00:00:52, 131.108.7.1/32 is directly connected, Loopback0 131.108.5.0/24 [100/80625] via 131.108.3.1, 00:00:52, 131.108.4.0/24 [100/80625] via 131.108.3.1, 00:00:52, 131.108.3.0/24 is directly connected, Serial1/1 131.108.1.0/24 [100/80225] via 131.108.3.1, 00:00:53,

Serial1/1 Serial1/1 Serial1/1 Serial1/1

On R1 in Example 2-50, you only see the directly connected routes, but on R2, you see the remote routes from R1. Why is this so? This scenario is a typical routing problem caused by the lack of understanding between VLSM and FLSM. IGRP on R1 is configured using a /24 bit subnet in all interfaces. On R2, you have applied a number of non-/24 subnets. You need to trick R1 into believing that all these networks are indeed /24 bit subnets by using summarization techniques on R2. To perform summarization from OSPF to IGRP, use the following command:

summary-address address mask
For example, to summarize the loopbacks and Ethernet on R2 as /24 bits to R1, perform the commands in Example 2-52 under the OSPF process. Example 2-52 displays the IOS configuration to enable the summary of the three networks on R2. Example 2-52 Enabling Redistribution on R2

R2(config)#router ospf 1 R2(config-router)#summary-address 131.108.7.0 255.255.255.0 R2(config-router)#summary-address 131.108.8.0 255.255.255.0 R2(config-router)#summary-address 131.108.9.0 255.255.255.0
Look at R1's routing table now. Example 2-53 displays the IP routing table on R1. Example 2-53 R1's IP Routing Table

R1#show ip route C C C C C 131.108.0.0/24 131.108.6.0 131.108.5.0 131.108.4.0 131.108.3.0 131.108.1.0 is is is is is is subnetted, 5 subnets directly connected, Loopback2 directly connected, Loopback1 directly connected, Loopback0 directly connected, Serial0/1 directly connected, Ethernet0/0

Still there are no routing entries. Can you think why IGRP on R1 is still not aware of the remote networks on R2? The problem is that OSPF assumes that only a nonsubnetted network will be sent. For example, in this case, you are using the Class B network 131.108.0.0. You also need to use the command redistributed connected subnets to advise OSPF to send subnetted networks. NOTE An alternative to using summarization in this scenario is static or default routes.

Example 2-54 displays the configuration required so that OSPF redistributes the Class B subnetted networks.

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CCNP Practical Studies: Routing
Example 2-54 Redistribution on R2

R2(config)#router ospf 1 R2(config-router)#redistribute connected subnets
Example 2-55 now displays R1's routing table. Example 2-55 R1's IP Routing Table

R1#show ip route 131.108.0.0/24 I 131.108.9.0 I 131.108.8.0 I 131.108.7.0 C 131.108.6.0 C 131.108.5.0 C 131.108.4.0 C 131.108.3.0 C 131.108.1.0 R1#

is subnetted, 8 subnets [100/100125] via 131.108.3.2, 00:00:23, Serial0/1 [100/100125] via 131.108.3.2, 00:00:23, Serial0/1 [100/100125] via 131.108.3.2, 00:00:23, Serial0/1 is directly connected, Loopback2 is directly connected, Loopback1 is directly connected, Loopback0 is directly connected, Serial0/1 is directly connected, Ethernet0/0

The remote subnets 131.108.7–9 now appear on R1 (shaded in Example 2-55). Example 2-56 and Example 2-57 display the full configurations on Routers R1 and R2. Example 2-56 R1 Full Configuration

version 12.0 ! service timestamps log uptime no service password-encryption ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.4.1 255.255.255.0 no ip directed-broadcast ! interface Loopback1 ip address 131.108.5.1 255.255.255.0 no ip directed-broadcast ! interface Loopback2 ip address 131.108.6.1 255.255.255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.1.1 255.255.255.0 ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 131.108.3.1 255.255.255.0 no ip directed-broadcast clockrate 128000

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CCNP Practical Studies: Routing
! router igrp 1 network 131.108.0.0 ! ip classless ! line con 0 transport input none line aux 0 line vty 0 4 end
Example 2-57 R2 Full Configuration

version 12.0 ! service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.108.7.1 255.255.255.255 ! interface Loopback1 ip address 131.108.8.1 255.255.255.128 interface Loopback2 ip address 131.108.9.1 255.255.255.224 ! interface Ethernet0/0 ip address 131.108.8.129 255.255.255.128 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.108.3.2 255.255.255.0 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 1 redistribute connected subnets summary-address 131.108.8.0 255.255.255.0 summary-address 131.108.7.0 255.255.255.0 summary-address 131.108.9.0 255.255.255.0 redistribute igrp 1 metric 1 subnets network 131.108.7.1 0.0.0.0 area 0 network 131.108.8.1 0.0.0.0 area 0 network 131.108.8.129 0.0.0.0 area 0 network 131.108.9.1 0.0.0.0 area 0 ! router igrp 1

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CCNP Practical Studies: Routing
redistribute ospf 1 metric 128 20000 255 1 1500 passive-interface Ethernet0/0 !Stop IGRP sending out updates to E0/0 and similarly lo0/1/2 because we are running !OSPF on these interfaces. passive-interface Loopback0 passive-interface Loopback1 passive-interface Loopback2 network 131.108.0.0 ! ip classless ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 end
The R2 routing table is more complicated. Example 2-58 shows R2's routing table. Example 2-58 show ip route on R2

C O C O C O I C I I C I

131.108.0.0/16 is variably subnetted, 12 subnets, 4 masks 131.108.8.128/25 is directly connected, Ethernet0/0 131.108.9.0/24 is a summary, 00:04:59, Null0 131.108.9.0/27 is directly connected, Loopback2 131.108.8.0/24 is a summary, 00:04:59, Null0 131.108.8.0/25 is directly connected, Loopback1 131.108.7.0/24 is a summary, 00:04:59, Null0 131.108.6.0/24 [100/80625] via 131.108.3.1, 00:00:38, Serial1/1 131.108.7.1/32 is directly connected, Loopback0 131.108.5.0/24 [100/80625] via 131.108.3.1, 00:00:38, Serial1/1 131.108.4.0/24 [100/80625] via 131.108.3.1, 00:00:39, Serial1/1 131.108.3.0/24 is directly connected, Serial1/1 131.108.1.0/24 [100/80225] via 131.108.3.1, 00:00:39, Serial1/1

Notice the two entries for the same network sent to null0, or the bit bucket. The longest match rule applies on all routers; so for example, when an IP packet arrives for the network 131.108.8.129, the IP routing entry sends that to the directly connected interface E0/0. Similarly, if a pack arrives for network 131.108.8.0/25, the packet is sent to the directly connected loopback 1 interface. This is commonly known as the longest match rule.

Scenario 2-5: Using the show, ping, trace, and debug Commands
The previous four scenarios covered four relatively easy networks. This scenario shows you how to use common show and debug techniques and ping and trace commands to determine why routing entries are missing, for example, or why some networks are unreachable. To see a real-life scenario using two routers, refer to Scenario 2-3 and view some of the output from the show and debug commands. This scenario also displays some simple ping and trace tests. All show, ping, trace, and debug commands are taken from Figure 2-6 in the previous scenario. You are familiar with the command show ip route from the previous scenarios, so start with that command on R1 from Figure 2-6. Here, you are only interested in IGRP learned routes. Example 2-59 displays only IGRP routes. Example 2-59 R1's IGRP Routes

R1#show ip route igrp 131.108.0.0/24 is subnetted, 8 subnets I 131.108.9.0 [100/100125] via 131.108.3.2, 00:01:01, Serial0/1 I 131.108.8.0 [100/100125] via 131.108.3.2, 00:01:01, Serial0/1 I 131.108.7.0 [100/100125] via 131.108.3.2, 00:01:01, Serial0/1

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Almost all troubleshooting techniques involve the ping command. Ping is a simple tool that sends an ICMP-request packet to the remote network and back. A successful ping receives an ICMP-reply. Example 2-60 displays a sample ping from R1 to R2 and the three remote networks: 131.108.7.1, 131.108.8.1, and 131.108.9.1. Example 2-60 Ping Tests from R1 to R2

R1#ping 131.108.7.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 131.108.7.1, timeout is !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max R1#ping 131.108.8.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 131.108.8.1, timeout is !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max R1#ping 131.108.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 131.108.1.1, timeout is !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max R1#

2 seconds: = 16/16/16 ms 2 seconds: = 16/16/16 ms 2 seconds: = 1/1/4 ms

This is an example of the standard ping command. At times, an extended ping is required. The extended ping enables you to provide the Cisco IOS with more parameters, such as the source address, the number of packets to send, the size of the datagram, and the timeout. The extended ping is a useful tool when users are complaining, for example, that when they FTP large files, the data is not transferred or a particular network of users cannot reach a remote destination. Example 2-61 is an example of an extended ping using the source address 131.108.1.1/24 (the Ethernet address of R1), a modified repeat count of 10, a default datagram size of 100 bytes, and a timeout of 2 seconds. To use the extended ping command, simply type ping, press Return, and the options appear. Example 2-61 also displays the options in an extended ping. Example 2-61 Extended ping Request on R1

R1#ping Protocol [ip]: Target IP address: 131.108.8.129 Repeat count [5]: 10 Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: y Source address or interface: 131.108.1.1 Type of service [0]: Set DF bit in IP header? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Loose, Strict, Record, Timestamp, Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. Sending 10, 100-byte ICMP Echos to 131.108.8.129, timeout is 2 seconds: !!!!!!!!!! Success rate is 100 percent (10/10), round-trip min/avg/max = 16/16/16 ms R1#

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Table 2-5 describes the possible output of a ping.

Table 2-5. Ping Output Symbols Output ! . U C I ? & Description Each exclamation point indicates receipt of a reply. Each period indicates the network server timed out while waiting for a reply. A destination unreachable error was received. A congestion-experienced packet was received. User interrupted test. Unknown packet type. Packet lifetime exceeded.

Table 2-6 describes the parameters of the extended ping command.

Table 2-6. Extended Ping Parameters Parameter Protocol [ip]: Description Supports the following protocols (not just ip): appletalk, clns, ip, novell, apollo, vines, decnet, or xns. The default parameter is ip so you can simply press Return. Prompts for the IP address or host name of the destination node you plan to ping. The default value is none. Number of ping packets sent to the destination address. The default value is 5. The maximum is 2147483647. Size of the ping packet (in bytes). The default is 100 bytes. The range of values allowed is between 1 and 2147483647 bytes. Timeout interval. The default is 2 (seconds). The range is between 0 and 3600. Specifies whether a series of additional commands appears. If you enter y for yes, you are prompted for the following information. (The default is no.) Enables you to vary the sizes of the echo packets being sent. This parameter determines the minimum MTU size configured along the network path from source to destination. This is typically used to determine whether packet fragmentation is causing network problems.

Target IP address: Repeat count [5]: Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: Sweep range of sizes [n]:

NOTE To terminate a large ping test, within a few seconds, type the escape sequence, which is Ctrl+Shift-^ followed by x.

Look at a simulated network failure to determine what's wrong with a remote network. View R1 IGRP routing table when the remote network 131.108.10.0/24 is down. Example 2-62 displays R1's IP routing table. Example 2-62 R1's IP Routing Table

R1#show ip route igrp 131.108.0.0/24 is subnetted, 9 subnets I 131.108.10.0/24 is possibly down, routing via 131.108.3.2, Serial0/1 I 131.108.9.0 [100/100125] via 131.108.3.2, 00:00:03, Serial0/1 I 131.108.8.0 [100/100125] via 131.108.3.2, 00:00:03, Serial0/1 I 131.108.7.0 [100/100125] via 131.108.3.2, 00:00:03, Serial0/1

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CCNP Practical Studies: Routing
You can see from Example 2-62 that the remote network 131.108.10.0/24 is possibly down. Use the command debug ip routing to see whether you can see the problem. This debug displays routing entries added or deleted into the IP routing table. Use the command on R1. Example 2-63 displays a command used to debug the IP routing table and displays how to force the IP routing algorithm, in this case IGRP, to add and delete remote routes by using the command clear ip route *. Example 2-63 debug ip routing and clear ip route * Commands

R1#debug ip routing IP routing debugging is on R1#clear ip route * R1# 02:03:45: RT: add 131.108.1.0/24 02:03:45: RT: add 131.108.3.0/24 02:03:45: RT: add 131.108.4.0/24 02:03:45: RT: add 131.108.5.0/24 02:03:45: RT: add 131.108.6.0/24 02:03:45: RT: add 131.108.9.0/24 02:03:45: RT: add 131.108.8.0/24 02:03:45: RT: add 131.108.7.0/24

via via via via via via via via

0.0.0.0, connected metric [0/0] 0.0.0.0, connected metric [0/0] 0.0.0.0, connected metric [0/0] 0.0.0.0, connected metric [0/0] 0.0.0.0, connected metric [0/0] 131.108.3.2, igrp metric [100/100125] 131.108.3.2, igrp metric [100/100125] 131.108.3.2, igrp metric [100/100125]

Example 2-64 displays another clear ip route * after the network 131.108.10.0/24 is restored. Example 2-64 clear ip route * on R1

R1#clear ip route * 02:07:25: RT: add 131.108.1.0/24 via 0.0.0.0, connected metric [0/0] 02:07:25: RT: add 131.108.3.0/24 via 0.0.0.0, connected metric [0/0] 02:07:25: RT: add 131.108.4.0/24 via 0.0.0.0, connected metric [0/0] 02:07:25: RT: add 131.108.5.0/24 via 0.0.0.0, connected metric [0/0] 02:07:25: RT: add 131.108.6.0/24 via 0.0.0.0, connected metric [0/0] 02:07:25: RT: add 131.108.10.0/24 via 131.108.3.2, igrp metric [100/8539] 02:07:25: RT: add 131.108.9.0/24 via 131.108.3.2, igrp metric [100/100125] 02:07:25: RT: add 131.108.8.0/24 via 131.108.3.2, igrp metric [100/100125] 02:07:25: RT: add 131.108.7.0/24 via 131.108.3.2, igrp metric [100/100125] 02:08:03: RT: delete route to 131.108.10.0 via 131.108.3.2, igrp metric [100/85] 02:08:03: RT: no routes to 131.108.10.0, entering holddown
This time, you see the route added, but it enters the holddown state, which means the remote network 131.108.10.0 is not accepted and inserted into the IP routing table during the holddown interval. This prevents routing loops. Now view the IP route table on R1. Example 265 displays the IP routing table (IGRP) on R1. Example 2-65 R1 IP Route IGRP-Only Table

R1#show ip route igrp 131.108.0.0/24 is subnetted, 9 subnets I 131.108.10.0/24 is possibly down, routing via 131.108.3.2, Serial0/1 I 131.108.9.0 [100/100125] via 131.108.3.2, 00:00:09, Serial0/1 I 131.108.8.0 [100/100125] via 131.108.3.2, 00:00:09, Serial0/1 I 131.108.7.0 [100/100125] via 131.108.3.2, 00:00:09, Serial0/1
When the IP network 131.108.10.0 goes into holddown mode, the entry in the IP routing table is displayed as possibly down during holddown. After a set interval, known as the flush timer, the entry is completely removed. Example 2-66 displays the IP routing table on R1 after this happens. Example 2-66 R1's IGRP Routing Table

R1#show ip route igrp 131.108.0.0/24 is subnetted, 8 subnets I 131.108.9.0 [100/100125] via 131.108.3.2, 00:00:29, Serial0/1 I 131.108.8.0 [100/100125] via 131.108.3.2, 00:00:29, Serial0/1 I 131.108.7.0 [100/100125] via 131.108.3.2, 00:00:29, Serial0/1

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CCNP Practical Studies: Routing
If the remote entry is re-advertised as a valid route after the holddown interval, the network 131.108.1.0/24 is re-inserted into the IP routing table. The command show ip protocol is a useful command that displays the characteristic of the protocols in use on a Cisco router. Perform this command on R1. Example 2-67 displays a sample output of the show ip protocol command on R1. Example 2-67 show ip protocol Command

R1#show ip protocol Routing Protocol is "igrp 1" Sending updates every 90 seconds, next due in 32 seconds Invalid after 270 seconds, hold down 280, flushed after 630 Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Default networks flagged in outgoing updates Default networks accepted from incoming updates IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 IGRP maximum hopcount 100 IGRP maximum metric variance 1 Redistributing: igrp 1 Routing for Networks: 131.108.0.0 Routing Information Sources: Gateway Distance Last Update 131.108.3.2 100 00:00:06 Distance: (default is 100) R1#
After 270 seconds, the route is marked as invalid, and after 630 seconds, the route is deleted. The holddown interval for IGRP is 280 seconds. Also notice that the default hop count is 100; you can set this to 255. The default constants are always displayed as their default values K1 = K3 = 1 and K2 = K4 = K5 = 0. Finally, the other most widely used command in today's networks is the trace command. The trace command makes use of the Time to Live (TTL). The TTL field is used to stop routing loops. Perform a trace route command over the World Wide Web. Example 2-68 describes the route hops from the source to destination for the site www.cnn.com. Example 2-68 Trace Route to www.cnn.com

ccie-term#trace www.cnn.com Type escape sequence to abort. Tracing the route to cnn.com (207.25.71.26) 1 sydney-c6k-1-vlan333.abc.com (100.64.205.2) 0 msec 2 sydney-c6k-1-vlan150.abc.com (100.64.177.2) 4 msec 4 msec 3 telstra-c6k-bbn1-msfc-vlan51.abc.com (100.64.176.2) 4 msec 4 telstra-gw.abc.com (103.41.198.241) 8 msec sydney-1.abc.com (64.104.192.196) 4 msec telstra-gateway.abc.com (213.41.198.241) 4 msec 5 telstra-gw.abc.com (213.41.198.241) 4 msec 213.41.198.233 8 msec 4 msec 6 213.41.198.233 4 msec 4 msec 213.41.198.234 4 msec 7 FastEthernet6-1-0.chw12.Sydney.telstra.net (139.130.185.53) 8 msec 8 FastEthernet6-1-0.chw12.Sydney.telstra.net (139.130.185.53) 4 msec GigabitEthernet4-2.chw-core2.Sydney.telstra.net (203.50.6.205) 8 msec FastEthernet6-1-0.chw12.Sydney.telstra.net (139.130.185.53) 4 msec 9 Pos4-0.exi-core1.Melbourne.telstra.net (203.50.6.18) 20 msec GigabitEthernet4-2.chw-core2.Sydney.telstra.net (203.50.6.205) 4 msec Pos4-0.exi-core1.Melbourne.telstra.net (203.50.6.18) 16 msec 10 Pos4-0.exi-core1.Melbourne.telstra.net (203.50.6.18) 16 msec Pos5-0.way-core4.Adelaide.telstra.net (203.50.6.162) 32 msec

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com (203.inet.net (203. Use the ping command to ensure all networks are reachable.126.194) 64 msec Pos5-0.telstra.Perth.paix1.Perth.162) 32 msec Pos6-0.qwest.inet.171.171.qwest.50.telstra. the time taken. Ensure that both Routers R1 and R2 have full connectivity to each other.4. The next three packets are sent with a TTL of 2 and this process is repeated until the final destination is reached.Perth.telstra.reach.inet.PaloAlto.30) 288 msec GigabitEthernet4-0.Adelaide.qwest.telstra.50.telstra.105) 296 msec 292 msec 15 sjo-brdr-02.net (203.5.50.47.net (203.qwest.inet.PaloAlto.4.6) 332 msec 328 msec 18 iah-core-03.126.8.com (203.inet.194) 60 msec 13 Pos1-0.net (205.171.net (203.8.5.53 - .6.com (203.qwest.wel-core3.wel-core3.net (205.net.171.qwest.146) 360 msec * 364 msec 20 atl-edge-05.6.CCNP Practical Studies: Routing Pos4-0.Melbourne.net (203.reach.145) 344 msec iah-core-03.telstra.171.net (203.171.qwest. The first router sees these packets and returns an error message.50.paix1.wel-core3.30) 288 msec sjo-brdr-02.Perth.inet.31.50.net (203. .net (205.113.171.69) 312 msec iah-core-01. Configure the network in Figure 2-7 for IP routing using the IP addressing scheme provided.qwest.124.50.telstra.wel-core3.171.net (205.194) 60 msec GigabitEthernet4-0.wel-gw1.30) 288 msec 14 Pos1-0.21.qwest.6.50.net.inet.130 ccie-term# The trace command displays the route taken from the source to destination.Perth.inet.qwest.146) 364 msec 360 msec 19 atl-core-01.6) 332 msec atl-core-01.22. Practical Exercise: RIP Version 2 NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. You must use IP RIP as your dynamic routing protocol.net (205.net (205.194) 60 msec 12 Pos6-0.inet.6.exi-core1.50. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own.50.net (205.105) 292 msec sjo-core-02.inet.6.way-core4. From Example 2-68.171.net (205.126.qwest.Perth.net (205.18) 64 msec Pos6-0.reach.net.50.171.telstra.69) 308 msec 304 msec 16 sjo-core-02.171.net (205.paix1.113. Now the source of the first hop is known.31.22) 364 msec 364 msec 21 208. The solution can be found at the end.145) 344 msec 344 msec 17 iah-core-01.inet.50.net (205.6.PaloAlto. NOTE The trace command works by first sending three packets with a TTL of 1. and whether multiple hops exist.22.wel-gw1.18) 60 msec Pos1-0.net (203. you can determine the next hop.18) 16 msec 11 Pos6-0.

or /30.1 255.0 no ip directed-broadcast ! interface Loopback2 ip address 131. The serial link contains a mask that is 255. The configurations in Example 2-69 and Example 2-70 answer these issues using RIPv2.54 - .252.255.1 255. even though you may have a dynamic routing protocol such as RIPv2 advertising the network's reachability and next hop details dynamically.255.255. Static routes are fine to configure. OSPF.255. Example 2-69 R1's Full Configuration version 12. experiment with RIPv1 and static routes. you should change the protocols to RIPv2. If you do have access to two routers.1 255.255.4.6.255.108. but you must be aware that static routes have an AD of 1.0 no ip directed-broadcast ! interface Loopback1 ip address 131.1.108.108.CCNP Practical Studies: Routing Figure 2-7.255. Another major disadvantage of static routes is that they do not scale well in large networks and can lead to routing loops or black holes (discarded packets) if configured incorrectly. Practical Exercise: Routing RIP Practical Exercise Solution You will notice that the entire IP addressing scheme is /24 except for the serial link between R1 and R2.0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131. In a changing network. or EIGRP and apply the skills you learned in this chapter to test connectivity. static information is more trusted. Because you have /24 and /30. IGRP.5. Examples 2-69 and 2-70 display the full working configuration on R1 and R2. Configure loopbacks with VLSM and experiment with debug commands to discover why IP entries are added or not advertised.255.108.0 ! interface Serial0/0 shutdown ! .255. the only way RIP can understand variable-length subnet mask is with RIPv2 or with the use of static routes.255.1 255. In that case.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131. static routes can be cumbersome to document and administrate. which means if you use any dynamic routing protocols.

108.255.108.108.7.255.255.0 no ip directed-broadcast ! interface Loopback2 ip address 131.2 255.255.2.108.255.255.3.3.1 255.0 no ip directed-broadcast ! interface Loopback1 ip address 131.108.252 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router rip version 2 network 131.255.108.8.255.108.55 - .252 clockrate 128000 ! router rip version 2 network 131.0 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.CCNP Practical Studies: Routing interface Serial0/1 ip address 131.255.108.255.1 255.9.0.255.1 255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.0.1 255.0 ! ip classless .1 255.255.0 ! line con 0 transport input none line aux 0 line vty 0 4 ! end Example 2-70 R2's Full Configuration ! service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.

0/24 R1#ping 131. 00:00:15. 00:00:05.0/24 C 131.7. 9 subnets.1 is not set variably subnetted.108.0/16 is R 131.108.2.108.0. You can find the answers to these questions in Appendix C.0/24 C 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).8. Serial0/1 [120/1] via 131. Serial0/1 [120/1] via 131. Serial0/1 [120/1] via 131. Loopback2 is directly connected.6.108.108.1 Type escape sequence to abort.108. Serial0/1 is directly connected.CCNP Practical Studies: Routing ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 ! end Review Questions These review questions are based on the Practical Exercise.108. 2 masks [120/1] via 131. Sending 5.108. 00:00:15. Use the router displays taken from R1 from the preceding Practical Exercise to answer the following questions.7.108.108.108.3. 00:00:15.2.2.1.108.2. 100-byte ICMP Echos to 131. View Example 2-71 for sample output taken from R1.3.3.1. 00:00:05.7.108.9.108.3.0.0/24 R 131.5. 9 subnets. Serial0/1 [120/1] via 131.2.108.108.3.7. Serial0/1 [120/1] via 131.0/24 R 131.0/24 C 131.1 Type escape sequence to abort. 00:00:05.108.1." Example 2-71 show ip route on R1 R1#show ip route Gateway of last resort 131.3.0/24 C 131. "Answers to Review Questions.0/24 variably subnetted. Loopback0 is directly connected. 100-byte ICMP Echos to 131. Serial0/1 [120/1] via 131.9.2.0/24 R 131.0/24 C 131. round-trip min/avg/max = 16/16/16 ms R1#ping 131.9. 00:00:15. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).4. 100-byte ICMP Echos to 131.9.108.3.108.108.0/24 R 131.8. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).3.2.8.108.0/30 R 131. Serial0/1 is directly connected. Loopback1 is directly connected.108. round-trip min/avg/max = 16/16/16 ms R1#ping 131.8. Sending 5.2. Serial0/1 .108.108.0/24 R 131.108.108.2. Sending 5.0/16 is R 131. 2 masks [120/1] via 131. Ethernet0/0 Type escape sequence to abort.56 - .108. this output includes the IP routing table and sample pings to the router R2.1.3.108.108. 00:00:05. round-trip min/avg/max = 12/15/16 ms R1#show ip route rip 131.2.

Enables RIP routing protocol. Table 2-7 summarizes the commands used in this chapter. Enables you to find the path taken from source to destination. a ping test is sent to three remote networks. In configuration mode. Enables IGRP routing in a particular autonomous system. Is the ping test successful or not? Explain why or why not? Why is the command version 2 configured on each router? Each remote routing entry is labeled with the following information: [120/1]. Enables OSPF routing. enables you to modify Ethernet parameters. Enables or disables an interface. The process ID is local to the router.57 - . All hardware interfaces are shut down by default. Table 2-7. Displays hardware information about a particular interface. In configuration mode. x interface loopback number interface ethernet interface serial ip domain-lookup ip subnet-zero ping trace show ip protocol debug hostname name [no] shutdown Purpose Displays IP routing table in full. You should have a strong knowledge base of routing principles to apply to the remainder of this book. . Enables EIGRP routing in a particular autonomous system. You can have more than one OSPF process running. what other methods could you use to ensure connectivity to the remote networks? 8: Summary You have now successfully worked through five routing principles scenarios using different routing protocols and have configured IP addressing across a sample two-router network.108. Stops the router sending routing updates on an interface.0/16? From R1. Escape sequence to escape from the current session and return to terminal server.0. What does the 120 represent and what does the 1 represent? Besides a ping test. Creates a loopback interface. The IOS command no ip domain-lookup disables automatic DNS lookups. Enables network advertisements from a particular interface and also the routing of the same interface through a dynamic routing protocol. Configures a name on a router. Enables automatic DNS lookup. Summary of Commands Used in This Chapter Command show ip route router rip router igrp autonomous system router eigrp autonomous system router ospf process id network passive-interface interface show controllers Ctrl-Shift-6. Displays all routing protocols in use on a Cisco router. Enables you to use subnet zero on a Cisco router. enables you to modify serial interface parameters. Enables you to send ICMP packets to local and remote destinations to test network connectivity.CCNP Practical Studies: Routing 1: 2: 3: 4: 5: 6: 7: What information is stored in an IP routing table as seen by R1? Which command do you use to view only RIP routes? Which command do you use to view only connected routes? How many subnets are known by R1 using the Class B network 131. Troubleshooting command used to display messages received and sent by a Cisco router.

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help you complete your understanding and ensure you have all the basic OSPF routing skills to complement your understanding of how to configure and maintain OSPF on Cisco Internet Operating System (IOS) routers. DD sequence numbering. the cost is calculated by using the formula cost = 10 / bandwidth. Five practical scenarios. included in the chapter. area ID. An Adjacency adjacency can have the following different states or exchange states: 1. such as router ID also but in addition include MTU sizes. Autonomous system A network under a common network administration. You can manually assign the router ID. Full state— Neighbor routers are fully adjacent because their link-state databases are fully synchronized. This table contains every link in the whole network. Area A group of routers that share the same area ID. checksum. OSPF shares information with every router in the network. which is the highest IP address configured on a Cisco router or the highest numbered loopback address. LSA packets contain information.CCNP Practical Studies: Routing Chapter 3. Table 3-1. 3. By default. It then briefly explains why OSPF is considered an improved routing protocol over Routing Information Protocol (RIP) by covering how OSPF discovers.59 - . OSPF is considered a difficult protocol to configure and requires a thorough understanding of terms that are commonly used. 2. A concrete understanding of how OSPF routing works is fundamental for any small or large network. Basic OSPF OSPF is a link-state routing protocol. Table 3-1 explains briefly the common OSPF terminology used throughout this chapter. Common OSPF Terms Description Information is shared between directly connected routers. This information propagates throughout the network unchanged and is also used to create a shortest path first (SPF) tree. This chapter covers how OSPF overcomes any limitations imposed by NBMA networks. which deals conceptually with IP routing principles and in particular link-state routing protocols. This router is responsible for ensuring adjacencies between all neighbors on a multiaccess network (such as . Establish bi-directional (two-way) communication— Accomplished by the discovery of the Hello protocol routers and the election of a DR. Basic Open Shortest Path First This chapter focuses on a number of objectives falling under the CCNP routing principles. All OSPF routers require area assignments. if authentication is used. Exchange state— Database Description (DD) packets continue to flow as the slave router acknowledges the master's packets. and the advertising router. Nonbroadcast multiaccess (NBMA) is a particular challenge in any network environment. (AS) Cost The routing metric used by OSPF. Router ID Each OSPF router requires a unique router ID. You can manually configure the 8 cost with the ip ospf cost command. Understanding basic Open Shortest Path First (OSPF) routing principles not only applies to the CCNP certification but to all Cisco-based certifications. Topology table Designated router Also called the link-state table. link-state type. 6. This chapter assumes knowledge of the previous chapter. Init state— When Hello packets have been sent and are awaiting a reply to establish two-way communication. Loading state— Link-state requests are sent to neighbors asking for recent advertisements that have not yet been discovered. The chapter starts by covering the basic OSPF concepts. Term Link state 5. Link-state protocols use the shortest path first (SPF) algorithm to populate the routing table. 4. and any options. Exstart— Two neighbor routers form a master/slave relationship and agree upon a starting sequence to be incremented to ensure LSAs are acknowledged. When two OSPF routers have exchanged information between each other and have the same topology table. chooses. Lower costs are always preferred. DD packets contain information. Routing tables begin to be populated. OSPF is operational because the routers can send and receive LSAs between each other. OSPF is commonly used in large service provider networks or large financial institutions. such as the router ID. and maintains routing tables.

Before covering various OSPF scenarios. place it in area 0.0.255 area 0 .255 area 0 dictates that you do not care (255.255. this chapter covers how OSPF is configured in single and multiple OSPF areas. A backup router designed to perform the same functions in case the DR fails. In a tie.0 255. non.255) what the IP address is. The DR is selected based on the router priority.CCNP Practical Studies: Routing Table 3-1.0. Step 3. External Links use the LSA type 5. OSPF has some basic rules when it comes to area assignment. Configuring OSPF in a Single Area When configuring any OSPF router. boundary router (ASBR) OSPF has so many features that the most efficient way to appreciate them is to enable OSPF on routers and observe how the routers dynamically discover IP networks. Summary links use LSA types 3 and 4.255. the following tasks are required: Step 1.0. but if an IP address is enabled on any interface. must be configured if you use more than one area assignment. Originated by area border routers (ABRs) and describe networks in the AS. Step 4. Area border router Router located on the border of one or more OSPF areas that connects those areas to the backbone (ABR) network. you must establish which area assignment to enable the interface for. OSPF must be configured with areas. A packet that contains all relevant information regarding a router's links and the state of those links. Describe the state and cost of the router's interfaces to the area. Step 2. or 0. Network links use LSA type 2. This ensures all routers do not need to maintain full adjacencies with each other.255. Use the network command to enable the interfaces. Common OSPF Terms Term (DR) Description Ethernet).0. you can choose any area.0.255.0.OSPF) devices for use with redistribution. Example 3-1 Configuring OSPF in a Single Area router ospf 1 network 0. although good OSPF design dictates that you configure area 0.0 255. The backbone area 0. the router with the highest router ID is selected. Example 3-1 displays OSPF with a process ID of 1 and places all interfaces configured with an IP address in area 0.0.255. Autonomous system ABR located between an OSPF autonomous system and a non-OSPF network. The network command network 0. You can configure OSPF in one area. To enable OSPF on a Cisco router and advertise interfaces. Identify area assignments.255. Use the command router ospf process ID to start OSPF. Network links Originated by DRs. Backup DR Link-state advertisement (LSA) Priority Router links Summary links Sets the router's priority so a DR or BDR can be correctly elected. External links Originated by autonomous system boundary routers (ASBRs) and describe external or default routes to the outside (that is.60 - . (Optional) Assign the router ID. Router links use LSA type 1.

0) with a Class C subnet mask (255. You build a small network and an OSPF routing table.255. Scenario 3-1: Configuring OSPF in a Single Area In this scenario. OSPF has authentication available. allows you to define the networks types and also allows static OSPF neighbor configurations. and troubleshoot it. (RIP has 15 hops only. .CCNP Practical Studies: Routing The following is a list of reasons OSPF is considered a better routing protocol than RIP: • • • • • • • • NOTE OSPF has no hop count limitations. and in particular Cisco IOS. or /24 mask). (RIPv2 does also. but RIPv1 does not. Configure the routers of OSPF area 1 and place the loopbacks in area 1 also. These five possible solutions available with Cisco IOS are listed for your reference. Scenarios The following scenarios are designed to draw together and further explore the content described earlier in this chapter and some of the content you have seen in your own networks or practice labs.255. You must also configure a number of loopback interfaces to populate the IP routing table. Figure 3-1 displays two routers named R1 and R2 connected through Ethernet. monitoring. Used in Ethernet and broadcast environments in which the election of DR/BDR takes place. The other two factors are the memory and Central Processing Unit (CPU) requirements that can affect even high-end router performance. and troubleshooting have a far greater IOS tool base than RIP. You can configure more than one OSPF process. The main challenge is that NBMA environments do not carry broadcast traffic but have the added characteristics that multiple destinations may be present. OSPF allows for load balancing with up to six equal-cost paths. but you must be mindful that the SPF calculations associated with multiple OSPF processes can consume a considerable amount of CPU and memory. Scenario 3-4 illustrates the behavior of OSPF in an NBMA environment. you configure two Cisco routers for OSPF routing using a Class B (/16) network (131. monitor. In a normal broadcast environment.0.61 - . OSPF converges much faster than RIP. NBMA mode. OSPF does have some disadvantages. OSPF and Nonbroadcast Multiaccess Environments A nonbroadcast multiaccess (NBMA) environment presents the OSPF designer a number of challenges. Table 3-2. Cisco IOS enables you to configure five main network types as displayed in Table 3-2. To overcome these problems. this is not a challenge because a packet can be sent to a broadcast or multicast address and be received by all recipients. including the level of difficulty and understanding required to configure. OSPF. OSPF over NBMA Using Cisco IOS Method Point-to-point nonbroadcast Point-to-point Point-to-multipoint Nonbroadcast Broadcast Description Used typically for Frame Relay interfaces.) OSPF understands variable-length subnet masks (VLSMs) and allows for summarization.108.0. There is not always one right way to accomplish the tasks presented. This is the default mode for subinterfaces. OSPF configuration. and using good practice and defining your end goal are important in any real-life design or solution. Used for multiple destinations.) OSPF allows for tagging of external routes injected by other autonomous systems. OSPF uses multicasts (not broadcasts) to send updates. because OSPF propagates changes immediately.

108. Example 3-3 R2 OSPF Configuration router ospf 2 network 131. Example 3-4 displays the three remote networks reachable through OSPF with a cost metric of 11 for all three. The next hop address is 131.31 area 1 network 131.0 0.0.0 0.0.0 area 1 NOTE R1 has a process ID of 1 and R2 has a process ID of 2.108.108. or an exact match.127 area 1 network 131.255 area 1. you could apply the one IOS command to enable all interfaces configured with an IP address in the range 131.128 0.0.31 area 1 Example 3-3 displays the OSPF configuration performed on R2.0.0.0 through 131. Assign all interfaces with the area assignment 1.255 with the command network 131. The process ID can be any number between 1–65535.1.0. because R2 has host (or /32 subnets) masks on loopbacks 2 and 3.2 through Ethernet 0/0. which displays the IP routing table on R1.0.0.1.0.0.0.127 area 1 network 131. To discover why loopbacks appear as /32 host routers.0 area 1 network 131.5.108. The process ID is locally significant only and doesn't need to match between routers. so.108.255 area 1 network 131. .108.0. You might ask yourself why some of the remote networks are displayed as a /32 route when you used a /27 mask.6. Also.108.0 0.0.0. Example 3-2 R1 OSPF Configuration router ospf 1 network 131.62 - .1.108. in fact.5. Configure R1 for OSPF first. Use the network command and match the IP subnet exactly.32 0.108.0.0 0.CCNP Practical Studies: Routing Figure 3-1.255. Basic OSPF Figure 3-1 displays the IP addressing and area assignments for Routers R1 and R2.0. Also note that this scenario uses VLSM.0.4. NOTE Routers R1 and R2 reside in one area.0.0.0 0.108.108.4. Example 3-2 displays the OSPF configuration performed on R1.255 area 1 network 131.108.2 0.0. examine Example 3-4.1 0.6.0.255.0. the inverse mask is 0.

Area 1 Process ID 1.1. 00:01:19. To figure out why. Wait 40.108.5.6. The associated cost of the remote network 131. Example 3-6 displays R1's routing table after these changes.0.108.1. Loopback1 O 131.0/27 is directly connected. by default.2.128/25 is directly connected. or as /32 routes.4. Example 3-6 R1 Routing Table R1#show ip route 131.108.5. State DR.32/27 [110/1010] via 131.1.1.0/25 is directly connected. Ethernet0/0 C 131. 00:02:22.32 is through Ethernet 0/0.2.128/25 is directly connected.108.2 Timer intervals configured.108.1/32 [110/11] via 131.108.CCNP Practical Studies: Routing Example 3-4 R1's IP Routing Table R1#show ip route 131.2 (Backup Designated Router) Suppress hello for 0 neighbor(s) .108.1. Loopback2 O 131.108.2. so you need to modify them also.0/27 is directly connected.5. Loopback0 C 131.108. 00:01:19. 4 masks C 131. Ethernet0/0 O 131.108. Router ID 131.108. Retransmit 5 Hello due in 00:00:06 Neighbor Count is 1.108. Ethernet0/0 C 131.108.1.0/16 is variably subnetted.108. line protocol is up Internet Address 131.108.108.6. Ethernet0/0 O 131.63 - . Ethernet0/0 C 131. The command ip ospf network point-to-point changes the route advertisement to /27.108.108.0/24 is directly connected.5. 00:02:22. Interface address 131.108.2. Ethernet0/0 R1# The remote network is displayed as a /32 route when a /27 mask is used because.0/16 is variably subnetted. Loopback2 O 131.1.108.2.0/24 is directly connected.2.108.4.33/32 [110/11] via 131.1 Backup Designated router (ID) 131.108.1/24. Ethernet0/0 C 131.1. 00:02:22.6. the subnet 131. Loopback1 O 131.5. Example 3-7 show ip ospf interface ethernet 0/0 on R1 R1#show ip ospf interface ethernet 0/0 Ethernet0/0 is up.6.108. Network Type BROADCAST.32/27 is 1010.1.108.1. To make things a little more interesting. 4 masks C 131.1/32 [110/11] via 131.0.5.108. Dead 40.1.108. Hello 10. modify the cost as well to 1000. it makes a calculation on total cost. Ethernet0/0 R1# In Example 3-6.108. Find out the cost associated with R1 Ethernet 0/0 by using the show ip ospf interface ethernet 0/0 command as displayed in Example 3-7.108. Interface address 131. Loopback0 C 131.1. R2(config)#int loopback0 R2(config-if)#ip ospf cost 1000 R2(config-if)#ip ospf network point-to-point The command ip ospf cost 1000 changes the cost to 1000. The path taken to the remote network 131. Priority 1 Designated Router (ID) 131.1. Example 3-5 Advertising Loopbacks as /27 on R2 and Changing the Default Cost to 1000 R2#conf t Enter configuration commands. Adjacent neighbor count is 1 Adjacent with neighbor 131. OSPF advertises loopbacks as host addresses. Change this default configuration and make the routes appear as /27 with the configuration on R2.2/32 [110/11] via 131.2. remember that OSPF calculates the total cost from source to destination. 7 subnets.108. one per line.5.1.4.2/32 [110/11] via 131. 7 subnets.108.108.108. The 1000 is the cost R2 assigns and advertises to R1.32 displayed is 27 bits.1.4. 00:01:19.5.0/25 is directly connected. When R1 receives the update. The remaining loopbacks are still /32. End with CNTL/Z. Cost: 10 Transmit Delay is 1 sec. as displayed in Example 3-5.5.

224 ! interface Ethernet0/0 ip address 131.128 ! interface Loopback1 ip address 131.0 ! hostname R1 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.4. Therefore.1 255. which equals 1010.255. Example 3-9 R2 Full Configuration version 12.108.0.108.255.0.0. Example 3-8 R1 Full Configuration version 12.108.255. Example 3-8 displays the full routing configuration on R1.1.108.4.CCNP Practical Studies: Routing R1# The cost associated with the path on the Ethernet segment is 10.255.5.255.5.5.127 area 1 network 131.255.128 0.0.108. Another method you can use to determine the cost with an Ethernet segment is to use the cost calculation.0 ! hostname R2 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.255.108.108.255 area 1 network 131.31 area 1 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-9 displays the full routing configuration on R2.4.64 - .1 255.0.108.33 255.1. the total cost is 1000 (as advertised by R2) plus 10.255.255.0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown router ospf 1 network 131.128 ! interface Loopback2 ip address 131.0.127 area 1 network 131.255.1 255.0 0.4.224 ip ospf network point-to-point ip ospf cost 1000 .0.0. cost = 108 / Bandwidth = 108 / 107 = 10.108.0 0.129 255.0 0.

32 0.0 area 1 ! line con 0 line aux 0 line vty 0 4 end Now. Figure 3-2 displays the routers in this scenario.0.255 ! interface Ethernet0/0 ip address 131.255 area 1 network 131.0.0 0.0.255 ! interface Loopback2 ip address 131.0.31 area 1 network 131.5. more complex network in Scenario 3-2.0.6. .1.255.255.0.6.0.1 255.255. apply the OSPF principles to a larger.108.108.255.65 - .1.CCNP Practical Studies: Routing ! interface Loopback1 ip address 131. This scenario uses four routers: R1 and R2 from scenario 3-1 and two new routers named R6 and R3.2 255. Scenario 3-2: Configuring OSPF in Multiple Areas Turn your attention to a far more complex OSPF scenario and apply some of the advanced features in OSPF.6.255.108.2 255.0 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 2 network 131.108.6.108.108.2 0.1 0.0.0 area 1 network 131.255.108.

"Routing Principles. ABRs contain the full topological database of each area they are connected to and send this information to other areas. and create an additional two new areas: Area 0 and Area 2. R6 is a backbone router and ABR. Notice the IP addressing in Figure 3-2 has a mixture of the Class B networks 131.CCNP Practical Studies: Routing Figure 3-2. but you need to modify R2 and enable OSPF on R3 and R6.0. Routers R2 and R6 in this case are referred to area border routers (ABRs) because more than one area is configured on each router. That makes a total of three areas: the backbone Area 0 between R3 and R6.0 and 141.35 cables. R3 and R6. .108. Area 2 covering the link between R6 and R2. In Figure 3-2. also know as area 0.0. enable OSPF on R3 and R6.3 area 2 Now. OSPF Router Types Description This router is within a specific area only. Table 3-3. Remember that you have a link to R6.0. Autonomous system ASBRs connect to the outside world or perform some form of redistribution into OSPF. Hence. you add two new routers. and R3 is a backbone router.0. Example 3-10 displays the modifications required on R2. Table 3-3 displays all the possible routers types.108.10. so you need to set IP addressing and clocking as you did in the Chapter 2. border router (ASBR) Backbone router Backbone routers are connected to area 0.0. All interfaces on internal routers are in the same area. OSPF Topology and IP Addressing In this scenario.0 with different subnets.108. and Area 1 covering the Ethernets between R1 and R2. Example 3-10 Configuration of R2 as ABR Router type Internal router R2(config)#router ospf 2 R2(config-router)#network 141. Internal router functions include maintaining the OSPF database and forwarding data to other networks. this scenario uses VLSM extensively to illustrate the capability of OSPF to handle VLSM.0." Example 3-5 uses Cisco serial back-to-back V.0. OSPF includes a number of different router types. R2 is an ABR. Backbone routers can be internal routers and ASBRs. Router R1 requires no configuration change. R1 is an internal router.66 - .0 0. Area border router (ABR) ABRs are responsible for connecting two or more areas.

2.12. Ethernet0 r6# Example 3-13 displays the remote networks on Router R3.0 is directly connected.10.0. examine the routing table on the backbone network to ensure that all networks are routable.4 0.0. 3 masks O 141.26 0. Serial1 C 141.108.108. the Ethernet network 131.128 0. Loopback1 O 141. Example 3-11 Enable OSPF on R6 with Process ID 6 r6(config)#router ospf 6 r6(config-router)# network r6(config-router)# network r6(config-router)# network r6(config-router)# network r6(config-router)# network r6(config-router)# network 141.108.0.108.12.0/16 is variably subnetted.10.0.108.108.10.108.6.4 0.0/25 is directly connected. 00:23:42.108.0 0. 00:00:32.67 - .108.108.9.0.0.108.128/25 [110/65] via 141.108.0. 00:23:42.108.12.1. Loopback0 C 141.31 area 0 131.108.0 0.5.9.5.0/16 is variably subnetted.10.0/24 in area 1 is not routable from R6.26.0. For example.0/25 [110/65] via 141.0 0.128/25 [110/65] via 141.0.0.127 area 0 141. Serial1 O IA 141.108.108.0.0. Loopback2 O 141.33.6.0.1. 00:00:32.128 0. Example 3-14 R3's IP Routing Table R3>show ip route 141.0/24 is subnetted.127 area 0 141.10.0. Serial0 C 141.0. Serial0 C 131.127 area 0 141.3 area 2 141.0/30 is directly connected.108.0. Loopback1 O 141. .10.3 area 0 141.128/25 is directly connected. Example 3-13 IP Routing Table on R6 r6#show ip route 141.108. Examine R3's routing table.10.0/30 [110/128] via 141. 8 subnets. 00:00:32.10. 00:23:42.3 area 0 141.108.0.1.0. Ethernet0 Once more.108.0 0.0/25 [110/65] via 141. Example 3-14 displays R3's IP routing table. Example 3-13 displays the IP routing table on R6. Example 3-14 doesn't display the networks in area 1 on Routers R1 and R2.4/30 is directly connected.0.10. Serial0 C 141.10.0 [110/74] via 141. start the OSPF process with the process ID 6 and enable the interfaces to advertise the networks as displayed by Example 3-11.0.108.9.108.9.108.0/25 is directly connected.108.10.9.108.6.0/24 [110/65] via 141.108. Serial1 O 141.255 area 0 Similarly.0.128/25 is directly connected.108.5.CCNP Practical Studies: Routing To enable OSPF on R6. 7 subnets.108.0 is directly connected. Example 3-15 displays R2's IP routing table.10.108. Loopback0 C 141.0.108.127 area 0 141. Loopback2 C 141. Serial1 C 141.255 area 0 Now that OSPF is configured on all four routers.4/30 is directly connected.0.108.0 0. but not the networks from R1 or R2.0.33.0/27 is directly connected.108.2.12.108.6.0/24 is subnetted. Example 3-12 Enable OSPF on R3 R3(config)#router ospf 3 R3(config-router)#network R3(config-router)#network R3(config-router)#network R3(config-router)#network R3(config-router)#network 141.108.0. 2 subnets O 131.108.9.10.108.108.108. Serial0 131. 00:23:42. Serial1 C 141.255 area 0 141. 1 subnets C 131.0 0.108.108.10. 4 masks C 141. Example 3-12 displays the OSPF configuration required on R3.0/24 is directly connected.1.108.33.1.1.1. Serial1 131.0.

Ethernet0/0 R2> Notice.108.108.CCNP Practical Studies: Routing Example 3-15 R2's IP Routing Table R2>show ip route 141. Serial1/0 O IA 141.108. you use a virtual link to attach areas that do not have a physical connection to the backbone or in cases in which the backbone is partitioned.1.0/16 is variably subnetted. 00:26:20. Area 2 is not partitioned from the backbone.108.1.108.1. Ethernet0/0 O 131. Figure 3-3 displays the areas and the requirement for a virtual link.68 - . 00:46:09.1.0/25 [110/846] via 141.10. Serial1/0 O IA 141.10.10.5.108.10. 3 masks O 131.108. 00:26:20. 8 subnets. Serial1/0 O IA 141. Area Assignments and the Virtual Link Requirement .108.108.9.2/32 is directly connected.2.10.1.108. If an area cannot be assigned to the backbone or is partitioned from the backbone.6. Therefore.4. Loopback1 O 131.2.1/32 is directly connected.12.128/25 [110/846] via 141. Serial1/0 C 141. Area 1 is not directly connected to the backbone. 00:08:05.108.10.108.6.9.0/30 is directly connected.129/32 [110/11] via 131. 00:26:20.0/25 [110/782] via 141.33. Ethernet0/0 C 131. When designing a network.108.2. as in the example shown in Figure 3-2.5. Serial1/0 131.0/24 is directly connected.108. Scenario 3-2 includes three areas.108.1.2.108.108. Serial1/0 C 131. Serial1/0 O IA 141.1/32 [110/11] via 131.2.32/27 is directly connected.128/25 [110/782] via 141.1. Loopback0 O IA 131.108. Ethernet0/0 C 131.0/24 [110/782] via 141.1. but not vice versa.108. 00:26:20. area 2 is directly connected to the backbone through Router R6.10.108.4/30 [110/845] via 141. however. 00:46:09. 00:46:09.0/24 [110/855] via 141. because Router R2 is connected to area 2.10.2. 00:09:06. Router R1 is missing IP networks.108.1. 00:08:15. Serial1/0 O IA 141. Loopback2 C 131.108.0/16 is variably subnetted.0.4. In fact. 3 masks O IA 141. 7 subnets. Figure 3-3.1/32 [110/11] via 131.108. The golden rule in any OSPF network is that all areas must be contiguous or all areas must be connected to the backbone. that R2 has access to the remote networks in area 0 or on the backbone.108.10.108.0.108.108.2. a virtual link is required.

in this case area 2. Hello 10. In this scenario. which displays the complete OSPF database. this command has many options.12. Cost of using 781 Transmit Delay is 1 sec.108. The following is a simplification: area area-id virtual-link router-id The area-id is the transit network between the two partitioned areas.108.108.12. Transit area 2. .12.6. Dead 40.69 - . You can find the router-id by using the show ip ospf database command.1 is up Run as demand circuit DoNotAge LSA allowed.1) (Process ID 6) You now have the information required to configure a virtual link between R3 and R6.1 Example 3-18 Configuring a Virtual Link on R6 R6(config)#router ospf 6 r6(config-router)#area 2 virtual-link 131. to ensure that the virtual link is active.2 Use the show ip ospf virtual-links command on R2. To create a virtual link.108. Examples 3-17 and 3-18 display the configuration performed on Routers R2 and R6. Now. Example 3-16 shows you how to discover the router IDs on R2 and R6.108. The virtual link allows information about area 1 to be sent to the backbone. Example 3-16 show ip ospf database Command on R2 and R6 R2>show ip ospf database OSPF Router with ID (131. Example 3-17 Configuring a Virtual Link on R2 R2(config)#router ospf 2 R2(config-router)#area 2 virtual-link 141. Wait 40. Note that the extensive amount of information typically supplied by the show ip ospf database command is not all displayed in Example 3-16. demonstrated in Example 3-19. via interface Serial1/0.CCNP Practical Studies: Routing The virtual link in this scenario is required from R2 to R6. Timer intervals configured. you use the following command: [no] area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds] [transmit-delay seconds] [dead-interval seconds] [[authentication-key key] | [message-digest-key keyid md5 key]] As you can see.2) (Process ID 2) r6>show ip ospf database OSPF Router with ID (141. Retransmit 5 Hello due in 00:00:07 Adjacency State FULL (Hello suppressed) Example 3-19 displays an active link to the remote OSPF router with the ID 141. configure a virtual link between R2 and R6. as demonstrated in Example 3-20.1.108. State POINT_TO_POINT.12. Another solution to this problem is to change the area 1 assignment to area 2 or to connect a physical link from area 1 to the backbone.6. view the routing tables on R3 to determine whether the area 1 networks have been inserted into the IP routing table. Example 3-19 show ip ospf virtual-links R2#show ip ospf virtual-links Virtual Link OSPF_VL0 to router 141.

255 ! interface Loopback2 ip address 131.2 255.6.1.108.4/30 is directly connected. and R6.10. 4 masks C 141. Serial1 C 131.5. Loopback0 C 141. Serial1 O IA 131. Serial1 O IA 131.108. Serial1 131.108.10.5. respectively. Serial1 O IA 131.9.255.0/30 [110/128] via 141. R3.4. Serial1 Router R3 discovers the remote networks from the partitioned area 1 through the virtual link between the routers R2 and R6 as demonstrated by the IP routing table in Example 3-20.108.108.6.6.108.255 ! interface Ethernet0/0 ip address 131.4.10.1. 00:01:44. Loopback1 O 141.108.108.1 255.128/25 [110/65] via 141. 00:01:43.10.6.108. Serial1 O IA 131.224 ip ospf network point-to-point ip ospf cost 1000 ! interface Loopback1 ip address 131.255. 00:01:43.129/32 [110/139] via 141.1.10.108.108.10.32/27 [110/1128] via 141.6.0 ! interface TokenRing0/0 shutdown .10. Examples 3-21.255.10.108.6. 00:01:43.1/32 [110/129] via 141.108.10.1/32 [110/139] via 141.10.108. 00:01:43.108.6. Serial1 O IA 131.10.108.108.1/32 [110/139] via 141. 00:01:43.108.3-22.0/27 is directly connected.255.12.108.108. R1's configuration is unchanged from scenario 3-1.CCNP Practical Studies: Routing Example 3-20 show ip route on R3 R3#show ip route 141. Serial1 O 131.255.0/24 [110/65] via 141.108.255. Serial1 O 141.6.255.33 255. 00:01:43.108.2 255.108.108. Ethernet0 O IA 131. 00:01:43. 00:01:43.0/25 [110/65] via 141.108.255.6.0/16 is variably subnetted. Serial1 C 141.70 - .108.5.0/16 is variably subnetted. Example 3-21 Full Configuration on R2 Current configuration: ! version 12. Serial1 O IA 141.108. Serial1 C 141.26. 3 masks O IA 131.2/32 [110/129] via 141.6. and 3-23 show the three configurations of routers R2.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.10. 00:01:43.10.0/24 [110/74] via 141.0.0/24 is directly connected. Loopback2 O 141.108.108.33.10.2.0/24 [110/138] via 141.108. 00:01:43.108.108.6.6.6.6. 8 subnets. 9 subnets.0/25 is directly connected. 00:01:43.6.6.108.0.1.128/25 is directly connected.9.108.108.

CCNP Practical Studies: Routing
! interface Serial1/0 ip address 141.108.10.1 255.255.255.252 ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 2 area 2 virtual-link 141.108.12.1 network 131.108.1.0 0.0.0.255 area 1 network 131.108.5.32 0.0.0.31 area 1 network 131.108.6.1 0.0.0.0 area 1 network 131.108.6.2 0.0.0.0 area 1 network 141.108.10.0 0.0.0.3 area 2 ! line con 0 line aux 0 line vty 0 4 login ! end
Example 3-22 displays R3's full configuration. Example 3-22 Full Configuration on R3

version 12.0 ! hostname R3 ! enable password cisco ! interface Loopback0 ip address 141.108.1.1 255.255.255.128 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.1.129 255.255.255.128 ip ospf network point-to-point ! interface Loopback2 ip address 141.108.2.1 255.255.255.224 ip ospf network point-to-point ! interface Ethernet0 ip address 131.108.33.1 255.255.255.0 ! interface Ethernet1 shutdown ! interface Serial0 shutdown ! interface Serial1

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ip address 141.108.10.5 255.255.255.252 ! router ospf 3 network 131.108.33.0 0.0.0.255 area 0 network 141.108.1.0 0.0.0.127 area 0 network 141.108.1.128 0.0.0.127 area 0 network 141.108.2.0 0.0.0.31 area 0 network 141.108.10.4 0.0.0.3 area 0 line con 0 line aux 0 line vty 0 4 ! end
Example 3-23 displays R6's full configuration. Example 3-23 Full Configuration on R6

! version 12.0 ! hostname r6 ! enable password cisco ! interface Loopback0 ip address 141.108.9.1 255.255.255.128 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.9.129 255.255.255.128 ip ospf network point-to-point ! interface Loopback2 ip address 141.108.12.1 255.255.255.0 ip ospf network point-to-point ! interface Ethernet0 ip address 131.108.26.1 255.255.255.0 media-type 10BaseT ! interface Ethernet1 shutdown ! interface Serial0 ip address 141.108.10.6 255.255.255.252 clockrate 125000 ! interface Serial1 ip address 141.108.10.2 255.255.255.252 clockrate 125000 ! interface Serial2 shutdown ! interface Serial3 shutdown ! interface TokenRing0 shutdown

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! interface TokenRing1 shutdown ! router ospf 6 area 2 virtual-link 131.108.6.2 network 141.108.9.0 0.0.0.127 area 0 network 141.108.9.128 0.0.0.127 area 0 network 141.108.10.0 0.0.0.3 area 2 network 141.108.10.4 0.0.0.3 area 0 network 131.108.26.0 0.0.0.255 area 0 ! line con 0 line aux 0 line vty 0 4 end
Now, you move on to learn about some common OSPF commands you can use to ensure that remote networks are reachable.

Scenario 3-3: How OSPF Monitors, Manages, and Maintains Routes
In this scenario, you re-examine in detail the network in Figure 3-2 and discover some of the common OSPF commands for monitoring, managing, and maintaining IP routing tables. This scenario also looks at ways to configure OSPF to modify IP routing table entries, such as cost metrics and DR/BDR election. Table 3-4 displays a summary of the commands executed in this scenario.

Table 3-4. OSPF Commands for Monitoring, Managing, and Maintaining IP Routing Tables Command show ip ospf show ip ospf database show ip ospf neighbor show ip ospf neighbor detail show ip ospf interface ip ospf priority ip ospf cost Description Displays the OSPF process and details such as OSPF process ID and router ID. Displays routers topological database. Displays OSPF neighbors. Displays OSPF neighbors in detail, providing parameters, such as neighbor address, hello interval, and dead interval. Displays information on how OSPF has been configured for a given interface. Interface command used to change the DR/BDR election process. Interface command used to change the cost of an OSPF interface.

Example 3-24 shows the output of the command show ip ospf taken from the backbone Router R3 in Figure 3-2. Table 3-5 explains how to read the most important information contained within the output. NOTE Scenario 3-2, and thus this scenario, have four routers with the following router IDs:

• • • •

R1— 131.108.5.1 R2— 131.108.6.2 R3— 141.108.12.1 R6— 141.108.2.1

This information is shown in the examples that follow.

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Example 3-24 show ip ospf Output

R3>show ip ospf Routing Process "ospf 3" with ID 141.108.2.1 Supports only single TOS(TOS0) routes SPF schedule delay 5 secs, Hold time between two SPFs 10 secs Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs Number of external LSA 0. Checksum Sum 0x0 Number of DCbitless external LSA 0 Number of DoNotAge external LSA 0 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Area BACKBONE(0) Number of interfaces in this area is 4 Area has no authentication SPF algorithm executed 3 times Area ranges are Number of LSA 13. Checksum Sum 0x54D76 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 9
Table 3-5. Explanation of the show ip ospf Command Output Taken from R3 Explanation Displays the process ID. In this case 141.108.2.1. The amount of time that the IOS waits before the SPF calculation is completed after receiving an update. The minimum LSA interval is five seconds and the minimum LSA arrival is one second on R3. Number of areas in this router is Displays the number of areas configured on the local router. In this example, R3 has all 1 interfaces in the backbone, or area 0. So only one area is displayed by this command. Area BACKBONE(0) Displays the area the router is configured for. R3 is a backbone router, so this output advises the area in backbone 0. Number of interfaces in this area Displays the number of interfaces in area 0. R3 has four interfaces in area 0. is 4 Area has no authentication Displays the fact that no authentication is used on R3. Example 3-25 shows the output of the command show ip ospf database taken from the backbone R3 in Figure 3-2. Table 3-6 explains how to read the most important information contained within the output. Example 3-25 show ip ospf database Output Field Routing process ID Minimum LSA interval 5 secs Minimum LSA arrival 1 sec

R3>show ip ospf database OSPF Router with ID (141.108.2.1) (Process ID 3) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.108.6.2 131.108.6.2 7 (DNA) 0x80000002 0x38EB 141.108.2.1 141.108.2.1 559 0x80000003 0xCC2 141.108.10.5 141.108.10.5 3110 0x8000000B 0x1AC 141.108.12.1 141.108.12.1 153 0x80000010 0xC3A Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.108.1.0 131.108.6.2 82 (DNA) 0x80000001 0xE663 131.108.4.1 131.108.6.2 82 (DNA) 0x80000001 0xC57F 131.108.4.129 131.108.6.2 82 (DNA) 0x80000001 0xC004 131.108.5.1 131.108.6.2 82 (DNA) 0x80000001 0xBA89 131.108.5.32 131.108.6.2 82 (DNA) 0x80000001 0x8ED4 131.108.6.1 131.108.6.2 82 (DNA) 0x80000001 0x4B02 131.108.6.2 131.108.6.2 82 (DNA) 0x80000001 0x410B 141.108.10.0 131.108.6.2 82 (DNA) 0x80000001 0x280C 141.108.10.0 141.108.12.1 1958 0x80000006 0x846B

Link count 1 5 5 7

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Table 3-6. Explanation of the show ip ospf database Command Field OSPF Router with ID (141.108.2.1) (Process ID 3) Router Link States (Area 0) Summary Net Link States (Area 0) Explanation The router ID and process ID on the router configured by the network administrator. Displays the link-state advertisements from connected neighbors discovered by the Hello protocol. Information displayed by ABRs.

To show you some different output, look at two more examples from Scenario 3-2: one from R2 and one from R6. Example 3-26 displays the show ip ospf neighbor command from R2. Example 3-26 show ip ospf neighbor from R2

R2>show ip ospf neighbor Neighbor ID Pri State 131.108.5.1 1 FULL/DR 141.108.12.1 1 FULL/ -

Dead Time 00:00:39 00:00:34

Address 131.108.1.1 141.108.10.2

Interface Ethernet0/0 Serial1/0

Router R2 has two neighbors: one across the Ethernet segment and another through the serial connection to R6. The show ip ospf neighbor command displays the neighbor router ID and the priority of the neighbor (both 1 in this example) as well as the DR. Notice that the DR is R1 as seen by R2. The state of the adjacency (Full) and the dead time are displayed. The dead time is the amount of time before the adjacency is declared dead or inactive if a Hello packet is not received. The dead time must be the same of the adjacent router. The dead time is four times the hello interval. The address field displays the remote router's IP address. In this case, the IP address assigned to R1 is 131.108.1. The interface field describes the outbound interface from which the neighbor was discovered. Example 3-27 displays the neighbors on R6 in more detail by adding the detail parameter to the show ip ospf neighbor command. Example 3-27 show ip ospf neighbor detail from R6

r6#show ip ospf neighbor detail Neighbor 141.108.2.1, interface address 141.108.10.5 In the area 0 via interface Serial0 Neighbor priority is 1, State is FULL, 6 state changes DR is 0.0.0.0 BDR is 0.0.0.0 Options 2 Dead timer due in 00:00:35 Neighbor 131.108.6.2, interface address 141.108.10.1 In the area 2 via interface Serial1 Neighbor priority is 1, State is FULL, 6 state changes DR is 0.0.0.0 BDR is 0.0.0.0 Options 2 Dead timer due in 00:00:33
Router R6 has no adjacency across any broadcast media, such as Ethernet. Therefore, the neighbors are all in a Full state but no DR or BDR is elected across the wide-area network (WAN) link, because the WAN link is considered a point-to-point link. To determine what type of OSPF network the given interface is, use the show ip ospf interface command. Example 3-28 displays this command in its most basic form taken from R6. You can provide more parameters, such as interface serial number. Example 3-28 show ip ospf interface from R6

r6#show ip ospf interface Ethernet0 is up, line protocol is up Internet Address 131.108.26.1/24, Area 0 Process ID 6, Router ID 141.108.12.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State WAITING, Priority 1 No designated router on this network No backup designated router on this network Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:01 Wait time before Designated router selection 00:00:11 Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s)

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Loopback0 is up, line protocol is up Internet Address 141.108.9.1/25, Area 0 Process ID 6, Router ID 141.108.12.1, Network Type POINT_TO_POINT, Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:00 Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback1 is up, line protocol is up Internet Address 141.108.9.129/25, Area 0 Process ID 6, Router ID 141.108.12.1, Network Type POINT_TO_POINT, Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:00 Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback2 is up, line protocol is up Internet Address 141.108.12.1/24, Area 0 Process ID 6, Router ID 141.108.12.1, Network Type POINT_TO_POINT, Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:00 Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial0 is up, line protocol is up Internet Address 141.108.10.6/30, Area 0 Process ID 6, Router ID 141.108.12.1, Network Type POINT_TO_POINT, Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:06 Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 141.108.2.1 Suppress hello for 0 neighbor(s) Serial1 is up, line protocol is up Internet Address 141.108.10.2/30, Area 2 Process ID 6, Router ID 141.108.12.1, Network Type POINT_TO_POINT, Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:06 Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 131.108.6.2 Suppress hello for 0 neighbor(s) r6#

Cost: 1 5

Cost: 1 5

Cost: 1 5

Cost: 64 5

Cost: 64 5

Router R6 has six interfaces configured with OSPF, so you should expect details about those interfaces. Example 3-28 displays all interface network types as point-to-point (loopbacks by default are configured as loopback, but the IOS command ip ospf network point-to-point configures the loopback as point-to-point networks) except the Ethernet segment, because Ethernet is a broadcast medium. Also notice that because R6 has no neighbors over the Ethernet network, no DR/BDR is elected, because there is no need. The dead interval is four times the hello interval on all interfaces. Now use some interface commands on the Figure 3-2 network to modify the behavior of the DR/BDR election process. Start by changing the designated router in area 1 and ensure that Router R2 becomes the DR. Example 3-29 displays the current DR and the configuration change on R2 to make the priority higher than R1 by setting the priority to 255.

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Example 3-29 Changing the IP OSPF Priority on R2

R2#show ip ospf neighbor Neighbor ID Pri State 131.108.5.1 1 FULL/DR 141.108.12.1 1 FULL/ R2#configure term Enter configuration commands, one per R2(config)#interface e 0/0 R2(config-if)#ip ospf priority 255 R2# show ip ospf neighbor Neighbor ID Pri State 131.108.5.1 1 FULL/DR 141.108.12.1 1 FULL/ R2# show ip ospf neighbor Neighbor ID Pri State 131.108.5.1 1 FULL/DR 141.108.12.1 1 FULL/ -

Dead Time 00:00:35 00:00:37 line.

Address 131.108.1.1 141.108.10.2

Interface Ethernet0/0 Serial1/0

End with CNTL/Z.

Dead Time 00:00:33 00:00:34 Dead Time 00:00:31 00:00:32

Address 131.108.1.1 141.108.10.2 Address 131.108.1.1 141.108.10.2

Interface Ethernet0/0 Serial1/0 Interface Ethernet0/0 Serial1/0

Example 3-29 stills displays the DR as R1 and not R2 even after the configuration setting changes the priority to 255, because the election process has already taken place and R1 is still the DR. Example 3-30 simulates a network outage by shutting down R1 E0/0. Now look at the OSPF neighbor on R1, as displayed by Example 3-30. Example 3-30 Shutting Down R1 E0/0 and show ip ospf neighbor Commands

R1(config)#interface e 0/0 R1(config-if)#shutdown 1w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to down 1w6d: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up 1w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up R1(config-if)#no shutdown 1w6d: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up 1w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 131.108.6.2 255 INIT/00:00:39 131.108.1.2 Ethernet0/0 R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 131.108.6.2 255 EXCHANGE/0:39 131.108.1.2 Ethernet0/0 R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 131.108.6.2 255 EXSTART/DR 00:00:39 131.108.1.2 Ethernet0/0 R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 131.108.6.2 255 LOADING/DR 0:00:39 131.108.1.2 Ethernet0/0 R1#show ip ospf nei Neighbor ID Pri State Dead Time Address Interface 131.108.6.2 255 FULL/DR 00:00:39 131.108.1.2 Ethernet0/0
Example 3-30 displays some interesting facts. The first is that when you shut down the interface and enable the Ethernet port E0/0 on R1, IOS displays messages to advise you of the changed state. Second, the first neighbor state is INIT, which means R1 sent Hello packets, which are awaiting R2's reply. The state of EXSTART/DR means the two routers have formed a master relationship. The LOADING state indicates that link-state requests have been sent. The FULL state indicates the two routers are fully adjacent or share the same OSPF database. The DR indicates that the designated router is the neighbor with the IP address 131.108.1.2, which is Router R2. Example 3-31 displays the neighbor state as seen by R2, which is now the backup designated router (BDR).

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Example 3-31 show ip ospf neighbor on R2

R2#show ip ospf neighbor Neighbor ID Pri State 131.108.5.1 1 FULL/BDR 141.108.12.1 1 FULL/ -

Dead Time 00:00:34 00:00:35

Address 131.108.1.1 141.108.10.2

Interface Ethernet0/0 Serial1/0

The final command in this scenario is the ip ospf cost command. You use this command to change the cost Cisco routers assign by default by using the formula OSPF cost = 108 / bandwidth. This command is not the only method you can use to change the cost. You can also use the bandwidth command on a particular interface and let the Cisco IOS use the bandwidth portion of the cost formula to calculate the new cost. NOTE You can also use the command auto-cost reference-bandwidth reference-bandwidth during the OSPF process to change the bandwidth portion of the cost calculation. You should set this command equally across all your routers if you choose to use it. The referencebandwidth is set to 108 by default.

Assume you have a request from the network administrator that all loopbacks on R1 being advertised to R2 have a total cost of 100. Example 3-32 displays the current cost on R2. Example 3-32 R2's OSPF Routing Table

R2#show ip route ospf 141.108.0.0/16 is variably subnetted, 7 subnets, 3 masks O 141.108.1.128/25 [110/846] via 141.108.10.2, 3d03h, Serial1/0 O 141.108.9.128/25 [110/782] via 141.108.10.2, 3d03h, Serial1/0 O 141.108.1.0/25 [110/846] via 141.108.10.2, 3d03h, Serial1/0 O 141.108.9.0/25 [110/782] via 141.108.10.2, 3d03h, Serial1/0 O 141.108.12.0/24 [110/782] via 141.108.10.2, 3d03h, Serial1/0 O 141.108.10.4/30 [110/845] via 141.108.10.2, 3d03h, Serial1/0 131.108.0.0/16 is variably subnetted, 9 subnets, 3 masks O 131.108.4.129/32 [110/11] via 131.108.1.1, 00:02:03, Ethernet0/0 O 131.108.33.0/24 [110/855] via 141.108.10.2, 3d03h, Serial1/0 O 131.108.4.1/32 [110/11] via 131.108.1.1, 00:02:03, Ethernet0/0 O 131.108.5.1/32 [110/11] via 131.108.1.1, 00:02:03, Ethernet0/0 O 131.108.26.0/24 [110/791] via 141.108.10.2, 3d03h, Serial1/0
The three loopbacks display a cost of 11. To increase this to 100, you can increase the cost per interface. Example 3-33 displays the cost change on R1 loopback interfaces from the default of 1 to 90. Remember that by default, the cost of a 10MB Ethernet interface is 10. Example 3-33 Changing the Default Cost on R1 E0/0

R1(config)#interface loopback 0 R1(config-if)#ip ospf cost 90 R1(config-if)#interface loopback 1 R1(config-if)#ip ospf cost 90 R1(config-if)#interface loopback 2 R1(config-if)#ip ospf cost 90
Changing the default cost from 1 to 90 means that the total cost R2 sees is 10, which is the default cost on an Ethernet interface plus the 90 you configured. Example 3-34 now displays the new OSPF routing table with the loopbacks from R1 with a new cost of 100.

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1. Serial1/0 O 141.10.4/30 [110/845] via 141.1/32 [110/100] via 131.1. 00:00:35.108. 3d03h.108. Ethernet0/0 O 131.2. Serial1/0 O 141.4.4.10. The next scenario shows you how to configure an advanced OSPF network using a three-router network over Frame Relay.108.108.108.0/25 [110/846] via 141.0/25 [110/782] via 141. 3d03h.1. 3d03h. 3 masks O 141. 3d03h. Serial1/0 Example 3-34 displays the cost to the remote networks on R1 as 100.2.108. Ethernet0/0 O 131.108.2. Figure 3-4 displays the three-router network over Frame Relay used in this scenario.1.0/24 [110/782] via 141.128/25 [110/782] via 141.26. Scenario 3-4: OSPF over Frame Relay in an NBMA Environment This scenario covers configuring OSPF over Frame Relay in an NBMA environment. 00:00:35. Included in Figure 3-4 are the IP addressing scheme. 3d03h.108.12. OSPF over Frame Relay .0/24 [110/855] via 141.108.2.108.108.0/16 is variably subnetted.129/32 [110/100] via 131.9.128/25 [110/846] via 141.0.108. This scenario helps you discover some of the advanced features of OSPF. Ethernet0/0 O 131.108. Serial1/0 O 141. Figure 3-4.2.10.10. such as DR election in an NBMA environment.10.10.108.0.1. 3d03h.2.108. 3d03h. 9 subnets.79 - .1.108.1/32 [110/100] via 131.CCNP Practical Studies: Routing Example 3-34 R2's OSPF Routing Table After the Cost Change R2#show ip route ospf 141.108.108. Serial1/0 O 131.1. 00:00:35.2.5. and OSPF area assignments.33.108.108.108. Frame Relay DLCI numbering.1.108.9.108.0/24 [110/791] via 141. 3 masks O 131.10.10.10.108. 3d03h. Serial1/0 O 141. Serial1/0 131. Serial1/0 O 141. 7 subnets.2.0/16 is variably subnetted.

1 106 broadcast NOTE In Examples 3-36 and 3-37. Figure 3-4 displays the Frame Relay DLCIs and Local Management Interface (LMI) types. you can start the OSPF configuration. because Frame Relay dynamically discovers the maps because R3 is a hub router using Frame Relay inverse Address resolution Protocol (ARP) protocol.0 R3(config-if)#router ospf 3 R3(config-router)#network 141.0.0.248 R3(config-if)# encapsulation frame-relay R3(config-if)# frame-relay interface-dlci 103 R3(config-fr-dlci)# frame-relay interface-dlci 108 Example 3-35 shows you how to configure the IP address and how to enable Frame Relay encapsulation.255.0 0. as displayed in Figure 3-4. Frame Relay inverse ARP automatically discovers the DLCI and next hop IP address. which is the path to R5.0 0.108.108. Example 3-38 OSPF and IP Address Configuration on R3 R3(config)#interface ethernet 0 R3(config-if)#ip address 141.1. like any protocol.255.1.80 - . Example 3-35 R3's Frame Relay Configuration R3(config)#interface serial 0 R3(config-if)#ip address 141.108. Example 3-39 displays the OSPF configuration on R4 along with the IP address assignment to E0.248 encapsulation frame-relay frame-relay interface-dlci 106 frame-relay map ip 141.255.1. but this is not the case on R3 in Example 3-35.1 255. which is the path to R4. and 108. Example 3-38 displays the OSPF configuration on R3 along with the IP address assignment to E0. respectively. The specific DLCIs are 103.255.108.108. R3 also requires the DLCI information.1 255.255.255.3.108. Now that you have enabled Frame Relay. needs to map Layer 2 of the Open System Interconnection (OSI) model to Layer 3.1. R4 and R5 map IP over Frame Relay.255.248 encapsulation frame-relay frame-relay interface-dlci 107 frame-relay map ip 141. Example 3-36 and Example 3-37 show the configurations of R4 and R5.1.1 107 broadcast Example 3-37 The Frame Relay Configuration on R5 interface Serial0 ip address 141. You do not use subinterfaces in this scenario to demonstrate an NBMA environment.CCNP Practical Studies: Routing This scenario involves three routers running OSPF over Frame Relay. .108. R3 is not configured for static mapping.3.0. Frame Relay.7 area 0 You must also enable OSPF on Routers R4 and R5.255. Start by configuring the Frame Relay parameters. Example 3-35 displays R3's Frame Relay configuration. Example 3-36 The Frame Relay Configuration on R4 interface Serial0 ip address 141.0.3 255.108.255 area 3 R3(config-router)#network 141.1.2 255.

108. of course) are not sent over a nonbroadcast OSPF network type.108.1. you do not modify the network type.108. OSPF can be configured a variety of ways to accomplish this.108. Hello 30. Network Type NON_BROADCAST.5. Example 3-40 OSPF and IP Address Configuration on R5 R5(config-if)#ip address 141.255.0 0.10. Ensure that OSPF adjacencies are up and in a FULL state on R3.1. but rather you statically configure a neighbor relationship from R3 to R4 and R5.0.7 area 0 Example 3-40 displays the OSPF configuration on R5 along with the IP address assignment to E0. Wait 120. Dead 120. Example 3-41 show ip ospf neighbor Command on R3 R3>show ip ospf neighbor R3> As you can see from the lack of output in Example 3-41. broadcasts or multicasts do not propagate over the Frame Relay.10. Interface address 141.255. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Example 3-42 displays no neighbor and the main fact that the link is considered a nonbroadcast link.0.0 R5(config-if)#interface ethernet 1 R5(config-if)#ip address 141.255.1 255.0.1 255.255.0 R4(config)#router ospf 4 R4(config-router)#network 141.108. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.4.3.7 area 0 NOTE Example 3-40 places the two Ethernet networks with the one OSPF statement.255 area 5 R5(config-router)#network 141.0. Figure 3-4 shows a classic example of OSPF over NBMA.0 0.5. In an NBMA environment. .108.108.1 255.1 No backup designated router on this network Timer intervals configured. Example 3-41 displays the OSPF neighbor state on router R3.108.5. Example 3-42 show ip ospf interface serial 0 Command on R3 R3>show ip ospf int s 0 Serial0 is up.255 area R4(config-router)#network 141. Router R3 has no adjacencies.1. enter the following command: neighbor ip address of neighbor Example 3-43 displays the configuration on R3 to remote routers R4 and R5.6. To demonstrate OSPF over NBMA in this scenario.0. That lack of relationships is because OSPF Hello packets (using multicast address.108.4. To enable a static OSPF neighbor relationship.0 0. line protocol is up Internet Address 141.0.81 - .0 0. Priority 1 Designated Router (ID) 141. Example 3-42 displays the OSPF network type on R3 link to R4 and R5.5.0 R5(config-if)#router ospf 5 R5(config-router)#network 141. Router ID 141.108.1/29.108.255.CCNP Practical Studies: Routing Example 3-39 OSPF and IP Address Configuration on R4 R4(config)#interface ethernet 0 R4(config-if)#ip address 141.255. The IOS on R3 in Example 3-41 tells you there are no OSPF relationships to R4 and R5. State DR.1. Cost: 64 Transmit Delay is 1 sec. Area 0 Process ID 3.0.

One more important task is required. The command neighbor 141.108.108. Example 3-46 displays the full working configuration of R3.0 ! interface Ethernet1 no ip address shutdown ! interface Serial0 ip address 141.0. for example.255.0 ! hostname R3 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.CCNP Practical Studies: Routing Example 3-43 Static Neighbor Configuration on R3 R3(config)#router ospf 3 R3(config-router)#neighbor 141.252 ! router ospf 3 network 141.108.108. The easiest way to make R3 the DR is to disable R4 and R5 from ever becoming the DR by applying a 0 priority on R4 and R5.7 area 0 .1.1 0 141.5. Router R4 and R5 are spoke.0 0.82 - .1.1 255.1.3.2 Interface Serial0 Serial0 The state shown in Example 3-45 displays a FULL adjacency and a state known as DROTHER.108.108.3 141.255.3 The command neighbor 141.1.108.108. Example 3-43 overcomes the need to change the network environment from nonbroadcast and allows a static configuration of remote OSPF routers. Example 3-44 demonstrates how to set the priority to 0. R3. must become the DR. Example 3-46 R3's Full Configuration version 12.1.255. which indicates that the neighbor was not chosen as the DR or BDR and cannot be because the priority has been set to zero. through R3.255.3 configures the neighbor to R5. routers.2 configures the neighbor to R4.1.0.108.108.255.2 0 State FULL/DROTHER FULL/DROTHER Dead Time 00:01:54 00:01:44 Address 141. or edge.2 R3(config-router)#neighbor 141.1. Example 3-44 IP OSPF Priority Set to 0 on R4 and R5 R4(config)#interface serial 0 R4(config-if)#ip ospf priority 0 R5(config)#interface serial 0 R5(config-if)#ip ospf priority 0 Examples 3-45 displays the OSPF neighbors on R3. Example 3-45 show ip ospf neighbor Command on R3 R3#show ip ospf nei Neighbor ID Pri 141.248 encapsulation frame-relay frame-relay interface-dlci 103 frame-relay interface-dlci 108 ! interface Serial1 ip address 141.255.5 255. because R3 has links to both R4 and R5 and information will be sent from R4 to R5. The hub router.1 255.1.10.108.1.108. in effect disabling any chance for R4 or R5 to become the DR.

0 interface Serial0 ip address 141.108.0 ! interface Ethernet1 ip address 141.4.108. Example 3-48 R5's Full Configuration version 12.0.108.5.108.0.83 - .108.248 encapsulation frame-relay ip ospf priority 0 frame-relay map ip 141.0 0.0 ! hostname R5 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.255.1 255.4.1.255. Example 3-47 R4's Full Configuration version 12.1 107 broadcast frame-relay interface-dlci 107 frame-relay lmi-type cisco ! interface Serial1 shutdown ! router ospf 4 network 141.2 ! line con 0 line aux 0 line vty 0 4 end Example 3-47 displays the full working configuration of R4.255.0.108.2 255.255 area 3 neighbor 141.1.0 0.0 ! hostname R4 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.1 255.0.255.0.255 area 4 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-48 displays the full working configuration of R5.0.108.1.0 .3 neighbor 141.1.3.255.255.108.7 area 0 network 141.1 255.CCNP Practical Studies: Routing network 141.0 0.1.108.255.108.6.255.

108.0.4.0.108.84 - . The two routers are named SanFran and Chicago.1 106 broadcast frame-relay interface-dlci 106 ! interface Serial1 shutdown ! router ospf 5 network 141. .1.108.CCNP Practical Studies: Routing ! interface Serial0 ip address 141.1. Also.0. Figure 3-5 displays a simple two-router topology. you use the hostname name command.255.248 encapsulation frame-relay ip ospf priority 0 frame-relay map ip 141.0. notice that the backbone segment is displayed as 0.0 0. Scenario 3-5: Verifying OSPF Routing This scenario covers common techniques used in OSPF networks to verify correct configuration in a single OSPF area.0. The backbone can be configured on Cisco routers as 0 or 0. NOTE Figure 3-5 displays two routers with the names SanFran and Chicago.0.3.0 0. Figure 3-5 displays the correct IP address assignment and OSPF area assignment.255. Example 3-49 displays SanFran's IP routing table.7 area 0 network 141.1.0.0. To change the name of a router.3 255.108. Figure 3-5. In this scenario.255 area 5 ! line con 0 line aux 0 line vty 0 4 ! end The final scenario covers common show and debug commands used to verify correct OSPF implementation. the configurations supplied are not the full working solutions to demonstrate the power of OSPF. Sample Network for Verifying OSPF Routing The network administrator of R1 has told you that a number of remote networks on R2 are not reachable by R1.0.

Area 0.108. line protocol is up Internet Address 131.108. Router ID 131.108.7. Priority 1 Designated Router (ID) 131.0.108. line protocol is up Internet Address 131. Interface address 131.1/24. Area 0. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.1.1.108. like loopbacks.7.7. Router ID 131.0 Process ID 1.108.6.1/24. State POINT_TO_POINT.5. Loopback1 directly connected.1. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up. Wait 120.CCNP Practical Studies: Routing Example 3-49 SanFran's IP Routing Table SanFran#show ip route 131. Area 0.0. Area 0. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Cost: 1 Loopback interface is treated as a stub Host Example 3-51 displays the loopbacks in OSPF process 2.0 Process ID 1. Hello 30.1 No backup designated router on this network Timer intervals configured.1.4. Example 3-51 show ip ospf interface Command on Chicago Chicago#show ip ospf interface Loopback0 is up. such as the Ethernet interface on R1 resides in area 0.0. are active as long as they are not administratively shutdown). Router ID 131.85 - . Cost: 90 Loopback interface is treated as a stub Host Example 3-50 displays a number of important details.0.1.1.0 is C 131. Cost: 90 Loopback interface is treated as a stub Host Loopback1 is up.1. Cost: 1 Transmit Delay is 1 sec.1. Hello 10. line protocol is up Internet Address 131.0.0. Dead 40. line protocol is up Internet Address 131.5. Loopback0 directly connected.108.0 Process ID 1.108.108. 3 subnets directly connected. Example 3-51 displays a sample output from the show ip ospf interface command. line protocol is up Internet Address 131.0 is C 131.108. State DR. Example 3-50 displays a sample output taken from the router SanFran. Network Type POINT_TO_POINT.108.108. Take the same steps on Chicago. Router ID 131. Network Type LOOPBACK. and the router SanFran is the elected DR.0.0. Network Type LOOPBACK.0.4.1. Router ID 131.0. .108. Wait 40.0.1/24. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback1 is up.108.108.0/24 is C 131.0 Process ID 2. Ethernet0/0 Example 3-49 displays no remote entries on R1. so OSPF looks like it is correctly configured on R1.5. Start by ensuring that OSPF is correctly configured on R1 by using the show ip ospf interface command.5.0.0 is R1# subnetted. Cost: 10 Transmit Delay is 1 sec. Area 0. Dead 120.1/24. Timer intervals configured. Network Type BROADCAST. Example 3-50 show ip ospf interface Command on SanFran SanFran#show ip ospf interface Ethernet0/0 is up. but the Ethernet interface is not enabled.5.0.0 Process ID 2.108.5. The loopbacks on Chicago and SanFran are active (software interfaces.0. Example 3-52 displays the OSPF configuration on Chicago.1/24. Network Type LOOPBACK. the network type over the Ethernet interface is broadcast. or the backbone.

0.0 area 0. line protocol is up Internet Address 131.1.CCNP Practical Studies: Routing Example 3-52 OSPF Configuration on Chicago router ospf 2 network 131. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback1 is up.0.0.1.108.0 0.255 area 0.108.108. hence OSPF cannot run.0 Chicago (config-router)#network 131.108.0.1.0.1. Example 3-54 show ip ospf interface Command on Chicago Ethernet0/0 is up.0 Process ID 2.0. Priority 1 No designated router on this network No backup designated router on this network Timer intervals configured. This address is a reserved address for the subnet 131. The command network 131.7. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Dead 40.0.1. Timer intervals configured.1.108.0.0 Process ID 2.0 0.0. enabled in OSPF area 0.1/24. Cost: 10 Transmit Delay is 1 sec.0.0. Wait 40.0/24.0. Network Type LOOPBACK.6.108. and check for OSPF adjacency. Wait 120. Retransmit 5 Hello due in 00:00:16 Wait time before Designated router selection 00:01:46 Neighbor Count is 0.1.0 area 0.0.0 0.1. in fact.0.0.0.0.108. Hello 10. Example 3-54 displays a sample output with the show ip ospf interface command.0 network 131. Dead 40.1.0 Example 3-52 displays the fault with the router Chicago.0.0.2 0.0.108.0. Network Type POINT_TO_POINT.0 area 0.0. line protocol is up Internet Address 131.108.7. Cost: 1 Loopback interface is treated as a stub Host Example 3-54 displays that the Ethernet interface is now. State POINT_TO_POINT.108.86 - . State WAITING. Network Type BROADCAST.7. Cost: 1 Transmit Delay is 1 sec. Remove this command and install the correct network and mask command.0 network 131.1.0 Process ID 2. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up.0.0. .0 Make sure that OSPF is enabled on Chicago's Ethernet interface.0 causes the router to enable OSPF for the interface configured with the IP address 131.0 0.108.6.0. Hello 10.108.1/24.0.0. Area 0.0. The fact that no adjacent neighbor is present still represents a problem.7. Example 3-53 Modifying the OSPF Configuration on Chicago Chicago(config)#router ospf 2 Chicago (config-router)#no network 131.0. Router ID 131.0. Example 3-55 displays the OSPF characteristic of the Router SanFran.7. line protocol is up Internet Address 131. Router ID 131.108. Area 0.255 area 0.0 0. Move back to the router named SanFran. Router ID 131.2/24.108. Area 0.0. Example 3-53 displays the removal of the incorrect command and insertion of the correct network statement.0.

5. whereas the configured interval on SanFran is 120 seconds.1 area 0.1.255.1 No backup designated router on this network Timer intervals configured. are the same.255.1. Hence.1.2 2w5d: Dead R 40 C 120. Wait 120.87 - . whereas the configured (displayed as C from the debug output) dead interval (Dead C 120) on SanFran is 120 seconds.1.2.255. the hello interval Chicago receives is set to 10 seconds. another mismatch.108.0. Hello 30. Example 3-56 advises you that the Chicago dead interval is 40 seconds. Hello R 10 C 30.0 The error message displayed by the IOS in Example 3-56 clearly states you have a mismatch in the hello interval. Example 3-56 displays the command being enabled and a sample output taken from the router SanFran. such as the hello interval or dead interval. Example 3-56 displays Dead R 40 C 120. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) No neighbor exists on this segment. These two clearly do not match. Priority 1 Designated Router (ID) 131.0 Process ID 1. NOTE The dead interval.1. In other words. Cost: 10 Transmit Delay is 1 sec.1/24. The sample debug output. there is a mismatch error. whereas the configured hello interval on SanFran is 30 seconds. line protocol is up Internet Address 131. Router ID 131.1. Similarly.0.7. the hello interval the Router SanFran uses (local router where the display is taken from) is different from the router sending out a Hello packet with the router ID 131. by default. Network Type BROADCAST. Therefore.CCNP Practical Studies: Routing Example 3-55 show ip ospf interface ethernet 0/0 Command on SanFran SanFran#show ip ospf interface ethernet 0/0 Ethernet0/0 is up. through the IP address 131. State DR.108. Example 3-57 displays the configuration change on SanFran to ensure hello and dead intervals are configured the same way. as displayed in Example 3-56. Hello R 10 C 30 Mask R 255. is four times the hello interval. Example 3-56 advises you that Chicago's hello interval is 10 seconds. advises you that the hello and dead interval should be correctly set on both routers: SanFran and Chicago. Remember that hello and dead intervals must match before neighboring routers can become fully adjacent.108. The first information tells you that the dead interval (displayed as Dead in the debug output) received from the router Chicago (Dead R 40) is set to 40 seconds.7.1. Example 3-56 debug ip ospf adj and Sample IOS Display SanFran#debug ip ospf adj OSPF adjacency events debugging is on SanFran# 2w5d: OSPF: Rcv hello from 131. Area 0. whereas the configured hello interval on SanFran is 30. . Router SanFran is configured with a hello interval of 10 seconds.1. OSPF routers never become adjacent (in other words.0.108.108.108.255.108. Dead 120.108.0 C 255. The hello interval is set to 10 seconds.0. which automatically configures the dead interval to 40 seconds thereby matching the hello and dead intervals set on the router named Chicago.0 from Ethernet0/0 131. Retransmit 5 Hello due in 00:00:11 Neighbor Count is 0. Interface address 131. never exchange OSPF databases) unless all OSPF parameters.108.5.2 2w5d: OSPF: Mismatched hello parameters from 131. Now introduce a new command using the debug command set: debug ip ospf adj This command enables IOS output of all events relating to adjacencies.

7. length 24 2w5d: OSPF: Rcv DBD from 131.1/32 O 131.108. state 2WAY 2w5d: OSPF: Neighbor change Event on interface Ethernet0/0 2w5d: OSPF: DR/BDR election on Ethernet0/02w5d: OSPF: Elect BDR 0.7. 5 subnets.108.5.0. .108. Ethernet0/0 is directly connected.1 2w5d: DR: 131.108.7.7.108.1 on Ethernet0/0 seq 0x11C4 opt 0x2 flag 0x7 l en 32 2w5d: OSPF: Set Ethernet0/0 flush timer 2w5d: OSPF: Remember old DR 131.0. seq 0x8000 0004 2w5d: OSPF: Rcv hello from 131.108.1 2w5d: OSPF: Elect DR 131.1 on Ethernet0/0.6.2.1.7.7.108.7.0 from Ethernet0/0 131.1 on Ethernet0/0 seq 0x1237 opt 0x2 flag 0x1l en 32 mtu 1500 state EXCHANGE 2w5d: OSPF: Exchange Done with 131.7.108.7.1.0/24 variably subnetted. Ethernet0/0 [110/11] via 131.1.5.CCNP Practical Studies: Routing Example 3-57 Changing Hello Interval to 10 Seconds on SanFran SanFran(config)#interface ethernet 0/0 SanFran(config-if)#ip ospf hello-interval 10 SanFran(config-if)#^Z SanFran# 2w5d: %SYS-5-CONFIG_I: Configured from console by console SanFran# 2w5d: OSPF: Rcv hello from 131.0.0/24 C 131.108.0.5.0. and an OSPF database exchange occurs.1 on Ethernet0/0 seq 0x1237 opt 0x2 flag 0x0 l en 32 2w5d: OSPF: We are not DR to build Net Lsa for interface Ethernet0/0 2w5d: OSPF: Synchronized with 131.108.108.0/32 through OSPF.108. Example 3-57 highlights the OSPF neighbor state from the initial INIT state to the FULL state.108.108.108. you see the hello process completed.1 (Id) BDR: 131.1 on Ethernet0/0 seq 0x1235 opt 0x2 flag 0x7 len 32 mtu 1500 state INIT 2w5d: OSPF: 2 Way Communication to 131.1 (id) 2w5d: OSPF: NBR Negotiation Done.108.108. Example 3-58 SanFran IP Routing Table SanFran#show ip route 131.1/32 C 131.108.7.6.1 area 0.2 2w5d: OSPF: End of hello processing 2w5d: OSPF: Rcv DBD from 131.7.1.1 on Ethernet0/0.0 from Ethernet0/0 131.0/24 C 131.5.1 area 0.108.108.108.2.108.0.0 2w5d: OSPF: Elect DR 131.7.88 - .0.108.108. state FULL 2w5d: OSPF: Include link to old DR on Ethernet0/0 2w5d: OSPF: Build router LSA for area 0.108.1 on Ethernet0/0 seq 0x1236 opt 0x2 flag 0x3 len 92 mtu 1500 state EXCHANGE 2w5d: OSPF: Send DBD to 131.7.108. Example 3-58 now displays SanFran's IP routing table.108.7.4.108.7.5.1/32 and 131.0. router ID 131. 00:01:25. Loopback1 is directly connected. 2 masks [110/11] via 131.1 2w5d: OSPF: Elect BDR 131. Loopback0 is directly connected.1.108.1.1.2 2w5d: OSPF: End of hello processing As soon as you correct the problem.108.108.1 on Ethernet0/0 seq 0x1236 opt 0x2 flag 0x0 l en 32 2w5d: OSPF: Database request to 131.108.1 on Ethernet0/0 2w5d: OSPF: Send DBD to 131.0/16 is O 131. Ethernet0/0 The Router SanFran now discovers the remote networks 131.0.7.7.0.1 on Ethernet0/0 seq 0x1235 opt 0x2 flag 0x2 l en 72 2w5d: OSPF: Rcv DBD from 131.7. 00:01:25.1 2w5d: OSPF: sent LS REQ packet to 131.1 (Id) 2w5d: OSPF: Send DBD to 131.2. Routers Chicago and SanFran are now OSPF neighbors. We are the SLAVE 2w5d: OSPF: Send DBD to 131. In other words.108.

0 ! interface Ethernet0/0 ip address 131. Example 3-59 Possible show and debug OSPF Commands SanFran#show ip ospf ? <1-4294967295> Process ID number border-routers Border and Boundary Router Information database Database summary interface Interface information neighbor Neighbor list request-list Link state request list retransmission-list Link state retransmission list summary-address Summary-address redistribution Information virtual-links Virtual link information <cr> SanFran#debug ip ospf ? adj OSPF adjacency events database-timer OSPF database timer events OSPF events flood OSPF flooding lsa-generation OSPF lsa generation packet OSPF packets retransmission OSPF retransmission events spf OSPF spf tree OSPF database tree NOTE Using the ? character on the command-line interface displays a list of commands available to the user. Example 3-59 takes advantage of this tool to display commands available to the network administrator.1 255. Cisco IOS is updated almost daily. Example 3-60 displays the full working configuration on SanFran. Example 3-60 The Full Working Configuration on SanFran version 12.0 hostname SanFran ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.108.0 ! interface Loopback1 ip address 131.108.255.0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown .1 255. Example 3-59 displays the debug and show commands possible on a Cisco router running IOS release 12.255.CCNP Practical Studies: Routing This scenario has introduced you to some powerful OSPF commands that you can use to discover why OSPF is not functioning correctly.255.255.4.108.10.89 - .255.5.255.1 255. so you need to reference the IOS documentation for new and ever-expanding commands.0.1.

0 area 0.1.108.1 255.0.108.0 interface Ethernet0/0 ip address 131.6.0 0.0 ! ip classless line con 0 line aux 0 line vty 0 4 ! end Example 3-61 displays the full working configuration on Chicago.0.255.0. The solution can be found at the end. Use the ping command to ensure all networks are reachable.108.0.0 ! hostname Chicago ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.108.2 255. Ensure that both routers R1 and R2 have full connectivity to Routers R3 and R6 in the backbone.255.CCNP Practical Studies: Routing ! router ospf 1 network 0. .255 area 0.0.0 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! router ospf 2 network 131.0.0 line con 0 line aux 0 line vty 0 4 ! end Practical Exercise: Routing OSPF NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. You must use OSPF as your only dynamic routing protocol.0.108.0.0.0.255.255.0 255.90 - . Example 3-61 The Full Working Configuration on Chicago version 12.2 0.1.0 ! interface Loopback1 ip address 131.0 network 131.0. Configure the network in Figure 3-6 for OSPF routing using the IP addressing scheme provided.255.6.7.7.0.255.0. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own.0 network 131.255 area 0.255.0.255.0.108.0 0.255 area 0.0.1 255.

255. You will find that because the areas are partitioned.252.4.255.128 ip ospf cost 90 ! interface Loopback1 ip address 131. This second virtual link is required in case of link failure or hardware failure from the Routers R1 and R2.255. Practical Exercise: Routing OSPF Practical Exercise Solution You will notice that the IP addressing scheme uses VLSM and the serial links use the subnet 141.255. and see how OSPF behaves when the link between R2 and R6 fails.0. you actually do need two virtual links to ensure full connectivity in any network failure situation. The following example configurations provide a solution using OSPF.CCNP Practical Studies: Routing Figure 3-6. This practical example is similar to Scenario 2-2 with the extra link between area 1 and area 0.108.255.91 - . The serial link contains a mask that is 255. Configure the loopbacks with VLSM and experiment with debug commands to discover why IP entries are added or not advertised.108.108. Remove the second virtual link from R1 to R3.128 ip ospf cost 90 ! interface Loopback2 .255. or /30. Example 3-62 displays R1's full working configuration.1 255.0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131. Example 3-62 R1's Full Configuration version 12. This means that you need to configure two virtual links: one from router R2 to R6 and another between R1 and R3.4.10.129 255.

255.255 ! interface Ethernet0/0 ip address 131.0 ip ospf priority 255 interface Serial1/0 .108.8 0.0.0.33 255.1.1 255.108.0.255.255.108.108.255 ! interface Loopback2 ip address 131.1.108.1.2 255.0 0.255.255.0.108.108.252 clockrate 125000 ! interface Serial0/1 no ip address shutdown clockrate 128000 ! router ospf 1 area 2 virtual-link 141.255.255 area 1 network 131.9 255.0.255.108.0 0.31 area 1 network 141.127 area 1 network 131.108.2.0 ! interface Serial0/0 ip address 141.1 255.255.92 - .1 255.0.10.2 255.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-63 displays R2's full working configuration.255.255.255.108.CCNP Practical Studies: Routing ip address 131.255.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.5.5.0 0.6.128 0.5.10.108.4.0.1 network 131. Example 3-63 R2's Full Configuration version 12.108.0.6.4.224 ip ospf cost 90 ! interface Ethernet0/0 ip address 131.255.127 area 1 network 131.255.0.0.224 ip ospf network point-to-point ip ospf cost 1000 ! interface Loopback1 ip address 131.

1 0.5 255.31 area 1 network 131.108.10 255.255.1 255.252 ! router ospf 3 .108.0 0.CCNP Practical Studies: Routing ip address 141.0 ! interface Serial0 ip address 141.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-64 displays R3's working configuration.255.255.255. Example 3-64 R3's Full Configuration version 12.255.0 hostname R3 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.255.255.1 255.6.10.10.128 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.129 255.108.1 network 131.0.0 area 1 network 131.255.108.128 ip ospf network point-to-point ! interface Loopback2 ip address 141.255.93 - .108.224 ip ospf network point-to-point ! interface Ethernet0 ip address 131.0 area 1 network 141.108.108.32 0.0.1.255.0.0.2 0.1 255.2.108.10.252 ! interface Serial1/1 no ip address shutdown ! interface Serial1/2 no ip address shutdown ! interface Serial1/3 no ip address shutdown ! router ospf 2 area 2 virtual-link 141.255 area 1 network 131.10.255.0.1 255.0.255.255.252 ! interface Serial1 ip address 141.108.1.0.108.255.108.0 0.108.33.0.1.0.5.6.12.0.

255.CCNP Practical Studies: Routing area 2 virtual-link 131.128 0. Example 3-65 displays R6's working configuration.108.0.4 0.6.108.6 255.0.12.10.26.33.255.0.0 0.0.108.0.127 area 0 network 141.108.0.255.255.108.2 network 131.0.255.127 area 0 network 141.1.255.0.0.252 clockrate 125000 ! interface Serial2 shutdown ! interface Serial3 shutdown ! router ospf 6 area 2 virtual-link 131.1 255.0 0.255.255.0.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Finally.0 0.108.2 255.255.94 - .0 hostname r6 ! enable password cisco ip subnet-zero ! interface Loopback0 ip address 141.3 area 0 network 141.0.0.0.108.0.255 area 0 network 141.108.0 media-type 10BaseT ! interface Serial0 ip address 141.0.127 area 0 network 141.255.9.1 255.255.128 ip ospf network point-to-point interface Loopback2 ip address 141.10.9.0.0.10.0 0.108. Example 3-65 R6's Full Configuration version 12.108.1 network 131.128 0.108.127 area 0 network 141.10.10.0.255.0.0.108.128 ip ospf network point-to-point interface Loopback1 ip address 141.0 ip ospf network point-to-point interface Ethernet0 ip address 131.2.5.108.0.26.8 0.3 area 2 network 141.0.255 area 0 network 141.129 255.108.12.108.108.0.9.0 0.1 255.252 clockrate 125000 ! interface Serial1 ip address 141.4 0.108.108.9.0 0.108.10.1.0.31 area 0 network 141.108.3 area 0 network 141.0 0.255 area 0 ! .

2. 100-byte ICMP Echos to 131.108.108.108.108.10.2 Type escape sequence to abort.10.32/27 [110/1010] via 131. 00:15:28. Loopback0 C 131. Serial0/0 O 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10.10.10.108. 00:15:29.2/32 [110/11] via 131. Sending 5.6. Serial0/0 O IA 141.108. 00:16:04. Sending 5.2.CCNP Practical Studies: Routing line con 0 line aux 0 line vty 0 4 end Review Questions Use router output taken from R1 from the previous Practical Exercise to answer the following questions.108.6.1/32 [110/11] via 131.129 Type escape sequence to abort.0.4.5.108. 00:15:28.0/24 [110/138] via 141.108.129.4.108.4/30 [110/128] via 141. round-trip min/avg/max = 1/2/4 ms R1#ping 131.5.108. Serial0/0 C 141. Serial0/0 O 141.108. 00:15:28.108.10.1.128/25 [110/65] via 141.108.0/27 is directly connected.108.108.108. 100-byte ICMP Echos to 131.12.1 Type escape sequence to abort.10.0/24 [110/129] via 141.10. 4 masks C 131. Serial0/0 O 141.108.5. Example 3-66 shows this sample output taken from R1 and includes the IP routing table and sample pings to area 1.5. 00:15:28.108.8/30 is directly connected. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10. round-trip min/avg/max = 1/1/4 ms R1#ping 131.108. 00:15:28.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.108.95 - .108.0/25 [110/65] via 141.33 Type escape sequence to abort.33.6. 100-byte ICMP Echos to 131. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/25 is directly connected.10.4.6. 00:16:06.0/30 [110/192] via 141.108.1.10.128/25 [110/129] via 141.2. Ethernet0/0 O 131.108.6.5. Serial0/0 O 141. 00:15:29.108. 00:15:31.108.108.108.108.1.4. 3 masks O 141.108. Sending 5.0/24 is directly connected. Loopback1 O 131.108. Serial0/0 O 131. 8 subnets. 100-byte ICMP Echos to 131. 100-byte ICMP Echos to 131.10.10. .108.1.26.1 Type escape sequence to abort.5. round-trip min/avg/max = 1/2/4 ms R1#ping 131.0. Loopback2 O 131.108. Ethernet0/0 C 131.10.10.108. 00:16:04.0/24 [110/74] via 141. 00:15:28. 9 subnets.10. Serial0/0 R1#ping 131. Ethernet0/0 O 131.1.10.33.10.108. round-trip min/avg/max = 1/2/4 ms R1#ping 131. round-trip min/avg/max = 1/1/4 ms R1#ping 131.108.128/25 is directly connected. Serial0/0 131.108.0/16 is variably subnetted.1.108. Sending 5.108.1.108.108.4.10. Ethernet0/0 C 131.0/16 is variably subnetted.4. Serial0/0 O 141.108.0/25 [110/129] via 141.10.1.9. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Example 3-66 R1's IP Routing Table and Ping Requests to Area 1 R1>show ip route Gateway of last resort is not set 141.9.10.

CCNP Practical Studies: Routing Sending 5.6.108. The answers to these question can be found in Appendix C. round-trip min/avg/max = 1/2/4 ms R1# View Example 3-66 to answer the following review questions.0/24 [110/74]? .0.1/24? Why is the remote network 141.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5)." 1: 2: 3: 4: 5: 6: Which information is stored in an IP routing table as seen by R1? Which command do you use to view only OSPF routes? How many subnets are known by R1 using the Class B networks 131. "Answers to Review Questions.33.6.108.108.96 - .2.0.0/32 displayed as learned through the denotation: O IA? What is the cost associated with the remote network 131.100.108.108.0/16? What path is taken to the remote network 141. 100-byte ICMP Echos to 131.0/16 and 141.

Interface command that changes the cost of an OSPF interface. Enables you to use subnet zero on a Cisco router. All hardware interfaces are shut down by default.97 - . Interface command that changes the DR/BDR election process. You saw that all OSPF areas must be connected to the backbone for proper and correct operation. Displays the OSPF process and details. received and sent by a Cisco router from or to neighboring OSPF routers. Displays OSPF neighbors in detail. You can have more than one OSPF running. enables you modify an interface number. . Troubleshooting command that displays messages. Displays information on how OSPF has been configured for a given interface. Creates a loopback interface. Table 3-7 summarizes the commands used in this chapter. In configuration mode. Disables automatic DNS lookup. Displays router's topological database. for example interface E0/0. and dead interval. Summary of IOS Commands used in this Chapter Command show ip route router ospf process id network mask show ip ospf show ip ospf database show ip ospf neighbor show ip ospf neighbor detail show ip ospf interface ip ospf cost ip ospf priority ip ospf network interface loopback number interface Ethernet mod/num interface serial mod/num no ip domain-lookup ip subnet-zero show ip protocol debug ip ospf adj hostname name [no] shutdown Purpose Displays IP routing tables. In configuration mode. Enables or disables an interface. Standard techniques using Cisco IOS show commands were demonstrated to ensure that you have all the required knowledge to monitor and maintain small or large OSPF networks. Interface command that changes the network type. The process ID is local to the router. interface S0/0. Displays OSPF neighbors. For example. hello interval. Enables OSPF routing. such as the state of the adjacency. Configures a name on a router. enables you to modify serial interface parameters by module and interface number. such as OSPF process ID and router ID.CCNP Practical Studies: Routing Summary You have now completed some basic and challenging OSPF scenarios and discovered how powerful OSPF is when enabled on Cisco IOS routers. Table 3-7. Displays all routing protocols in use on a Cisco router. providing such parameters as neighbor address. OSPF can be configured in single or multiple areas. Enables network advertisements out of a particular interface and also the routing of the same interface through OSPF.

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therefore. Advanced OSPF and Integrated Intermediate System-toIntermediate System This chapter focuses on a number of objectives falling under the CCNP routing principles. For partitioned areas. In Scenario 3-2 in Chapter 3. the amount of bandwidth used over the network increases. . OSPF treats the area as a separate area. Considering the demands on CPU and memory along with reduced IP routing tables. which can cause severe delays in sending user-based traffic because convergence times increase. the CPU on a router is interrupted and a new OSPF tree is calculated. The use of authentication to ensure OSPF updates are secure and the use of multicast updates to conserve bandwidth. but sending and flooding the network with new topological information is extremely CPU intensive. Faster convergence times ensuring updates and changes are propagated across the network. "Basic Open Shortest Path First. and if this database is too large. This chapter contains five practical scenarios to complete your understanding and ensure you have all the OSPF routing skills to complement your understanding of how to configure and maintain OSPF in large IP networks. Chapter 3.CCNP Practical Studies: Routing Chapter 4. The core reason that OSPF is configured in multiple areas is to reduce routing table sizes. The OSPF database is exchanged every 30 minutes in full. All OSPF areas must be connected to the backbone in case of network failure. No limitation of network diameter or hop count. therefore. When an area cannot reside physically or logically on the backbone. The number of paths is limited only by the Internet Operating System (IOS). The use of multiple areas ensures that the flooding and database management required in large OSPF networks is reduced within each area so that the process of flooding the full database and maintaining full network connectivity does not consume a large portion of the CPU processing power. most Cisco certification exams test heavily on OSPF. This chapter covers some of the ways OSPF deals with large Internet Protocol (IP) routing environments and how you can configure OSPF to reduce IP routing tables and the CPU and memory requirements of access or edge routers. OSPF routers in any area share the same topological view (also known as the OSPF database) of the network. The following topics are covered in this section: • • • Connecting multiple OSPF areas VLSM and summarization with OSPF OSPF over multiarea NBMA Connecting Multiple OSPF Areas An OSPF area is defined as a logical grouping of routers by a network administrator. so all routers share the same topological database. which in turn reduces the topological database and CPU/memory requirements on a router. you saw how to configure an OSPF network that is partitioned from the backbone. a virtual link is required. Running the shortest path first (SPF) algorithm itself is not CPU intensive. Limiting factors include only CPU and memory resources. and it lays the foundations for future certifications in any field of networking. Routing tables become very large even with only 50 routers. every time the exchange occurs. you should now have a good understanding of why OSPF requires more than one area. The use of areas to minimize Central Processing Unit (CPU) and memory requirements. OSPF supports the following features: • • • • • • • Variable-length subnet masks (VLSM). Integrated IS-IS is covered in detail in Scenarios 4-3 and 4-4. OSPF is not just configured in one large area. and no routing information flows to the backbone. The ability to tag OSPF information injected from any autonomous systems. Understanding advanced OSPF routing principles not only applies to the CCNP Routing certification but to all Cisco-based certifications. Every time a network change occurs. you do not have IP connectivity." started by covering some of the basic Open Shortest Path First (OSPF) concepts. Advanced OSPF OSPF is an industry-standard routing protocol developed by the Internet Engineering Taskforce (IETF) as a replacement for legacy routing protocols that did not scale well in large environments. A simple cost metric that you can manipulate to support up to six equal cost paths. OSPF is a popular IP routing protocol.99 - . Integrated Intermediate System-toIntermediate System (IS-IS) is another link-state protocol common in today's networks used to route IP.

An ABR contains the full topological database for each area it is connected to and sends this information to other areas. Typical OSPF Area Assignment and OSPF Routers .CCNP Practical Studies: Routing Virtual links add a layer of complexity and might cause additional problems when applied to large IP networks. Figure 4-1 displays a typical OSPF area assignment and the function of these routers. Table 4-1 summarizes the four OSPF area types and their functions. Backbone routers can be internal routers or ASBRs. you must be aware of the following design restrictions: • • • NOTE Virtual links must be configured between two area border routers (ABRs). Rather than re-address the networks. Backbone routers are connected to area 0.0. Stub areas are covered later in this chapter. To understand why logical links are required in today's networks. which is also represented as area 0. The transit area must have full routing knowledge of both partitioned areas. All interfaces on internal routers are in the same area. Internal router functions include maintaining the OSPF database and forwarding data to other networks. Figure 4-1. It is best to avoid virtual links in the real world.100 - . ASBRs connect to the outside world or perform some form of redistribution into OSPF. Both companies use OSPF and have their own individual backbones. a virtual link can provide immediate IP connectivity. OSPF Router Types Router Type Internal router Area border router (ABR) Autonomous system boundary router (ASBR) Backbone router Description This router is within a specific area only. When configuring a virtual link.0. The transit area cannot be a stub area.0. consider the case were Company XYZ buys Company ACME. Table 4-1. Remember that all routers must be connected to the backbone logically or you must use a virtual link. ABRs are responsible for connecting two or more areas.

TIP Before flooding any neighboring routers with LSAs. Six Common Supported LSA Types on Cisco IOS Routers LSA Packet Name Type 1 Router link advertisements 2 Network link advertisements 3 4 5 6 Function Describes the state and cost of the router's own interfaces. Volumes I and II. (LSA type 3. sends out a link-state advertisement (LSA). Stub areas are discussed later in this chapter. or 5 will not be sent. Routers that connect to. Stubs come in three types. Totally stubby areas are discussed later in this chapter. Table 4-2 describes the six most common LSAs and their functions. OSPF sends the LSA database and derives the IP routing table from LSAs. Unlike distance vector protocols (for example. depending on its function. by Jeff Doyle and Jennifer DeHaven Carroll (Volume II only) explain all the advanced concepts you could ever need. Summary link advertisements (ABRs) Summary link advertisements (ASBRs) Autonomous system (AS) external An LSA sent to a router that connects to the Internet. the routers residing in the backbone (area 0) are called backbone routers. Table 4-2. this section first goes over the link-state advertisement types and when to use them in an OSPF environment. A stub area is defined as an area that contains a single exit point from the area. for example. So. This LSA type sends out information into the autonomous system (AS) but outside of the area (interarea routes). OSPF does not actually send its routing table to other routers. The OSPF standard defines a number of LSAs types. An link advertisements advertisement sent from ABR to the ASBR. Ensure the neighboring router is in a state of adjacency.CCNP Practical Studies: Routing In Figure 4-1. Instead.) Step 3. Used on multiaccess networks. A backbone router connecting to another area can also be an ABR. An LSA is a packet used by such routing protocols as OSPF (that is. RIP). Before covering these new areas in detail. The interface cannot be connected to a totally stubby area. Each router. and a not-so-stubby area (NSSA). Step 2. 4.) For a detailed summary of OSPF and the packet types. . the Internet and redistribute external IP routing tables from such protocols as Border Gateway Protocol (BGP) are termed autonomous system boundary routers (ASBRs). and that is exactly what it means in OSPF. link-state routing protocols) to send information to neighboring routers describing networks and path costs. a totally stubby area. Areas that reside on the edge of the network with no exit point except one path can be termed a stub area. These are originated by the designated router (DR). Not-so-stubby areas (NSSA) An advertisement bound to an NSSA area. Originated by ABRs only. A stub in the English dictionary means a dead end. you can have a backbone router perform ASBR functions as well as ABR functions. Cisco IOS routers must first undergo the following: Step 1. These additional areas provide even more functionality in OSPF. The interface cannot be a stub area (LSA type 5. the Cisco Press titles Routing TCP/IP. for example. OSPF supports a number of LSA types as well as three other area types: a stub area. Originated by ASBRs describing IP networks external to the AS.101 - .

no adjacency is formed. Type 4 or 5 LSAs are not permitted. called the E bit. OSPF runs over the IP layer (also called the Network layer) of the Open System Interconnection (OSI) model. and not-so-stubby areas. otherwise. respectively. Those functions must be performed by ABRs or ASBRs. The only way to achieve a route to unknown destinations is. Additional Area Types Area Function Type Stub area This area does not accept LSA types 4 and 5. Typically used to provide a default route. thereby. total stubby areas. a bit. LSA Types and Area Restrictions Area NSSA Totally stubby Stub TIP All OSPF packets are sent using IP protocol port number 89. This advertisement will not be propagated to the rest of the network. and not-so-stubby areas in more detail. and 5.CCNP Practical Studies: Routing Table 4-3 summarizes the functions of these new areas. and 5) area does not allow external routes. totally stubby. Although similar to a stub area. This area is designed to allow LSAs of type 7 only. a type 7 LSA (if the P bit area is set to one) will be convert to a type 5 LSA and flooded throughout the rest of the network. Table 4-4. a default route injected by the ABR. a totally stubby area blocks LSAs of type 3 stubby as well. called stubby areas. All routers that form any OSPF neighbor relationship must have the E bit set to 0 as well.102 - . NOTE A stub area cannot be a transit for a virtual link. area Not-so. When a router is defined as a stub area. This solution is Cisco-proprietary and is used to further reduce a topological database. 4. 4. Table 4-4 summarizes the LSA types by area and indicates which LSAs are permitted or disallowed in certain areas.This area is used primarily for connections to an ISP. If the P bit is set to zero. in the Hello packet is set to 0. Take important note of the LSA type allowed or not allowed to fully appreciate the value of a stub area. Totally This area blocks LSA types 3. Basically. Nor is redistribution allowed. Table 4-3. Yes Yes Yes 1/2 LSA Type Permitted? 3/4 6 Yes No No No Yes No 7 Yes No No . no translation takes place. The scenarios that follow cover stub. Also a stub (does not permit LSA types 4 and 5) area or totally stubby (does not permit LSA types 3. This is a design limitation by the protocol itself. All stubby advertised routes can be flooded through the NSSA but are blocked by the ABR. which are summary links and external link advertisements. The only way to appreciate these new areas is to configure them and view the OSPF database.

1.109. do not carry the subnet mask when they send out updates.15. for example.0.0 to 131. Routing Information Protocol (RIPv1) and Interior Gateway Routing Protocol (IGRP). Example 4-1 displays R1's routing table. Figure 4-2 displays this two-router topology with the routers named R1 and R2. When an LSA packet or routing update is received or sent. Instead of populating R1's routing table with 15 IP route entries. there can be no support for VLSM. You configure OSPF in two ways to summarize networks using Cisco IOS routers: • • Interarea summarization creating type 3 or 4 LSAs External summarization with type 5 LSAs Consider an OSPF network containing two routers across an Ethernet segment. no other router can share the same router ID) Subnet mask Attached router Metric Because the subnet mask is carried along with the update.CCNP Practical Studies: Routing VLSM and Summarization with OSPF OSPF supports a number of features. you can use summarization. Without a mechanism that sends the subnet mask. Summarization occurs using the LSA type 4 packet or by the ASBR.109. Sample Network for OSPF Summarization Example R2 is sending R1 15 OSPF routes ranging from 131. OSPF can support VLSM.103 - . The two main features that interest most network designers are that it supports VLSM and provides the ability to summarize networks. . the packet includes the following information: • • • • • LSA type Router ID (unique IP address. Figure 4-2.

E1 routes add the total cost to destination. whereas E2 routes include only the cost to the external network.2.0 255.2.108.108. you can configure R2 to mask the networks by masking the first 15 networks with the IOS area area ID range address mask command. Ethernet0/0 O IA 131.109.0 [110/11] via 131.2.0 [110/11] via 131. External OSPF routes are routing entries in OSPF route tables injected by an external routing protocol. Ethernet0/0 O IA 131.2. Intra-area routes are indicated by O.2.108.109.0. 00:00:58.2.0 [110/11] via 131.109. 14 subnets O IA 131.2. 00:00:48. 00:00:48. R2 can perform interarea summarization.2.109. 00:00:58. you can summarize a simple network with 15 IP networks by using 1 IP routing entry.1.2. 00:00:58.4. 00:02:54. 00:00:58.0 Example 4-3 displays R1's routing table now.0 [110/11] via 131.108. such as BGP or IGRP. hence.108.109. Ethernet0/0 O IA 131.2.109.109.2.0 [110/11] via 131. Example 4-2 Summary of R2 R2(config)#router ospf 1 R2(config-router)#area 1 range 131.255. Ethernet0/0 O IA 131.2.2.CCNP Practical Studies: Routing Example 4-1 R1's OSPF Routing Table R1>show ip route ospf 131. Remember that previously there were 15 IP routing entries. Ethernet0/0 O IA 131. Ethernet0/0 The remote networks are indicated by O IA.109.108. Ethernet0/0 O IA 131. 00:00:58.10.108. indicated by Cisco IOS as O E2. .2.0 [110/11] via 131.2.108.2.2.13. Ethernet0/0 O IA 131.0 [110/11] via 131. and external type 2 routes. 00:00:48.109. you can also externally summarize IP routes by using the summary ip-address mask command. 00:02:33.2. Ethernet0/0 O IA 131. NOTE Two more types of OSPF routes exist: external type 1 routes. In OSPF. Ethernet0/0 O IA 131.109. Example 4-1 displays an IP routing table telling you that R2 is in area 0 and another area (ABR). 1 subnets O IA 131.0 [110/11] via 131.2.108. 00:00:00.0 [110/11] via 131.104 - . Because the networks 1 to 15 are contiguous. When calculating the cost to a remote network.0/20 is subnetted.109.2.109.109.14.2. Ethernet0/0 O IA 131.109. Example 4-2 displays the summary applied to R2 under the OSPF router process ID of 1.2.5.2.2.2. 00:00:58.109. Ethernet0/0 O IA 131. indicated by Cisco IOS as O E1.12. which indicates interarea routes.9.108.2.2.109.0.3.6.0 [110/11] via 131.0 [110/11] via 131. Ethernet0/0 O IA 131. 00:01:08.0 [110/11] via 131.109.240.0/24 is subnetted. Ethernet0/0 R1# By using OSPF summarization techniques.2.108.108. OSPF summarization examples are included among the five scenarios in this chapter.0 [110/11] via 131.8.108.0.11.108. Example 4-3 OSPF Route Table on R1 After Summarization R1#sh ip route ospf 131.109. 00:00:58.2.2.108.0 [110/11] via 131.0 [110/11] via 131.0.15. Ethernet0/0 O IA 131.0 [110/11] via 131.109. Ethernet0/0 O IA 131.2.108.7.2. 00:00:58.2. 00:00:48.

which are each in only one area.105 - . the following commands and steps are required to configure OSPF in a multiarea OSPF Network: The network command enables OSPF across interfaces. which could only route IP) at the same time: one for IP and another for Decnet Phase V. Next. and the edge routers R3 and R4. IS-IS was designed to provide two routing mechanisms (in competition with OSPF forum. Routers R1 and R2 are Level 1/Level 2 (L1/L2) routers. . because all remote or edge sites need to transit the NBMA network. you need to be familiar with some new terms and definitions to fully understand IS-IS. Routers that connect areas are called L2 routers. As with any new protocol. IS-IS has routers perform Level 1 (L1) and Level 2 (L2) functions. in a large NBMA environment. Routers that have no direct connectivity to any other area are called L1 routers. This chapter covers integrated IS-IS IP routing capabilities only. Any stubby configurations to reduce memory and CPU requirements. are L2 routers. The same commands that applied in Chapter 3 are used in large NBMA environments. To summarize the command set used in large NBMA environments. IS-IS is a common routing protocol typically used in large ISP environments. the backbone (area 0) assignment encompasses the NBMA connections themselves. Any command that manipulates the OSPF cost metrics for equal costs path load balancing. Typically. this chapter describes another common link-state routing protocol used in large IP routing environments. Any virtual links that may be required. Both L1 and L2 routers maintain link-state databases. In Figure 4-3. namely Intermediate System-to-Intermediate System (IS-IS). In brief. An L1 router performs the functions similar to those an OSPF internal router performs. Even so. IS-IS was developed at the same time OSPF was being developed. A L1/L2 router performs similar functions to an ABR in OSPF. Integrated Intermediate System-to-Intermediate System Integrated IS-IS is a link-state routing protocol.CCNP Practical Studies: Routing OSPF over Multiarea NBMA OSPF over a multiple-area NBMA network presents some challenges to a network designer as you discovered in Chapter 3. Instead of using areas as OSPF does. Summarization enables networks to reduce IP routing table sizes by using area range on ABRs and the summary address subnet mask command for an ASBR. but few people consider it an alternative to OSPF.

IS-IS has many similarities to OSPF. IS-IS uses hello packets to form neighbor relations with other IS-IS enabled routers.106 - . such as a PC.CCNP Practical Studies: Routing Figure 4-3. You start by building an OSPF network and then use the methods described in this chapter to help reduce the size of IP routing tables. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs. IS-IS uses areas to form a hierarchy. including the following characteristics: • • • • • • IS-IS maintains a link-state database. There is no one right way to accomplish many of the tasks presented. and using good practice and defining your end goal are important in any real-life design or solution. IS-IS supports VLSM. IS-ES is the protocol—Connectionless Network Protocol (CLNP)—between an end system. IS-IS on broadcast networks elects a designated router (DR). To configure IS-IS on a Cisco IOS router. such as hello interfaces. . Configure any IS-IS interface parameters. IS-IS Terminology Diagram NOTE IS-IS is the protocol between two IS-IS-enabled routers. you must perform the following configurations and tasks: • • • Enable IS-IS with the command router isis. Configure area parameters. and enable IS-IS to send out updates from an interface. IS-IS support routing authentication mechanisms. and an IS-IS enabled router.

108.0/24 131.108.108. Assume all IP traffic is between the edge. you configure several loopback address assignments on R1 and R2. or access.108.34–35/32 131. routers and the backbone network in area 0.0–31/32 131.108.108.108.0 Area 0 0 0 0 10 10 10 11 30-bit subnet masks applied to all WAN links 0 To start OSPF on the eight routers.255. Typically in an environment like this. you configure an eight-router.108. or printers) reside in the backbone and the end users are connected to the remote sites. . three-area network with OSPF.130.129. the hosts (devices. To send and receive LSAs per interface.16.128.107 - . use the same process ID of 1 on all routers. Table 4-5.0/24 131. In this scenario. large computer hosts.0/24 131. Figure 4-4. and remember that the process ID is locally significant only.36. use the network command.32–33/32 131.108. Table 4-5 displays the IP address assignment used in Figure 4-4.108.0–15/32 131. To simulate a large network environment. Figure 4-4 displays the OSPF topology and area assignment.0/24 131. such as mainframes.2. you must first enable the OSPF process by using the command router ospf process ID. OSPF Topology and Area Assignment This scenario represents a typical OSPF network with semi-redundancy and a hierarchical address assignment.131.CCNP Practical Studies: Routing Scenario 4-1: Configuring OSPF with Multiple Areas In this scenario.0 131. IP Address and Area Assignments Router R1 R2 R3 R4 R5 R6 R7 R8 WAN links LAN link between R3 and R4 IP Address Range 131.

11.0/24 is directly connected.0/24 [110/11] via 131.22.2. Ethernet0/0 O 131.108. Serial0/0 .1.0.16/30 [110/855] via 131.0/24 [110/11] via 131. 00:12:47. Loopback10 C 131.12/30 [110/128] via 131.108.131.108 - .108. Ethernet0/0 O 131. with the IP subnet 131.255. Ethernet0/0 O 131.108.108. Before you can configure a virtual link.108.108.2.255.108. Area 11 is partitioned from the backbone and hence requires a virtual link so that all OSPF routers have a routing entry for the subnet 131. Loopback3 C 131.108. 00:12:47. Serial0/0 O IA 131.255. 00:12:47. of course.1.108. Loopback5 C 131.1.8.108. Because the cost is lower through the Ethernet LAN segment. and R7 are listed in Example 4-4.20. Loopback1 C 131.0/24 [110/11] via 131. 00:05:29. The three remote networks on the access Routers R5.108.108.108. 00:00:18.3.1.0/24 [110/11] via 131.To R6 O IA 131.To R5 O IA 131. Loopback0 C 131.13. Configure a virtual link between R4 and R8.0/24 is directly connected. 00:17:10. 00:09:16. 00:12:47.20/30 [110/855] via 131. 00:08:21.2.108. Loopback9 C 131.108.0/24 is directly connected. The show ip ospf database command displays the local router ID.2.108. R1 chooses the path to R2 as the preferred path.108. Ethernet0/0 O 131. Ethernet0/0 O 131.OSPF external type 2.2.24.108. Serial0/0 . 00:12:47.108.0/24 is directly connected.131. but the network on R8 is not.0/24 [110/11] via 131.0/24 is directly connected.4. Loopback13 C 131. Loopback12 C 131. Serial0/0 O 131.108.2.108.0/24 is directly connected. 00:10:15. 00:12:47.0/24 is directly connected.108.18. There is. 00:12:47.0/24 [110/11] via 131.108.2.2.2.0/24 [110/11] via 131.108.108. 39 subnets. Example 4-4 R1 Routing Table R1#show ip route Codes: C .108.19.108.26.108.23.108.108.2.108.255.25.CCNP Practical Studies: Routing From Figure 4-4. Ethernet0/0 O 131.108. 00:17:10.108.0/24 [110/138] via 131.12. Loopback6 C 131.108.108.0/24 is directly connected.9.14.108.108. 00:07:51. resides in area 11.15.108.27.2.1. Ethernet0/0 O 131.OSPF.2.108.OSPF inter area N1 . Loopback8 C 131.4/30 [110/791] via 131.1.0/24 [110/865] via 131.108.255.36. E2 . Ethernet0/0 .108.0/24 [110/138] via 131.0/24 [110/11] via 131. 00:12:47.8/30 [110/128] via 131. Ethernet0/0 O 131. R6.2. 00:12:47.108. 00:07:02.108.255. 131.0/16 is variably subnetted. Loopback2 C 131.108.0/24 [110/11] via 131.108.30.129.108.2.2. 00:12:47.0/24 is directly connected.2.0/24 [110/11] via 131.1.108. Loopback11 C 131.1.7. Example 4-4 displays the IP routing table on R1 after OSPF has been configured on all the routers in this network.OSPF NSSA external type 1. O . Ethernet0/0 O 131.108.16.0/30 is directly connected.1.2.2.108.2.255.0/24 is directly connected.108.1.0/24 [110/11] via 131. Ethernet0/0 O IA 131.29. which is R2.0/24 [110/11] via 131.108.128. you must know the router ID on R4 and R8.5.1.28. Ethernet0/0 O 131.108. Ethernet0/0 O 131.0/24 [110/11] via 131.1. 00:17:10.108. Ethernet0/0 O 131. Ethernet0/0 O 131.2.108. Ethernet0/0 C 131.108.2. Ethernet0/0 Example 4-4 displays the remote routers learned through Ethernet interface and the next hop address of 131.0/24.17.255.255. Ethernet0/0 O 131. another path on R1 through the serial link to R2. which is typically a loopback address or the highest IP address assignment.0/24 [110/11] via 131. 2 masks O IA 131.108.10.108. Serial0/0 O IA 131.1. Ethernet0/0 O 131.108.1.0/24 is directly connected.0/24. 00:12:47.2.6. Ethernet0/0 O 131.108. IA .108.108.1.255.0/24 [110/11] via 131. Ethernet0/0 O 131.0/24 is directly connected.1.108.1.0/24 [110/11] via 131. N2 .108. Loopback4 C 131.108.OSPF external type 1.21.2.To R7 C 131.OSPF NSSA external type 2 E1 .1.108.31.1.0/24 is directly connected.108.1. 00:12:44.108.0/24 [110/11] via 131. Ethernet0/0 O IA 131.1.2. Loopbacks are .0/24 is directly connected. 00:12:47. Loopback7 C 131.2. 00:17:10.130.2.1. 00:12:47.108.1.0/24 is directly connected.2.connected.108. the remote network on Router R8.

255.2.26. Serial0/0 O IA 131.108. Ethernet0/0 O 131.108.108. To configure a virtual link. 00:00:48.2. 00:00:47.1. 00:00:47.255.2. 00:00:48.108.2.0 because of the virtual link configuration. Ethernet0/0 O 131.D ID (IP addr) associated with virtual link neighbor R8(config-router)#area 10 virtual-link 131. 00:00:48.B.28.108.0/24 [110/11] via 131.108.0/24 [110/11] via 131.0/24 [110/11] via 131.20/30 [110/855] via 131.0/24 [110/11] via 131.8/30 [110/128] via 131.108.108. Ethernet0/0 O 131.22.108.2.1.108.2.2. Ethernet0/0 O 131.108.108.108.21.108.255.255.2. R1.108.108.108. A router ID that is a physical interface is prone to network failure and OSPF recalculations.131.255.1.1.255.108.1.0/24 [110/138] via 131. Example 4-7 Virtual Link Configuration and Options on R8 R8(config-router)#area 10 ? authentication Enable authentication default-cost Set the summary default-cost of a NSSA/stub area nssa Specify a NSSA area range Summarize routes matching address/mask (border routers only) stub Specify a stub area virtual-link Define a virtual link and its parameters R8(config-router)#area 10 virtual-link ? A.2. Ethernet0/0 O IA 131. Ethernet0/0 O 131.1. Ethernet0/0 O 131.12/30 [110/128] via 131.255. Ethernet0/0 O 131.108.CCNP Practical Studies: Routing always preferred because a loopback interface is logically never going to become unavailable unless the network administrator removes it. Ethernet0/0 O 131.108.108. 00:00:48. 00:00:48.1. 00:00:48.2. 00:00:47.108.108. along with the remote network 131. Example 4-6 Virtual Link Configuration on R4 R4(config-router)#router ospf 1 R4(config-router)#area 10 virtual-link 131. and the router ID is the IP address of the remote router.2.2.16/30 [110/855] via 131.22 Example 4-7 displays the virtual link configuration on R8 along with the IOS ? command to display the available options. Serial0/0 O IA 131.128.0/24 [110/11] via 131.108. 2 masks O IA 131.0/24 [110/11] via 131.130.255.2. 00:00:48. 00:00:48.108.108.1.C.108.255.2. Example 4-5 displays the router ID on Routers R4 and R8.108.1.108. 00:00:47.1.255.0/16 is variably subnetted.2. 00:00:48.1.108.1.108.27. Serial0/0 O 131. Ethernet0/0 O IA 131.24.2. 00:00:47.29.255.23. 00:00:48.6 Example 4-8 displays the IP routing table on the core router.2.0/24 [110/865] via 131.0/24 [110/865] via 131. Ethernet0/0 O IA 131.0/24 [110/11] via 131.6) (Process ID 1) R8#show ip ospf database OSPF Router with ID (131.0/24 [110/11] via 131.255.0/24 [110/138] via 131.2.4/30 [110/791] via 131. Ethernet0/0 O 131.0/24 [110/11] via 131. 00:00:48.129.108.0. 00:00:48.22) (Process ID 1) Example 4-6 displays the virtual link configuration on R4.1.108.2.0/24 [110/11] via 131.108.1. Ethernet0/0 O 131.108. 00:00:48. 00:00:48.108. Ethernet0/0 .108. Example 4-8 show ip router ospf Command on R1 R1#show ip route ospf 131. 41 subnets.1. 00:00:47.131.31. Serial0/0 O IA 131.108. which lead to network downtimes.1.108.108.108. Example 4-5 Router ID on R4 and R8 R4#show ip ospf database OSPF Router with ID (131. Ethernet0/0 O IA 131.255.2.108. The transit area in this example is area 10.30. Ethernet0/0 O 131.0/24 [110/11] via 131.108.108.108.108.25.109 - . use the IOS command area transit area router-id.

00:00:50. 00:00:49.1 255. Pay particular attention to the shaded sections and the router functions within the OSPF network.255.255.108.0/24 131.1 255.2. 131.1.108.19.0 ip ospf network point-to-point ! interface Loopback3 ip address 131. 00:17:10.0/24 131.255. 00:00:50.1.108.20. number of retransmission 1 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 1. R1 is a backbone router.255.0 ip ospf network point-to-point ! interface Loopback4 . Transit area 10.0 ip ospf network point-to-point ! interface Loopback1 ip address 131. The routing table. Timer intervals configured.255. 131.1. use the show ip ospf virtual-links command. has over 20 IP route entries.255. Example 4-9 show ip ospf virtual-links on R4 R4#sh ip ospf virtual-links Virtual Link OSPF_VL0 to router 131.108. 131.2. 00:00:50.CCNP Practical Studies: Routing O O O O O O 131.16.108. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 To view the status of the virtual link.1.255. 00:00:49.0/24 131. even with only eight routers. Cost of using 64 Transmit Delay is 1 sec. retransmission queue length 0.108.108.5. look at the full working configurations on all routers.36.108.2.0/24 131.22 is up Run as demand circuit DoNotAge LSA allowed. Wait 40.17.2.0 ip ospf network point-to-point ! interface Loopback2 ip address 131.1.0/24 [110/11] [110/11] [110/11] [110/11] [110/11] [110/11] via via via via via via 131.255. Retransmit 5 Hello due in 00:00:09 Adjacency State FULL (Hello suppressed) Index 2/4. Before using summarization on this network to reduce the IP routing table size.108.110 - .2.108.108. Dead 40.3.2.108.108. Also note how the clockrate command is used to enable back-to-back serial high-level data link control (HDLC) connections among Cisco routers.108.1 255. 131. maximum is 1 Last retransmission scan time is 0 msec.2.108. Example 4-9 displays sample output from this command used on R4. Hello 10. maximum is 0 msec You have successfully configured a complex network with eight Cisco routers in multiple areas.18.1 255. via interface Serial2.255. Example 4-10 R1's Full Configuration hostname R1 ! logging buffered 64000 debugging enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.4.0/24 131. 131.108. State POINT_TO_POINT. Example 4-10 displays R1's full working configuration.1.

255.0 ip ospf network point-to-point ! interface Loopback7 ip address 131.255.0 ip ospf network point-to-point ! interface Loopback11 ip address 131.1 255.108.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 131.111 - .6.108.8.15.255.255.108.13.1 255.255.108.108.255.255.255.1 255.0 ip ospf network point-to-point ! interface Loopback13 ip address 131. .255.255.255.1 255.255.252 clockrate 125000 ! interface Serial0/1 shutdown ! router ospf 1 network 131.14.255.1 255.108.255.1 255.255.0 0.255.0 ! interface Serial0/0 ip address 131.7.108.12.108.0 ip ospf network point-to-point ! interface Loopback5 ip address 131.108.1.1 255.CCNP Practical Studies: Routing ip address 131.1 255.0 ip ospf network point-to-point ! interface Loopback8 ip address 131.108.1 255.255.0 ip ospf network point-to-point ! interface Loopback12 ip address 131.108.255.255.9.10.108.108.255.255.255.255 area 0 ! line con 0 line aux 0 line vty 0 4 end Example 4-11 displays R2's full working configuration.1 255.11.255.0.1 255.0 ip ospf network point-to-point ! interface Loopback10 ip address 131.1 255.255.255.0.0 ip ospf network point-to-point ! interface Loopback9 ip address 131.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 131.

0 ip ospf network point-to-point ! interface Loopback7 ip address 131.255.1 255.1 255.28.255.1 255.255.108.108.0 ip ospf network point-to-point ! interface Loopback2 ip address 131.1 255.25.255.0 ip ospf network point-to-point ! interface Loopback4 ip address 131.0 ip ospf network point-to-point ! interface Loopback9 ip address 131.108.255.255.1 255.19.255.108.1 255.1 255.0 ip ospf network point-to-point ! interface Loopback11 ip address 131.108.108.255.1 255.255.0 ip ospf network point-to-point ! interface Loopback1 ip address 131.26.255.22.0 ip ospf network point-to-point ! interface Loopback3 ip address 131.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 131.255.255.108.255.1 255.0 ip ospf network point-to-point ! interface Loopback13 ip address 131.0 ip ospf network point-to-point ! interface Loopback8 ip address 131.27.255.CCNP Practical Studies: Routing Example 4-11 R2's Full Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.255.1 255.255.24.0 ip ospf network point-to-point ! .21.255.0 ip ospf network point-to-point ! interface Loopback5 ip address 131.108.1 255.255.108.1 255.108.17.255.255.108.108.0 ip ospf network point-to-point ! interface Loopback10 ip address 131.255.20.1 255.255.23.18.16.255.255.255.112 - .

30.36.108.252 ! interface Serial1 ip address 131.255.108.108.0.0 ! interface Serial0 ip address 131.255.255.255.2 255.0 0.0 ip ospf network point-to-point ! interface Loopback15 ip address 131.3 255.0 ip ospf network point-to-point ! interface Loopback16 ip address 131.255.CCNP Practical Studies: Routing interface Loopback14 ip address 131.255.1 255.108.255.252 clockrate 128000 ! interface Serial2 .255.255.252 clockrate 128000 ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 1 network 131.255.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 131.255.255 area 0 ! ip classless ! line con 0 line aux 0 line vty 0 4 ! end Example 4-12 displays R3's full working configuration.31.0 ! interface Serial1/0 ip address 131.108.5 255.1.108.1 255.2 255.255.255.255.255.108. Example 4-12 R3's Full Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.113 - .108.0.108.255.9 255.255.255.255.255. R3 is an ABR.1 255.29.

0 0.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-14 displays R5's full working configuration.12 0.108.0.255 area 10 network 131.0.36. R5 is an internal OSPF area.108.4 255.255.0.255.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-13 displays R4's full working configuration.108.CCNP Practical Studies: Routing ip address 131.252 clockrate 128000 ! interface Serial2 ip address 131.252 clockrate 128000 ! interface Serial3 shutdown ! router ospf 1 area 10 virtual-link 131.8 0. R4 is an ABR.255.13 255.255.255.108.0 0.3 area 0 network 131.108.3 area 10 network 131.0.36.0.252 clockrate 128000 ! interface Serial3 shutdown ! router ospf 1 network 131.108.255.20 0.0.255. .108.255.255.108.108.255.255.252 ! interface Serial1 ip address 131.22 network 131.255.3 area 10 network 131.0.6 255.0.108.255.108.0.255.108.0 ! interface Serial0 ip address 131.255.255 area 10 network 131.0 0.21 255.0.255.0.16 0.255. Example 4-13 R4's Full Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet 0 ip address 131.0.0.0.255.108.0.255.36.3 area 0 network 131.17 255.114 - .255.108.4 0.255.0.

255.1 255. Example 4-15 R6's Full Configuration hostname R6 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 131.CCNP Practical Studies: Routing Example 4-14 R5's Full Configuration hostname R5 ! enable password cisco ! interface Ethernet0 ip address 131.255.0.0 ! interface Serial0 ip address 131.115 - .108.1 255.255.108.255.255.129.0. R6 is an internal OSPF router.8 0.108.252 ! interface Serial1 shutdown ! router ospf 1 network 131.0.255.0 ! interface Serial0 ip address 131.255.16 0.255.0 0.255 area 10 network 131.255.0.10 255.0.0 0.18 255.129.0. R7 is an internal OSPF area.108.0.3 area 10 ! line con 0 line aux 0 line vty 0 4 end Example 4-15 displays R6's full working configuration.255 area 10 network 131.108.252 interface Serial1 shutdown ! router ospf 1 network 131.255.108.0.128.128.108.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-16 displays R7's full working configuration. Example 4-16 R7's Full Configuration hostname R7 ! enable password cisco ! ip subnet-zero no ip domain-lookup .108.255.255.

1 255. requiring a virtual link because area 11 is not connected to area 0.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Scenario 4-2: Configuring OSPF Summarization This scenario covers the same network topology shown in Figure 4-4. R2.108. The access-level routers.14 255.0 0.31. Example 4-17 R8's Full Configuration hostname R8 enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131. R5. R8 is an internal OSPF area. For the core routers in area 0.0 interface Serial0 ip address 131.255.108. The first method you can apply is intra-area summarization on the backbone Routers R1 and R2.255. This detail is required so you do not perform any summarization on the core network and maintain a full IP routing topology in the core (or backbone) network. do not typically require an IP routing entry for every network in the core because they require access to only the core network in area 0.108.108.1 255.108.255. R7. OSPF.255 area 10 network 131. Therefore.255.0.131. The aim of any network designer is to use summarization wherever possible.1.CCNP Practical Studies: Routing interface Ethernet0 ip address 131. the backbone.130.108.0 to 131.0.130. and R8. you need to have a more detailed view of the network.12 0. which pass on routing information to other core or remote routers.255.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-17 displays R8's full working configuration.252 ! interface Serial1 shutdown ! router ospf 1 network 131.255 area 11 network 131.6 network 131. R6.0 0. R3. and R4.255.255.255.108.108.108.255.108.255.22 255.20 0. these routers are perfect examples of how you can use .255.255.255. as you have seen.0.0.0.252 interface Serial1 shutdown ! router ospf 1 area 10 virtual-link 131.255. namely R1. has some advanced features to allow summarization.0.0.0.108.131.116 - .0 ! interface Serial0 ip address 131. A total of 30 networks (contiguous) exist from 131.

108. 04:14:52.9.255.255. so you can configure stubby networks.255.108. Serial0 O IA 131.9. Serial0 O IA 131.255.108. 03:51:35. Serial0 O IA 131. 04:14:53.130.108.9.9.108. 03:51:15.1. Serial0 O IA 131. 04:14:52.0/24 [110/139] via 131. 04:14:51. Serial0 O IA 131.OSPF inter area N1 .19.108.255.255.108.255. 04:14:53.20/30 [110/983] via 131.108.108. 04:14:52.108.108.255.0/24 [110/129] via 131.108.OSPF NSSA external type 1. Serial0 O 131.0/24 [110/11] via 131. Serial0 O IA 131.255. 04:14:53.108.108.108. 03:51:04.9.108.9.0/24 [110/129] via 131.108. 03:51:25.8/30 is directly connected.9. use some summary commands. Serial0 O IA 131. 04:14:53.9.0/24 [110/129] via 131.255.255.1. 04:14:53.0/24 [110/129] via 131. Serial0 O 131. Serial0 O IA 131.108.108.108. Serial0 C 131.0.6.108.108. 04:14:52. Example 4-18 R5's Current IP Routing Table R5#show ip route Codes: C . 03:51:25.OSPF external type 1.108.108.9.255.108.255. Serial0 O IA 131.26.108.9.108.0/24 [110/129] via 131.0/24 [110/139] via 131. 04:14:50.108. Only a single exit point to the core of the network exists.108.255. 04:14:51.108.9.108. Serial0 O IA 131.108. 03:51:14.18.9.0/24 [110/138] via 131. 03:51:25.108. 04:14:53.108.9. 04:14:53.108. Serial0 O IA 131.9.OSPF NSSA external type 2 E1 .9.4/30 [110/919] via 131.255.255.108. Serial0 O IA 131. 04:14:52. 03:51:25.108.255.255.9. 03:51:25.0/24 [110/138] via 131.108.108.25.0/24 [110/993] via 131.108.108.12.9.255. 03:51:14.0/24 [110/139] via 131.255.connected.117 - .255. Serial0 C 131.108.9.108. 03:51:25.108. Serial0 O IA 131.255.108.108.0/24 [110/129] via 131.108.9.0 to 131.255. 2 masks O IA 131.EGP 131. Serial0 O IA 131.0/24 [110/139] via 131. Serial0 O IA 131. Serial0 O IA 131. 04:14:50.3.2.108. Example 4-19 displays the use of the IOS area area ID range mask command on R3.108.108. 04:14:51.128.0/24 [110/129] via 131.255. 41 subnets.255.0/30 [110/128] via 131. Example 4-18 displays R5's IP routing table.108.31.9.0/24 [110/129] via 131. O .255.16.255. Serial0 O IA 131.0/24 [110/139] via 131.108.13.255.8.9. 03:51:14.108.0/24 [110/129] via 131.OSPF external type 2.108.0/24 [110/139] via 131.255.108.0/24 [110/129] via 131. 04:14:53.108.108. E2 .108. E .9.21.108.255.255.108.0/24 [110/139] via 131.31.108.11.9. 04:14:51.9.5.108.9. Serial0 O IA 131.24.255.255. N2 .7. Serial0 O IA 131. Serial0 O IA 131.10.0/24 [110/129] via 131.16/30 [110/983] via 131.29.255. Serial0 O IA 131.108.255. .108. First.OSPF.9.108.108. Serial0 O IA 131.108.255. Serial0 Use OSPF summarization for the core IP networks ranging from 131.108.9.0/24 [110/139] via 131.108.108.255.9.15. Serial0 O IA 131.9.108. Serial0 O IA 131.108.23. Serial0 O IA 131.255.255.129.9. Serial0 O IA 131.20.9. Serial0 O IA 131.255.9.0/24 [110/129] via 131.0/24 [110/139] via 131.0/24 [110/139] via 131.108. 04:14:53. 04:14:52.255. 04:14:52.255. Serial0 O IA 131.0/24 [110/139] via 131.0/24 [110/139] via 131.28.4. Serial0 O 131.0/16 is variably subnetted.255. Serial0 O IA 131.108.0/24 [110/139] via 131. IA .108. 04:05:58. Serial0 O IA 131. Ethernet0 O IA 131.9.108.30.255 on Routers R3 and R4. Serial0 O IA 131. 04:14:53.36. Serial0 O IA 131.131. 03:51:04.0/24 [110/139] via 131.9.9.0/24 is directly connected.27.108.0/24 [110/129] via 131.CCNP Practical Studies: Routing summarization to reduce the size of routing tables.22.12/30 [110/128] via 131.108.14. 04:14:51.0/24 [110/139] via 131.9.255. Serial0 O IA 131.9. 03:51:14.255. Serial0 O IA 131.9.108. 04:14:53.9. Serial0 O IA 131.108.0/24 [110/993] via 131.108.9.0/24 [110/139] via 131.108.108.0/24 [110/129] via 131.108.108.17.9.255.

0/19 [110/129] via 131. 3 masks O IA 131.0 View the IP routing table on R5.9.OSPF NSSA external type 2 E1 .OSPF external type 2 131. Serial0 O IA 131.108.108.255.130.108.0 255.108. Example 4-20 Summary on R4 R4(config)#router ospf 1 R4(config-router)#area 0 range 131. 00:46:25.CCNP Practical Studies: Routing Example 4-19 Summary on R3 R3(config)#router ospf 1 R3(config-router)#area 0 ? authentication Enable authentication default-cost Set the summary default-cost of a NSSA/stub area nssa Specify a NSSA area range Summarize routes matching address/mask (border routers only) stub Specify a stub area virtual-link Define a virtual link and its parameters R3(config-router)#area 0 range 131.255.0. hence. round-trip min/avg/max R5#ping 131.255.2.1. 05:14:53. Serial0 O IA 131.129.108.108. Also displayed in Example 4-21 are a few ping requests to IP networks covered in the summary range 131.224.108. 100-byte ICMP Echos to 131. Serial0 O IA 131.OSPF inter area N1 .connected.255.9.0 ? A.255. Serial0 C 131.1 Type escape sequence to abort. Serial0 O IA 131.108.1. 100-byte ICMP Echos to 131. 05:09:00. which are networks covering the range 131. Serial0 C 131.131. IA .108. 05:09:00.36.9.255.0/30 [110/128] via 131.0/24 [110/993] via 131.128. Example 4-20 displays the OSPF summary on R4.255.OSPF.OSPF external type 1.255.224.2.0 255. Routers R3 and R4 are ABRs.108.1 Type escape sequence to abort.1.1. Sending 5.108.108.255. Serial0 O 131.108.108. 11 subnets.108.255.1.0/24 is directly connected. Serial0 O IA 131. timeout is !!!!! (R1 Ethernet e0/0 address) Success rate is 100 percent (5/5).108.108.0.108.108.16/30 [110/983] via 131. 05:09:00.1.9. E2 .108. N2 . Example 4-21 displays R5's routing table after network summarization is configured on R3 and R4.108.255. Sending 5. timeout is !!!!! Success rate is 100 percent (5/5).0 to 131.0/24 [110/138] via 131.108. Serial0 O 131.255. O . 05:09:00.255. Ethernet0 O IA 131.255.108. 100-byte ICMP Echos to 131.108. you can perform network summarization on R3 and R4.1.9.108.0/19.255. round-trip min/avg/max R5#ping 131.B. timeout is 2 seconds: = 32/32/32 ms 2 seconds: = 28/31/32 ms 2 seconds: .3.9.108. Serial0 O 131.0. 05:09:01.0/24 [110/11] via 131.9. 05:09:00.255. Sending 5. Example 4-21 Summary on R5 R5#show ip route Codes: C .8/30 is directly connected.108.255.118 - .108.108. 05:00:08.108. Serial0 R5#ping 131.108.9.9.1 Type escape sequence to abort.4/30 [110/919] via 131.0.0. 05:09:00.255.255.0/24 [110/993] via 131.12/30 [110/128] via 131.C.9.0/16 is variably subnetted.OSPF NSSA external type 1.31.3.108.108.108.D IP mask for address R3(config-router)#area 0 range 131.108.0 The IOS tells you only ABRs can perform OSPF summarization.20/30 [110/983] via 131.

1. you can configure a stub network. use the area area id stub command.31. and R8. round-trip min/avg/max = 32/32/32 ms R5#ping 131.1 Type escape sequence to abort. You cannot configure a stub network on R8 because you have a virtual link. Sending 5. Figure 4-5 displays the change of area assignments to remove the necessity of a virtual link between R8 and R4. Example 4-22 displays the stub configuration on R3.108. The same occurs on Routers R6. Create a stub network between Routers R3 (the ABR) and R5. round-trip min/avg/max = 32/32/36 ms By using a simple command on the ABRs. configure the following commands on R8: . Example 4-23 Configuring a Stub Area R4(config)#router ospf 1 R4(config-router)#area 10 stub % OSPF: Area cannot be a stub as it contains a virtual link R4(config-router)# You cannot create a stub between R4 and R8 because of the virtual link.108.31. Cisco's IOS displays the message in Example 4-23. you have significantly reduced the IP routing table size on R5 to nine remote OSPF entries. Also because R5 and R7 have single exit points to the core. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). R7. So.119 - . 100-byte ICMP Echos to 131.CCNP Practical Studies: Routing !!!!! Success rate is 100 percent (5/5). To create a stub network. change the area assignments on R8 to area 10 so you can create a stub. Example 4-22 Stub Configuration on R3 R3(config)#router ospf 1 R3(config-router)#area 10 stub If you attempt to configure a stub network on R4. To change the area assignment on R8 from 11 to 10.

0 0. .255 area 10 Because a change has been made to OSPF area assignment.255. the neighboring router must also be configured as a stub.0 0.CCNP Practical Studies: Routing Figure 4-5. view the IP routing table on R5.0.108. R5 has not yet been configured as a stub. Example 4-24 displays R5's OSPF neighbor state after you configure the ABR R3 as a stub network in area 10.255 area 11 network 131. and in this case.255.0.108. Example 4-24 show ip ospf neighbor Command on R5 R5#show ip ospf neighbor Neighbor ID 131.108.108.0.0. Example 4-26 displays the new IP routing table after the stub configuration is completed on both Routers R3 and R5. Example 4-25 Stub Configuration on R5 R5(config)#router ospf 1 R5(config-router)#area 10 stub R5#sh ip ospf neighbor Neighbor ID 131.9 Interface Serial0 Now. you must ensure that OSPF is still active on R5.13 Pri 1 State DOWN/ Dead Time Address 131.255.9 Interface Serial0 The OSPF relationship between R3 and R5 is down because if one router is configured as a stub.108.131. Example 4-25 displays the configuration of a stub network on R5 and the OSPF relationship change to full adjacency.120 - .255. OSPF Sample Network After R8 Area Change no network 131.13 Pri 1 State FULL/ Dead Time 00:00:38 Address 131.131.108.

Serial0 O IA 131. you can assume that all IP traffic from the edge routers is destined for the core network. it provides a default route. Serial0 O IA 131.9.255. All IP traffic is destined for the core anyway.0 131.0/24 is directly connected.129. you can configure OSPF to stop the entries labeled as O IA (interarea routes) from populating the edge routers by configuring a stubby network with the no-summary option by applying the IOS area area id stub no-summary command. Serial0 O IA 131.108. so there is no reason for R5 or R6 to have network entries for every individual IP route in the core.0/24 [110/128] via 131. View the IP routing table on R5 in Example 4-29 and compare it to Example 4-26.0/24 [110/993] via 131.108.108. 00:01:22.108.131.108.36.9.255. You have a gateway of last resort. Example 4-27 displays the configuration of the core router.9.0/24 [110/993] via 131.108.9.4/30 [110/919] via 131.0/24 [110/11] via 131.0/16 is variably subnetted.255. Configuring a stub network performs exactly this function.0.9.255.108.108. 10 subnets.20/30 [110/983] via 131. 3 masks O IA 131.12/30 [110/128] via 131.0. R3.9. Serial0 O 131.255.0 through the next hop address 131. To ensure OSPF full adjacency is achieved between R3.108.108.108.255.108. 00:01:23. Now. Example 4-28 displays the no-summary option configured on R5. Serial0 O*IA 0.255. To further reduce the IP routing table.108.108.8/30 is directly connected.9.255. 00:01:22. area 10 in this case.108. 00:01:23.108.255.255.0/19 [110/129] via 131.255. This option prevents the ABR from sending summary link advertisements from other areas except the area that connects R5.0. 00:01:22.108.131. . Example 4-27 Preventing Summary LSAs from Other Areas R3(config)#router ospf 1 R3(config-router)#area 10 stub no-summary You also complete the area 10 stub no-summary on the remaining routers. you must configure both the core and edge routers. Serial0 You now have on R5 a default route labeled 0.9 to network 0.0.108. and R8. Serial0 O 131.255.0.255.255.108.0/30 [110/128] via 131. Serial0 O 131.108.9 (R3). Serial0 O IA 131. Example 4-29 displays R5 IP routing table.255.CCNP Practical Studies: Routing Example 4-26 R5's Routing Table R5#sh ip route Gateway of last resort is 131.9.108. which effectively means any packets to unknown destinations are sent to the next hop address 131.9.108.121 - .0.128.16/30 [110/983] via 131.255. with the no-summary option. Serial0 C 131. Serial0 O IA 131.108.0. R6.9 (R3). 00:01:22.108. R5. 00:01:22. 00:01:22. 00:01:22.255. Example 4-28 no-summary Command Option on R5 R5(config)#router ospf 1 R5(config-router)#area 10 stub no-summary R5's routing table should now contain even fewer entries.0/0 [110/65] via 131. R7. Ethernet0 O IA 131.255.0. 00:01:22.255.9. Serial0 C 131.255. R4. 00:01:22.108.108.108.9.

9. The shaded portion highlights the configuration required for the stub network.108.255.108.108. The shaded portion highlights the configuration required for the stub network.255.129.0.0.0.0 255.108. Example 4-32 R5's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.3 area 10 network 131. Example 4-31 R4's OSPF Working Configuration router ospf 1 area 0 range 131.9.0.108.0. Serial0 O 131.255.12 0.0.108.255.0/24 [110/148] via 131.108.0 area 10 stub no-summary network 131.9 to network 0. Serial0 The only networks displayed now are the default network and networks residing in the same area as Router R5.3 area 10 network 131.108.108.0 0.255.0. The shaded portion highlights the configuration required for the stub network.3 area 0 network 131.12/30 [110/128] via 131.224.255.0.0.9.108.CCNP Practical Studies: Routing Example 4-29 R5's IP Routing Table R5#show ip route Gateway of last resort is 131.0.108.131. which is area 10.0.255.255.0/24 [110/74] via 131.0 0. the OSPF routing process changes because the remaining configuration is identical to that in Examples 4-10 to 4-17.255.108. 00:01:04.255.122 - .108.0. 00:01:04.108.9. 00:01:04.9.255.16 0.0.255. Example 4-30 displays R3's OSPF configuration.108.130.108.128.0 131.0.0/24 is directly connected.0. 00:01:04. 9 subnets. The use of the stub configuration is effective in this type of network topology.0. 2 masks O 131.20/30 [110/138] via 131. 00:01:04.128.255 area 10 network 131. Serial0 C 131. 00:01:04.8/30 is directly connected.108. List the full OSPF working configurations of the ABR Routers R3 and R4 and the edge routers that are configured as stubby networks.255. You now have only 8 remote entries instead of over 30.3 area 10 Example 4-32 displays R5's OSPF working configuration.0/0 [110/65] via 131.108.255.0.0 area 10 stub no-summary Example 4-31 displays R4's full OSPF working configuration.255.20 0.3 area 0 network 131.9.0. Example 4-30 R3's OSPF Working Configuration router ospf 1 network 131.0.108.0.108.0. Serial0 O*IA 0.255.108.0/16 is variably subnetted.108. as shown in Example 4-18.0 0.108.36.0 255. Serial0 O 131.0.9. NOTE The configuration in Example 4-30 contains only the message in Example 4-23. Serial0 O 131.0.224.255.0.0 0.36.255 area 10 network 131. Serial0 O 131.16/30 [110/138] via 131.108.255 area 10 area 0 range 131.8 0. Ethernet0 O 131.0.4 0.255.108.255.9.108.0/24 [110/148] via 131.255.108.108.36.3 area 10 network 131.0/24 [110/138] via 131. 00:01:04.0. Serial0 C 131.108. Serial0 O 131. 00:01:04.3 area 10 ! .4 0.0.255.108.255.108.

12 0.0 0.20 0.0. . The shaded portion highlights the configuration required for the stub network. in a three-router topology.0. Example 4-35 R8's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.0 0. Scenario 4-3: Configuring Integrated IS-IS This scenario shows you how to configure another link-state protocol.123 - .3 area 10 Example 4-35 displays R8's OSPF working configuration.8 0. with the routers named R4.108. The topology for this scenario is displayed in Figure 4-6.0.0.0. you can configure a simple two-router network with loopback address and follow the steps completed here on a smaller scale and continually view the IP routing table to see the benefits of summarization and stubby networks.0. and R9.0.0.255 area 10 network 131.255 area 10 network 131. R8.0.108.255 area 10 network 131.255.3 area 10 TIP To best appreciate OSPF and the features covered here.108.108. Example 4-34 R7's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.0.0 0.131.0. Example 4-33 R6's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.255.129. The shaded portion highlights the configuration required for the stub network.3 area 10 Example 4-34 displays R7's OSPF working configuration.130.108.255. The shaded portion highlights the configuration required for the stub network. IS-IS.CCNP Practical Studies: Routing Example 4-33 displays R6's OSPF working configuration.0.108.

and Government OSI Profile (GOSIP) format as described in the following list: Simple format: Area System ID SEL OSI format: Domain Area System ID SEL GOSIP format: AFI ICD DFI AAI Reserved RDI Area System ID SEL . which describes the area and system ID. NOTE Three methods (referred to as network entities) can define the area: simple format. IS-IS supports VLSM.CCNP Practical Studies: Routing Figure 4-6. you use these routers to connect to an OSPF router. OSI format. IS-IS with VLSM Where this scenario covers redistribution.124 - . Note that VLSM is in use. and you configure the three routers to be in domain 1 using the network entity known as the simple format. The IP addressing scheme is displayed in Figure 4-6.

b055. You must also enter the global command clns routing.64fc. net ID is 00.0001. Example 4-37 Configuration on R8 R8(config)#router isis R8(config-router)#net 00.98e8. for IS-IS. The MAC addresses of the respective routers are as follows: • • • R4— 0050. configure the first router. typically an interface Media Access Control (MAC) address Each IS-IS routers must be configured with the following: • • • Enable IS-IS with the command router isis optional area tag.00 R8(config-router)#exit R8(config)#clns routing R8(config)#int ethernet 0 R8(config-if)#ip router isis R8(config)#interface serial 0 R8(config-if)#ip router isis R8(config-if)#interface serial 1 R8(config-if)#ip router isis . net ID is 00.5460.0001. Figure 4-6 shows a small three-router network. The tag groups routers in one domain.CCNP Practical Studies: Routing These fields are defined as follows: • • • • • • • • AFI— Authority and format identifier (47 for Cisco routers) ICD— International code designator DFI— Domain specific part AAI— Administrative authority identifier RDI— Routing domain identifier (autonomous system number) SEL— Network Service Access Port (NSAP) Area— Used by L2 routers System ID— Used by L1 routers.0050. R4.0001.64fc. All routers reside in one area.d7bd.00 R9— 00e0. Example 4-36 Configuration on R4 R4(config)#router isis R4(config-router)#net 00.00 Now. Example 4-37 displays the configuration of IS-IS on R8.98e8.98e8.0001.0001.0001.00e0.00 R8— 00b0.28ca.00b0.5460. The areas are encoded as 00.d7bd.00b0. Enable IS-IS per interface with the command ip router isis. net ID is 00.28ca. Example 4-36 displays the configuration required to enable IS-IS on Router R4.125 - .b055.5460.0050. and the system IDs are the MAC addresses from the local Ethernet interface. Configure the network interfaces with the command net network-entity-title.64fc.d7bd.00 R4(config-router)#exit R4(config)#clns routing R4(config)#int ethernet 0 R4(config-if)#ip router isis R4(config-if)#inter serial 3 R4(config-if)#ip router isis R4(config-if)#int serial 2 R4(config-if)#ip router isis The first configuration completed on R4 enables the IP routing and then enables Connectionless Network Service (CLNS) and interface configuration on all participating IS-IS interfaces.

2 masks 141. Serial2 [115/20] via 141.255. .0/16 is variably subnetted.255.4. L2 .108.108.28ca.108. The IS-IS metric is between 0 and 63.2. Serial3 141. Example 4-40 Sample Output of show clns isis-neighbor Command from R4 R4#sh clns is-neighbors System Id R8 R9 Interface Se2 Se3 State Up Up Type Priority L1L2 0 /0 L1L2 0 /0 Circuit Id 00 00 Format Phase V Phase V R4 has two CLNS neighbors.108. Example 4-38 Configuration on R9 R9(config)#router isis R9(config-router)#net 00. as does OSPF.255.126 - .3.CCNP Practical Studies: Routing Example 4-38 displays the configuration completed on R9.0001.108.255. Example 4-40 displays the IS-IS neighbor states with the show clns isis-neighbor command. IS-IS supports equal cost path load balancing.255.00e0. This means all routers share the same IS-IS link-state database.0.b055. Ethernet0 141. As with OSPF.8/30 is calculated with two paths: one path through Serial 2 and the other through Serial 3.IS-IS level-2.IS-IS inter area C C C i L1 i L1 i L1 141. 6 subnets. and the total metric is calculated from source to destination. Example 4-39 R4's IP Routing Table R4#sh ip route Codes i .0/24 [115/20] via 141. which is displayed in Example 4-41.0/24 [115/20] via 141.108.108.2.108. The administrative distance for IS-IS is 115 and is followed by the metric. Now look at a few examples of the most commonly used show commands. Serial3 R4's routing table has four remote entries. ia . To view the linkstate database on an IS-IS router. The default metric is set to 10.108.0/30 is directly connected.108.255.IS-IS level-1. Serial2 141.108.5. In other words.255. namely Routers R8 and R9.255.0/24 is directly connected.IS-IS. Notice the path to the remote network 141.8/30 [115/20] via 141. use the command show isis database. Serial2 141. examine the IP routing tables for IP connectivity.108.5.00 R9(config-router)#exit R9(config)#clns routing R9(config)#int ethernet 0 R9(config-if)#ip router isis R9(config-if)#interface serial 0 R9(config-if)#ip router isis R9(config-if)#interface serial 1 R9(config-if)#ip router isis Now that IS-IS is configured on all three routers.4/30 is directly connected.2. all of which are labeled L1 (level 1 route) because all three routers reside in area 1 as configured by the net command. Example 4-39 displays R4's IP routing table. Serial3 141. the command set for monitoring IS-IS is large. L1 .

108. LSP Seq Link-state packet (LSP) Sequence number for the LSP that allows other systems to determine whether they Num have received the latest information from the source.28CA. OL Overload bit.B055.255. Detects whether the area is partition-repair capable.252 ip router isis clockrate 128000! interface Serial3 .17 255. This indicates that the router is also a Level 2 router and it can reach other areas.255. IS-IS. P P bit.108.0 ip router isis ! interface Serial0 shutdown ! interface Serial1 ip address 131.255.255.2.255.00-00 * 0x00000009 R8.01-00 0x00000002 IS-IS Level-2 Link State Database: LSPID LSP Seq Num R4.127 - .B055.255. in seconds.00-00 0x0000000B Table 4-6 summarizes the output in Example 4-41. Example 4-42 displays R4's full working configuration.255.00-00 0x00000007 00E0.28CA. Field Descriptions of show isis database Command Field Description LSPID The link-state protocol data unit (PDU) ID. Checksum LSP Holdtime Amount of time the LSP remains valid.B055.CCNP Practical Studies: Routing Example 4-41 Sample Output of show isis database Command from R4 R4#sh isis database IS-IS Level-1 Link State Database: LSPID LSP Seq Num R4. LSP Checksum of the entire LSP packet. Example 4-42 R4's Full Configuration hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup ! clns routing ! interface Ethernet0 ip address 141. LSP Checksum 0xE25D 0xFE0A 0x3A8A 0x87A6 LSP Checksum 0xA3ED 0x49DC 0x0C26 LSP Holdtime 921 788 475 517 LSP Holdtime 928 794 926 ATT/P/OL 0/0/0 0/0/0 0/0/0 0/0/0 ATT/P/OL 0/0/0 0/0/0 0/0/0 Table 4-6.28CA. as OSPF. Before you look at redistributing IS-IS with OSPF. here are the full working configurations of the three routers in this IS-IS topology.1 255.00-00 0x00000007 00E0.108.252 clockrate 128000 ! interface Serial2 ip address 141.6 255.255.00-00 * 0x00000007 R8. ATT Attach bit. is an advanced link-state routing protocol that you can use in large environments to route IP.00-00 0x0000000A 00E0.

98e8.108.255.d7bd.5 255.4.255.255.255.255.1 255.108.2 255.252 ip router isis ! router isis net 00.255.255.108.108.0001.128 - .255.5460.255.108.0 ip router isis ! interface Serial0 ip address 141.10 255.252 ip router isis clockrate 128000 ! router isis net 00.108.00 line con 0 line 1 8 line aux 0 line vty 0 4 ! end Example 4-44 displays R9's full working configuration.0 ip router isis ! interface Serial0 ip address 141.255.252 ip router isis ! interface Serial1 ip address 141.252 ip router isis .255.255.255.3.255.0001.CCNP Practical Studies: Routing ip address 141.1 255.1 255.255.00b0.00 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-43 displays R8's full working configuration.64fc. Example 4-43 R8's Full Configuration hostname R8 ! enable password cisco ! ip subnet-zero no ip domain-lookup clns routing ! interface Ethernet0 ip address 141.0050. Example 4-44 R9's Full Configuration hostname R9 ! clns routing ! interface Ethernet0 ip address 141.255.

108.10 Type escape sequence to abort.0001. IS-IS Command Summary Command area-password password domain-password password isis password password ip router isis [tag] clns routing default-information-originate show isis database summary-address address mask show isis spf-log Description Configures IS-IS Level 1 authentication Configures the domain password for L2 routers Configures authentication between two IS-IS routers Enables IS-IS per interface Enables routing of CLNS packets Generates a default route inside the IS-IS domain Displays the link-state database Configures address summarization Displays the number of times the SPF calculation has been completed .b055.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).3. round-trip min/avg/max = 16/17/20 ms R4#ping 141.252 ip router isis clockrate 128000 ! router isis net 00. round-trip min/avg/max = 28/36/60 ms R4#ping 141.108. Table 4-7 summarizes the most common IS-IS configuration and show commands. 100-byte ICMP Echos to 141.255.9 Type escape sequence to abort.108.129 - .108.3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.CCNP Practical Studies: Routing ! interface Serial1 ip address 141.4.255.1.108.4.9.255. 100-byte ICMP Echos to 141. Sending 5. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5.108.00e0. Sending 5. Table 4-7.9 255.1 Type escape sequence to abort.10.255. 100-byte ICMP Echos to 141.28ca.108. 100-byte ICMP Echos to 141.1 Type escape sequence to abort.1.255. round-trip min/avg/max = 28/46/104 ms R4# The IS-IS IOS command set is comprehensive.108. Example 4-45 Sample Ping Requests from R4 R4#ping 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/20 ms R4#ping 141.00 ! line con 0 line 1 8 line aux 0 line vty 0 4 ! end Example 4-45 displays some sample ping requests and replies to the remote network to demonstrate IP connectivity among all three routers.255.

you must define a cost metric.130 - . The ? tool is used to bring up the available options. you integrate the IS-IS network you configured in Scenario 4-3 with an OSPF network. For OSPF.108. To configure redistribution between any IP routing protocols.108.15. OSPF and Integrated IS-IS Network Topology Because R4 is within both the OSPF and IS-IS domain. you can configure redistribution between OSPF and IS-IS.0 to 131.CCNP Practical Studies: Routing Scenario 4-4: OSPF and Integrated IS-IS Redistribution In this scenario. you must configure a metric that is used within the IP dynamic routing protocol. for example. Figure 4-7 displays the OSPF network and IS-IS. Figure 4-7.255. Example 4-46 Routing OSPF to IS-IS on R4 R4(config)#router isis R4(config-router)#redistribute ? bgp Border Gateway Protocol (BGP) connected Connected egp Exterior Gateway Protocol (EGP) eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) igrp Interior Gateway Routing Protocol (IGRP) isis ISO IS-IS iso-igrp IGRP for OSI networks level-1 IS-IS level-1 routes only level-1-2 IS-IS level-1 and level-2 routes level-2 IS-IS level-2 routes only metric Metric for redistributed routes .2. Router R1 has loopbacks ranging from 131. Example 4-46 displays the configuration of OSPF redistribution from OSPF to IS-IS on R4 and the step-by-step process required to ensure that all the OSPF routes are advertised as IS-IS routes in the IS-IS domain.

255.108.9. i . you need to define the OSPF process ID from which the OSPF routes will be injected.3.4/30 is directly connected.108. the chosen value of 10 is used.255. 6 subnets.108. Ethernet0 i L1 141.0 [115/30] via 141. ia .108. and L1/2. you configure L2 routes. Serial1 i L2 131.0.8/30 is directly connected.131 - . L1 . Any value between 0 and 63 is a valid metric. L2 .0/16 is variably subnetted.255. Finally.108.connected. Serial1 131.14. 2 masks C 141.9. In this scenario.255.108. Serial1 i L2 131. Serial1 .255.255. L2.255.9. Serial1 i L1 141.IS-IS inter area 141.IS-IS.108.0. Serial1 C 141.108. you need to define an IS-IS metric.108.0 [115/30] via 141.9.108.255.0 [115/30] via 141. Example 4-47 R8's IP Routing Table R8#show ip route Codes: C . The OSPF process ID is 1.IS-IS level-2.0/30 [115/20] via 141. Serial0 i L1 141.CCNP Practical Studies: Routing metric-type OSPF/IS-IS exterior metric type for redistributed routes mobile Mobile routes odr On Demand stub Routes ospf Open Shortest Path First (OSPF) rip Routing Information Protocol (RIP) route-map Route map reference static Static routes <cr> R4(config-router)#redistribute ospf ? <1-65535> Process ID R4(config-router)#redistribute ospf 1 ? level-1 IS-IS level-1 routes only level-1-2 IS-IS level-1 and level-2 routes level-2 IS-IS level-2 routes only match Redistribution of OSPF routes metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference vrf VPN Routing/Forwarding Instance <cr> R4(config-router)#redistribute ospf 1 level-2 ? match Redistribution of OSPF routes metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference <cr> R4(config-router)#redistribute ospf 1 level-2 metric ? <0-63> ISIS default metric R4(config-router)#redistribute ospf 1 level-2 metric 10 When redistributing from OSPF to IS-IS.9.) Three options are available when you are redistributing from OSPF to IS-IS: L1.0/24 [115/30] via 141.0/24 is directly connected. Because OSPF uses cost as the metric for making routing decisions and IS-IS uses L1 or L2.108.108. 15 subnets i L2 131.0/24 [115/20] via 141. Example 4-47 displays the IP routing table on R8.108.4.108. (The router type along with IS-IS metric is between 0–63.9.108. you must define the IS-IS router type.254.15.IS-IS level-1. Serial1 C 141.0/24 is subnetted. View the IP routing table inside in IS-IS network.108.108.255.2.

108.255.108. Serial0 i L2 131.108.108.108.. Serial0 i L2 131.7.9.108. Serial0 [115/50] via 141. Serial1 i L1 141.8.0 [115/20] via 141.255.. Sending 5.108.4/30 [115/50] via 141.0 [115/20] via 141.108.255.108. Serial0 i L2 131. Example 4-48 Sample Ping Request to 131.10.13.9.255.2.108.108.0 [115/30] via 141. Serial1 131.12. and a metric of 30.0/16 is variably subnetted.1. The reason the ping request receives no replies is because R8 sends the request to the next hop address of 141.2.108.108. Example 4-48 displays a sample ping request from R8 to the L2 IS-IS route 131.1 Type escape sequence to abort.108. Serial1 131.255.0 [115/20] via 141.1.255.CCNP Practical Studies: Routing i i i i i i i i i i i i L2 L2 L2 L2 L2 L2 L2 L2 L2 L2 L2 L2 131. which comes from the addition of the 10 used in redistribution and the two hop counts between R4 to R9 and R9 to R8.2.108.0/24 [115/20] via 141.108.255.6.108.0 [115/30] via 141.0 [115/20] via 141. Serial0 i L2 131.108.108.0 [115/30] via 141. i .255.9.108.108.108.3.1. Example 4-49 IP Routing Table on R9 R9#sh ip route Codes: C .1 from R8 R8#ping 131.3.11.8. Serial0 i L2 131. Serial0 i L2 131.255. Ethernet0 131.108.255.1. Serial0 i L2 131. L1 .255.2. Serial0 i L2 131.255. Serial0 i L2 131.0 [115/20] via 141.0 [115/30] via 141..108. * candidate default 141.0 [115/20] via 141.1.4. 2 masks C 141.255.255.1.11.108. Success rate is 0 percent (0/5) R8# The ping request receives no replies.9.0 [115/20] via 141.108.IS-IS level-1.108.0 [115/30] via 141.1. timeout is 2 seconds: .1.1. Serial0 .108.3. 6 subnets.108.5. L2 .108.2.108.1.108. 15 subnets i L2 131. Serial1 131.108.0 [115/30] via 141.9.0 [115/20] via 141.1 (R2's loopback address). 100-byte ICMP Echos to 131.255.9.9. Serial0 i L2 131.255.255.108.0/30 is directly connected.108.7. Serial1 131.12. Serial1 i L1 141.255.0 [115/30] via 141.108. Try to ping the remote address.10.255. Serial1 C 141.108.1.108.8/30 is directly connected. Serial1 131.108.108.13.255.0 [115/20] via 141.108.108.1. Serial0 C 141.255. Serial1 131.255.IS-IS level-2.108.108.9. Serial1 131.255.108.108.108.6.108.0/24 [115/20] via 141.108.255.0 [115/20] via 141.0.9 (R9) and R9 sends the request to R4. Example 4-49 displays R9's IP routing table confirming the next hop address.108.108.0/24 is subnetted.5.9. Serial0 i L2 131.0 [115/20] via 141.108.1.0 [115/30] via 141.connected.255.255.132 - . Serial1 131.108.254.255.9.108. Serial1 131. R8 has a routing entry for this network.0 [115/30] via 141.0 [115/20] via 141.108.255.4.108.1.2.0 [115/30] via 141.255.255.108.9.108. Serial0 i L1 141.0 [115/20] via 141.1.255.108.15.14.0. Serial0 i L2 131.0 [115/20] via 141..1.255.108.108.0 [115/30] via 141.255.255.IS-IS.255.4.108. Serial1 Example 4-47 displays the remote OSPF routes redistributed from the OSPF backbone on R1 into IS-IS as L2 routes. Serial1 131.2.108.9.1.108. Serial0 i L2 131.108.0/24 is directly connected.108.1.0 [115/20] via 141.108.9.108. Serial0 i L2 131. Serial1 131.0 [115/30] via 141.108.10.9.10.108.108.

Example 4-51 R1's OSPF Routing Table R1#sh ip route ospf R1# NOTE R4's routing table contains all the OSPF network entries advertised by R1.1 R4>ping 131. . Example 4-50 Sample Ping from R4 to 131.2. Remember that R1 is configured for OSPF only.108. round-trip min/avg/max = 1/2/4 ms R4> The last hop you need to look at is R1.108.2. ping requests are replied to when R4 pings the address 131. and because R1 and R4 are maintaining a full OSPF adjacency and the next hop address is a directly connected LAN.108. Sending 5. R4 can ping the remote address as confirmed by Example 4-50. Example 4-51 displays R1's OSPF routing table.1 (R4). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).CCNP Practical Studies: Routing Example 4-49 displays the next hop address of 141.108.1.2.133 - .108.1 Type escape sequence to abort.1. 100-byte ICMP Echos to 131.2. Now.255.

108.CCNP Practical Studies: Routing The reason that R1 has no remote OSPF entries and hence has no return path to the remote routers R8 or R9 in the IS-IS domain is that you have not redistributed from IS-IS to OSPF. which is required whenever redistribution is configured to a classless domain and a 30-bit mask on serial connections. Ethernet0/0 .0.0 is subnetted using a Class C address.3.0/16 is variably subnetted.8/30 [110/100] via 131.108. 00:00:00.254. 2 masks O E2 141.0. 00:00:00. Example 4-53 displays R1's OSPF routing table.254. Ethernet0/0 O E2 141. view R1's IP routing table. configure IS-IS to OSPF redistribution.108. Example 4-52 displays the configuration options when redistributing from IS-IS to OSPF.4.108.108.2. Ethernet0/0 O E2 141.255.0/24 [110/100] via 131. Example 4-52 Configuring IS-IS to OSPF Redistribution R4(config)#router ospf 1 R4(config-router)#redistribute isis ? level-1 IS-IS level-1 routes only level-1-2 IS-IS level-1 and level-2 routes level-2 IS-IS level-2 routes only metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> WORD ISO routing area tag R4(config-router)#redistribute isis level-1-2 ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> R4(config-router)#redistribute isis level-1-2 metric 100 ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> R4(config-router)#redistribute isis level-2 metric 100 metric? metric metric-type R4(config-router)#redistribute isis level-2 metric 100 metric-type ? 1 Set OSPF External Type 1 metrics 2 Set OSPF External Type 2 metrics R4(config-router)#redistribute isis level-1-2 metric 100 metric-type 1 subnets NOTE The keyword subnets is required here because 141. configure redistribution on R4.2. you must also advise the OSPF domain of the IS-IS routes. 3 subnets. So far you have only configured one-way redistribution.0/24 [110/100] via 131. but this time. Example 4-53 R1's OSPF Routing Table R1>sh ip route ospf 141. 00:00:00.108.2. Once more.108.254.134 - . Now.108.

0/24 [110/100] via 131.0/30 [110/110] via 131. Confirm connectivity by pinging from R8 to R1 loopback addresses 131. Sending 5.2.108.108. Ethernet0/0 You have seen the power of the command redistribute. Sending 5.108.254.4.254.254.4.108.3. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.108.5.0/24 [110/100] via 131. Example 4-56 Sample Pings from R8 to R1 R8#ping 131. Example 4-54 displays the configuration of locally connected routes to be injected into IS-IS on R4.4. timeout is !!!!! Success rate is 100 percent (5/5). 00:07:29. Sending 5. round-trip min/avg/max R8#ping 131. 00:07:29.0. Sending 5.8. timeout is !!!!! 2 seconds: = 16/17/20 ms 2 seconds: = 16/17/20 ms 2 seconds: = 16/17/20 ms 2 seconds: = 16/17/20 ms 2 seconds: = 16/17/20 ms 2 seconds: = 16/18/20 ms 2 seconds: . timeout is !!!!! Success rate is 100 percent (5/5).108. Ethernet0/0 O E2 141.10. You also need to redistribute any locally connected routers on R4.2.255. By simply using keywords.1.1. 6 subnets.1 Type escape sequence to abort. round-trip min/avg/max R8#ping 131. Sending 5.108.108.108.108. 100-byte ICMP Echos to 131.108.1.7. round-trip min/avg/max R8#ping 131. as displayed in Example 4-56. Ethernet0/0 O E1 141.2. timeout is !!!!! Success rate is 100 percent (5/5).7.1.254.8/30 [110/100] via 131.2. 100-byte ICMP Echos to 131.1/24 through 131. timeout is !!!!! Success rate is 100 percent (5/5). 2 masks O E2 141.255.1 Type escape sequence to abort. Ethernet0/0 O E1 141.0/24 [110/110] via 131. 00:07:29.1 Type escape sequence to abort.0/16 is variably subnetted. 00:07:39.108.108.CCNP Practical Studies: Routing Three remote networks are present. but none of the directly connected links on R4 are present.6.108. round-trip min/avg/max R8#ping 131.8.135 - . round-trip min/avg/max R8#ping 131.1.108. Ethernet0/0 O E2 141.108. Sending 5.4/30 [110/110] via 131.2.2.108.108. Example 4-54 Redistribute Connected on R4 R4(config-router)#router ospf 1 R4(config-router)# redistribute connected subnets metric 100 metric-type 1 Example 4-55 now displays the full IP network present in the IS-IS domain.108.1/24.108.3. Configure this and use type 1 OSPF routes this time. 00:07:39.254.1.1 Type escape sequence to abort. timeout is !!!!! Success rate is 100 percent (5/5).2. you can redistribute routes with the appropriate metric and route type (1 or 2 in OSPF or L1/L2 in IS-IS).108.108. Example 4-55 show ip route ospf Command on R1 R1>sh ip route ospf 141.2. timeout is !!!!! Success rate is 100 percent (5/5).108.6. You can now provide connectivity between the two different routing domains.108. Sending 5. round-trip min/avg/max R8#ping 131.1 Type escape sequence to abort.5.2. 100-byte ICMP Echos to 131.108. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.255.108.3. 00:07:39.108. 100-byte ICMP Echos to 131.108. Ethernet0/0 O E1 141.2. 100-byte ICMP Echos to 131.1.254.108.

12. Example 4-59 show ip route isis Command on R9 R9#sh ip route isis 141.108. Serial1 i L2 131.108.1.108.15.0 [115/158] via 141.10.0 [115/158] via 141.2.255.255. Serial1 i L2 131.108.1/24.108.0/16 is variably subnetted.10. Serial1 i L2 131.4.1 12 msec 8 msec * Assume the link between R9 and R4 fails.14.108.1 8 msec 8 msec 12 msec 2 131.255.10.6 20 msec 16 msec 16 msec 3 131.0 [115/158] via 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10.10. Serial1 i L2 131.108.0/24 [115/30] via 141.255.9.108. 100-byte ICMP Echos to 131.0.2.136 - . Example 4-59 displays R9's IS-IS routing table when the link failure to R4 occurs.108. Serial1 i L2 131.108.0 [115/158] via 141.1 1 141.10.255.108.108. Serial1 i L2 131. Tracing the route to 131.6.108.108.255.108. round-trip min/avg/max = 16/18/20 ms R8#ping 131. Serial1 i L2 131.108.0 [115/158] via 141. Serial1 i L2 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.108.13.2.0 [115/158] via 141.2.255. Serial1 i L2 131.255.0 [115/158] via 141.0 [115/158] via 141.108.4/30 [115/20] via 141. Serial1 i L2 131.255.10.108. Example 4-57 Trace Route to 131. Tracing the route to 131.1 Type escape sequence to abort.9.2.0 [115/158] via 141.255.108.108.108.108.0. Sending 5.108.0/24 is subnetted.108.108.1 Type escape sequence to abort.255.108.108. Serial1 .1.11.8.1 16 msec 16 msec * The new IP routing table on R9 contains a path to all OSPF routes through the Serial connection to R8.10.108.108. Serial1 i L2 131. Serial1 i L1 141.10.10.108.255. Serial1 i L1 141.108.10.0/24 [115/20] via 141. round-trip min/avg/max = 16/18/20 ms R8# A sample trace from R9 to R1 displays the route path taken to the network 131.255.10.10. Serial1 i L2 131.108.10. so the only path to the OSPF backbone is through R8.108.108.108. 15 subnets i L2 131.10.255.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).108.254.2.0 [115/158] via 141. 5 subnets.108.0 [115/158] via 141.10.1 Type escape sequence to abort.1 Type escape sequence to abort.108. as displayed in Example 4-57.255.254.255.10.108. round-trip min/avg/max = 16/17/20 ms R8#ping 131.5.10.2.10. 100-byte ICMP Echos to 131.108.108.108.254.1 from R9 R9#trace 131.108.108. 2 masks i L1 141. Sending 5.108.255.1 1 141.9.255.7. Serial1 131.255.10 8 msec 8 msec 12 msec 2 141. Example 4-58 Trace on R9 Through R8 R9# trace 131.255.0 [115/158] via 141.108.0 [115/158] via 141. Example 4-58 displays a sample trace when the primary path fails.3.108.

This is not a practical scenario but rather a presentation of some design guidelines to help you in real-life network situations you might come across in designing today's complex IP networks.108. The following are some general guidelines when designing a large OSPF network. Anything between 40–50 is an acceptable number.137 - . no matter what failure or scenario. Manageability— This point refers to proactive management. the maximum is 1000. Any large network should be able to foresee new challenges before the network grinds to a halt. The bigger your budget. Practical Exercise: OSPF and RIP Redistribution NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter.2.255. The IETF standards committee provides the following sample design guidelines: • • • TIP The minimum number of routers per domain is 20. By no means are these rules standard. The solution can be found at the end. You can manage and configure OSPF so that the preceding five criteria are fully supported. You must use only RIPv1 and OSPF as your IP routing . Scalability— As the network grows in size. you should try to accomplish five basic goals with dynamic routing protocols: • • • • • Functionality— The network works. When architecting a network. you cannot invest in anything better than the following two quality Cisco Press titles: Routing TCP/IP by Jeff Doyle and OSPF Network Design Solutions by Tom Thomas.0 [115/158] via 141. the maximum is 350.10. cost drives most network designers. The number of areas per domain is 1. the maximum is 60. and they are provided here for reference so you can easily refer to a sample network design and the common rules experts adhere to in large OSPF networks. such as new acquisitions. 100 routers require 100log 100 or 100 x 2 = 200. Adaptability— With ever-increasing new technologies. Serial1 Scenario 4-5: Recommendations for Designing OSPF Networks This scenario presents some of the design recommendations found in common literature. For example. Implementing a hierarchical IP addressing scheme and performing summarization wherever possible are two key points in any large OSPF network. The minimum routers per single area is 20.CCNP Practical Studies: Routing i L2 i L2 131. Mel. Determine the number of routers in each area. the better able you are to provide users the ability to work around network failures. OSPF is such a large topic that many books have been written about it. Cost effectiveness— In reality. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. The number of calculations any given router must perform given m LSAs is mlogm. Keeping these calculations to a minimum means the CPU/memory requirements are also kept low.10.3.108. the network must always be functioning.0 [115/158] via 141.255. your network should cope with and embrace new features. Serial1 131. Configure the edge router named Sydney for RIP and ensure IP connectivity among all four routers. and Simon. that is. your initial topology or design must be able to cope with growth and new challenges. such as Voice over IP. For a concise guide to OSPF and a more detailed guide.108. Configure the network in Figure 4-8 for OSPF between the three routers named SanFran.108.

CCNP Practical Studies: Routing protocols. The following are the full working configurations of all four routers with the shaded portions highlighting critical configuration commands. (RIPv2 does). Also.255. because you are using RIPv1. you must also provide summary addresses for all networks. Figure 4-8. RIP-to-OSPF Redistribution Practical Exercise Solution The router named Simon is configured in the OSPF area 0 (backbone) and the RIP domain and needs to run redistribution between OSPF and OSPF. Router SanFran is connected to the Internet. Example 4-60 Full Working Configuration of Router Sydney hostname Sydney ! logging buffered 64000 debugging enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0/0 ip address 141. but not /24 because RIPv1 does not carry subnet mask information in routing updates.0 no ip directed-broadcast . Ensure that a default route appears on all routers so users can connect to the Internet.108. so you need to configure SanFran to provide a default route to the rest of the internal network by using the OSPF command default-information originate always.255. Configure summarization wherever possible to minimize IP routing tables.1 255. This IOS command injects a default route into the OSPF domain and Router Simon because redistribution also injects a default route into the RIP domain.138 - . Sydney is running RIP only.1. Example 4-60 displays the full working configuration of Router Sydney.

108. Because RIPv1 is classless and the subnet 141. Example 4-61 Full Working Configuration of Router Simon Building configuration.255.255.108.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Simon ! enable password cisco ! ip subnet-zero no ip domain-lookup ! cns event-service server ! interface Ethernet0 ip address 141. Simon advertises the non /24 subnets as Class C networks so the RIP domain (Sydney router) can inject them into the routing table.0) are assumed to be Class C.0.255. Simon is running OSPF and RIP. Current configuration: ! version 12.CCNP Practical Studies: Routing ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown ! router rip network 141. You must always be careful when redistributing information from one routing domain into another.139 - .255.108.255.255.108.108.255.0..255.1 255.252 clockrate 128000 ! .108..5 255.108.255.252 clockrate 128000 ! interface Serial3 ip address 141.1 255. all interfaces in this Class B network (141.0 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-61 displays the full working configuration of Router Simon.128 ! interface Ethernet1 ip address 141.4 255.1.0 ! interface Serial0 shutdown ! interface Serial1 shutdown ! interface Serial2 ip address 141.2.255.0/24 is configured locally.1.

0.0.255.255.0 0.108.108.255.108.108.0 redistribute connected subnets redistribute rip metric 10 subnets network 141.255.2.255.252 ! interface Serial1 shutdown ! router ospf 1 network 141.255 area 0 ! router rip redistribute ospf 1 metric 2 passive-interface Ethernet0 -> Stops RIP updates on OSPF interfaces passive-interface Serial2 passive-interface Serial3 network 141.255.0 255.255.4.0 255.108.4.255.255.108.248 ! interface Serial0 ip address 141.255.255.255.0 0.0 255.0.108.0.255.2.255.255 area 0 ! line con 0 line 1 8 line aux 0 line vty 0 4 ! end .255.3.255.127 area 0 network 141.108.108.0.3.1 255.108.0 255.0 ! = ip route 141.255.0.0 summary-address 141.CCNP Practical Studies: Routing router ospf 1 summary-address 141. Example 4-62 Full Working Configuration of Router Mel hostname Mel enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 141.0 255.0 255.0 summary-address 141.0.108.255.140 - .108.3.6 255.0 Null0 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-62 displays the full working configuration of Router Mel.255.255.0 Null0 ip route 141. Mel is running OSPF only.0 0.0 summary-address 141.

0 R C R R R R* 141.108. which is the Internet connection.255.108.0.141 - .0.1. 00:00:05.1.0." 1: 2: 3: What does the routing entry shaded in Example 4-64 display? In Example 4-64.4 to network 0.4.108.252 ! interface Serial1 shutdown ! router ospf 1 network 141. what is the hop count or metric to the remote network 141.108.108. 00:00:05.0 [120/2] via 141. 00:00:05.0.0.0 [120/1] via 141.4.0 Serial1 ! line con 0 line aux 0 line vty 0 4 ! end Review Questions Based on the following IP routing table.3.108.255. Ethernet0/0 141.0. 00:00:05. Example 4-63 Full Working Configuration of Router SanFran hostname SanFran ! no ip domain-lookup ! interface Ethernet0 ip address 141. Example 4-64 Sydney IP Routing Table Sydney#show ip route Gateway of last resort is 141.0/0 [120/2] via 141.0 0. Ethernet0/0 141.1.108. Ethernet0/0 The answers to these question can be found in Appendix C.1. Under the routing OSPF process.108.0/24 is subnetted.108.4.108.255.2.1.0.108.2.0 [120/1] via 141.255. Ethernet0/0 141.4.0 [120/2] via 141.0. 00:00:05.CCNP Practical Studies: Routing Example 4-63 displays the full working configuration of Router SanFran.0.255.4.1. 5 subnets 141.0.108.108. "Answers to Review Questions.108.0 is directly connected.108.240 ! interface Serial0 ip address 141. this default route is injected by using the default-information originate always command. SanFran has a default static route pointing to Serial 1.108. Ethernet0/0 141.4.0/24 take? .1 255.2 255.1.108.0/24? What path does the packet sent to the IP subnet 171.255. Example 4-64 displays the IP routing table of Router Sydney.0.255.0 0.255.4. Ethernet0/0 0.255 area 0 default-information originate always ! ip route 0. answer the following questions relating to the preceding Practical Exercise on OSPF/RIP routing.

Enables a more specific route on loopback interfaces. mod/num interface serial mod/num In configuration mode. [no] shutdown Enables or disables an interface. redistribute Redistributes from one IP routing protocol to another. no ip domain-lookup Disables automatic DNS lookup. enables you to modify serial interface parameters by module and interface number. Although only one solution per scenario is presented. The process ID is local to the router. enables you modify the Ethernet. area area id range mask Enables interarea summarization in OSPF. show ip ospf show ip ospf database show ip ospf neighbor show ip ospf virtuallinks show ip ospf interface Displays information about how OSPF is configured for a given interface. interface loopback Creates a loopback interface. Enables network advertisements from a particular interface and also the routing of the same interface through OSPF. Displays OSPF neighbors. hostname name Configures a name on a router. interface S0/0.142 - . for example. What are they and what IOS command is used to provide summarization? Why does creating areas reduce the size of the OSPF database? Summary OSPF and integrated IS-IS have the advantage of being an industry-wide standard and have a long-term success rate of routing IP in large IP networks. Displays the OSPF process and details. Why are static routes injected into the router named Simon? How many OSPF neighbor adjacencies do you expect to see on the router named Simon? Two methods are used in OSPF to summarize IP networks. Displays OSPF virtual links. Summary of IOS Commands Used in This Chapter Command show ip route router ospf process id network mask Purpose Displays IP routing tables. . ip ospf name-lookup Enables OSPF DNS lookup. You can have more than one OSPF running. ip subnet-zero Enables you to use subnet zero on a Cisco router. for example. Enables OSPF routing. if any.CCNP Practical Studies: Routing 4: 5: 6: 7: 8: What type of OSPF routers are the Routers Simon. such as OSPF process ID and router ID. summary network mask Enables summarization of external routes in OSPF. All hardware interfaces are shut down by default. number ip ospf network point. The capabilities of link-state routing protocols are demonstrated in this chapter along with some challenging scenarios. Mel. there are many alternative ways to enable OSPF and Integrated IS-IS to meet the needs of any network in today's large networking environments. interface Ethernet0/0. Table 4-8. to-point interface ethernet In configuration mode. Displays a router's topological database. Table 4-8 summarizes the OSPF commands used in this chapter. and SanFran.

EIGRP is commonly referred to as a hybrid routing protocol or an advanced distance-vector routing protocol. (The default is four paths. Some of the main features of EIGRP when used to route IP data are as follows: • • • • • • The metric is based on a composite that considers delay. It then explains of how EIGRP can be configured and monitored. and MTU sizes to ensure the best possible path to any destinations containing dual paths. The five scenarios in this chapter help to complete your understanding of EIGRP and ensure that you have all the basic IP networking knowledge to complement your understanding of today's most widely used networking protocol. EIGRP supports authentication of routing updates. this chapter covers a protocol developed by Cisco Systems used on Cisco IOS routers only. EIGRP sends incremental updates when network changes occur. IPX. EIGRP uses DUAL to maintain a loop-free topology. EIGRP includes support for VLSM. in particular. Incremental updates— Instead of sending the complete IP routing table. and AppleTalk traffic. Enhanced Interior Gateway Routing Protocol Now that you have learned about and practiced with some basic and advanced routing protocols. . EIGRP can be used to route IP. only network changes are sent. EIGRP was developed by Cisco to provide enhancements to IGRP and. EIGRP uses up to 50 percent of the bandwidth of an interface and can be configured to go lower or higher. Hello protocol— EIGRP uses hello packets to discover neighboring routers.143 - . Table 5-1 defines some of the common terminology used when discussing EIGRP networks. This chapter concentrates on IP routing with EIGRP. Enhanced IGRP combines the characteristics of distance-vector protocols and link-state protocols.) By default. The chapter starts by covering the basic Enhanced Interior Gateway Routing Protocol (EIGRP) concepts. Periodic updates are not sent. EIGRP can load share up to six paths. You discover how EIGRP learns about new neighbors and how EIGRP operates in NBMA networks. EIGRP has been designed with the following features: • • • Diffusing Update Algorithm (DUAL)— Like any routing protocol. but it uses link-state properties when changes occur or when detecting new neighbors. IP. EIGRP sends hello packets to find new neighbors and maintain neighbor adjacencies. Like OSPF.CCNP Practical Studies: Routing Chapter 5. as with OSPF. Introduction to Enhanced Interior Gateway Routing Protocol (EIGRP) Cisco Systems followed the development of IGRP with Enhanced IGRP. to provide support for large IP networks and reduce the convergence time for IP routing updates. EIGRP uses distance-vector properties to determine the best path to a network. bandwidth. To achieve this goal.

Two-Router EIGRP Network To start EIGRP on a Cisco router.108.0 is. a Class B network. Next.1. Term Discovering and Maintaining Routes in EIGRP EIGRP uses hello packets to discover new neighboring routes. and after it finds a neighbor. view the configuration after you enter the network 131.1. typically a hello packet with no data Holdtime The length of time a router waits for a hello packet before tearing down a neighbor adjacency Smooth Route Trip Time (SSRT) The amount of time required to send a packet reliably to an acknowledgment Retransmission Timeout (RTO) The amount of time required to respond to an acknowledge packet Feasible distance Metric to remote network." This chapter covers EIGRP in greater detail using a simple two-router topology. by default.1.108. EIGRP Terms Meaning Neighbor A router in the same autonomous system (AS) running EIGRP Hello A packet used to monitor and maintain EIGRP neighbor relationships Query A query packet that is sent to neighboring routers when a network path is lost Reply A reply packet to a query packet ACK Acknowledgment of a packet. Example 5-1 R1 EIGRP Configuration R1(config)#router eigrp 1 R1(config-router)#network 131. "Routing Principles.144 - . Figure 5-1. you must first enable EIGRP with the command router eigrp autonomous system while in global configuration mode.0 command. the AS needs to be the same. For routers sharing the same IP domain.0 Notice that 131. lowest is preferred Feasible successor A neighboring router with a lower AD Successor A neighboring router that meets the feasibility condition Stuck in Active (SIA) An EIGRP router waiting for an acknowledgment from a neighboring router Active The time during which a router is querying neighboring routers about a network path Passive Normal operation of a route to a remote destination You have already configured IGRP and EIGRP in Chapter 2. Figure 5-1 displays a simple two-router EIGRP network in Autonomous System 1. . This section shows you how to enable EIGRP on both routers in Figure 5-1.108.CCNP Practical Studies: Routing Table 5-1. Example 5-1 displays the configuration of EIGRP on R1. the Cisco routers advertise all IP network entries.

This URL can be accessed for free and contains every command available on Cisco routers and switches. Example 5-5 displays the EIGRP topology table on R1 using the IOS show ip eigrp topology command. Example 5-3 R2 EIGRP Configuration R2(config)#router eigrp 1 R2(config-router)#network 131. Example 5-4 EIGRP Neighbors on R1 R1#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 0 131. .1.0.. For example. router eigrp 1 network 131. or reply packets that the IOS software is waiting to send to the neighbor.CCNP Practical Studies: Routing Example 5-2 displays the running configuration of R1.108. that the Cisco IOS Software waits to hear from the peer before declaring it down.0 .htm for more information. use the show ip eigrp neighbors command. Q Cnt indicates the number of update. the network 131. Any updates or changes are sent immediately and both routers maintain topology tables. NOTE IOS version 12. Consult the latest command reference on the Cisco Web site at www. 131. For example.0 command places the Ethernet interface of R1 in EIGRP 1. A topology table is created from updates received from all EIGRP neighbors.108. Smooth Round Trip Time (SRTT) is the number of milliseconds it takes for an EIGRP packet to be sent to this neighbor and for the local router to receive an acknowledgment of that packet. or reply packet that was received from this neighbor.15.108.1.. Example 5-3 displays the same EIGRP configuration on R2.4(T) supports the use of the wildcard mask.108.0/24. The AS is set to 1 on both routers to enable both routers to share IP routing information.1 0.0.cisco. you can configure the Class B network. query.2.108.2. which are covered in this chapter. To view EIGRP neighbor relations between two Cisco routers.0. query. truncated for clarity. which works as the OSPF wildcard mask does. you use hello packets to ensure that both routers are active and running.1.1.0 R2 has a number of loopbacks to populate the IP routing tables ranging from 131.2 Et0/0 Hold Uptime SRTT (sec) (ms) 12 00:00:34 4 RTO Q Seq Cnt Num 200 0 1 Example 5-4 displays the neighbor R2 with the IP address 131.com/univercd/home/home. Retransmission timeout (RTO) indicates the amount of time the IOS software waits before resending a packet from the local retransmission queue. Example 5-2 R1 EIGRP Configuration . Sequence number (SEQ NUM) is the last sequenced number used in an update.108. EIGRP needs only the major network boundary when using the network command. The EIGRP topology table is used to maintain IP routing entries in the IP routing table.. instead of entering the address 131.108.145 - .0.0.0.0 to 131.108.0. EIGRP supports summarization and VLSM. in seconds. To maintain EIGRP between R1 and R2.0. and the outbound interface the EIGRP neighbor (in this case R2) was discovered.108. Example 5-4 displays the EIGRP neighbors on R1.. The holdtime indicates the length of time. R1 discovered a remote EIGRP neighbor through the Ethernet interface (displayed as Et0/0).

108. 1 successors.6.108.4.2 (409600/128256).1.108. FD is 409600 via 131.2 (409600/128256).108.0/24.108.1.108.0/24.1. FD is 281600 via Connected. Ethernet0/0 P 131. For example.108. Ethernet0/0 P 131.146 - .108. .0/24.108. 1 successors.2 (409600/128256).1.Active.1. Any changes sent among neighboring routers are sent reliably (using sequence packets and ensuring packet delivery). 1 successors. which increases convergence time.2 (409600/128256). Table 5-2 summarizes the contents of the topology table in Example 5-5.108.CCNP Practical Studies: Routing Example 5-5 R1's EIGRP Topology Table R1#show ip eigrp ? interfaces IP-EIGRP interfaces neighbors IP-EIGRP neighbors topology IP-EIGRP Topology Table traffic IP-EIGRP Traffic Statistics R1#show ip eigrp topology IP-EIGRP Topology Table for process 1 Codes: P .0/24. if a network failure does occur.8. Ethernet0/0 P 131.108. Entries in this topology table can be updated by changes in the network or interface failures. 1 successors.2 (409600/128256).108.1. Ethernet0/0 P 131.108.0/24. Ethernet0/0 P 131.2 (409600/128256). Ethernet0/0 P 131. FD is 409600 via 131.1. FD is 409600 via 131.2 (409600/128256). 1 successors. and with a finite time.14. 1 successors.9.5. 1 successors. Ethernet0/0 P 131. 1 successors. FD is 409600 via 131.0/24.0/24. 1 successors.0/24. Also.2 (409600/128256). 1 successors. FD is 409600 via 131. DUAL is based on detecting a network change within a finite amount of time.1.0/24.1. updates are sent and received quickly. U .0/24.11. FD is 409600 via 131.1.108.2. 1 successors. FD is 409600 via 131. FD is 409600 via 131. Ethernet0/0 P 131.13.10.108.0/24. notice the number of different IOS show commands possible.0/24. the topology table receives an update to recalculate the path to the remote entry using the algorithm called Diffusing Update Algorithm (DUAL).7.108. Because the algorithm is calculated almost instantaneously. 1 successors.108.2 (409600/128256).2 (409600/128256). Ethernet0/0 P 131. Ethernet0/0 P 131.108.108.108.2 (409600/128256). Ethernet0/0 P 131. FD is 409600 via 131.108.108. Q . DUAL is an algorithm developed by Cisco that performs the calculations on the topology table.2 (409600/128256). in order.1. FD is 409600 via 131.1. 1 successors.15.1.Update.108.0/24. Ethernet0/0 P 131. FD is 409600 via 131.1.Query. Ethernet0/0 P 131. R .2 (409600/128256). FD is 409600 via 131.Reply status P 131. Ethernet0/0 Example 5-5 displays a wealth of information about all the remote entries EIGRP discovers. 1 successors.108. FD is 409600 via 131.108.108. r .1.Reply.108. 1 successors.0/24.Passive.108. FD is 409600 via 131.2 (409600/128256).0/24. Ethernet0/0 P 131.108. A .3.12.

108.1. 00:31:02.108. These indicate the destination IP network number and mask. Indicates that a reply packet was sent to this destination. the feasibility condition is met.2. Ethernet0/0 If you simulate a network failure by shutting down the network 131.2.1.11. Ethernet0/0 D 131.2. R1 has only one path.108.255.108.1.1. it does not have to send a query for that destination.108. or 3. Ethernet0/0 D 131. Indicates that a query packet was sent to this destination. It can be the number 0. Ethernet0/0 D 131.108.108.108.3.255. and that path is a feasible successor. 1.1.9.108. Ethernet0/0 D 131. Query.1.108.0 [90/409600] via 131. 15 subnets D 131. Replies State Via (409600/128256) Ethernet0/0 Now that R1 has established a relationship with R2. Ethernet0/0 D 131. 00:31:02. 00:31:02.) Example 5-6 displays R1's IP routing table.2. Update.1. 00:31:02.2.15. The remaining entries on the list are feasible successors.2.EIGRP.0 [90/409600] via 131. 00:31:04. Number of replies that are still outstanding (have not been received) with respect to this destination.1.0 [90/409600] via 131.108.0 [90/409600] via 131. This information appears only when the destination is active.4. (Active means the remote entry is being recalculated.14.0 on R2. The first number is the Enhanced IGRP metric that represents the cost to the destination.5.0.1.108. Feasible distance.0 [90/409600] via 131.108. 00:31:02. Flag that is set after the software has sent a query and is waiting for a reply.2.0/24 and so on successors FD Definition State of this topology table entry.108. hence only one successor.2.1.2.0 [90/409600] via 131.8. EX . Interface from which this information was learned. with all entries in a passive state.108. Exact enhanced IGRP state that this destination is in. Example 5-6 R1's IP Routing Table R1#show ip route Codes: D . 00:31:02. you can expect to see remote IP routing entries. No Enhanced IGRP computations are being performed for this destination.147 - .1.0 [90/409600] via 131.EIGRP external 131.2. Ethernet0/0 D 131.2.7.108. by maintaining a topology table.1.CCNP Practical Studies: Routing Table 5-2.108. The first N of these entries.12.0 [90/409600] via 131. 00:31:02. Ethernet0/0 D 131.13.0 [90/409600] via 131.108.108.6.1. This value is used in the feasibility condition check. Ethernet0/0 D 131.108.0/24 is subnetted. are the current successors.0 [90/409600] via 131.2. Reply. where N is the number of successors. Example 5-7 displays R1's new topology table.0 [90/409600] via 131.108.0.108. Indicates that an update packet was sent to this destination.108. 00:31:02.108.108. 00:31:02.0 [90/409600] via 131.2.15.108. Ethernet0/0 C 131. Number of successors. Ethernet0/0 D 131. Ethernet0/0 D 131.108. Reply status.2.2.10.0 [90/409600] via 131. Ethernet0/0 D 131. EIGRP Topology Table Definitions Term Codes P A U Q R r 131.0 is directly connected. After the software determines it has a feasible successor. Ethernet0/0 D 131.108. IP address of the peer that tells the software about this destination.1. The second number is the Enhanced IGRP metric that this peer advertises.15. 00:31:02. Active. in this case 255. R1's next hop address is 131.108.2. Ethernet0/0 D 131.1.108. 00:31:02.108. Enhanced IGRP computations are being performed for this destination. This information appears only when the destination is in active state.108. This number corresponds to the number of next hops in the IP routing table. 00:31:02. 2. If the neighbor's reported distance (the metric after the slash) is less than the feasible distance.0 [90/409600] via 131. Passive. 00:31:02.1. .108.

3. and look at R1's topology table after you alter all the networks from Class C networks to a range of variable-length subnet masks (VLSM). 1 successors.1.108.108. modify the IP networks on R2.6. Ethernet0/0 P 131.148 - .108.0/24.108.14.0/24. 1 successors.5.108. 1 successors. For remote entries with multiple routes.0/24. Ethernet0/0 P 131.108.108. you can discover the number of paths available and why EIGRP chooses a certain path.2 (409600/128256). FD is 409600 via 131.2 (409600/128256).0/24. so by simply viewing the topology table.0/24.108. FD is 281600 via Connected.108.1.1.8.2 (409600/128256).0/24. FD is 409600 via 131.2 (409600/128256). Example 5-8 displays R1's topology table after the networks on R2 have been changed. EIGRP uses the feasible condition (FC) to determine the best path.2 (409600/128256).0/24. all updates contain an entry for the subnet mask. To demonstrate this. EIGRP maintains IP routes by using DUAL and maintaining an EIGRP topology table. therefore.108.108.12.CCNP Practical Studies: Routing Example 5-7 R1's Topology Table R1#show ip eigrp topology IP-EIGRP Topology Table for process 1 P 131.108.108. Ethernet0/0 P 131.1.4.108. FD is 409600 via 131. FD is 409600 via 131. Ethernet0/0 P 131. Ethernet0/0 Example 5-7 does not display the remote entry 131.108.0/24.108. Ethernet0/0 P 131. Ethernet0/0 P 131.10.0/24. The EIGRP routing algorithm always chooses the path to a remote destination with the lowest metric.1. 1 successors. 1 successors. FD is 409600 via 131.2 (409600/128256).1.1.108.1.2 (409600/128256). FD is 409600 via 131.108. FD is 409600 via 131. Ethernet0/0 P 131.1. FD is 409600 via 131.0/24. Ethernet0/0 P 131. Ethernet0/0 P 131.1.7. FD is 409600 via 131.108.108.15.108.108.0/24. Ethernet0/0 P 131.11.1. .2 (409600/128256). 1 successors. FD is 409600 via 131.108.0/24. 1 successors. EIGRP supports the use of VLSM. and.108.1. 1 successors. FD is 409600 via 131.108. FD is 409600 via 131.108. 1 successors. 1 successors.108.1.0/24.0/24.9.108. 1 successors.2 (409600/128256).2 (409600/128256). The topology table maintains all paths to remote networks.2 (409600/128256).0/24. Ethernet0/0 P 131.2 (409600/128256). 1 successors. Ethernet0/0 P 131. Ethernet0/0 P 131. FD is 409600 via 131.2 (409600/128256). it is not present in the IP routing table.1. 1 successors. 1 successors.13.2.

12.0/27. Example 5-9 R1's EIGRP Routing Table R1#show ip route eigrp 131. 1 successors.108.1.108. Ethernet0/0 P 131.2 (409600/128256). 15 subnets.2. FD is 409600 via 131.2.108.1. FD is 409600 via 131.2.108. 00:02:24. Ethernet0/0 P 131.1. FD is 409600 via 131. 1 successors.108.108. Ethernet0/0 D 131. Ethernet0/0 D 131.1.108. 00:02:27.1.0/24.2 (409600/128256). FD is 409600 via 131.108.2 (409600/128256).108.2 (409600/128256).108. Ethernet0/0 D 131.108.108.0.1. Ethernet0/0 D 131.0/29 [90/409600] via 131.15. FD is 409600 via 131.9.108.0/24 [90/409600] via 131.2.108.0/30 [90/409600] via 131.108.0/27.108.108. Ethernet0/0 D 131.14.108.0/28.1. 1 successors.2. 00:02:37.0/30.0/26 [90/409600] via 131.1.2 (409600/128256).108.108.108.2.3.108.108.0/30 [90/409600] via 131.108.108.108.1.108.5.0/24. Ethernet0/0 D 131.0/24.108. 1 successors.1.7.0/27 [90/409600] via 131.15. Ethernet0/0 Example 5-8 displays a range of non-Class C networks.108.0/25 [90/409600] via 131.108.1.2 (409600/128256). Ethernet0/0 P 131.2.1.2 (409600/128256).1.2. 00:58:15. 00:02:22.108. 00:02:39. 1 successors. Ethernet0/0 D 131.1.0/29 [90/409600] via 131. FD is 409600 via 131.11.2 (409600/128256).108.0/29.108.0/25. FD is 409600 via 131.4.108. FD is 409600 via 131. 1 successors.108.108.0/16 is variably subnetted.108. Ethernet0/0 P 131. 00:02:35. Ethernet0/0 D 131.108.13.2 (409600/128256). Ethernet0/0 P 131. 1 successors. 00:02:20.10.5. demonstrating the powerful use of VLSM with EIGRP. FD is 409600 via 131.108.10.108.108. Ethernet0/0 P 131.2 (409600/128256).0/30.2.108. FD is 281600 via Connected. 1 successors. Ethernet0/0 . FD is 409600 via 131.1.0/26.149 - . 00:02:29.108.6.0/30 [90/409600] via 131. Ethernet0/0 P 131.108.0/29.1.0/28 [90/409600] via 131. 1 successors.108.2 (409600/128256).108.2. 1 successors. Ethernet0/0 D 131.2.0/25 [90/409600] via 131. Ethernet0/0 D 131.2 (409600/128256).108. Ethernet0/0 P 131.108.1. Ethernet0/0 P 131.108.7. 1 successors. 00:02:25.1.4.8.1. 1 successors. Ethernet0/0 P 131.2 (409600/128256).0/27 [90/409600] via 131. 00:02:34.1.9.0/24 [90/409600] via 131.108. Ethernet0/0 P 131. 00:02:30.1.2.108.11.0/27. Example 5-9 displays the new IP routing table for completeness. FD is 409600 via 131.1.14. FD is 409600 via 131.1.1.108.3.108. Ethernet0/0 P 131. FD is 409600 via 131. Ethernet0/0 D 131.12. Ethernet0/0 D 131. 00:02:32.CCNP Practical Studies: Routing Example 5-8 R1's Topology Table R1#show ip eigrp topology IP-EIGRP Topology Table for process 1 P 131.0/25.0/30.1.2.13.2.8.6. 1 successors.108.2. Ethernet0/0 P 131.1. FD is 409600 via 131.2. 7 masks D 131.1.108.108. Ethernet0/0 D 131. Ethernet0/0 P 131.1. 00:20:15.2 (409600/128256). 1 successors.108. 1 successors.108.0/27 [90/409600] via 131.1.

8. up to 50 percent of any link can be consumed by EIGRP. this is also configurable using the ip bandwidth-percent eigrp AS percent command. The following two conditions are required before load balancing over unequal paths can take place: • • The local best metric must be greater than the metric learned from the next router.0–131. The multiplier times the local best metric for the destination must be greater than or equal to the metric through the next router.0 255. Example 5-11 Summary on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip summary-address eigrp 1 131. you can use the bandwidth command to adjust the composite EIGRP metric so that you can perform equal-cost load balancing on unequal speed links. To manually summarize networks. you must disable this feature with the no auto-summary IOS command. (By default.15.108. so you must ensure that EIGRP packets or updates are sent over a nonbroadcast network. The bandwidth command does not always have to reflect the actual bandwidth of the interface. EIGRP Route Summarization and Large IP Network Support EIGRP supports the use of summarization to conserve IP routing table size.255.8. The bandwidth command is used in EIGRP metric calculation and defines the amount of bandwidth. To perform static summarization.255–131. Re-examine Figure 5-1 and summarize the networks 131.8.0 are contiguous. EIGRP automatically summarizes at the major network boundaries.15.108.0 to 131. First.255–131.108.108.248. Example 5-11 displays the summary command completed on R2's link to R1.255.8.0 to incorporate the range of networks from 131.8. Summarization in EIGRP can be configured on any router in the same AS.15.0 R1 should now have only one remote routing entry for the networks 131.) EIGRP does not have any way of statically defined neighboring. Example 5-10 displays the disabling of automatic summarization on R2. The allocated bandwidth for EIGRP must be the same on each virtual circuit between two remote routers. The IOS variance command provides another method for achieving unequal load balancing. The use of the bandwidth command should reflect the true speed of any interface. you must advertise the supernet.15.108. you can apply the mask 255. for example.248.255 as displayed in Example 5-12.255.108.CCNP Practical Studies: Routing EIGRP in NBMA Environments You can successfully configure EIGRP over NBMA networks if you apply the following rules: • • • EIGRP traffic should not exceed the committed information rate (CIR). even though the path might be over a slower wide-area network (WAN) link. By default.108.255. Example 5-10 Disabling Automatic Summarization on R2 R2(config)#router eigrp 1 R2(config-router)#no auto-summary Because the networks 131. In fact. EIGRP aggregated traffic over all virtual circuits should not exceed the access line speed. you must disable automatic summarization on R2. on an interface level with the ip summary address eigrp autonomous system mask command.108.150 - . Setting a variance value lets the Cisco IOS Software determine the feasibility of a potential route.108. . under the routing process.

0/16 is D 131.108.2. As with any legacy protocol. you can use several Cisco IOS enhancements. 00:01:13. 00:01:13.2. Scenario 5-1: Configuring EIGRP In this scenario.2. Assume the core backbone network resides on the Ethernet between R1 and R2. and with proper configuration.108.255. In the following five scenarios.5. and Border Gateway Protocol (BGP) are far more common routing protocols. [90/409600] via 131.1. 00:01:13. especially in today's large IP-based network. Intermediate System-to-Intermediate System (IS-IS).0 or /24). [90/409600] via 131. it can be well-maintained.0. 00:01:13.2.8.108.0/24 D 131.1.108. to fine-tune EIGRP.1. Open Shortest Path First (OSPF).108. 00:01:13.2. 00:01:14. [90/409600] via 131. the number of routers in your network. [90/409600] via 131. EIGRP can scale in a well-designed IP network.1.108. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs. 8 subnets.108.0/24 D 131.108.0/24 D 131.1. 2 masks [90/409600] via 131. and the abilities to use good practice and define your end goal are important in any real-life design or solution.108. Several factors can contribute to a poorly designed network.3.108.108.108. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 To support large IP networks.0 with a Class C subnet mask (255.108.108.4.255.2.0. 00:01:13.0/21 D 131.0/24 D 131. There is no one right way to accomplish many of the tasks presented. [90/409600] via 131. Figure 5-2 displays a network with seven routers in AS1 and one remote router in AS2.1.151 - . the used-by date of EIGRP is fast approaching.108.108. load balancing.1.CCNP Practical Studies: Routing Example 5-12 R1's EIGRP Routing Table R1#show ip route eigrp 131.0/24 variably subnetted. you configure eight Cisco routers for IP routing using a Class B (/16) network 131.2. [90/409600] via 131. . and reducing the load on WAN links with the bandwidth command.2. the network diameter of your network (hop count in EIGRP is still 255).6. The serial links will use a two-host subnet to demonstrate the use of VLSM with EIGRP. such as the amount of routing information exchanged between routers.7. and the number of alternative paths between routers. such as network summarization. you configure and monitor some sample EIGRP networks and apply the knowledge you have gained.0/24 D 131.

0/24 IP Address Range Start by enabling EIGRP on all the routers in AS 1.1-15.108.255.36. The same configuration commands are applied to all routers in AS 1 because the same Class B network.128. Example 5-13 Enabling EIGRP on R1 R1(config)#router eigrp ? <1-65535> Autonomous system number R1(config)#router eigrp 1 R1(config-router)#network 131.108.108.108.0/24 131.130.108./24 131. 131.1/24 131.CCNP Practical Studies: Routing Figure 5-2. Note the use of VLSM across the WAN Links.1.1/24 131.2.108.34.1-33. EIGRP in AS 1 and AS 2 The IP address assignment for the WAN links is described in Table 5-3.255.0.129.32.1-31.108.108.0/24 131. is in use.0.0 Example 5-13 configures R1 with EIGRP in AS 1 and enables EIGRP updates to be sent and received on all interfaces configured with an address in the range 131.0/24 131.1-35.0/30 131.1/24 131.255. issue the show ip eigrp interfaces command.0–131.108. To display the interface running EIGRP.108.0.108.131.152 - .108.1. IP Address Assignments Router R1 R2 R3 R4 R5 R6 R7 R8 WAN links LAN link 131.0.108. Table 5-3. . Example 5-13 displays enabling EIGRP on R1.16.0/24 168.

108.108.2). R1 has established a neighbor relationship to R2 through Ethernet 0/0 and R3 through S0/0. Example 5-15 displays the sample output taken from R1.2 131.108. Example 5-16 displays R1's EIGRP IP routing table. display the neighbors on R1 by using the show ip eigrp neighbors command on R1. Next.1.1. note that you have EIGRP neighbors through E0/0 and S0/0.108. In other words.2 Se0/0 Et0/0 Hold Uptime SRTT (sec) (ms) 14 03:41:45 57 10 03:43:42 2 Q Cnt 342 0 200 0 RTO Seq Num 3 4 Two neighbors are formed with R1. Example 5-15 show ip eigrp neighbors Command on R1 R1#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 1 0 131.1. namely R2 (131.CCNP Practical Studies: Routing Example 5-14 displays the interfaces running EIGRP on R1. .255. Also.153 - .2) and R3 (131. Example 5-14 Sample Output of show ip eigrp interfaces on R1 R1#show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Interface Peers Un/Reliable SRTT Et0/0 1 0/0 2 Se0/0 1 0/0 57 Lo0 0 0/0 0 Lo1 0 0/0 0 Lo2 0 0/0 0 Lo3 0 0/0 0 Lo4 0 0/0 0 Lo5 0 0/0 0 Lo6 0 0/0 0 Lo7 0 0/0 0 Lo8 0 0/0 0 Lo9 0 0/0 0 Lo10 0 0/0 0 Lo11 0 0/0 0 Lo12 0 0/0 0 Lo13 0 0/0 0 Pacing Time Un/Reliable 0/10 0/15 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 Multicast Flow Timer 50 50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pending Routes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Example 5-14 displays a number of physical (E0/0 and Se0/0) interfaces running EIGRP and a number of loopbacks numbered from 0 to 13.

18.108.108. Ethernet0/0 D 131. Example 5-18 EIGRP in AS 2 on R8 R8(config)#router eigrp 2 R8(config-router)#network 168.2.108.26.0/24 [90/409600] via 131.108.108. 00:04:15. Ethernet0/0 D 131.2. Ethernet0/0 D 131.108.1.1. Ethernet0/0 D 131.0.131.0/24 [90/409600] via 131.108.30.4/30 [90/20537600] via 131.108.108. Ethernet0/0 D 131. .2.108.28.23.1.108.1.1. Example 5-17 EIGRP in AS 2 on R4 R4(config)#router eigrp 2 R4(config-router)#network 168. 00:04:15.255.0/24 [90/409600] via 131.108.2. Ethernet0/0 D 131. Example 5-17 displays the EIGRP configuration on R4 in AS 2 (network 168.108. 00:00:10. Ethernet0/0 R1 has a dual path to three remote networks because the composite metric is the same.22.108.0/24 [90/409600] via 131.108.1.1. Ethernet0/0 D 131.24.1. Serial0/0 [90/21529600] via 131.255.108. 00:04:16. Next. Serial0/0 D 131.0/30.17. 00:04:16.130.255.131.0/24 [90/409600] via 131. 00:04:15. The serial link between R4 and R8 contains the network 168.2.0/24 [90/21529600] via 131.108. Ethernet0/0 D 131.108.108.108.255. Ethernet0/0 D 131.108. Serial0/0 D 131. 00:04:15.108.0/24 [90/409600] via 131.2.29. 00:04:16.2.129.2.1.128. 00:00:10.8/30 [90/21504000] via 131.2. Example 5-19 displays the EIGRP neighbors on R4. 00:04:15.108.255.1.0 Example 5-18 displays the EIGRP configuration on R8 in AS 2 (network 168.2.0/24 [90/20537600] via 131.0. 00:04:15.131.27. 00:04:15.108.0/24 [90/409600] via 131. Serial0/0 D 131.2.108.255. Serial0/0 [90/21555200] via 131.2.1. 00:04:14. 00:04:14.108.31. 00:04:14.0/24 [90/409600] via 131.1. 00:00:15. Ethernet0/0 D 131.0.108.108. 00:04:15.2. Ethernet0/0 [90/21529600] via 131.36.108.0/24 [90/409600] via 131.108.108.1.0/24 [90/409600] via 131.108. 00:04:16.0/24 [90/409600] via 131. 2 masks D 131.0/24 [90/21555200] via 131.108.108.255.108.108. 00:04:15.255.108. configure EIGRP on R4 and R8 in AS 2. Ethernet0/0 D 131.2. 00:04:16.25.255.0/24 [90/409600] via 131.0/24 [90/409600] via 131.154 - .0 You should expect to see a neighbor between R4 and R8.2.108.12/30 [90/21504000] via 131.0/24 [90/409600] via 131.16/30 [90/21529600] via 131. 00:04:16.20.108.0).1.2. Serial0/0 D 131.255. Ethernet0/0 D 131.2. Serial0/0 D 131.0/16 is variably subnetted.0/24 [90/409600] via 131.21.108. R4 resides in two autonomous systems: 1 and 2. Ethernet0/0 D 131.2. Serial0/0 D 131.20/30 [90/21529600] via 131.108.2.2. 00:04:15.2. Ethernet0/0 D 131. 00:00:15. R1 has no path to the remote network on R8 in EIGRP AS 2.108.0/24 [90/21529600] via 131.0.1.255. 00:04:15.1.108.2.108.131. Ethernet0/0 D 131.108.1.0.108. Ethernet0/0 D 131. 00:04:14. 00:04:15.2.0).1.2.0/24 [90/409600] via 131.108.19.16.1. 00:04:15.108.108. Ethernet0/0 D 131.255.108.108. 00:04:15.108.108. 41 subnets.2.108.2.131.2.255.CCNP Practical Studies: Routing Example 5-16 show ip route eigrp on R1 R1#show ip route eigrp 131.2.2. Ethernet0/0 D 131.1.

131.131.CCNP Practical Studies: Routing Example 5-19 show ip eigrp neighbors on R4 R4#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 2 131.2.5 Se0 1 131. Display the IP routing table on R8. The ? tool is used here to highlight the parameters the Cisco IOS requires.155 - .108. 2 masks C 168.108. R4 must provide two-way redistribution. (EIGRP and IGRP automatic redistribution occurs only if the AS is the same. and ensure connectivity to the rest of the network. Example 5-21 displays the configuration of two-way redistribution between AS 1 and 2. R4 must be configured for redistribution because EIGRP does not automatically redistribute among different autonomous systems.) If the routers in AS 1 want to send data to AS 2.0/16 is variably subnetted.2.0/24 is directly connected.255. 2 subnets.108.255.0.36. Serial0 C 168. R4 has established EIGRP neighbors with routers in AS 1 and AS 2. TIP You must be careful when performing any redistribution to ensure that networks residing in one domain do not contain routes or subnets in the redistributed domain.2 Se2 Hold Uptime SRTT (sec) (ms) 14 00:09:02 640 11 00:14:09 15 12 00:18:22 1 Hold Uptime SRTT (sec) (ms) 12 00:04:04 239 Q Cnt 3840 0 1164 0 200 0 RTO RTO Seq Type Num 4 92 157 Q Seq Type Cnt Num 1434 0 3 Router R4 resides in two different autonomous systems: 1 and 2. in 10 microsecond units R4(config-router)#redistribute eigrp 2 metric 125 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R4(config-router)#redistribute eigrp 2 metric 125 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R4(config-router)#redistribute eigrp 2 metric 125 20000 255 1 ? <1-4294967295> IGRP MTU of the path . Ethernet0 R8 has no remote EIGRP entries because R4 is not redistributing IP networks from EIGRP AS 1 into 2. Example 5-20 show ip route neighbors on R8 R8#show ip route 168. Example 5-20 displays the IP routing table on R8.0/30 is directly connected. Hence. Route maps or distributed lists should always be applied to ensure routing loops do not occur.131.18 Se1 0 131. Example 5-21 Redistribution on R4 Between AS 1 and 2 R4(config)#router eigrp 1 R4(config-router)#redistribute eigrp ? <1-65535> Autonomous system number R4(config-router)#redistribute eigrp 2 ? metric Metric for redistributed routes route-map Route map reference <cr> R4(config-router)#redistribute eigrp 2 metric ? <1-4294967295> Bandwidth metric in Kbits per second R4(config-router)#redistribute eigrp 2 metric 125 ? <0-4294967295> IGRP delay metric.3 Et0 IP-EIGRP neighbors for process 2 H Address Interface 0 168.1.131.

1. 00:02:58. Serial0 D EX 131.2.22.1.0. 00:02:58. 00:02:59.108.108.131.1.EIGRP external 168.2.27. 00:02:57. Serial0 .131.131.2. Serial0 D EX 131.0/24 [170/26112000] via 168. 00:02:59. Serial0 C 168.108.2.1.131. 00:02:59.0/24 [170/26112000] via 168.108. Serial0 D EX 131.1.131. 00:03:00. 00:02:59.1. 00:02:59.1. 00:02:58.108.131.255.5.21. 3 masks D EX 131. 00:02:59.1.108.1.1. D .0/24 [170/26112000] via 168. Serial0 D EX 131.108.108. 00:02:58.131.0/24 [170/26112000] via 168.131. 00:02:58.131. Serial0 D EX 131.130.0/16 is variably subnetted.1.108.18.108. Serial0 D EX 131.131.0/24 [170/26112000] via 168.108. 00:02:58.1.0/24 [170/26112000] via 168.0/16 is variably subnetted.1.131.0/24 [170/26112000] via 168.131.255.0/24 [170/26112000] via 168.17.2. Serial0 D EX 131.108. 00:02:59.connected.131.131.0/24 [170/26112000] via 168. Serial0 D EX 131. Serial0 D EX 131.1. Serial0 D EX 131.0/24 [170/26112000] via 168.108.2.131.108.0/24 is directly connected.1.4/30 [170/26112000] via 168.255.131. Serial0 D EX 131.2.156 - . 00:03:00. 00:02:59.131. 00:03:00. Serial0 D EX 131.2. 00:02:58.131.108.108. Serial0 D EX 131. 00:02:58.108.2. Serial0 D EX 131.31.131.3.131.131.108.1.1. Serial0 D EX 131. Serial0 D EX 131. Serial0 D EX 131. 00:02:59.131.36.131. 00:02:58.2.0/30 is directly connected. 00:02:59.108. 00:02:59.0/24 [170/26112000] via 168.1. Serial0 D EX 131. 00:02:58. 00:03:00.4. 00:02:58. Serial0 D EX 131.1.2.25.108.131. EX .108. 00:03:00. Serial0 D EX 131. 00:02:58.1. Serial0 D EX 131. Serial0 D EX 131.2.131.131.255.2.CCNP Practical Studies: Routing R4(config-router)#redistribute eigrp 2 metric 125 20000 255 1 1500 R4(config-router)#router eigrp 2 R4(config-router)#redistribute eigrp 1 metric 125 20000 255 1 1500 After you configure redistribution on R4.0/24 [170/26112000] via 168.2.1.0/24 [170/26112000] via 168.131.131. 41 subnets. Serial0 D EX 131.2.131.8.1.108.16.2.2. 00:03:00.131.108. Serial0 D EX 131.7.131.131.0/24 [170/26112000] via 168.20.131.9. Serial0 D EX 131.1.2.0/24 [170/26112000] via 168.28. Serial0 D EX 131.2.1.6.2.12/30 [170/26112000] via 168.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168.108. 00:02:57.108.108.1.0/24 [170/26112000] via 168.108.128. Serial0 D EX 131. 00:02:57.1.1.2. Serial0 D EX 131.0/24 [170/26112000] via 168.131.108. 00:02:58. 00:02:59.24.0/16 [170/26112000] via 168. 2 subnets.0/24 [170/26112000] via 168.1.1.2. Serial0 D EX 131.0/24 [170/26112000] via 168.2.0/24 [170/26112000] via 168.108.1.2. Serial0 D EX 131.108.108. 00:02:59.131. Example 5-22 show ip route Command on R8 R8#show ip route Codes: C .131.2.0/24 [170/26112000] via 168.1.0/24 [170/26112000] via 168.14.1.30.2.2.129.0/24 [170/26112000] via 168. Example 5-22 displays R8's IP routing table.1.23.29.1.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168.108.2.108. Serial0 D EX 131.2.2.0. Ethernet0 131.0/24 [170/26112000] via 168.16/30 [170/26112000] via 168.19.1.131.108.10.2. 00:02:58.108.1.108.1.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168.108.255.2.26.108.131.11.131.2.1. Serial0 D EX 131.108.0.108.2.131. 00:03:00. 00:02:59.0/24 [170/26112000] via 168. Serial0 D EX 131.2. Serial0 D EX 131.2.2.108.1. you can expect to see R8 with IP routing information from AS 1.2.108. Serial0 D EX 131.1. Serial0 D EX 131.131.2. 00:02:59.2. 00:02:58.1.0/30 [170/26112000] via 168. Serial0 D EX 131.13.1. Serial0 D EX 131.1.15.EIGRP. 00:03:00.131. 2 masks C 168.0/24 [170/26112000] via 168.2.131.0/24 [170/26112000] via 168.131.2.12.8/30 [170/26112000] via 168. Serial0 D EX 131.0/24 [170/26112000] via 168.2. Serial0 D EX 131.

108. Notice that all the networks from AS 1 are tagged as D EX.1 255.255.1 255.108.255.5.12.0 ! interface Loopback6 ip address 131.0 ! interface Loopback8 ip address 131.255. such as the bandwidth statement used to match the wire speed between routers.108. Before you configure EIGRP to summarize wherever possible in Figure 5-2.1 255.255.CCNP Practical Studies: Routing R8 has an expanded IP routing table.0 ! interface Loopback5 ip address 131.15.255.0 ! interface Loopback13 ip address 131.255. or external EIGRP.108.108.108.108.1 255.255.108.255.108.2.255.255.255. Take particular note of the shaded sections.255.0 ! interface Ethernet0/0 .0 ! interface Loopback12 ip address 131.0 ! interface Loopback1 ip address 131.255.1 255.108. Example 5-23 displays R1's full working configuration.255.3.7.8.255.255.255.255.108.255.255.10.1 255.108.0 ! interface Loopback3 ip address 131.255.1 255.1 255.1 255.255.255.0 ! interface Loopback2 ip address 131. The bandwidth statement ensures proper calculation of the EIGRP composite metric and also ensures that EIGRP does not consume more than 50 percent of the bandwidth.4.1 255.108.1 255.0 ! interface Loopback11 ip address 131.0 ! interface Loopback9 ip address 131.255.14.0 ! interface Loopback7 ip address 131.157 - .1 255.1 255. By default.255. Cisco IOS routers set the bandwidth to 1544 kbps. here are the full working configurations of all eight Cisco routers running EIGRP.9.0 ! interface Loopback10 ip address 131.255.1 255.255.13.255. Example 5-23 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.0 ! interface Loopback4 ip address 131.11.6.108. and the AD distance is 170 (or less trusted than Internal EIGRP set at 90).

108.108.20.1 ! interface Loopback3 ip address 131.108.108.108.1 ! interface Loopback1 ip address 131.0 ! line con 0 line aux 0 line vty 0 4 ! end Example 5-24 displays R2's full working configuration.255.0 255.0 ! interface Serial0/0 bandwidth 128 ip address 131.255.255.255.255.0 255.0 .0 255.108.1 ! interface Loopback4 ip address 131.1.25.0 255.0 255.18.255.1 ! interface Loopback6 ip address 131.108.108.0 255.0 255.0 255.255.1 ! interface Loopback5 ip address 131.0 255.17.108.108.255.255.1 ! interface Loopback8 ip address 131.108.255.1 ! 255.252 clockrate 128000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131. Example 5-24 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.1 255.255.1 ! interface Loopback2 ip address 131.255.255.255.255.23.19.0.1 ! interface Loopback7 ip address 131.108.158 - .255.21.255.1 ! interface Loopback9 ip address 131.255.255.16.CCNP Practical Studies: Routing ip address 131.255.255.108.1 255.255.255.255.24.22.255.

30.108.255.255.1.3 255.1 ! interface Loopback14 ip address 131.2 255.255.27.255.255.0 255.0.108.0 ! ip classless ! line con 0 line aux 0 line vty 0 4 end Example 5-25 displays R3's full working configuration.1 ! interface Loopback16 ip address 131.108.255.CCNP Practical Studies: Routing interface Loopback10 ip address 131.255.28.0 ! interface Ethernet0/0 ip address 131.159 - .255.255.1 ! interface Loopback11 ip address 131.2 255.0 media-type 10BaseT ! interface Serial0 ip address 131.108.108.0 255.255.108.5 255.255.255.255.255.255.255.26.255.108.255.0 255.0 255.255. Example 5-25 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.108.29.1 ! interface Loopback15 ip address 131.255.108.1 255.108.31.0 ! interface Serial1/0 bandwidth 128 ip address 131.36.252 clockrate 128000 ! interface Serial1/1 shutdown router eigrp 1 network 131.108.0 255.1 ! interface Loopback13 ip address 131.255.252 bandwidth 125 ! .255.

255.252 clockrate 125000 ! interface Serial2 bandwidth 125 ip address 168.9 255.252 bandwidth 125 clockrate 125000 ! interface Serial2 ip address 131.108.131.0 ! interface Serial0 bandwidth 125 ip address 131.6 255.160 - .13 255.1 255.255.CCNP Practical Studies: Routing interface Serial1 ip address 131.0.0. Example 5-26 R4's Full Working Configuration hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.252 bandwidth 125 clockrate 125000 ! interface Serial3 no ip address shutdown ! router eigrp 1 network 131.108.255.255.108.255.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-26 displays R4's full working configuration.255.255. R4 is redistributing between the two EIGRP autonomous systems.255.255.255.255.255.36.252 clockrate 125000 ! interface Serial3 ip address 141.2.255.255.255.108.0 ! router eigrp 2 redistribute eigrp 1 metric 125 20000 255 1 1500 network 168.17 255.252 ! interface Serial1 bandwidth 125 ip address 131.108.1 255.108.255. 1 and 2.252 clockrate 125000 ! router eigrp 1 redistribute eigrp 2 metric 125 20000 255 1 1500 network 131.108.255.0 ! .0.108.4 255.255.255.131.

255.161 - .108.10 255.255.128. Example 5-27 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 131.108.255.252 ! interface Serial1 shutdown ! router eigrp 1 network 131.0 ! interface Serial0 bandwidth 125 ip address 131.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-28 displays R6's full working configuration.129.255.255.0 ! interface Serial0 bandwidth 125 ip address 131.0.255.0 ! line con 0 line aux 0 line vty 0 4! end Example 5-29 displays R7's full working configuration.1 255.252 ! interface Serial1 shutdown ! router eigrp 1 network 131.108. .255.255.255.108.18 255.255.CCNP Practical Studies: Routing line con 0 line aux 0 line vty 0 4 end Example 5-27 displays R5's full working configuration. Example 5-28 R6's Full Working Configuration hostname R6 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 131.108.1 255.0.108.

1.255.2 255.255.162 - .108.CCNP Practical Studies: Routing Example 5-29 R7's Full Working Configuration hostname R7 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 131.255.0 ! line con 0 line aux 0 line vty 0 4 ! end .2.108.252 ! interface Serial1 shutdown ! router eigrp 2 network 168.1 255.0 ! interface Serial0 bandwidth 125 ip address 131.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-30 displays R8's full working configuration.252 ! interface Serial1 shutdown ! router eigrp 1 network 131.255.255.14 255.255.255.0.131. Example 5-30 R8's Full Working Configuration hostname R8 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 168.0. R8 is running EIGRP in AS 2 only.0 ! interface Serial0 bandwidth 125 ip address 168.255.131.1 255.108.255.131.130.

36.131.4.128.163 - .4.0.14. 11:13:47.4.4.108.0/30 is directly connected.108.1.0/24 [170/25625600] via 131. Serial2 D 131. Ethernet0 D 131.255. 10:54:34.0/16 is variably subnetted.0.108.108.4/30 [90/21017600] via 131.16/30 [90/21017600] via 131.255.12/30 is directly connected.108. 11:17:46. 11:17:46.255 reside on two routers.131.0 to 131.108.0/24 [90/21043200] via 131.130. 31 subnets or IP routing entries populate the routing tables in AS 1 and AS 2.129.255.31.CCNP Practical Studies: Routing Scenario 5-2: Summarization with EIGRP In this scenario.0.108.108.1. Ethernet0 131. 10:54:34.36. Example 5-31 displays the IP routing table on R3.108.8/30 is directly connected.0/16 [170/25625600] via 131.131.108.108. Serial1 C 131.108. 2 masks D 131. Serial2 D 131. Serial1 .10.108. 3 subnets.255.108.108.255.36. Ethernet0 C 131.108.0/16 is variably subnetted. 40 subnets. 3 masks D EX 168. Figure 5-3.36. Serial0 D 131.0/30 [170/25625600] via 131. Ethernet0 D EX 168. Ethernet0 D EX 168.2.36.0/24 [90/21017600] via 131. R1 and R2 Connected Networks The networks ranging from 131.131.108.255.0/24 [90/21017600] via 131.4.255. 11:17:45. Ethernet0 C 131. 11:13:41.4. you use summarization with the network configured for EIGRP in Scenario 5-1 and reduce the IP routing table size within an AS and external to the AS.108.108. Example 5-31 R3's IP Routing Table R3#show ip route 168. Figure 5-3 displays the connected routes being advertised by R1 and R2. in other words. 10:54:34.36.

255.0/24 [90/21145600] via 131. 11:17:49.108.108.1.255.108.36.108. Serial0 131.36. Ethernet0 [90/21145600] via 131.1.255.108.0/24 [90/21145600] via 131.108.4.255.108. Serial0 131.108.4. Ethernet0 131. Serial0 R3 has 31 separate network entries for the ranges 131.1.108. 11:17:50.0/24 [90/21120000] via 131.16.1.30.108. 11:17:49.1.108. 11:17:47. 11:17:50. Ethernet0 [90/21145600] via 131.108. 11:17:50.108.4.23. Serial0 131.108. Ethernet0 [90/21145600] via 131.0/24 [90/21120000] via 131.10. Serial0 131.108. Serial0 131.108. Serial0 131. 11:17:47.19.1.255. Serial0 131.26. The subnet mask covering this range is 255.0/24 [90/21145600] via 131.108.36.1.1.4. 11:17:48.7. 11:17:50.108.36. Serial0 131.108. 11:17:48. Ethernet0 [90/21145600] via 131.6.255. 11:17:47. Example 5-32 Summary Configuration on R1 with ? Tool R1(config)#interface serial 0/0 .4.108. 11:17:50. Ethernet0 [90/21145600] via 131. Serial0 131.25.8.31.22.108. 11:17:48. 11:17:51.255.31.108.108.15.15.36.0/24 [90/21145600] via 131.0/24 [90/21145600] via 131.108. Ethernet0 [90/21145600] via 131.108.255. 11:17:49.0/24 [90/21145600] via 131.255. 11:17:50. Example 5-32 displays the interface configuration required for summarizing the networks ranging 131.0/24 [90/21145600] via 131.1.108.4. 11:17:51.17.36.1.108.108.255.1.1. 11:17:49.108.255. Serial0 131.1.108.108.108. Serial0 131.4.240. 11:17:49.4.108.14.108.36.108.1. 11:17:48.0–131.108.108.255.255.1. 11:17:49. Ethernet0 [90/21145600] via 131.255. Serial0 131.1. 11:17:49.108.0/24 [90/21017600] via 131.108.255.108.255.0/24 [90/21145600] via 131.4.108.108. You can clearly summarize the networks on R1 and R2 to reduce the IP routing table.1. 11:17:48. Serial0 131. 11:17:47. Serial0 131.108.108.11.108. 11:17:50. Serial0 131.164 - .1.1.108.1.CCNP Practical Studies: Routing C D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D 131. Ethernet0 [90/21145600] via 131.0/24 [90/21120000] via 131.2.0/24 [90/21145600] via 131. Serial0 131.18.1.108.29.27. Serial0 131.0/24 is directly connected.24.108. Ethernet0 [90/21145600] via 131.108. Ethernet0 [90/21145600] via 131. Serial0 131. 11:17:51. 11:17:50. Serial0 131.108. To summarize the EIGRP network.255. Serial0 131. Serial0 131.108. 11:17:51.36. Serial0 131.0/24 [90/21120000] via 131.9.108.108.108.108. 11:17:47.255.12.108.0/24 [90/21145600] via 131.1.0/24 [90/21120000] via 131.36. Serial0 131.108. 11:17:47.1.108.108. 11:17:47.36.0/24 [90/21120000] via 131.36.108.1.4. Ethernet0 [90/21145600] via 131. Ethernet0 [90/21145600] via 131.0. 11:17:50. Serial0 131.0/24 [90/21120000] via 131.0/24 [90/21120000] via 131. 11:17:50.1.255.108.0/24 [90/21145600] via 131.255.255.0/24 [90/21120000] via 131.0/24 [90/21145600] via 131.28.108.0/24 [90/21120000] via 131.108.1. 11:17:48. 11:17:50.108.255.0/24 [90/21120000] via 131. 11:17:49.1.36. 11:17:48. 11:17:50.108. Apply summarization on R1 for its directly connected links.108.1. Serial0 131.1.4.108. 11:17:47.0/24 [90/21145600] via 131.108.255.108.108.255.255.0/24 [90/21120000] via 131.21.4.255.4.4.108.1.1.108.1. Serial0 131. Ethernet0 [90/21145600] via 131.255.108.1. Ethernet0 [90/21145600] via 131.13.108. 11:17:48. 11:17:49.255.0/24 [90/21145600] via 131.1. 11:17:48.255.0/24 [90/21145600] via 131. you apply the ip summary-address eigrp AS IP address mask command.36.255. Ethernet0 [90/21145600] via 131.4. Serial0 131. 11:17:50.0/24 [90/21120000] via 131.255.255.108.3.255.108.36.36. Serial0 131.108.4.108.36.108. 11:17:47.36.108. 11:17:48.4.5. Serial0 131.0–131. 11:17:49.0/24 [90/21145600] via 131.108. 11:17:47. Serial0 131. Ethernet0 [90/21145600] via 131.20.255.108.0/24 [90/21120000] via 131.108.

36.108. Ethernet0 D EX 168.13. 00:02:48.36. 00:02:50.108.4. Ethernet0 D 131. 00:02:50.CCNP Practical Studies: Routing R1(config-if)#ip summary-address ? eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) R1(config-if)#ip summary-address eigrp ? <1-65535> Autonomous system number R1(config-if)#ip summary-address eigrp 1 ? A.4.27. Ethernet0 D 131.108. 3 masks D EX 168.108.108.108.108.255.108.0.0/24 [90/21145600] via 131.108. 00:02:50.108. Serial0 D 131. 00:02:49.0/24 [90/21171200] via 131.255.36.108.36.1. 00:02:51.108. Serial2 D 131. Serial0 D 131.4.108.36.12. Ethernet0 D 131.4. Serial0 D 131.108. 00:02:51.108.0/24 [90/21171200] via 131.108.36. Ethernet0 D 131.108. 00:02:49.4.29.4.C.4.0/24 [90/21145600] via 131. 41 subnets.255.8.108.4.0/20 [90/21120000] via 131. 00:02:49.1. display the IP routing table on R3.108. 00:02:45.108. Ethernet0 D 131.108.0.4.108. Ethernet0 [90/21145600] via 131.0/24 [90/21043200] via 131.108. Ethernet0 [90/21145600] via 131.165 - .0/24 [90/21145600] via 131.36. 00:02:45.31.1. Serial0 D 131. Ethernet0 [90/21145600] via 131.36. 00:02:49. Example 5-33 R3's IP Routing Table R3#show ip route eigrp 168.0/16 is variably subnetted.255.108.10.108.108. Ethernet0 131.22. Ethernet0 .1. 00:02:51.36.108.0/24 [90/21171200] via 131.21.108.108.255.0/24 [90/21171200] via 131.23.0/24 [90/21171200] via 131.36.108.4. 00:02:51.36. Ethernet0 D 131. 00:02:48.108.9.108.255.108. 00:02:50.108. 00:02:46.15. 00:02:45.5.4. 00:02:52. Ethernet0 D 131. 00:02:53. 00:02:52. Serial0 D 131. 00:02:49.1.131.16/30 [90/21017600] via 131.108.255.36. Ethernet0 [90/21145600] via 131.4.36. Ethernet0 [90/21145600] via 131.0 255. Ethernet0 [90/21145600] via 131.36.0/24 [90/21171200] via 131. Ethernet0 [90/21145600] via 131. 00:02:45.36.108. 3 masks D 131.7. 00:02:51.36.6.0/24 [90/21171200] via 131. Ethernet0 [90/21145600] via 131.108. 00:02:48. 00:02:45. 00:02:49.0/24 [90/21145600] via 131.255.108.36.108.25.108.B.0/24 [90/21171200] via 131.4.255.36.1.108.108.255.108. 00:02:48. Ethernet0 D EX 168.36.36. 00:02:51. 00:02:49.30.4.255.28.108.240. 00:02:51.0/30 [170/25625600] via 131.108.0. Serial0 D 131.0/24 [90/21043200] via 131.108.1.255.24.108.0/16 is variably subnetted. 00:02:52. Ethernet0 D 131.0/24 [90/21171200] via 131.131.108.36.36.0 Next.255.0/24 [90/21171200] via 131. Ethernet0 D 131.108.4.1.4.108.108.108.14.0/24 [90/21145600] via 131.4.108.4.0/24 [90/21171200] via 131.108. 3 subnets.4. 00:02:51.108.1.0/24 [90/21145600] via 131.2. 00:02:46.108.255.36. 00:02:49.255.108.108.0/24 [90/21145600] via 131.0/24 [90/21171200] via 131.36.14.108.4/30 [90/21017600] via 131.108. Ethernet0 D 131.1.0/16 [170/25625600] via 131.36.4.131.108.108.130.128.0/24 [170/25625600] via 131.0/24 [90/21145600] via 131.108. 00:02:49.129. Serial0 D 131. 00:02:49. Ethernet0 D 131. Ethernet0 D 131.0/24 [90/21145600] via 131. Ethernet0 D 131.108.108.1. Serial0 D 131. Serial0 D 131.36.0/24 [90/21171200] via 131. Serial0 D 131. 00:02:48.4.4.36. Serial0 D 131.10. 00:02:49.36.0/24 [90/21145600] via 131. 00:02:51.0.4. Ethernet0 D 131.108.1.0/24 [90/21017600] via 131. 00:02:46.4.4. 00:02:53.108.0/24 [90/21145600] via 131. Ethernet0 D 131. Ethernet0 [90/21145600] via 131.36.36.108. Example 5-33 displays the IP routing table on R3 after summarization is configured on R1.4.108. Serial1 D 131.26.131. Ethernet0 D 131. 00:02:49. 00:02:49.4. Ethernet0 D 131.36.108.1.108. Ethernet0 D 131. Ethernet0 [90/21145600] via 131.D IP address R1(config-if)#ip summary-address eigrp 1 131.0/24 [90/21017600] via 131.3. 00:02:51.108.36.4.108.108.108.4.4.1.255.4.4.2.108.4.0/24 [90/21171200] via 131.11.108.108.108.

0/24 [90/21145600] [90/21145600] 131.0 255.108.15.255.108. Ethernet0 R3's IP routing table has been significantly reduced from 31 network entries for the subnets ranging from 1 to 31 to two network entries.36.36.36.108.36.255. .108. 00:02:51.240. 3 masks D 131. Serial2 D 131. Serial0 D 131.108.108.0/20 [90/21145600] via 131.1.16. Ethernet0 131.255.108. 00:02:17. 00:02:17.1.255.36. 00:02:50. Ethernet0 131.108. Ethernet0 D 131. 00:02:50.0/24 [90/21043200] via 131. 00:02:17. Serial0 R3 still has the 15 network entries advertised through the next hop address 131.129.4/30 [90/21017600] via 131.255.108.1. Example 5-36 show ip route eigrp on R3 R3#show ip route eigrp 168.255. Cisco EIGRPenabled routers always accept an incoming route with a more specific destination.108.0–131.4.1.0.36. 00:02:51. The interface that R1 and R2 are adjacent to. 00:02:14. Ethernet0 D 131.0. (This encompasses the range 131.0/24 [90/21145600] [90/21145600] via via via via via via via via via via via 131.0/24 [90/21043200] via 131. 00:12:20.255.255.0.0/24 [90/21017600] via 131.108.20. Ethernet0 D 131.0 to 131.255.131.0/24 [90/21145600] [90/21145600] 131. 00:02:14.108.17.0/20.131.0/16 [170/25625600] via 131.1.4.166 - . Example 5-35 displays the summary configuration on R2.108.108. 00:02:51.255. Example 5-34 configures summarization on R1 pointing to R2. Prior to summarization.0/24 [90/21145600] [90/21145600] 131.4. Ethernet0 D EX 168. 00:02:51.255. is where you need to apply the same summary command used in Example 5-32.1. Example 5-35 Summary on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip summary-address eigrp 1 131.0 255.36.131.255. Ethernet0 131. Ethernet0 D 131.108.0 in R3's routing table.0/24 [90/21145600] [90/21145600] 131.1.108.0. 00:02:50.1.108.4.10.36. When you performed summarization.128.2.36. 00:02:50. Ethernet0 131. 00:02:50.4.108.4. there were 41 subnets.108.108.4.36. Serial0 131.108.31.108.0/20 [90/21120000] via 131. or R4.0/16 is variably subnetted. Serial1 D 131.108.0/30 [170/25625600] via 131.CCNP Practical Studies: Routing D D D D D [90/21145600] 131. Ethernet0 D EX 168. Serial0 131.36.16. Ethernet0 131.108. Serial0 [90/21145600] via 131.1.0/24 [170/25625600] via 131.4.4.0.108. Ethernet0 131.108.16. 00:12:20.16.108. Two summary commands are required: one to R1 through Ethernet 0/0 and another to R4 through Serial 1/0.16/30 [90/21017600] via 131. 00:02:14.0 R2(config-if)#interface serial1/0 R2(config-if)#ip summary-address eigrp 1 131.108. 00:02:22. now only 12 subnets are present in the Class B network 131.) R3 has two paths to the remote router R1.240. 00:02:51.108.16.4. as well as the summary address 131.108. 00:02:14.4.130. Serial0 131.108.36.108.108.0.108.108. 00:02:50.0/16 is variably subnetted.108. 12 subnets. 3 subnets.108.4. namely Ethernet 0/0.0/24 [90/21017600] via 131.108.240.108.108. you must perform the same summary configuration on R2 because R2 has 15 directly contiguous networks ranging from 131. you must also provide the same summary address to R2. Serial0 131.4. Serial0 131.18. you configured only R1 to summarize to R3. 3 masks D EX 168.255.108.1.1.108.14.108.255.0 255.0 Example 5-36 displays the IP routing table on R3.255.108.36.108.0 Before you look at R3's IP routing table.108.131.255. 00:02:17.36. Example 5-34 Summary on R1 Pointing to R2 R1(config)#interface ethernet 0/0 R1(config-if)#ip summary-address eigrp 1 131.19.4.255. 00:02:17.1.108.

Ethernet0 D 131.108. Null0 131. Figure 5-4 displays the four-router topology along with the IP addressing scheme.0 ip summary-address eigrp 1 131.131. 11:30:01.5.108.255.108. Ethernet0 D 131.252 ip summary-address eigrp 1 131. Also.255.8/30 [90/21017600] via 131.0.3.108.108.12/30 [90/21017600] via 131.108.255.131.255.255.130.108.36.0. Example 5-37 show ip route eigrp Command on R4 R4>sh ip route eigrp 168.108. 00:06:28.0 255.1. Ethernet0 D 131.2.131.255.0/16 is a summary.167 - .240.255.0/16 is variably subnetted.255.0.108.18. Serial2 D 168. 11:30:01.CCNP Practical Studies: Routing Also.1. 11:30:01. Serial0 D 131.255.5 255.108. Ethernet0 D 131.36. 00:06:29.108. Example 5-39 Summary EIGRP Configuration on R2 interface Ethernet0/0 ip address 131.0. while load balancing is taking place for R1's directly connected networks. Ethernet0 [90/21145600] via 131.36.108.0 clockrate 128000 Scenario 5-3: EIGRP and VLSM This scenario demonstrates the capability of EIGRP to handle VLSM with a simple four-router topology.0.0/20 [90/21145600] via 131.255. in turn.0/16 is variably subnetted.255.1 255. Ethernet0 D 131.255.108.255.3.16.36. Serial0 Because R4 is directly connected to R2.0 ip summary-address eigrp 1 131.108.36.108.0/24 [90/21043200] via 131.131.240.5. 13 subnets. Serial1 D 131.3.1.108.108.108.255.108.255.0/20 [90/21120000] via 131.2. there is only one path (lower metric) taken to R2's directly connected interfaces. 00:06:28.108.3.0/30 [90/21017600] via 131.108. Example 5-37 displays R4's IP routing table to demonstrate similar benefits.108.0/24 [90/21017600] via 131.255.3.108.255. 11:29:40.0/24 [90/21017600] via 168.108. 11:30:01.3.108. Example 5-38 Summary EIGRP Configuration on R1 interface Ethernet0/0 ip address 131.129.240.1. 00:06:27. 11:29:38.0 clockrate 125000 Example 5-39 displays the summary EIGRP configuration on R2.108.0.0 255. . summarization reduces the EIGRP topology table.0 ! interface Serial1/0 bandwidth 128 ip address 131.2 255. 11:30:01.16.255.0 255. 3 masks D 168.255.0/24 [90/21043200] via 131.108.255. 00:06:28.252 ip summary-address eigrp 1 131.255. The added benefit of summarization is that a network failure on any one network is not propagated to remote networks to which a summary route is sent.16. Serial0 D 131.240. Example 5-38 displays the summary EIGRP configuration on R1.108.1 255.128.0/24 [90/21017600] via 131. 3 subnets. note that load balancing is in place to R2's directly connected loopbacks because the EIGRP metrics are the same through serial 0 and Ethernet 0.5.0 255. 4 masks D 131.36.0 ! interface Serial0/0 bandwidth 128 ip address 131.

0.0 and 10.0. are configured on the Ethernet interfaces on R3 and R4. so you do not need to configure any redistribution.18.0.20/30 [90/20537600] via 131. VLSM and EIGRP Topology Four routers in Figure 5-4 reside in the same AS.108. Ethernet0/0 C 131.108.128/25.1.0/8. Both routers reside in AS 1 and are connected to only the network 131. 10.0 network 10.108.108. R3 is . 10.1.108.0.16/30 is directly connected.1.1.108.2. Serial0/0 131.108.0.168 - . Also. Example 5-41 EIGRP Configuration on R3 and R4 router eigrp 1 network 131.0.0.0.1.1. Serial0/0 R1's IP routing tables display a total of two dynamically learned EIGRP routers: one route to the network 131.108.0 View the IP routing table on R1 to ensure that all subnets are routable through R1.0. 4 subnets.108. 00:06:19. is reserved for private use and not routable in the Internet.0 through R3. Take a closer look at the remote IP network on R3. VLSM is used on all four routers.20/30 (the serial link between R2 and R4) and one to network remote network 10. Example 5-42 displays R1's routing table. Example 5-40 displays the EIGRP configuration on routers R1 and R2.1.0/16 is variably subnetted.0. respectively. 3 masks C 131.0 R3 and R4 require both 131.0.0 network statements.0. The Class A address. 00:08:55.0/8 [90/20537600] via 131. so the EIGRP configuration is the same on R1 and R2.0.1. as displayed by Example 5-41.108.108.0/25 and 10. Enable EIGRP in AS 1 on all four routers.0/28 is directly connected.0.1.0. Ethernet0/0 D 131. the Class A addresses.1.CCNP Practical Studies: Routing Figure 5-4. Example 5-42 R1's IP Routing Table R1#show ip route D 10. Example 5-40 EIGRP Configuration on R1 and R2 router eigrp 1 network 131.1.

108. both routers assume the default Class A mask of 255.0/28 is directly connected.1.1. 2 masks C 131.1.0.2. Example 5-44 Disabling Auto Summary on R1 and R2 R1(config)#router eigrp 1 R1(config-router)#no auto-summary R2(config)#router eigrp 1 R2(config-router)#no auto-summary Example 5-45 displays the IP routing table on R1. automatically summarizes at the network boundary for any IP networks not locally configured.0.0.1.255. 2 masks D 131.1.108.0/8 [90/20537600] via 131.1.255.0 network.0.20/30 (the serial link between R1 and R3) and the entire Class A network 10. 00:00:24. Example 5-47 Summary Configuration on R4 R4(config)#interface serial 0 R4(config-if)#ip summary-address eigrp 1 10. you must still summarize on the edge routers: R3 and R4.16/30 [90/20537600] via 131. Routers R1 and R2 do not contain more specific routing entries for the 10.108. or R3.128 255.128 R3 and R4 send an update to R1 and R2. Example 5-48 displays R1's IP routing table.1.CCNP Practical Studies: Routing configured with the network 10.108.0.108.22. Therefore. Summarize 10.1. by default.1.1.0.0. .1.108.0. Example 5-46 Summary Configuration on R3 R3(config)#interface serial 0 R3(config-if)#ip summary-address eigrp 1 10. Example 5-46 displays the summary on R3.0. 3 subnets. yet R1 assumes that the entire Class A network is available through Serial 0/0. Serial1/0 131.108.1.108. Ethernet0/0 R1 still assumes the entire Class A network is through R3 because even after you disable automatic summarization.108.1. 3 subnets. Ethernet0/0 R2 also has two remote EIGRP routes: one pointing to the remote network 131. Ethernet0/0 C 131. EIGRP.255.1.18. Example 5-43 R2's IP Routing Table R2#show ip route D 10.0/8 [90/20537600] via 131.1.0/25 on R3 and 10.108.255.1.1. 00:00:24. Example 5-44 displays the disabling of automatic summarization on R1 and R2.0/16 is variably subnetted. 00:02:15.0.1. Because R1 and R2 do not have any interfaces configured in the Class A address 10.0.0/25. Disable automatic summarization on R1 and R2.0.128 Example 5-47 displays the summary on R4.128/25 on R4.108. Example 5-45 R1's EIGRP IP Routing Table R1#show ip route eigrp D 10.1. 00:02:16. You can turn this feature off with the no auto-summary command under the EIGRP routing process.169 - .0/16 is variably subnetted. Example 543 displays R2's IP routing table. Serial1/0 D 131.0.20/30 [90/20537600] via 131.1. Serial0/0 131.0.0 through R4.0 255.20/30 is directly connected.0.0.

1.0. displays R2's IP routing table.1.240 ! interface Serial0/0 bandwidth 128 ip address 131. Example 5-50 displays R1's full working configuration.20/30 [90/20537600] via 131.0.0.1. 2 subnets.128/25 [90/20563200] via 131.0/16 is variably subnetted. Ethernet0/0 D 10.1.108. Example 5-50 R1's Full Working Configuration hostname R1 ! logging buffered 64000 debugging enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0/0 ip address 131.0/28 is directly connected.0/8 is variably subnetted.108. Ethernet0/0 C 131.1.2. Serial0/0 D 10.108.108.108.170 - .255.1.1. 2 subnets.0/16 is variably subnetted.1.108. 2 masks C 131. Serial1/0 131.0/8 is variably subnetted. Serial0/0 Example 5-49.128/25 [90/20537600] via 131.0.255. 2 masks C 131.108.108.108.108.0.22.108.1.1.0. 00:02:07. .1. when configured appropriately.108. and sends the subnet mask along with the network information.20/30 is directly connected. Ethernet0/0 C 131.2.0/0 [90/20537600] via 131.0 no auto-summary ! line con 0 line aux 0 line vty 0 4 end Example 5-51 displays R2's full working configuration.1.108.0/0 [90/20537600] via 131.0.1.255.1.1.108.1.16/30 [90/20537600] via 131.1.1. 00:02:00. Ethernet0/0 EIGRP supports VLSM. 2 masks D 10. 3 subnets. 00:01:29.108. 3 subnets. Ethernet0/0 D 131. Example 5-49 R2's IP Routing Table R2#show ip route 10.1 255. 00:03:17.252 clockrate 125000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131.17 255.0/28 is directly connected. 2 masks D 10.1.108.255. Serial1/0 D 131.1.1. 00:04:46.CCNP Practical Studies: Routing Example 5-48 R1's IP Routing Table R1#show ip route 10. and you have just seen how careful you must be when using EIGRP as your IP routing protocol. Ethernet0/0 131.1. 00:06:06. for completeness.1.16/30 is directly connected. EIGRP supports VLSM as all IP routing updates do.108.1.18.

0 .1.1.2 255.255.1 255.108.252 ip summary-address eigrp 1 10.0.108.255.255.128 bandwidth 125 ! interface Serial1 shutdown interface Serial2 shutdown interface Serial3 shutdown ! router eigrp 1 network 131.171 - .255.240 ! interface Serial1/0 bandwidth 128 ip address 131.1.255. Example 5-52 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 10.1.0 no auto-summary line con 0 line aux 0 line vty 0 4 ! end Example 5-52 displays R3's full working configuration.255.0.CCNP Practical Studies: Routing Example 5-51 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.255.21 255.18 255.108.0 255.1.1.108.252 clockrate 128000 ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown! interface Serial1/3 shutdown ! router eigrp 1 network 131.128 ! interface Serial0 ip address 131.255.1.255.108.255.

Example 5-53 R4's Full Working Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 10.22 255.255.CCNP Practical Studies: Routing network ! line con line aux line vty ! end 10.255.1.0 network 131.128 255.0.1.108.108.128 interface Serial0 bandwidth 125 ip address 131.0 0 0 0 4 Example 5-53 displays R4's full working configuration.255.0.0 ! line con 0 line aux 0 line vty 0 4 end .0.0.255.129 255.1.255.1.172 - .255.252 ip summary-address eigrp 1 10.128 ! interface Serial1 shutdown interface Serial2 shutdown interface Serial3 shutdown ! router eigrp 1 network 10.1.0.

Finally. to R7 and waste CPU and WAN bandwidth because R7 is configured for IGRP only. and OSPF. The Class B network. There is no reason to send EIGRP updates. is present on all routers.CCNP Practical Studies: Routing Scenario 5-4: Configuring Advanced EIGRP and Redistribution In this scenario. for example. R3 must ensure that EIGRP updates are sent to interfaces E0 and Serial 0 only.0. Start by configuring R3. namely EIGRP in AS 1. and OSPF NOTE The IGRP domain is configured with a Class C mask everywhere because IGRP does not support VLSM. IGRP in AS 10.108. The classful behavior of IGRP and EIGRP means you must be careful when using the same class network among different routing domains. IGRP.0. you must make the interfaces not in IGRP AS 10 passive. as displayed in Figure 5-5. The same condition applies to the IGRP process. R3 and R4 need to have redistribution configured among the different routing domains.0. you configure a network composed of six Cisco routers running a combination of IP routing protocols. the Class B address.173 - .0. 131. 141. Router R3 needs to run EIGRP in AS 1 and IGRP 10. Example 5-54 displays the EIGRP and IGRP configuration on R3. you should also make interfaces not in IGRP 10 passive.108. . IP Routing Topology Using EIGRP. The Class A network resides in OSPF area 0. is located in IGRP AS 10. Figure 5-5. and because you are using the same Class B address.

in 10 microsecond units R3(config-router)#redistribute eigrp 1 metric 128 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R3(config-router)#redistribute eigrp 1 metric 128 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R3(config-router)#redistribute eigrp 1 metric 128 20000 255 1 ? <1-4294967295> IGRP MTU of the path R3(config-router)#redistribute eigrp 1 metric 128 20000 255 1 1500 Next.0. in 10 microsecond units R3(config-router)#redistribute eigrp 1 metric 128 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R3(config-router)#redistribute eigrp 1 metric 128 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R3(config-router)#redistribute eigrp 1 metric 128 20000 255 1 255 Example 5-56 displays redistribution from EIGRP to IGRP. Example 5-55 Redistribution on R3 R3(config)#router igrp 10 R3(config-router)#redistribute eigrp 1 ? metric Metric for redistributed routes route-map Route map reference <cr> R3(config-router)#redistribute eigrp 1 metric ? <1-4294967295> IGRP bandwidth metric in kilobits per second R3(config-router)#redistribute eigrp 1 metric 128 ? <0-4294967295> IGRP delay metric.108.108. Example 5-56 Redistributing EIGRP into IGRP on R3 R3(config-router)#redistribute eigrp 1 ? metric Metric for redistributed routes route-map Route map reference <cr> R3(config-router)#redistribute eigrp 1 metric ? <1-4294967295> IGRP bandwidth metric in kilobits per second R3(config-router)#redistribute eigrp 1 metric 128 ? <0-4294967295> IGRP delay metric. you have not configured any redistribution on R3.0 R3(config-router)#passive-interface ethernet 0 R3(config-router)#passive-interface serial 0 As yet.0 R3(config-router)#passive-interface serial 2 R3(config)#router igrp 10 R3(config-router)#network 131. Even though the metric used by IGRP and EIGRP is the same. Example 5-57 displays R7's IP routing table. Example 5-55 displays how to configure redistribution from IGRP to EIGRP.CCNP Practical Studies: Routing Example 5-54 EIGRP and IGRP Configuration on R3 R3(config)#router eigrp 1 R3(config-router)#network 131. examine R7's IP routing table to see whether the EIGRP networks are installed.0. you must still advise EIGRP of the metric values because the AS numbers are different.174 - . Configure redistribution between EIGRP and IGRP (both ways) on R3. .

255.0/30 networks.108. 6 subnets.255.1.108.2. Example 5-60 displays the redistribution from OSPF into EIGRP 1.CCNP Practical Studies: Routing Example 5-57 show ip route on R7 R7#show ip route 141. 1 subnets C 141.108.128 255.108.108.255.5.108.108.108. 100-byte ICMP Echos to 131. Example 5-58 Static Route Configuration on R7 R7(config)#ip R7(config)#ip R7(config)#ip R7(config)#ip route route route route 131.0 is directly connected.0.6 Type escape sequence to abort.0/24 is subnetted. Serial0 S 131.108.9.1.0/24 is directly connected.128/25 is directly connected. 1 subnets C 141.255.255. Sending 5. 00:00:57.8/30 is directly connected.1.108.0 is directly connected. 100-byte ICMP Echos to 131.252 255.108.0 [100/84100] via 131. are not present in R7's routing table.108.108. 3 masks S 131.255. 00:00:05.254.255.128. round-trip min/avg/max = 16/16/20 ms R7#ping 131. round-trip min/avg/max = 28/32/36 ms R7#ping 131.128.108.0/24 [100/84100] via 131.108.255.0/30 is directly connected.254.0/24 is subnetted.108. Serial0 R7#ping 131.255. Those networks in the EIGRP domain that are not Class C networks.254. Serial0 I 131.0.108. is not present on R7's IP (IGRP) routing table because IGRP does not support VLSM.255.255.1. You can use static routes on R7 to correctly identify the networks in the EIGRP domain. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. Sending 5. such as the Serial link between R1 and R2 (/30) or the Ethernet segment between R3 and R4 (/25).255.128/25 and 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255. "Basic Border Gateway Protocol. Serial0 S 131. You can use static routes to overcome this limitation because static router have a more trusted administrative distance of 1.108.2. 100-byte ICMP Echos to 131.108.0 131.0 is directly connected.6.108.108.8 255.0.252 255. .108.108.255.0.255.108.255.9 Type escape sequence to abort. Serial0 S 131. Ethernet0 131. 131.255.0/16 is variably subnetted.255.4 131. Sending 5.0/24 is subnetted.108.2. Serial0 R7 IGRP entries are only those networks that are classful or Class C because the directly connected serial interface to R3 is a Class C mask. Example 5-59 R7's IP Routing Table and Ping Requests R7#show ip route 141.108. timeout is 2 seconds: !!!!! Configure R4 for redistribution because R4 is attached to the EIGRP 1 domain and OSPF.255.255. (You have yet to learn how to configure static routes.254. Serial0 I 131.108.252 Serial0 Serial0 Serial0 Serial0 Example 5-59 displays R7's routing table along with some successful pings to the non-Class C networks.5 Type escape sequence to abort. Serial0 C 131. Once more.") Example 5-58 displays the static IP routing configuration on R7 pointing to the remote networks 131.128 131. 2 subnets C 131. Ethernet0 131.2.128/25.255.108. static routes are covered in Chapters 6.175 - . The variably subnetted network.4/30 is directly connected. you need to make any interfaces not required in the EIGRP domain passive.

EX .176 - . Serial0/0 D 131.108. Ethernet0/0 131. 00:19:05.0. 00:08:30.1.108.255.0.255.2.EIGRP.108.108. so you must apply the keyword subnets when redistributing from EIGRP to OSPF.0/8 [90/25657600] via 131.2.108. Example 5-61 Redistribution from EIGRP to OSPF on R4 R4(config-router)#router ospf 1 R4(config-router)#redistribute eigrp ? <1-65535> Autonomous system number R4(config-router)#redistribute eigrp 1 ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> R4(config-router)#redistribute eigrp 1 metric 100 ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> R4(config-router)#redistribute eigrp 1 metric 100 subnets View the IP routing table on R1 in EIGRP 1 to ensure that R1 has a path to every network in this topology. 00:19:06. 00:19:06. 00:19:06.108.0/16 is variably subnetted. 3 masks D 131.255.2. Example 5-62 displays R1's IP routing table.1.0.108.2.0/24 [90/21504000] via 131.1. 6 subnets.255.255. 00:19:06.8/30 [90/21529600] via 131. 00:19:06.connected D . Remember. EIGRP domains have subnetted networks. as well as the external EIGRP network routing from OSPF and IGRP.2.108. Serial0/0 D 10.108.0.2. Serial0/0 [90/25657600] via 131.0/16 [170/21529600] via 131.255. Ethernet0/0 C 131. D EX 141.2.254.108. in 10 microsecond units R4(config-router)#redistribute ospf 1 metric 128 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R4(config-router)#redistribute ospf 1 metric 128 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R4(config-router)#redistribute ospf 1 metric 128 20000 255 1 ? <1-4294967295> IGRP MTU of the path R4(config-router)#redistribute ospf 1 metric 128 20000 255 1 1500 Example 5-61 displays the redistribution from EIGRP into OSPF. .EIGRP external. Ethernet0/0 [90/21529600] via 131.0/30 is directly connected.0/24 is directly connected.108.128/25 [90/20537600] via 131.255. Serial0/0 C 131.108. Serial0/0 D 131.1.255. Serial0/0 R1 has an IP routing entry for all EIGRP networks in AS 1.4/30 [90/20537600] via 131.108.108.CCNP Practical Studies: Routing Example 5-60 Redistribution on R4 from OSPF to EIGRP R4(config)#router eigrp 1 R4(config-router)#passive-interface s2 R4(config-router)#redistribute ospf 1 metric ? <1-4294967295> Bandwidth metric in Kbits per second R4(config-router)#redistribute ospf 1 metric 128 ? <0-4294967295> IGRP delay metric.108. Ethernet0/0 D 131.2.108. 00:08:30.2. Example 5-62 R1's IP Routing Table R1>sh ip route Codes: C .

Example 5-64 show running-config on R1 hostname R1 ! logging buffered 64000 debugging enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.108.1.108.0 line con 0 .255.129. round-trip min/avg/max = 28/31/32 ms R1>ping 10.252 clockrate 125000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 131.1. round-trip min/avg/max = 16/16/16 ms R1>ping 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort.1 255.1.255. Example 5-63 Sample Ping Request from R1 R1>ping 141.108. Example 5-63 displays a ping request and reply from R1 to all the remote networks in Figure 5-5.1.255.2. round-trip min/avg/max = 32/33/36 ms R1>ping 131.108.108.255. 100-byte ICMP Echos to 10. 100-byte ICMP Echos to 131. Sending 5.1 Type escape sequence to abort.9 Type escape sequence to abort. Sending 5.108. round-trip min/avg/max = 16/16/16 ms You have just configured a complex network with three different IP routing protocols and have successfully enabled network IP connectivity among all routers.108.1.129 Type escape sequence to abort. Sending 5.9.108.2.177 - . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255. Example 5-64 provides the full working configuration of R1.1.0 ! interface Serial0/0 bandwidth 125 ip address 131.108. Sending 5. ping from R1 to all the remote networks.108.128.255.CCNP Practical Studies: Routing To confirm network connectivity.0. 100-byte ICMP Echos to 131. round-trip min/avg/max = 28/30/32 ms R1>ping 131.128. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.255.255.1 Type escape sequence to abort. Sending 5.108. 100-byte ICMP Echos to 141.1 255.1.

1.108.255.255.255.255.1 255.129 255.0 bandwidth 125 clockrate 125000 ! interface Serial3 shutdown ! .2.255.CCNP Practical Studies: Routing line aux 0 line vty 0 4 ! end Example 5-65 provides the full working configuration of R2.255.178 - .2 255.0 line con 0 line aux 0 line vty 0 4 end Example 5-66 provides the full working configuration of R3.255.128 ! interface Serial0 ip address 131.0.108.108.255. Example 5-65 show running-config on R2 hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0/0 ip address 131.252 clockrate 128000 ! interface Serial1/1 shutdown ! router eigrp 1 network 131.252 bandwidth 125 ! interface Serial1 shutdown ! interface Serial2 ip address 131.255.0 ! interface Serial1/0 bandwidth 128 ip address 131. Example 5-66 show running-config on R3 hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.108.108.2 255.108.255.255.5 255.254.255.

0 ! router igrp 10 redistribute eigrp 1 metric 128 20000 255 1 1500 passive-interface Ethernet0 passive-interface Serial0 network 131.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-67 provides the full working configuration of R4.128 interface Serial0 shutdown ! interface Serial1 shutdown ! interface Serial2 bandwidth 125 ip address 131.0.0 ! router ospf 1 redistribute eigrp 1 metric 100 subnets network 131.108.CCNP Practical Studies: Routing router eigrp 1 redistribute igrp 10 metric 128 20000 255 1 255 passive-interface Serial2 network 131.108.0.108.0.255.3 area 0 line con 0 line aux 0 line vty 0 4 end Example 5-68 provides the full working configuration of R7.0.9 255.255. Example 5-67 show running-config on R4 hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131. .130 255.8 0.179 - .255.2.255.255.108.108.108.0.255.252 clockrate 125000 ! interface Serial3 shutdown ! router eigrp 1 redistribute ospf 1 metric 128 20000 255 1 1500 passive-interface Serial2 network 131.

0 ! interface Serial1 shutdown ! router igrp 10 network 131.255.252 Serial0 ip route 131.255.0.254.10 255.255.180 - .108.CCNP Practical Studies: Routing Example 5-68 show running-config on R7 hostname R7 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 141.255 area 0 network 131.0.255.128.1.3 area 0 ! line con 0 line aux 0 line vty 0 4 ! end .255.128 255.8 0.108.0.1.255.2 255.0.255.2.0.128 Serial0 ip route 131.252 interface Serial1 shutdown ! router ospf 1 network 10.255.255.255.1 255.0 ! interface Serial0 bandwidth 125 ip address 131.255.1.255.255.255. Example 5-69 show running-config on R8 hostname R8 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 10.255.108.108.108.255.4 255.108.0 0.108.8 255.0 network 141.252 Serial0 ip route 131.108.255.108.1 255.0 ! ip route 131.0 255.0.1.0 ! interface Serial0 bandwidth 125 ip address 131.252 Serial0 ! line con 0 line aux 0 line vty 0 4 end Example 5-69 provides the full working configuration of R8.255.255.255.255.108.

2 131. NOTE This scenario uses the network in Figure 5-5 (the one you configured in Scenario 5-4) to demonstrate these commands.108. The EIGRP process is also identified as 1.2 Se0/0 Et0/0 Hold Uptime SRTT (sec) (ms) 14 00:48:21 14 10 01:22:13 1 Q Cnt 1140 0 200 0 RTO Seq Num 558 337 Example 5-70 shows that R1 has two remote EIGRP neighbors: one through Serial 0/0 and another through Ethernet 0/0. Example 5-71 displays the topology table with the show ip eigrp topology command. Example 5-70 show ip eigrp neighbors Command on R1 R1>show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 1 0 131.255. .CCNP Practical Studies: Routing Scenario 5-5: Verifying EIGRP Configuration This final scenario looks at ways the Cisco IOS enables you to monitor and verify EIGRP IP routing within a Cisco router network.1. This scenario covers the following show commands: • • • • show ip eigrp neighbors— Displays EIGRP neighbors show ip eigrp topology— Displays the topology table show ip eigrp interfaces— Displays interfaces in which EIGRP is sent and received show ip eigrp traffic— Displays the number of EIGRP packets sent and received Example 5-70 displays the use of the show ip eigrp neighbor taken from R1. This scenario uses the network in Figure 5-5 to demonstrate some common show commands that verify that EIGRP is operating correctly.108. not only in the real-life networks you will come across but also on your certification exams—particularly when you take the next step in your career and try for CCIE certification.181 - . Properly using show and debug commands can be valuable.

0/30. Ethernet0/0 The table in Example 5-71 contains a wealth of information.255. Ethernet0/0 P 131. 2 successors.0. With every version of IOS. 1 successors. Example 5-72 displays sample output from R1 with the show ip eigrp interfaces command.108. Example 5-73 displays the output from the show ip eigrp traffic command. 1 successors.108.255. 2 successors.2 (25657600/25632000). A . Serial0/0 via 131.108. The output in Example 5-72 displays two interfaces running EIGRP in AS 1 and one peer per interface. R .2 (20537600/281600). Because a reply has not been received. Ethernet0/0 P 131. Serial0/0 via 131.0/24.108.2 (21504000/20992000).2 (21529600/21017600).108.Query. .0. there are always new commands and changes in IOS displays. FD is 20512000 via Connected. The P on the left side indicates that remote networks are passive and routable.128/25. FD is 20537600 via 131. Use the ? tool to view all your options. A remote entry in an active state (SIA) results in a loss of network connectivity because EIGRP is querying the remote EIGRP neighbors about the path to the remote network in question.1.2.CCNP Practical Studies: Routing Example 5-71 show ip eigrp topology Command on R1 R1>sh ip eigrp topology IP-EIGRP Topology Table for process 1 Codes: P .Update.1. Serial0/0 P 131. the EIGRP topology table installs the remote network in an active state.255.2 (20537600/20512000).255.Reply status P 10.Reply. Serial0/0 P 131.0/16. Serial0/0 P 141.0/24.0/8. 1 successors.108.254.2 (21529600/21017600). Any active entry (displayed as A) should concern you if any entries remain active or stuck in active (SIA). FD is 20537600 via 131.4/30.108. Serial0/0 P 131. FD is 21529600 via 131.182 - . r .108.108. FD is 21529600 via 131. 1 successors. replies.8/30. Example 5-73 show ip eigrp traffic Command R1>show ip eigrp traffic IP-EIGRP Traffic Statistics for process 1 Hellos sent/received: 387565/387575 Updates sent/received: 545/219 Queries sent/received: 98/47 Replies sent/received: 47/84 Acks sent/received: 283/265 The traffic commands summarize the number of hello packets R1 receives and sends.255. FD is 21504000 via 131. queries.108. Q .1.1. Example 5-74 displays the debug commands possible with EIGRP on Cisco IOS running version 12-0.255.255. Ethernet0/0 P 131. 1 successors. namely to R2 through Ethernet 0/0 and R3 through Serial 0/0. and acknowledges R1 uses to ensure that EIGRP is running correctly and with adjacent EIGRP routers.Active.2 (21529600/21504000).108. U . Example 5-72 show ip eigrp interfaces Command R1>show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Interface Peers Un/Reliable SRTT Et0/0 1 0/0 1 Se0/0 1 0/0 14 Pacing Time Un/Reliable 0/10 5/190 Multicast Flow Timer 50 250 Pending Routes 0 0 This command is extremely useful when you are trying to explain why neighbors are not adjacent.Passive. 1 successors.108.0. FD is 281600 via Connected.108.108. You must be in privilege mode to view the debug command set. FD is 25657600 via 131.10-enterprise code.108.2 (25657600/25145600).255. Traffic commands show how many updates.

Practical Exercise: EIGRP NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. Figure 5-6.CCNP Practical Studies: Routing Example 5-74 debug ip eigrp ? Command on R1 R1#debug ip eigrp ? <1-65535> AS number neighbor IP-EIGRP neighbor debugging notifications IP-EIGRP event notifications summary IP-EIGRP summary route processing <cr> For a comprehensive list of EIGRP commands. Therefore. visit the Cisco web site for free information at www. You use route maps to ensure that networks are not advertised incorrectly. Ensure that SanFran has all the remote entries being advertised by Router Sydney and the router in the RIP domain. you should make sure passive interfaces are not running RIP. any redistribution you configure on the Router Sydney has to ensure that these networks are not propagated. EIGRP Network Practical Exercise Solution All routers in this practical exercise use the same Class B network.com/univercd/home/home.108.cisco. You can also use distribute lists. namely 131.0. Summarize wherever possible to reduce the IP routing table on the Router SanFran.0/24.183 - . The solution can be found at the end. To stop EIGRP updates from being sent to the RIP domain. Configure the network in Figure 5-6 for EIGRP in autonomous system 1. you must also use passive interfaces on Router Sydney. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. to avoid a routing loop.htm. The RIP network attached to Brussels shares the identical subnet in the EIGRP 1 domain. Likewise for RIP. .

108.2.255. Route maps are covered in more detail in Chapters 6 and 7.1. you can provide a summary in EIGRP AS 1 covering the networks 171.0 255.1 255.1 255.1 255.0 clockrate 128000 ! router eigrp 1 .0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown router eigrp 1 network 131. "Advanced BGP.108.255.109.0–171.255.255.108.109.255. route maps have been applied to redistribution on Router Sydney.0.0 ! interface Loopback1 ip address 171.255.252.0 no ip directed-broadcast ip summary-address eigrp 1 171.252.0 Example 5-75 displays the configuration required on Router SanFran.1 255.CCNP Practical Studies: Routing For summarization. Example 5-75 SanFran's Full Working Configuration hostname SanFran ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.1.255.108.184 - .0 ! interface Serial1/0 bandwidth 128 ip address 131.255.1.0.3. To make the configuration a little more interesting.0 255.109.0 interface Ethernet0/0 ip address 131.1 255.255.3.0.255.255.109.109.109.0 ! interface Loopback2 ip address 171.255.255.255.0 no auto-summary ! line con 0 line aux 0 line vty 0 4 end Example 5-76 displays the configuration required on Router Sydney.2 255.0 with the following command: ip summary-address eigrp 1 171.108." Example 5-76 Sydney's Full Working Configuration hostname Sydney ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 171.255.1.

255. Example 5-78 show ip route Command on SanFran SanFran#show ip route D D C 171.109.108. 1 subnets 171.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-78 displays SanFran's IP routing table.0.0 [90/20537600] via 131.255 access-list 1 permit any route-map riptoeigrp permit 10 match ip address 1 ! route-map eigrptorip permit 10 match ip address 1 line con 0 line aux 0 line vty 0 4 end Example 5-77 displays the configuration required on Router Brussels.0 no auto-summary ! router rip redistribute eigrp 1 metric 2 route-map eigrptorip passive-interface Ethernet0/0 network 131.2 255.0/22 is subnetted.0.1.0.108.255.108.0 0. 2 subnets 131.0.0 [90/409600] via 131.108.0.0 network 171.108.0 ! interface Serial0 bandwidth 125 ip address 131.255. Example 5-77 Brussels' Full Working Configuration hostname Brussels ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.108.109.1.0 router rip network 131.108.255.1.255. Ethernet0/0 .108.0 ! access-list 1 deny 131. which shows the remote RIP link and the summary address advertised by Router Sydney.2.0 is directly connected.2.255.1.108.1 255.185 - . 00:05:41. Ethernet0/0 131. 00:05:41.0.108.108.0.1.0.109.CCNP Practical Studies: Routing redistribute rip metric 128 20000 255 1 1500 route-map riptoeigrp passive-interface Serial1/0 network 131. Ethernet0/0 131.0/24 is subnetted.0.

00:13:26 ago.109. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).2.1.0. Hops 1 SanFran#ping 171. type internal Redistributing via eigrp 1 Last update from 131.109. distance 90. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171. Examples 5-79 and 5-80 are from the previous Practical Exercise.1.0/22 Known via "eigrp 1"." Example 5-79 displays the detailed paths to the three remote networks. Refer to the examples to answer the first question.0.109. Sending 5.108.1.1. minimum MTU 1500 bytes Loading 1/255. Hops 1 SanFran#ping 171.0 Routing entry for 171.1.108.3. 100-byte ICMP Echos to 171.109.108. Sending 5. 00:13:38 ago Routing Descriptor Blocks: * 131.0 and 171. 00:13:26 ago Routing Descriptor Blocks: * 131.108.109. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171. 00:13:38 ago.108.0. type internal Redistributing via eigrp 1 Last update from 131.109.1. minimum MTU 1500 bytes Loading 1/255.109.1.2. distance 90.109. from 131.2 on Ethernet0/0.2 on Ethernet0/0.109.2. from 131.2. timeout is 2 seconds: !!!!! . 00:13:32 ago. metric 409600.2 on Ethernet0/0.0. Hops 1 SanFran#ping 171.109. minimum bandwidth is 10000 Kbit Reliability 255/255. metric 409600. The answers to these questions can be found in Appendix C.2.1 Type escape sequence to abort.1.1. from 131.1.1 Type escape sequence to abort.108.0 Routing entry for 171.2.0/24.0/22 Known via "eigrp 1".2.109. via Ethernet0/0 Route metric is 409600. minimum bandwidth is 10000 Kbit Reliability 255/255.109.186 - .0/22 Known via "eigrp 1". via Ethernet0/0 Route metric is 409600.3. metric 409600. 100-byte ICMP Echos to 171.1 Type escape sequence to abort. via Ethernet0/0 Route metric is 409600. Sending 5.108. as seen by Router SanFran along with a successful ping to the remote networks.109. "Answers to Review Questions.1. Example 5-79 show ip route and ping on SanFran SanFran#show ip route 171. traffic share count is 1 Total delay is 6000 microseconds.1. 171.108. 171.109. 00:13:32 ago Routing Descriptor Blocks: * 131.108.0 Routing entry for 171. type internal Redistributing via eigrp 1 Last update from 131.1.CCNP Practical Studies: Routing Review Questions The following questions are based on material covered in this chapter. minimum bandwidth is 10000 Kbit Reliability 255/255. 100-byte ICMP Echos to 171.1.3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). traffic share count is 1 Total delay is 6000 microseconds.109.2.2.1. minimum MTU 1500 bytes Loading 1/255.2.3. distance 90. traffic share count is 1 Total delay is 6000 microseconds.1.

4.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).109. you see the output displayed in Example 5-80.4.187 - .109.109. and 3. 2.1.0/24 on SanFran. round-trip min/avg/max = 1/3/4 ms If you perform a show ip route to the network 171.109.108. Example 5-80 show ip route 171.4.2 Et0/0 Hold Uptime SRTT (sec) (ms) 11 00:18:37 4 RTO Q Seq Cnt Num 200 0 353 Why does EIGRP need to be manually configured to redistribute into another autonomous system? When is the EIGRP topology table updated? What is the purpose of the command no auto-summary? What is the variance command used for? What does the term Stuck in Active mean? .0 on SanFran SanFran#show ip route 171. Which networks does the entry 171. 1: 2: 3: Example 5-79 displays the IP routing table of the Router SanFran.0.0/22 embrace? What is the default administrative distance for EIGRP internal routes? Which IOS command is used to display the output in Example 5-81? Example 5-81 Neighbors Output IP-EIGRP neighbors for process 1 H Address Interface 0 4: 5: 6: 7: 8: 131.0 % Subnet not in table The reason that subnet 4 is not included in the IP routing table is that the summary address configured on Router Sydney includes only the subnets 1.

showing how EIGRP interacts with other classful and classless routing algorithms. Summary of IOS Commands Command router eigrp autonomous system network network no auto-summary ip summary-address eigrp AS address mask bandwidth link speed variance multiplier show ip eigrp neighbors show ip eigrp topology show ip eigrp traffic Purpose Enables EIGRP routing under a common administrative control known as the autonomous domain (AD) Enables EIGRP on a router interface Disables automatic network summarization Manual network summary command Configures actual bandwidth on a WAN interface Allows EIGRP to load balance across unequal paths Displays EIGRP neighbors Displays the EIGRP topology table Shows EIGRP traffic on the router .188 - . Summarization is described to demonstrate the powerful nature of EIGRP and its capability to take advantage of VLSM to optimize IP address space usage across small or large IP networks. Table 5-4 summarizes the most useful commands from this chapter. along with some detailed configurations. EIGRP terminology and the fundamental operation of EIGRP is covered in this chapter. it is a potentially useful protocol for routing IP. Table 5-4.CCNP Practical Studies: Routing Summary Although EIGRP is not an industry standard across routing vendors.

Basic Border Gateway Protocol (BGP4) Defined The different versions of BGP range from 1–4. Any network entry must reside in the BGP table first. Routers configured for BGP are typically called BGP speakers. This chapter contains five practical scenarios to complete your understanding of basic BGP and to help you appreciate the complexity of BGP. results in an update message. Full routing tables are exchanged only during the initial BGP session. BGP peers exchange full BGP routing tables initially. BGP4 is defined in industry standard RFC 1771. You can. BGP supports variable-length subnet masking (VLSM) and summarization (sometimes called classless interdomain routing [CIDR]). Update messages— Any change that occurs. BGP has a complex array of metrics. however. Chapter 7. Any network changes result in update messages. BGP is called a path-vector protocol because BGP carries a sequence of AS numbers that indicate the path taken to a remote network. The default standard is BGP Version 4 and is referred to as BGP4. Before you look at some simple examples. BGP4 uses the following four message types to ensure that peers are active and updates are sent: • • • • Open messages— These messages are used when establishing BGP peers. No other routing protocol in use today relies on TCP. After that.000 BGP network entries. Updates are sent over TCP port 179. The Internet consists of over 80. BGP has its own BGP table.CCNP Practical Studies: Routing Chapter 6. This chapter covers the basics of Border Gateway Protocol (BGP). such as the Internet. BGP enables you to create an IP network free of routing loops among different autonomous systems. "Advanced BGP. unless a change occurs. ensuring that only useful data is sent. The capability of BGP4 to guarantee routing delivery and the complexity of the routing decision process ensure that BGP will be widely used in any large IP routing environment. this chapter covers BGP4 in a little more detail to ensure that you have a good appreciation of the way networks connect to the Internet or in large organizations. BGP4 is covered only slightly in the CCNP routing examination. Keepalives— These messages are sent periodically to ensure that connections are still active or established. the following section describes the BGP attributes. only BGP updates are sent between peers. This allows TCP to ensure that updates are sent reliably. BGP uses TCP as the transport layer protocol. BGP sessions are maintained by keepalive messages. However. leaving the routing protocol to concentrate on gathering information about remote networks and ensuring a loop-free topology. which include the next hop address and origin. This information is stored so that routing loops can be avoided. An AS is a set of routers under the same administrative control. and 4 on a Cisco IOS router.189 - ." covers more advanced BGP topics and scenarios. BGP uses Transmission Control Protocol (TCP) as its Layer 4 protocol (TCP port number 179). the industry standard is Version 4. Basic Border Gateway Protocol This chapter focuses on Border Gateway Protocol Version 4 (BGP4). The key characteristics of BGP include the following: • • • • • • • • • BGP is termed a path vector protocol. and there is no doubt that only BGP can handle such a complex routing table. such as a loss of network availability. and any two BGP routers that form a BGP TCP sessions are called BGP peers or BGP neighbors. . called attributes. Notification— These messages are used only to notify BGP peers of receiving errors. 3. configure BGP Versions 2.

Weight This Cisco-only attribute is used in local router selection. Table 6-1 describes the well-known and optional attributes used in BGP4. IBGP is a connection between two BGP speakers in the same AS. . A higher local preference is always preferred. BGP attributes are carried in update packets. The weight value is between 0–294967295. Weight is not sent to other BGP peers.CCNP Practical Studies: Routing BGP Attributes BGP has a number of complex attributes used to determine a path to a remote network. Table 6-1. Typically. Well-Known and Optional BGP Attributes Attribute Origin Description This attribute is mandatory and defines the origin of the path and can have three different values: • • • AS_Path Next Hop Local Preference MED IGP indicates the remote path originated from within the AS. These attributes allow greater flexibility and enable a complex routing decision to ensure that the path to a remote network is the best possible path. EBGP is a connection between two BGP speakers in different autonomous systems. Community Communities allow routes to be tagged for use with a group of routers sharing the same characteristics.190 - . always chooses a single path to a specific destination. A lower MED is always preferred. This information is not used for router selection. BGP installs the network with an origin set to IGP. Originator ID This attribute is used to prevent routing loops. Aggregator This is the router ID responsible for aggregation and is not used in the router-selection process. This information is not used for router selection. BGP. when the network command or redistribution is configured. This attribute describes the next hop address taken to a remote path. and a higher weight value is always preferred. Internal BGP (IBGP) and External BGP (EBGP) are the two types of BGP sessions. Cluster-List This attribute is used in route-reflector environments. Incomplete means the BGP route was discovered using redistribution or static routers. The network designer can also manipulate these attributes.) BGP always propagates the best path to any peers. EBG means learned through an External Gateway Protocol. Figure 6-1 displays a simple three-router BGP topology and the different BGP connection types: IBGP and EBGP. This attribute indicates to the AS the preferred path to exit the AS. Multiexit Discriminator informs BGP peers in other autonomous systems which path to take to a remote network. when supplied with multiple paths to a remote network. This attribute describes the sequence of autonomous systems that the packet has traversed. (Load balancing is possible with static routes. typically the BGP peer. Atomic This attribute advises BGP routers that aggregation has taken place and is not used in the router-selection process.

In other words. prefer EBGP over IBGP. saves bandwidth. therefore. if all paths are equal. Step 5. consider it. You can disable this feature with the no synchronization command. Step 10. If the origin codes are the same. the routers must be synchronized. Prefer the route with the shortest AS path. Step 8. prefer the route with the lowest MED. before sending the route information. The BGP routing decision is quite complex and takes into account the attributes listed in Table 6-1. IBGP and EBGP IBGP peers also make certain that routing loops cannot occur by ensuring that any routes sent to another AS are known through an interior routing protocol. Step 4.191 - . such as Open Shortest Path First (OSPF). prefer the path with lowest BGP router ID. If the MED is the same. Step 2. The process a Cisco router running BGP4 takes is as follows: Step 1. Finally. IGP is preferred to EGP followed by incomplete. If the weight is the same. which reduces any unnecessary traffic. Step 7. The benefit of this additional rule in IBGP TCP sessions is that information is not sent unless the remote path is reachable. prefer the route this local router originated. If the local preference is the same. Step 3. prefer the largest local preference attribute. which is covered later in this chapter. Prefer the closest path. . If this is equal. prefer the route with the origin set to originated (through BGP). Step 6. Step 9. If the next hop address is reachable.CCNP Practical Studies: Routing Figure 6-1. and. Prefer the route with the highest weight (Cisco IOS routers only).

Example 6-1 IBGP on R1 R1(config)#router bgp ? <1-65535> Autonomous system number R1(config)#router bgp 1 R1(config-router)#neighbor 131.108.1 255. the following command is required: router bgp autonomous system number To define networks to be advertised.0 to 131.2. Because these networks are local to R1 and present in R1's IP routing table as connected routes.108.0. Example 6-3 EBGP on R3 R3(config)#router bgp ? <1-65535> Autonomous system number R3(config)#router bgp 2 R3(config-router)#neighbor 131.192 - . you can apply the network command as displayed in Example 6-5.3. you use the network command to advertise networks that originate from the router and need to be advertised through BGP.108. .1 remote-as 1 R2(config-router)#neighbor 131. no BGP entries are on any routers.108.1 remote-as 1 At this stage.108. Example 6-1 displays the IBGP configuration on R1 to R2. apply the following command: network network-number mask network-mask You must be aware that the network command is not used in the same way you use it when you apply networks in OSPF or EIGRP.255.255. you see how to configure IBGP and EBGP among the three routers in Figure 6-1.255. Use some loopback interfaces on R1 and advertise them through BGP to R2 and R3.2.108.4.255. Example 6-2 IBGP/EBGP on R2 R2(config)#router bgp 1 R2(config-router)#neighbor 131.1.1 255. To identify peer routers.0 You must next advertise these loopbacks with the network command. With BGP.255.1 255.255.108.CCNP Practical Studies: Routing Configuring BGP To start BGP on a Cisco router. because no network statements have been applied.0 R1(config-if)#interface loopback 1 R1(config-if)#ip address 131.255. Example 6-4 Loopback Configuration on R1 R1(config)#interface loopback 0 R1(config-if)#ip address 131.2 remote 1 Example 6-2 displays the IBGP configuration to R1 and EBGP configuration to R3.0 R1(config-if)#interface loopback 2 R1(config-if)#ip address 131. ranging from 131.255.108. Example 6-4 displays the three new loopback addresses on R1.2 remote-as 2 Finally.108. Example 6-3 displays the EBGP connection from R3 to R2.1. apply the following command: neighbor ip-address | peer-group name remote-as autonomous system number Next.4.

108.0 R1(config-router)#network 131.108.108.0 or local interfaces).0/24 Next Hop 0.108.1.1 131.4.1.3. * valid. d damped. Example 6-8 show ip route on R2 R2#show ip route 131.0 0. > best.0 R1(config-router)#network 131.255.0. you must disable synchronization or configure an IGP routing protocol. The local router ID is 131.108.255.1 Status codes: s suppressed. does not propagate the loopbacks to R3. Example 6-7 displays the BGP table on R2.EGP.109.IGP.0 mask 255.0/24 is subnetted.0.EGP.0. local router ID is 131.incomplete Network * i131. Example 6-6 show ip bgp on R1 R1#show ip bgp BGP table version is 4. Example 6-8 confirms this with only the locally connected routes visible on R2. in turn.0.0/24 Next Hop 131.2.255.1 131. * valid.108.108.108.0. d damped.0.1.1.internal Origin codes: i .108. Notice that R2 has set the local preference to 100 (default value).0 is directly connected. ? . > best.0. Example 6-6 also displays the path as i.0 is directly connected. ? . Disable synchronization on R1 and R2.255. local router ID is 171. Example 6-7 show ip bgp on R2 R2#show ip bgp BGP table version is 7.193 - .0.108.255. the origin attribute is set to i or IGP. therefore.1.4.108. .108.3.0 mask 255. using the command show ip bgp. e .1. i . R3 does not have any entries at all.4. h history. and it learns the remote loopbacks on R1 through the next hop address 131.1 Metric LocPrf Weight Path 0 100 0 i 0 100 0 i 0 100 0 i R2's local router is 131. h history.3.3.2. R2's IP routing table does not have the BGP entries inserted because of synchronization. e .2.108.0 0. or advertised through BGP.108. i .108.0/24 * i131.108.2.255.0 Example 6-6 displays the BGP table on R1. R2.internal Origin codes: i .1.0/24 *> 131. either in the BGP table or IP routing table.0.1. Serial1/0 C 131. 2 subnets C 131.incomplete Network *> 131.0/24 * i131.IGP. Ethernet0/0 To enable BGP to insert the routes.108.108. Example 6-9 displays the no synchronization command on R1 and R2.255.1.0 Metric LocPrf Weight Path 0 32768 i 0 32768 i 0 32768 i The BGP table on R1 displays three local networks (next hop is 0.108.1.1 Status codes: s suppressed.0 mask 255. or R1's Ethernet interface. Because R1 and R2 are running only IBGP and no other interior gateway protocol.CCNP Practical Studies: Routing Example 6-5 network Command on R1 R1(config)#router bgp 1 R1(config-router)#network 131.0/24 *> 131.

.internal Origin codes: i .108.1 0 1 i *> 131.1.CCNP Practical Studies: Routing Example 6-9 Disabling Synchronization on R1/R2 R1(config)#router bgp 1 R1(config-router)#no synchronization R2(config)#router bgp 1 R2(config-router)#no synchronization Example 6-10 displays R2's routing table.194 - . and use back-to-back serial connections among Cisco routers.0/24 131.108.2.2 Status codes: s suppressed.108. OSPF is configured between R1 and R2.108. Example 6-11 displays R3's BGP and IP routing table.2.0–131.255.255.IGP.incomplete Network Next Hop Metric LocPrf Weight Path *> 131.108.1.108.1.1.108.108. The following five scenarios examine how BGP is configured and monitored and how BGP can use policy-based routing to change the routing decision of any IP network using powerful tools.0 is directly connected. Ensure that the loopback addresses on R1 (131.1.4.4.108. Serial1/0 B 131. and to ensure a loop-free topology.3. Example 6-10 R2's Routing Table R2#sh ip route 131.0/24. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs.0/24 is subnetted. i . 00:00:43 B 131.0 [200/0] via 131.108.0/24 131.3.0–131. transverse autonomous system number 1.255.0) are reachable from R3 and R4. do not disable synchronization on any router. such as route maps and the changing the BGP attributes.108. * valid. ? .108.108.1 0 1 i *> 131.0 [200/0] via 131. Ethernet0 Notice that the next hop address on R3 is R2.108. 131.1 0 1 i R3>show ip route 131.1. 00:00:43 C 131.108. Serial0 B 131.255.5. 00:00:43 B 131. as displayed in the BGP table in Example 6-11. 5 subnets C 131.2.108.108.108.0 [20/0] via 131.2.108. Again. d damped.0/24) and R2 (131.255. 00:02:09 B 131.108.5.108.108.0 is directly connected.2.108.4. Ethernet0/0 The three remote networks are inserted into the IP routing tables as BGP-learned networks. local router ID is 131.0.108.1.1. There is no one right way to accomplish many of the tasks presented.255.108.108.1. 00:02:09 B 131.0 is directly connected.0 to 131.108.7.255.EGP.0 [200/0] via 131.0 [20/0] via 131.0/24 131.1.255. h history.4. Example 6-11 R3's BGP and IP Tables R3>show ip bgp BGP table version is 10.0.3. > best.108. and the abilities to use good practice and define your end goal are important in any real-life design or solution.0 [20/0] via 131. e .108. Scenario 6-1: EBGP and IBGP Configure the four-router topology in Figure 6-2 for IBGP and EBGP. 5 subnets C 131. The AS path on R3 indicates that the remote networks.108.0 is directly connected.255.0/24 is subnetted. use loopback interfaces to help populate BGP tables.108. 00:02:09 C 131.1.

7.255 0. notice that this network contains a potential routing loop.0. so you discover how BGP helps you avoid loops.1. you configure BGP on four routers and ensure that all BGP peers have remote IP routing entries.255 area area area area 0 0 0 0 Example 6-14 confirms that OSPF neighbors are active to R2.255 0.2 Interface Ethernet0/0 .1.0.108.108.0.108.0 131.255 0.108.1.0.195 - .0 131.0/24.0. Example 6-12 R1 OSPF Configuration R1(config)#router ospf 1 R1(config-router)# network R1(config-router)# network R1(config-router)# network R1(config-router)# network 131. Example 6-13 R2 OSPF Configuration R2(config)#router ospf 1 R2(config-router)#network R2(config-router)#network R2(config-router)#network R2(config-router)#network 131. IBGP/EBGP In this scenario.108.5.0 131.108.0.4.0.1.0 0.108.3.0.0 131.1 1 FULL/BDR Dead Time 00:00:36 Address 131.0.0 131.0 131.255 0. Example 6-12 displays the OSPF configuration on R1.0 0.0.0.108.0.108.CCNP Practical Studies: Routing Figure 6-2.0.255 area area area area 0 0 0 0 Example 6-13 displays the OSPF configuration on R2.255 0.0. the loopbacks are placed in area 0.6. R1 and R2 are running OSPF across the Ethernet subnet 131.0.2.108.255 0.7.0. Also.108. Example 6-14 show ip ospf neighbor on R1 R1#show ip ospf neighbor Neighbor ID Pri State 131.

108.108.108.0 mask 255.0 mask 255. Example 6-15 displays the IBGP configuration to R2 and the EBGP configuration to R3.6.108.255.108. Example 6-17 Inserting Local Loopback on R1 R1(config)#router bgp 1 R1(config-router)#network 131. Example 6-18 displays the network configuration on R2.internal Origin codes: i .255. . h history.2 Metric LocPrf Weight Path 0 100 0 ? R1's BGP table has no information about the locally connected loopbacks 131.108.6 remote-as 3 Now that you have configured BGP4 (by default.0 R2(config-router)#network 131.1 Status codes: s suppressed.0.4. 131. Example 6-16 displays R1's BGP table.255.0. Example 6-19 displays the BGP table on R1 after the loopbacks on R1 and R2 are advertised through BGP. e .3.incomplete Network *i131. local router ID is 131.255.108. * valid.3.255.IGP. Example 6-18 Inserting Local Loopback on R2 R2(config)#router bgp 1 R2(config-router)#network 131.CCNP Practical Studies: Routing Next. enable IBGP between R1 and R2 and EBGP connections between R1/R3 and R2/R4.108.255.0 through R2.0 Next Hop 131. BGP Version 4 is enabled on Cisco IOS routers). i .0 mask 255.4. d damped.4.0 The same network configuration is required on R2.196 - .0.0 R1(config-router)#network 131.255.0 R2(config-router)#network 131.108. you must use the clear ip bgp * command to clear the TCP sessions (* for all BGP TCP peers).108.0 NOTE Whenever you make BGP configuration changes on Cisco IOS routers.108.7.108.0 R1(config-router)#network 131. > best.1.2 remote-as 1 R1(config-router)# neighbor 131. You use the clear ip bgp ip–address-of-peer command to clear a specific BGP peer. ? .108. Example 6-16 R1's BGP Table R1#show ip bgp BGP table version is 1.255.255.0.255.0 mask 255.0 mask 255. both on R1. Example 6-15 IBGP/EBGP Configuration on R1 R1(config-router)#router bgp 1 R1(config-router)# neighbor 131.1.108.255.2.255. You need to use the network command to configure the local interfaces. or 131.EGP.0. Example 6-17 displays the network configuration on R1.0 mask 255.255. and the only network in the BGP table is the remote network 131.2.5.108.

incomplete Network * i131.108.2).108.0. * valid.0.0/24 131.0.7.1.0 0 32768 i * i131.0/24 131. Also. Example 6-21 R1's BGP Table R1#show ip bgp BGP table version is 5.2).incomplete Network Next Hop Metric LocPrf Weight Path *>i131. BGP automatically summarizes at the network boundary. Note that the information relates to the BGP peer to R2 and R3.108.0.108.2 0 100 0 i * i131.0 *> 131.108. By default.0/24 * i131. as you discover shortly.CCNP Practical Studies: Routing Example 6-19 R1's BGP Table R1#show ip bgp BGP table version is 4.0. You can change any BGP attribute.0. Example 6-22 displays the remote BGP peers on R1.0/24 131.2. and the local preference is 100 for the remote networks.1.IGP. h history.3.5.108. local router ID is 131.6. d damped.108.0/24 *> 131. To turn off this behavior.0.EGP. > best.1.2 131.0 reachable through R2 (131.108. These settings are set by default. local router ID is 131.1 Status codes: s suppressed.0 0 32768 i *> 131.108.0.2 command. ? .4.1.EGP.1 Status codes: s suppressed.0/24 * i131.108.0 131. you can expect the BGP table on R1 to contain only specific network entries.108. d damped.0. .108.108.0/24 *> 131.108. e .1.1.108.0.0 0.2 131.197 - . Example 6-20 Disabling Automatic Summarization on R1 and R2 R1(config)#router bgp 1 R1(config-router)#no auto-summary R2(config)#router bgp 1 R2(config-router)#no auto-summary After clearing the BGP session to R2 with the clear ip bgp 131.6.0.1.2.108. e .108.5. ? . notice that the default weight on R1 is set to 32768 (for local networks). > best.108.108.0/24 0. i . Example 6-20 displays this configuration completed on R1 and R2.0/24 0.0 0.1.7. h history.1.1. you apply the no auto-summary command. * valid.108.2 0.0/24 * i131.IGP.2 0 100 0 ? *> 131.3.0/24 131.108.0 0 32768 i *> 131.0/24 Next Hop 131.108.108.2 0 100 0 i * i131.internal Origin codes: i .108.1.108.4.0. The first entry in Example 6-19 displays the remote network 131.1.0.108.4.internal Origin codes: i .0.4.108. Example 6-21 displays R1's BGP table.108.2 Metric LocPrf Weight Path 0 100 0 ? 0 32768 i 0 32768 i 0 32768 i 0 100 0 i 0 100 0 i 0 100 0 i R1 has three local interfaces in BGP and three remote networks advertised by R2 (next hop address is 131. which displays the remote BGP peers and their states. i .0/24 0.2 0 100 0 i One of the most important commands used in BGP networks is the IOS show ip bgp neighbor command.

input: 0 Event Timers (current time is 0x190F313B): Timer Starts Wakeups Retrans 9 0 TimeWait 0 0 AckHold 10 3 SendWnd 0 0 KeepAlive 0 0 GiveUp 0 0 PmtuAger 0 0 DeadWait 0 0 mis-ordered: 0 (0 bytes) Next 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 sndwnd: delrcvwnd: 16178 509 iss: 249485567 snduna: 249485774 sndnxt: 249485774 irs: 3880799333 rcvnxt: 3880799843 rcvwnd: 15875 SRTT: 510 ms. with data: 10. RTTO: 3547 ms. due to User reset 4 accepted prefixes consume 128 bytes 0 history paths consume 0 bytes Connection state is ESTAB. internal link Index 1.2.108. remote router ID 131. ACK hold: 200 ms Flags: higher precedence. 0 in queue Prefix advertised 14. RTV: 1263 ms. Mask 0x4 BGP version 4.1. You have yet to configure BGP on R3.255. unread input bytes: 0 Local host: 131. due to User reset 0 accepted prefixes consume 0 bytes 0 history paths consume 0 bytes No active TCP connection The BGP neighbors on R1 are established to R2. remote AS 1.108. withdrawn 0 Connections established 7. table version = 0 Last read 00:17:54. Local port: 11632 Foreign host: 131. keepalive interval is 60 seconds Minimum time between advertisement runs is 5 seconds Received 1297 messages.1. I/O status: 1. maxRTT: 300 ms.255. hold time is 180. KRTT: 0 ms minRTT: 0 ms. 0 notifications. remote router ID 0. Mask 0x2 BGP version 4. 0 notifications. Offset 0. with data: 8. Foreign port: 179 Enqueued packets for retransmit: 0. dropped 6 Last reset 00:04:39. 0 in queue Prefix advertised 0. 0 notifications.108. suppressed 0.CCNP Practical Studies: Routing Example 6-22 show ip bgp neighbors on R1 R1#sh ip bgp neighbors BGP neighbor is 131.6. total data bytes: 509 Sent: 13 (retransmit: 0).108.0. total data bytes: 206 BGP neighbor is 131. Offset 0. withdrawn 0 Connections established 0. hold time is 180. keepalive interval is 60 seconds Minimum time between advertisement runs is 5 seconds Received 0 messages. remote AS 3. suppressed 0. external link Index 2.1.1. 0 in queue Sent 0 messages. Anything other than the keyword established between two BGP indicates a problem.2.1 BGP state = Established. 0 notifications. dropped 0 Last reset 00:17:55.0 BGP state = Active. The possible BGP states are as follows: . 0 in queue Sent 1290 messages. table version = 5. but not to R3.198 - .0. up for 00:04:30 Last read 00:00:30.108. nagle Datagrams (max data segment is 1460 bytes): Rcvd: 16 (out of order: 0).

108. Example 6-23 displays the BGP configuration on R3. Foreign port: 179 .255. OpenConfirm— BGP is waiting for a keepalive message.1.0 R3(config-router)#neighbor 131. I/O status: 1.108. 0 notifications. unread input bytes: Local host: 131.108. Active— BGP is trying to acquire a remote peer by initiating a new TCP connection.255.1.0/24 as originating from AS 3. withdrawn 0 Connections established 2. I/O status: 1.6.2.199 - . Example 6-24 show ip bgp neighbors on R1 (Truncated) R1>show ip bgp neighbors BGP neighbor is 131. 0 notifications.CCNP Practical Studies: Routing • • • • • • Idle— BGP is waiting for a starting event. suppressed 0.. Offset 0.2. withdrawn 1 Connections established 7. 0 notifications. dropped 1 Last reset 00:38:38. table version = 8.255..6.255. 0 in queue Prefix advertised 16.108. Next.255.1 BGP state = Established. dropped 6 Last reset 00:59:05. which is initiated by an operator of BGP.1. keepalive interval is Minimum time between advertisement runs is 30 seconds Received 46 messages.108. Local port: 179 Foreign host: 131. unread input bytes: Local host: 131. hold time is 180. due to User reset 4 accepted prefixes consume 128 bytes 0 history paths consume 0 bytes Connection state is ESTAB. Established— After a keepalive message is sent. you enable EBGP between R1 and R3.1 BGP state = Established.108.108. Example 6-23 EBGP Configuration on R3 R3(config)#router bgp 3 R3(config-router)#network 141. 0 notifications. table version = 8. R1> R1 has two established peers: one IBGP peer to R2. due to Peer closed the session 1 accepted prefixes consume 32 bytes 0 history paths consume 0 bytes Connection state is ESTAB. 0 in queue Prefix advertised 8. up for 00:38:16 Last read 00:00:16.108. external link Index 2. remote AS 1. remote router ID 131.1. so that R3 advertises the network 141.5. Mask 0x4 BGP version 4.1. Mask 0x2 BGP version 4.108.255. OpenSent— BGP is waiting for an open message from the remote peer. remote router ID 141.108. internal link Index 1.108. along with the network statement.5 remote-as 1 The BGP peers on R1 are displayed in Example 6-24 (truncated for clarity). such as clearing the BGP peers.0 mask 255. 0 in queue Sent 1347 messages..255. remote AS 3. 0 in queue Sent 48 messages.. Local port: 11632 Foreign host: 131. Connect— BGP is waiting for the TCP connection to be completed. BGP neighbor is 131. keepalive interval is Minimum time between advertisement runs is 5 seconds Received 1351 messages. 60 seconds 0 60 seconds 0 . hold time is 180. note the EBGP connection between R3 (AS 3) and R4 (AS 2). Foreign port: 11001 . and an EBGP peer to R3. Offset 0. suppressed 0. up for 00:58:56 Last read 00:00:56.1.1. this is the final stage of BGP peer negotiation during which both peers exchange their BGP tables. Also.

local AS number 2 BGP table version is 9.255.B.B.C.1.108.C.0/8 A.1.9 4 3 7 8 13 0 0 00:01:15 5 Table 6-2 summarizes the descriptions and field definition.108.1.0.0 mask 255.0 The show ip bgp summary command is a useful command that summarizes all BGP peers. Example 6-25 Configuring BGP on R4 R4(config)#router bgp 2 R4(config-router)#neighbor 131.CCNP Practical Studies: Routing Example 6-25 enables EBGP between R4 and R2.0.108.108. as displayed by the IOS show ip bgp summary command. e. main routing table version 9 8 network entries and 8 paths using 1064 bytes of memory 4 BGP path attribute entries using 208 bytes of memory 1 BGP AS-PATH entries using 24 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 8/0 prefixes.255. 35.108..200 - .D Network in the BGP routing table to display cidr-only Display only routes with non-natural netmasks community Display routes matching the communities community-list Display routes matching the community-list dampened-paths Display paths suppressed due to dampening filter-list Display routes conforming to the filter-list flap-statistics Display flap statistics of routes inconsistent-as Display only routes with inconsistent origin ASs ipv4 Address family neighbors Detailed information on TCP and BGP neighbor connections paths Path information peer-group Display information on peer-groups quote-regexp Display routes matching the AS path "regular expression" regexp Display routes matching the AS path regular expression summary Summary of BGP neighbor status vpnv4 Display VPNv4 NLRI specific information | Output modifiers <cr> R4#show ip bgp summary BGP router identifier 151.255.255.108. 8/0 paths.255. Example 6-26 show ip bgp summary on R4 R4#show ip bgp ? A. Example 6-26 displays the BGP peers on R4 in a summarized format.9 remote 3 R4(config-router)#network 151.1 4 1 32 22 13 0 0 00:01:21 7 131.255.D IP prefix <network>/<length>. . scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131.1 remote-as 1 R4(config-router)#neighbor 131.g.

00:06:10 B 131. PfxRcd. Example 6-27 R3's IP Routing Table R3#show ip route 141.3.108.0/24 [20/0] via 131. or lowest IP address.108. 12 subnets.255.255.108. 1 subnets B 151.0/24 [20/0] via 131. loopback address.108.255.108.0. IP address of a neighbor. view some IP routing tables to ensure that you are routing IP.4.108.10.108.201 - .1/32 [20/0] via 131. To view more information about how the BGP entries were learned.108.108. 00:06:10 B 131.1. Field Summary for show ip bgp summary Field BGP router identifier BGP table version main routing table version Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd Description In order of precedence and availability.108. Number of messages waiting to be sent to that neighbor.255.255.0/24 [20/0] via 131.0 [20/0] via 131.108. The length of time that the BGP session has been in the Established state.0/24 is subnetted.108.108.1.10. in Example 6-26.108.8/30 is directly connected.255.7.2. 00:56:24 151.108. Next.0/24 [20/0] via 131. When the maximum number (as set by the neighbor maximum-prefix command) is reached. Number of messages from that neighbor waiting to be processed. 00:56:23 B 131. 00:06:10 B 131.0.0/24 [20/0] via 131. appears in the entry. the neighbor is shut down.5.5.108.255.108.108.108. the string.108. 00:06:10 B 131. or the current state. Serial0 C 131. Ethernet0 131. 00:06:11 B 131. 00:06:11 B 131.10.6. Typically you see only version 4.5. and the connection is idle.0 is directly connected.255.0.108.255. router identifier specified by the bgp router-id command.2.0/24 is subnetted.5. Current state of the BGP session/the number of prefixes the router has received from a neighbor or peer group.0/24 [20/0] via 131. 1 subnets C 141.108. view the BGP table with the show ip bgp command. 00:56:22 B 131.108.10.255.108.3.1/32 [20/0] via 131.1/32 [20/0] via 131. 00:56:23 B 131.4/30 is directly connected.108.108.4. Example 6-27 displays R3's IP routing table.108. 00:05:46 R3 has a full set of BGP routes for all BGP AS networks. as displayed in Example 6-26.255.0/24 [20/0] via 131.108.108. Example 6-28 displays R3's BGP table.5. 3 masks C 131. BGP version number spoken to that neighbor. BGP messages sent to that neighbor. if the state is not Established.0/16 is variably subnetted.10.10. Last version of BGP database injected into main routing table. BGP messages received from that neighbor.255. No information below the state indicates an active peer.1. Last version of the BGP database sent to that neighbor.255. Serial3 B 131. Internal version number of BGP database. . For Example.1/24. Peer autonomous system.1.10. the router ID of R4 is 151.CCNP Practical Studies: Routing Table 6-2.

0/24 131.108. or the link to R1.10 0 2 1 i *> 131.255.0/24 131.incomplete Network Next Hop Metric LocPrf Weight Path * 131.4.255.108.1.255.10 command.10 0 2 1 ? *> 131.1.5.0/24 131. The next decision is based on the path with the shortest AS path.108.0/24 131.1/32 131.5 0 0 1 i *> 131.108.255. local router ID is 141.5.5 0 1 ? *> 131. Start by analyzing why the remote network 131.1.108.255.3.4.1 Status codes: s suppressed.10 0 2 1 i *> 131.5 1 0 1 ? *> 131.3.108. BGP does not load balance and always chooses one path. Example 6-31 displays the BGP table on R3 after the BGP TCP peer is established again.255.108.108.0/24 131.108. not originated by local router).108. is preferred as the path through R4.1.108.255.0/24 131.108. i .255.108.0/24 131.255.108.IGP.0/24 0.CCNP Practical Studies: Routing Example 6-28 R3's BGP Table R3#show ip bgp BGP table version is 16.108. weight equal.255.108.internal Origin codes: i .5 0 0 1 i *> 131.255.1/32 131. ? .1/32 131.202 - .0/24 131. ? .1.EGP.10 weight 1 Example 6-30 displays the BGP table on R3 after the configuration change.108.108.0.0. d damped.255.6.1.255.108.108.0 has a dual path and why the next hop address 13.108.108.108.108.5 0 0 1 i *> 131.108.0 0 32768 i *> 151.4.108. local preference the same.10 0 2 1 i *> 141.108. e . d damped.108.108.108.0 0 32768 i *> 151.255.0/24 131. (There are many ways to accomplish this task. > best.10 0 2 1 i *> 131. local router ID is 141.1.10 0 2 1 ? *> 131.108.108. h history.EGP.1/32 131.255.3.108.108.255. h history.0.255.10 0 2 1 ? *> 131. .0/24 131.108.108.255. i . e .0. (Static routes can be used to change this behavior.10 0 2 1 ? *> 131.108.108.0/24 0.108.108.108.255.) Example 6-29 Changing the Weight on R3 R3(config)#router bgp 3 R3(config-router)#neighbor 131.10 0 2 1 ? *> 131.2.0/24 131.108.10 0 2 1 ? *> 131.108.3. The path to R1 is through one AS path only as opposed by two AS paths to R4.10 0 2 1 i *> 131.5.255.255.internal Origin codes: i .108.108.108.108.1/32 131.10 0 0 2 i A lot of information is stored here.) R3 chooses the path through the serial link to R1 because the BGP algorithm decision is based on 10 parameters and because the first four are the same (next hop reachable.1. Because weight has a higher preference than AS path.108.incomplete Network Next Hop Metric LocPrf Weight Path * 131.255.108.1/32 131. change the weight on R3 to prefer the path through R4.6.5 0 0 1 i *> 131.1 Status codes: s suppressed.IGP. Example 6-29 displays how to use the neighbor command to set all entries advertised through R4 to a weight value of 1 so that the network advertised by R4 has a higher weight value for the network 131.108.108.2.5 0 0 1 i *> 131. > best.108.5 0 0 1 i *> 131.1.0/24 131. Clear the BGP TCP peer session on R3 to R4 with the clear ip bgp 131.0/24 131.255. Example 6-30 show ip bgp on R3 R3#show ip bgp BGP table version is 16.4.255.10 0 2 1 ? *> 131.0/24 131.7. * valid.10 0 2 1 i *> 141.2.0/24 only.2.255.255.108.10 0 2 1 ? *> 131.1.7.108.10 0 0 2 i The change is not implemented because you must first clear the BGP peer session.108. * valid.0/24 131.0/24 131.255.

255.108.1.0 0.10 1 2 1 i *> 131.1 255.108.internal Origin codes: i . * valid.255.10. Example 6-32 display R1's full working configuration.255.1.3.5 100 0 1 i *> 131.108.108.0/24 131.internal Origin codes: i .255.108.108.1.108.1 Status codes: s suppressed.255.0/24 0.108.0/24 131.0/24 through R1 has a shorter AS path (through AS 1 only) because weight has a higher preference than AS path in the BGP routing decision.108.108.255.108.108.108.255. d damped.255.255.1 255.108.0/24 131.10 1 2 1 i *> 131.1.255.1 Status codes: s suppressed.108.1/32 131.5.108.10 1 2 1 ? *> 131.255.108.0 ! interface Serial0/0 ip address 131.EGP.108.0/24 131.108.0/24 is now preferred through R4 (weight is 1) as opposed to the link through R1.4.5 100 0 1 i *> 131.255.108.108.5 255.0.252 clockrate 125000 ! router ospf 1 network 131.1. e .1.3.255. or R4.0/24 131.2.255.108.108. local router ID is 141.1 255.5 100 0 1 i *> 131.2.1 255.108.255. local router ID is 141.108.108. > best. e .0/24 131. d damped.1.5 100 0 1 ? *> 131.0. h history.EGP.10 1 2 1 ? * 131.4.1/32 131. the path to 131. i .0/24 131.0 ! interface Ethernet0/0 ip address 131. h history.108.0 ! interface Loopback2 ip address 131.255.108.10 1 2 1 ? *> 131.10 1 2 1 ? *> 131.203 - . ? .0 0 32768 i *> 151.0.1. * valid.255.CCNP Practical Studies: Routing Example 6-31 show ip bgp on R3 R3#show ip bgp BGP table version is 32.108.3.incomplete Network Next Hop Metric LocPrf Weight Path *> 131.255.IGP.IGP. have the weight value set to 1.255 area 0 .10 1 2 1 i *> 141.255. > best.2.255. Provided here for your reference are the four configurations on the Routers R1 through R4. ? .255.108.7.255.6.108.0/24 131.108. All entries advertised through the next hop address 131. i .1.0 ! interface Loopback1 ip address 131.4.incomplete Network Next Hop Metric LocPrf Weight Path R3#show ip bgp BGP table version is 16.10 0 1 2 i Even though the path to the remote network 131.0.1/32 131.108. Example 6-32 R1's Full Working Configuration hostname R1 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.255. You have successfully configured a four-router topology with BGP4.108.108.255.

255 area 0 network 131.6 remote-as 3 no auto-summary line con 0 line aux 0 line vty 0 4 end Example 6-33 display R2's full working configuration.2 255.6.108.1.0 0.255.108.0.2 remote-as 1 neighbor 131.255 area 0 network 131.255.6.0 ! interface Ethernet0/0 ip address 131.0 0.2 remote-as 2 no auto-summary ! line con 0 line aux 0 line vty 0 4 end .255.108.108.0 network 131.0.255.0.255.108.108.0.0 mask 255.108.255.0 0.0 0.0 mask 255.255.1 255.7.255.7.0 mask 255.0.255.255.255 area 0 network 131.0 interface Loopback1 ip address 131.3.255.5.0 mask 255.CCNP Practical Studies: Routing network 131.255 area 0 ! router bgp 1 network 131.108.4.0.0 mask 255.3.255.1 255.0.255.255 area 0 network 131.0.204 - .1.0 network 131.7.255.108.0 ! interface Serial1/0 ip address 131.0.0 neighbor 131.1.4.0.108.255.0 ! interface Loopback2 ip address 131.0 mask 255.108.0.0.108.5.255.108.255.2.108.108.255.0 clockrate 128000 ! router ospf 1 network 131.5.0.6.108.108.108.108.255.255 area 0 network 131.108.0 0.255. Example 6-33 R2's Full Working Configuration hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.0 redistribute ospf 1 metric 100 neighbor 131.0 0.1.0.255 area 0 ! router bgp 1 network 131.255.255.255.108.0 0.1 remote-as 1 neighbor 131.1 255.1 255.0 network 131.255.0 network 131.255.108.2.

10 weight 1 ! line con 0 line aux 0 line vty 0 4 ! end Example 6-35 display R4's full working configuration.255.0 mask 255.255.255.1 255.255.255.255.9 255.255.108.252 ! interface Serial1 shutdown ! router bgp 2 network 151.108.108.255. Example 6-35 R4's Full Working Configuration hostname R4 ! enable password cisco no ip domain-lookup interface Ethernet0 ip address 151.255.1.255.1.255.255.1 255.108.255.1.252 ! router bgp 3 network 141.6 255.1.0 media-type 10BaseT ! interface Serial0 ip address 131.5 remote-as 1 neighbor 131.255.255.1 remote-as 1 neighbor 131.108.2 255.10 remote-as 2 neighbor 131.0 mask 255.255.255. Example 6-34 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 141.108.255.108.255.108.255.255.108.0 neighbor 131.CCNP Practical Studies: Routing Example 6-34 display R3's full working configuration.9 remote-as 3 ! line con 0 .205 - .252 bandwidth 125 ! interface Serial1 shutdown ! interface Serial2 shutdown ! interface Serial3 ip address 131.255.0 neighbor 131.108.108.108.0 interface Serial0 ip address 131.

synchronization is not an issue in this network.1 remote-as 2 R1(config-router)#neighbor 161.1.255.0/24 (Ethernet 0/0).0 R1(config-router)#neighbor 161.1 update-source Ethernet0/0 Example 6-37 displays the EBGP configuration on R2. the peer address is 131.CCNP Practical Studies: Routing line aux 0 line vty 0 4 end Scenario 6-2: BGP and Static Routes In this scenario. if the next hop address in EBGP is not used. you use static routes to load balance BGP over a dual-path connection between two routers.0/24.1 ebgp-multihop R2(config-router)#neighbor 131.108. To achieve any form of load balancing of two or more network paths.1. Because you are running EBGP.1 (Ethernet 0/0). you can use static routes to the remote peer address. The IOS command to enable EBGP multihop is neighbor peer address ebgpmultihop.1. Figure 6-3 displays a simple two-router BGP topology. and in the case of R2. Example 6-37 EBGP Configuration on R2 R2(config)#router bgp 2 R2(config-router)#network 161.1. and in the case of R2.255. it is 161. the next hop peer address is 161.0 mask 255.255.1. In the case of R1. BGP Topology Enable BGP on R1 and configure the network command to advertise the Ethernet IP network 131. Figure 6-3.0 R2(config-router)#neighbor 131.1. Example 6-36 displays the EBGP configuration (with multihop) on R1. you need to peer the BGP neighbors using the Ethernet IP addresses.1 update-source Ethernet0/0 .108. In the case of R1.1.1.108. Example 6-36 EBGP Configuration on R1 R1(config)#router bgp 1 R1(config-router)#network 131.108.1 ebgp-multihop R1(config-router)#neighbor 161.0 mask 255.1 remote-as 1 R2(config-router)#neighbor 131.1. BGP needs to advertise the update source IP address to EBGP.108.1.108. you must enable EBGP multihop so that the EBGP peer is established. BGP chooses only one path to a remote network.108. With BGP.108.108.1.1. to achieve load balancing.255. Also.1/24. because the next hop address is not a directly connected address.1/24. Also.108.108.206 - .108. such as in this scenario in which you want to achieve load balancing.108. it is 131.1.

CCNP Practical Studies: Routing Now that R1 and R2 are configured with EBGP.1.1.108.0 BGP state = Active.0/30 is directly connected.1. 0 in queue Prefix advertised 0.255.1.207 - .108. Example 6-40 Static Route Configuration on R1 R1(config)#ip route 161. Example 6-40 displays the IP static route configuration on R1.108. external link Index 1.108.255. remote AS 2. remote router ID 0. Serial0/1 C 131. suppressed 0. Example 6-41 Static Route Configuration on R2 R2(config)#ip route 131.255.0 255. hold time is 180.108.255.0. Example 6-39 show ip route on R1 R1#show ip route 131.255.255.1.0 serial 1/1 The BGP peers on R1 display the established peer to R1.0 serial 1/0 R2(config)#ip route 131. Offset 0. Serial0/0 C 131. ensure that BGP peer sessions are up with the show ip bgp neighbor command.0/24 is directly connected. table version = 0 Last read 00:03:37.108.255. Example 6-41 displays the IP static route configuration on R2.1.0 serial 0/1 To ensure that R2 can route to the remote network 131. Example 6-39 displays R1's IP routing table.108.4/30 is directly connected. To discover why.0 255.1. dropped 0 Last reset never 0 accepted prefixes consume 0 bytes 0 history paths consume 0 bytes External BGP neighbor may be up to 255 hops away. keepalive interval is 60 seconds Minimum time between advertisement runs is 30 seconds Received 0 messages.0. Mask 0x2 BGP version 4.108. Configure two static routes on R1 pointing to the remote network through Serial 0/0 and Serial 0/1.108. Example 6-38 show ip bgp neighbors on R1 R1#show ip bgp neighbors BGP neighbor is 161.1.255. .0. 0 notifications.108.0 255.0 255. Example 6-38 displays the peers on R1.0/24 and thereby cannot establish a TCP session to R2.108. 0 in queue Sent 0 messages.0 serial 0/0 R1(config)#ip route 161. 2 subnets.0/16 is variably subnetted.255.0. 2 masks C 131.1. display the IP routing table on R1. No active TCP connection R1 has no peer relationship to R2. 0 notifications.255. Ethernet0/0 R1 does not have any entries for the remote network 161. Example 6-42 shows a truncated display of the peer with R2. install two static routes pointing to R1 over Serial 1/0 and Serial 1/1. withdrawn 0 Connections established 0.

108. Sending 5.1/24 from R1.1 (Serial0/1). Take note of the shaded sections. d=161.1.1 (local). Mask 0x2 BGP version 4.. round-trip min/avg/max = 16/17/20 ms 00:09:27: IP: s=131.1. len 100.[truncated display] Ensure that load balancing is taking place by pinging the remote network 161.1. sending 00:09:27: IP: s=161.108. external link Index 1.1 (Serial0/0).1.1 (Serial0/0). d=161.108. 0 in queue Sent 7 messages. . due to User reset 1 accepted prefixes consume 32 bytes 0 history paths consume 0 bytes External BGP neighbor may be up to 255 hops away. len 100. dropped 0 Last reset 00:04:21.1.1.1 (Serial0/0).1. len 100. in effect you are load balancing BGP by using static routes.255. keepalive interval is 60 seconds Minimum time between advertisement runs is 30 seconds Received 7 messages. .1 (Serial0/0). sending 00:09:27: IP: s=161.1. Example 6-43 shows the ping request after the debug ip packet command is enabled. len 100. len 100. d=131. sending 00:09:27: IP: s=161. d=161. len 100. therefore.1.255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. withdrawn 0 Connections established 1.5 (Serial0/1). and the reply is received through Serial 0/1.CCNP Practical Studies: Routing Example 6-42 show ip bgp neighbors on R1 R1#show ip bgp neighbors BGP neighbor is 161. sending 00:09:27: IP: s=161.1 Type escape sequence to abort. rcvd 3 You can see from Example 6-43 that the first ping request is sent through Serial 0/0 and the reply is received through Serial 0/0.1 (Serial0/0).108. len 100. table version = 3.1 BGP state = Established.5 (local). remote router ID 161. but because IP at Layer 3 is load balancing.1 (Serial0/1).108. rcvd 3 00:09:27: IP: s=131.255.108.5 (Serial0/1). rcvd 3 00:09:27: IP: s=131.1. d=131.108.255. so you can see on which outbound interface the ping request is sent. Example 6-44 displays the full working configuration of R1.255. Offset 0.1 (Serial0/0).108.1.1 (Serial0/0). d=161. 0 notifications.108.108.108. d=131. 100-byte ICMP Echos to 161. suppressed 0. This command enables you to view where IP packets are sent to and received from. 0 in queue Prefix advertised 1.1 (Serial0/0).255. which contain the critical commands used to achieve load balancing between R1 and R2. len 100.1 (Serial0/0).1 (Serial0/1).1.108.108.108. d=131.208 - .108.108.5 (local).108.1 (local). d=161.108. 0 notifications. Example 6-43 Debug Output on R1 R1#debug ip packet IP packet debugging is on R1#ping 161. len 100.108. rcvd 3 00:09:27: IP: s=131.1. len 100. It is important to note that BGP still only sends packets through one path.108. sending 00:09:27: IP: s=161. hold time is 180.1. The second ping request is sent through Serial 0/1. up for 00:03:51 Last read 00:00:51.108.1 (local). d=131.1 (Serial0/1).255.108. remote AS 2.1.108. Turn on debug ip packet. rcvd 3 00:09:27: IP: s=131.1.255.108.255.255. load balancing is occurring.1.

1 255.1 255.1.108.108.0 255.255.255.1 ebgp-multihop 255 neighbor 161.255.1.255.1.255.0 Serial0/1 ! line con 0 line aux 0 line vty 0 4 end Example 6-45 displays R2's full working configuration.255. .108.255.0 no ip directed-broadcast ! interface Serial0/0 ip address 131.108.0 mask 255.1.255.252 clockrate 125000 ! router bgp 1 network 131.1 remote-as 2 neighbor 161.255.255.108.5 255.209 - .255.0 255.0 Serial0/0 ip route 161.CCNP Practical Studies: Routing Example 6-44 R1's Full Working Configuration hostname R1 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.255.1 update-source Ethernet0/0 ! ip route 161.255.108.255.252 clockrate 125000 ! interface Serial0/1 ip address 131.108.1.1.108.1.108.0 neighbor 161.

0 Serial1/0 ip route 131.255.0 ! interface Serial1/0 ip address 131.255.108.0 neighbor 131.252 interface Serial1/1 ip address 131.255.0 255.252 ! router bgp 2 network 161.1 ebgp-multihop 255 neighbor 131.108.1 255.1. Policy-based routing is used for the following main reasons: • • • To control traffic flow direction either by source or destination address To change the next hop address To change the way traffic is sent to a neighboring router The advantages of using policy routing is the ability to load share to provide high-quality service and cost saving.255.108.0 255.255.108.CCNP Practical Studies: Routing Example 6-45 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 161. based on data traffic.108.1.255. for expensive links.1.6 255.0 Serial1/1 ! line con 0 line aux 0 line vty 0 4 end Scenario 6-3: BGP with Policy-Based Routing In this scenario.0 mask 255.1.108.108.255.1 remote-as 1 neighbor 131.108.108. .1.255.255.1 update-source Ethernet0/0 ! ip route 131.1.255. except this time you configure two EBGP sessions between R1 and R2 and use BGP to route dynamically without static routing. you configure EBGP using the next hop addresses and use policy-based routing to allow certain network design policies to affect IP routing decisions.2 255.1. Figure 6-4 displays the same two-router network used in Scenario 6-3.255.210 - .255.255.255.

i .108.255.255.1.0 R2(config-router)#neighbor 131.0 mask 255.2 remote-as 2 R1(config-router)#neighbor 131.IGP.0 R1(config-router)#neighbor 131.0 131. Example 6-46 displays the EBGP configuration on R1. Example 6-48 BGP Table on R1 R1#show ip bgp BGP table version is 3.1. 131.108.2 because of its lower IP addresses.108. all other parameters that BGP bases decisions on are equal in this case. d damped.108.1.255.5 remote-as 1 Example 6-48 displays the IP BGP table on R1 after the two BGP sessions are established. local router ID is 131.108.255. (Notice. you don't need EBGP multihop because you are using a directly connected peer.1 remote-as 1 R2(config-router)#neighbor 131. Assume that all traffic from the Ethernet segment on R1 .108.2.108.255. Two-EBGP Session Topology Configure two EBGP TCP sessions between R1 and R2.0/24 * 161. Example 6-47 EBGP on R2 R2(config)#router bgp 2 R2(config-router)#network 161.CCNP Practical Studies: Routing Figure 6-4.incomplete Network *> 131.255.255. e .6 remote-as 2 Example 6-47 displays the two EBGP sessions configured on R2.211 - .EGP.0.108.0/24 because BGP does not load balance as you discovered in Scenario 6-2.0.1.108. * valid. h history.255.255.internal Origin codes: i .108. ? .2 Metric LocPrf Weight Path 0 32768 i 0 0 2 i 0 0 2 i Example 6-48 displays R1 choosing the path through the next hop address.108. to reach the remote network 161.255.6 131.255.) Example 6-46 EBGP on R1 R1(config)#router bgp 1 R1(config-router)#network 131.5 Status codes: s suppressed.1.108.108. > best.0/24 *> Next Hop 0.108.255. The path is chosen through 131.0 mask 255.255.

.108.6.1.1 default-originate R2(config-router)#neighbor 131. you apply the policy statement on the outbound interface and reference a route map. Example 6-51 confirms this when you view the IP routing table on R1.255.255. Internet-based traffic). First.108.108.0.0.0. Example 6-49 Default Route Configuration on R2 R2(config)#router bgp 2 R2(config-router)#neighbor 131. or Serial 1/1.6 and all other traffic is sent through 131. suppose you want to send internal traffic through one path and all Internet traffic through the second link.0/24 * 161. which will be through the second link (Serial 1/0).108. configure R2 to advertise a default route to R1. Policy routing is based on incoming packets only.1.255. Serial1/1 C 131.108. * valid.0 *> *> 131. 2 masks C 131.EGP.0.0/24 is subnetted.108.255.108. Next.108. To configure policy routing.212 - .IGP.108. 3 subnets.108. Example 6-49 displays the configuration on R2 so that it sends a default BGP route to R1.0/0 [20/0] via 131.255.255.255. and all traffic destined for the Internet is sent through Serial 1/0.1.1.1.108. ? .2.2 Metric LocPrf Weight 0 0 0 32768 0 0 0 0 Path 2 i 2 i i 2 i 2 i Example 6-50 tells you that R1 is choosing all traffic through the next hop address 131.255.255.2.5 default-originate Example 6-50 displays the BGP default route in R1's BGP table. Example 6-51 show ip route Command on R1 R1>show ip route Gateway of last resort is 131.0. Two default statements are configured for redundancy purposes. To illustrate policy-based routing.108.0/30 is directly connected.0 131.0 (Serial 1/1) than for all other destinations (for example.0 131.108.5 Status codes: s suppressed.1 (Serial 1/0 to R2). Ethernet0/0 161.2.1.0.0. h history.0/24 are sent through the next hop address 131.255. Example 6-50 show ip bgp Command on R1 R1>show ip bgp BGP table version is 4.0. you learn to configure policy-based routing to illustrate how you can use route maps to achieve this.108.1.6 131. Serial1/0 C 131.2 0.108.108. so you need to apply the policy command on the Ethernet interface on R1.internal Origin codes: i .0.2 to network 0.4/30 is directly connected. 1 subnets B 161.0.108. i . But.0 must be sent through the next hop address 131.0 [20/0] via 131.108. 00:13:58 Policy routing needs to be configured on R1 to ensure that IP ICMP packets destined for the remote network 161.255.108.108.108.108.255.CCNP Practical Studies: Routing bound for 161.108.108. > best.incomplete Network * 0.255. configure R1 to choose a different next hop address for IP ICMP packets destined for the remote network 161. e . local router ID is 131.255. d damped. You can force BGP to complete this task by using policy-based routing or changing BGP attributes.1.0/24 is directly connected.0/24 *> Next Hop 131.0/16 is variably subnetted.108.6 131. 00:23:11 B* 0. The IOS command is ip policy route-map route-map-name.255.

0/16 is variably subnetted.108.4/30 is directly connected.108.2.0.0/24 is subnetted.255. Serial1/1 C 131. 3 subnets.0/0 [20/0] via 131.0. 00:22:52 B* 0.108. 2 masks C 131. Remember that BGP. you cannot verify policy routing with the IP routing table.1). Example 6-52 Policy Configuration on R1 R1(config)#interface E0/0 R1(config-if)#ip policy route R1(config-if)#ip policy route-map ? WORD Route map name R1(config-if)#ip policy route-map nondefault Next. Example 6-55 displays an extended ping using the source address 131.0 [20/0] via 131.0.108.1.6.0/24 through Serial 1/1 (next hop address 131.108. This example assigns a route map called nondefault.0/4.0/30 is directly connected.108. Example 6-53 Route Map Configuration on R1 route-map default permit 10 match ip address 100 set ip next-hop 131.255.108.108.255.108.6 access-list 100 permit icmp 131. Example 6-53 sets all IP ICMP traffic from the Ethernet segment on R1 destined for 161.1 Type of service [0]: Set DF bit in IP header? [no]: Validate reply data? [no]: .0.108.0/24 is directly connected.108. 00:22:52 Example 6-54 stills displays that all remote networks are routed through 131.108.1.0 0.213 - .1.108.2.1–131.255. is sending all traffic through Serial 1/0 on R1.1.1 (R1's Ethernet interface) to the remote network 161.2.255.108.CCNP Practical Studies: Routing Example 6-52 displays the policy routing interface configuration on R1.0.1.0 0. or Serial 1/0. 1 subnets B 161.0.0.6) and all default traffic through Serial 1/0 (next hop address 131.1.255.108.255.108. Example 6-54 displays R1's IP routing table. Unfortunately.1.255 161.1. Serial1/0 C 131. The route map name is an arbitrary name you can assign.255 through the next hop address 131.255. as displayed in Example 6-50.255. Ethernet0/0 161.108. Example 6-55 Extended Ping on R1 R1#debug ip policy Policy routing debugging is on R1#ping Protocol [ip]: Target IP address: 161.108.0.108.108.255 The route map on R1 policy routes any IP ICMP packets with a source address in the range 131. Example 6-52 uses the ? tool to illustrate the options available to you. An extended ping request along with a debug ip policy on R1 displays any policy routing.1 Repeat count [5]: Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: y Source address or interface: 131.1.108. Example 6-54 show ip route on R1 R1#show ip route 131. you must set the conditions on R1 so that policy routing can occur.108.1.1.

255.255.1.1 Type escape sequence to abort.1 (local). permit 00:26:57: IP: s=131. policy routed 00:26:57: IP: local to Serial1/1 131. Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. d=161.255. Record.255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).normal forwarding 00:30:35: IP: s=131.108.214 - . policy rejected . d=161. Timestamp. len 100. len 100.255. item 10. len 100.6 00:26:57: IP: s=131.108. d=141. policy routed 00:26:57: IP: local to Serial1/1 131. len 100.1 (local).1.1 (Serial1/1).normal forwarding . len 100. len 59.108.108. d=161.CCNP Practical Studies: Routing Data pattern [0xABCD]: Loose.108.108.1 (local). d=141. item 10.1. Example 6-56 displays a ping request to the unknown network 141.108.108.1 (local).108.normal forwarding 00:30:35: IP: s=131. permit 00:26:57: IP: s=131. 100-byte ICMP Echos to 141. d=161. policy match 00:26:57: IP: route map default.6 00:26:57: IP: s=131.108.1. len 100.1 (Serial1/1). policy rejected .108.1.1 (local). or the next hop address 131.1 (Serial1/1).108. len 100. d=161.1 (local). permit 00:26:57: IP: s=131.255.255.1 (local). d=161.1.108.108.1.1 on R1 and the subsequent policy debug output.255.108. d=141.108.1.1.1 (local).1.108. policy match 00:26:57: IP: route map default.normal forwarding 00:30:37: IP: s=131.1.108.1. round-trip min/avg/max = 16/18/20 ms 00:26:57: IP: s=131. round-trip min/avg/max = 16/16/20 ms 00:30:35: IP: s=131.108.6 Example 6-55 displays the five ping requests successfully policy routed through Serial 1/1.255. d=131. Strict. policy rejected .1. 100-byte ICMP Echos to 161.108.255.1. len 100.255.108.108. policy match 00:26:57: IP: route map default.108. d=141.1.1 (Serial1/1).108. policy match 00:26:57: IP: route map default. Example 6-56 ping 141. d=161. item 10.1. Sending 5.6.108.1 (local).1 (local).108. len 100.1. item 10. policy rejected -.1. len 59.108.1.1.108.normal forwarding 00:30:39: IP: s=131.1.normal forwarding 00:30:35: IP: s=131.1 (Serial1/1). len 100.1. permit 00:26:57: IP: s=131. policy routed 00:26:57: IP: local to Serial1/1 131.1 (local).108.1. d=161.1 (local).1.1.1.1 (local).1 (local).108.1.108. policy routed 00:26:57: IP: local to Serial1/1 131. d=161.1.1. len 100.1 (local).108.normal forwarding 00:30:35: IP: s=131.5 (local).1. len 100. item 10.108. policy routed 00:26:57: IP: local to Serial1/1 131. d=161.255.6. d=131.255.1 on R1 R1#ping 141.1. d=141.108.108.255.1.6 00:26:57: IP: s=131.1 (local). Sending 5.108. policy rejected .108.108. policy match 00:26:57: IP: route map default.6 00:26:57: IP: s=131.1. permit 00:26:57: IP: s=131.1.1.108.1. len 100. policy rejected .1.255.1.108. policy rejected -.1.108. len 100.1.108. len 100. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.108.2.108.108.1.

policy match 01:04:00: IP: route map default. policy routed 01:04:00: IP: local to Serial1/1 131. len 49.6 01:04:00: IP: s=131.1. d=161.1. len 52. permit 01:04:00: IP: s=131.108. you can do this if you want Telnet sessions to go through one interface or another.1.1.108. len 43. d=161.108.1 (local).6 01:04:00: IP: s=131.6 01:04:00: IP: s=131.1 (local).1 /source-interface ethernet 0/0 Trying 161. item 10.108.108.6 01:04:00: IP: s=131.108.1 (Serial1/1).108. len 43.1 (local). policy routed 01:04:00: IP: local to Serial1/1 131.1.1.1. item 10. policy match 01:04:00: IP: route map default.1.1.108.1. Open R2> 01:04:00: IP: s=131.108. policy routed 01:04:00: IP: local to Serial1/1 131.108.255 161.1 (local). d=161.108.1.0 0. Example 6-57 displays the access-list configuration to allow Telnet sessions through Serial 1/1.108. Example 6-57 Allowing Telnet to Be Policy Routed on R1 access-list 100 permit tcp 131.108. d=161. item 10.1 (local).108.1.1.108.1. d=161.108.255.108. permit 01:04:00: IP: s=131.108.108.6 01:04:00: IP: s=131.1 (Serial1/1). item 10.1. len 49.1 (Serial1/1)..1.0.1 (local).108.0/24 through the next hop interface 131.108.1 (Serial1/1). d=161. len 44.1.1.0.1 (local). d=161.108.255.108.1.1 (local).1.1.6 01:04:00: IP: s=131.1. d=161.255.0. policy match 01:04:00: IP: route map default.1 (local). item 10. hence. Configure R1 to send all Telnet traffic originated from the network 131.1.1. d=161. d=161.1 (local). policy match 01:04:00: IP: route map default.1 (local). permit 01:04:00: IP: s=131. d=161.6 01:04:00: IP: s=131. permit 01:04:00: IP: s=131.255.108. len 52.1.1 . permit 01:04:00: IP: s=131. permit 01:04:00: IP: s=131.215 - . len 40.108.1.108. policy routed 01:04:00: IP: local to Serial1/1 131.1 (local).108.1 (Serial1/1).108.108. len 44. d=161.1. item 10. policy routed 01:04:00: IP: local to Serial1/1 131.1.255.108.1 (local).1.1. len 40.1.1.108. d=161.108.1. policy match 01:04:00: IP: route map default.255. len 40. policy routed 01:04:00: IP: local to Serial1/1 131.1.1.255 eq telnet Example 6-58 Sample debug ip policy Output on R1 R1#debug ip policy Policy routing debugging is on R1#telnet 161.108.0 0.108.CCNP Practical Studies: Routing R1 sends all packets to an unknown destination through normal forwarding through Serial 1/0.1. d=161.108. policy match 01:04:00: IP: route map default.108. item 10..255.108.1.1 (local). you can also base routing on port numbers.1 (Serial1/1). len 43.1. permit 01:04:00: IP: s=131.1. d=161.1.1 (Serial1/1). With the use of extended access lists. policy routed . the IP datagram is forwarded through the normal outbound interface.108. permit 01:04:00: IP: s=131.108.1 (Serial1/1).0.255. The debug output in Example 6-56 displays a nonmatching policy. policy routed 01:04:00: IP: local to Serial1/1 131.1. len 43. len 40.1.108.108. This simple scenario demonstrates the powerful use of policy-based routing on source and destination addresses.1 (local). For example.6.1. len 43. policy match 01:04:00: IP: route map default. item 10.1. policy match 01:04:00: IP: route map default.108.108.108. len 43.1 (local).1. d=161.108.

1.1 (Serial1/1).108. R2 has no login on vty 0 4 lines. len 40.255.255.0.6 line con 0 line aux 0 line vty 0 4 no login ! end Example 6-60 displays R2's full working configuration.1.108. Example 6-59 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Ethernet0/0 ip address 131.108. d=161.1.108.108.1 (local).CCNP Practical Studies: Routing 01:04:00: 01:04:00: 01:04:00: 01:04:00: routed 01:04:00: IP: IP: IP: IP: local to Serial1/1 131.108.0 0.1.1. therefore.6 Example 6-58 displays a sample debug output when you telnet to 161.0.1 (local).108.255.255.5 255.255.255.0 0.108.255 161.252 clockrate 128000 ! router bgp 1 network 131.0 neighbor 131.1.252 clockrate 128000 ! interface Serial1/1 ip address 131.255. when you telnet from R1 to R2.255.108.2 remote-as 2 neighbor 131. policy match route map default. permit s=131.108. Example 6-59 displays R1's full working configuration.1. item 10.1. R1 sends all Telnet traffic through Serial 1/1. policy IP: local to Serial1/1 131. Because a policy is matched on access list 100.255.108.108.255 161.0.1.0 0.1 255.255.0 ip route-cache policy ip policy route-map default ! interface Serial1/0 ip address 131.255.255.255 eq telnet route-map default permit 10 match ip address 100 set ip next-hop 131.1 255. d=161.1.0.0 mask 255.0.6 remote-as 2 ! ip local policy route-map default access-list 100 permit icmp 131.1.1 from R1 using the source address of 131.0.255. you are immediately placed at the R2 prompt.108.216 - . .108.1.255.255. len 40.255 access-list 100 permit tcp 131.1.0 0.108.108.0.0.6 s=131.108.108.108.1.

108.255.1 (Remote AS 1001).1.5 remote-as 1 neighbor 131.255.252 router bgp 2 network 161.108.252 interface Serial1/1 ip address 131.1 (Remote AS 1002).255.1 255. A community is a group of routers sharing the same property.255.1.255.0 mask 255.100.108. In this scenario. such as the community attribute and peer groups.255.1.108. such as no-export (do not advertise to EBGP peers) and noadvertise (do not advertise this route to any peer).255.217 - .108.108. A peer group is a group of BGP neighbors sharing the same update policies.1 remote-as 1 neighbor 131.5 default-originate ! line con 0 line aux 0 line vty 0 4 no login ! end Scenario 6-4: BGP with Communities and Peer Groups BGP deals with large BGP peers by using many different scalable solutions. and R2 peers to an EBGP peer with the IP address 151.294.0 ! interface Serial1/0 ip address 131.1.967.255. can substitute for community-number. including an Internet connection on R1 and R2. R1 peers to an EBGP peer with the IP address 141. The no advertise community attribute advises a BGP router carrying this attribute that the route advertised should not be advertised to any peers.1 default-originate neighbor 131.108. NOTE The community attribute is a number defined in the range 1 to 4. Some well-known community attributes.255.255.CCNP Practical Studies: Routing Example 6-60 R2's Full Working Configuration hostname R2 ! enable password cisco ! interface Loopback0 ip address 141. use the neighbor command: neighbor {ip address | peer group} send-community Figure 6-5 displays a simple four-router topology.255. In this scenario.108.255.1. you configure a well-known BGP community and discover the advantages of peer groups. The no export community attribute advises a BGP router carrying this attribute that the route advertised should not be advertised to any peers outside the AS.1 255.0 neighbor 131.108.255. .255. you discover how BGP uses the community attribute along with a peer group to ensure that IBGP is scalable in a large network environment.255 ! interface Ethernet0/0 ip address 161. To apply the community attribute to a remote BGP neighbor.255. Typically.200.6 255.199.255.2 255. The IOS set community community-number [additive] command is used to define a value.

108.1. which informs the neighboring router not to use R1 for any traffic not destined for the network 131. Figure 6-5. is the Internet gateway.1.199. Example 6-62 Route Map Configuration on R1 R1(config)#route-map setcommunity R1(config-route-map)#set community ? <1-4294967295> community number aa:nn community number in aa:nn format additive Add to the existing community local-AS Do not send outside local AS (well-known community) no-advertise Do not advertise to any peer (well-known community) no-export Do not export to next AS (well-known community) none No community attribute <cr> R1(config-route-map)#set community no-export .199. IBGP Example 6-61 displays the community attribute setting on R1.199.1 R1(config-router)#neighbor 141. so the Internet routers do not use R1 as a transit path. Example 6-61 BGP Configuration on R1 R1(config)#router bgp 1 R1(config-router)#neighbor 141.218 - . you set the community attribute (well-known) no-export on R1 and R2. so to ensure that R1 and R2 are not the transit paths for any ISP-based traffic.199.1.1 remote-as 1001 send-community route-map setcommunity ? route-map setcommunity out R1 is configured for EBGP and IBGP.CCNP Practical Studies: Routing large companies have more than one Internet connection.1 R1(config-router)#neighbor 141.0. You have yet to apply the route map named setcommunity (arbitrary name). Example 6-62 displays the route map configuration on R1.0/16.1. The EBGP connection to the remote peer address. Therefore.199.1. 141.1. you must send the 6community to the remote peer and apply an outbound route map. Apply the well-known community no-export.1 in Apply map to incoming routes out Apply map to outbound routes R1(config-router)#neighbor 141.

R1–R4. To create a BGP peer group. Also set the next-hop-self attribute on all IBGP peer sessions.1. use the neighbor peer-group command. and sets the weight to 1000.CCNP Practical Studies: Routing Notice that the ? tool displays all the community variations. to demonstrate the power of peer groups. For a small network such as this. you need to complete the same set of IOS commands (seven IOS commands in total) and have different route maps and access lists. Example 6-63 Community Configuration on R2 R2(config)#router bgp 1 R2(config-router)#neighbor 151.1.108.1.100.2 send-community R1(config-router)#neighbor 131. You must ensure that the ISP connected to R2 does not use R2 as a transit path. this is not scalable.219 - . Example 6-63 configures R2 to ensure that the ISP is not using the network of Routers R1–R4 as a transit path. and R4). for IBGP.1 send-community R2(config-router)#neighbor 151.2 distribute-list 1 in R1(config-router)#neighbor 131. Clearly with a large network.100. including a community number and the two other well-known community values: local-AS and no-advertise. the name is an arbitrary name.1.100. Take advantage of peer groups and configure one policy. First. Next.0 To configure R1 to set the same attributes and conditions to R3 and R4.1 se R2(config-router)#neighbor 151.1. again.108.108.0. Example 6-65 creates a peer group on R1 named internal. or R4.2 route-map setattributes in R1(config-router)#neighbor 131.1. Example 6-64 R1's IBGP Configuration to R2 R1(config-router)#neighbor 131.1 remote-as 1002 R2(config-router)#neighbor 151. configure the four routers.1. R3. Assume the network designer has asked you to ensure that R1 does not receive any default routes from R2. and set the same policies on all four routers. . to the peer groups.108. and apply that policy on R1 to all three remote routers (R2. configure IBGP on R1.2 weight 1000 R1(config)#route-map setattributes R1(config-route-map)#set community 2000 R1(config)#access-list 1 deny 0.1.108.2 next-hop-self R1(config-router)#neighbor 131.0.100.1 remote-as 1002 R2(config-router)#neighbor 151. Ensure that R1 sets the community to the value 2000. such as the weight and community value. the configuration on R1 can grow quite large. Example 6-66 displays all the available options you can assign to a peer group. R3. beginning in router configuration mode.1. Example 6-65 Peer Group Command on R1 R1(config)#router bgp 1 R1(config-router)#neighbor internal peer-group You must then assign the options.100. Example 6-64 configures R1 for IBGP to R2 only. sends the community value of 2000.1. sets the next-hop-self attribute (no defaults routes permitted).1 route-map setcommunity out R2(config-router)#exit R2(config)#route-map setcommunity R2(config-route-map)#set community no-export The route map name is the same as the name used on R1 because route map names are locally significant on Cisco routers.

Take note of the shaded sections that configure R1 to set local-based policies to all three IBGP peers. Example 6-67 displays the setting of a distribution list to stop a default route from being accepted on R1. Example 6-67 Peer Group Definitions R1(config-router)#neighbor R1(config-router)#neighbor R1(config-router)#neighbor R1(config-router)#neighbor internal distribute-list 1 in internal next-hop-self internal remote-as 1 internal route-map setattributes in Finally. The beauty of using peer groups is that you can add more BGP peers by using only one command.108. Peer groups can also be applied to EBGP peers and are commonly used in large ISP networks in which many thousands of customers might have Internet connections.220 - .1.6 peer-group internal neighbor 131. and R4 members of the peer group called internal.14 peer-group internal R1 has defined three remote IBGP peers with one statement that sets all the parameters defined by the peer group internal. Chapter 7 describes two other main methods used in BGP networks to scale in large networks.CCNP Practical Studies: Routing Example 6-66 Peer Groups Options R1(config-router)#neighbor internal ? advertise-map specify route-map for conditional advertisement advertisement-interval Minimum interval between sending EBGP routing updates default-originate Originate default route to this neighbor description Neighbor specific description distribute-list Filter updates to/from this neighbor ebgp-multihop Allow EBGP neighbors not on directly connected networks filter-list Establish BGP filters maximum-prefix Maximum number of prefix accept from this peer next-hop-self Disable the next hop calculation for this neighbor password Set a password peer-group Configure peer-group prefix-list Filter updates to/from this neighbor remote-as Specify a BGP neighbor remove-private-AS Remove private AS number from outbound updates route-map Apply route map to neighbor route-reflector-client Configure a neighbor as Route Reflector client send-community Send Community attribute to this neighbor shutdown Administratively shut down this neighbor soft-reconfiguration Per neighbor soft reconfiguration timers BGP per neighbor timers unsuppress-map Route-map to selectively unsuppress suppressed routes The shaded sections in Example 6-66 contain the options you set. R3. every BGP routers has a peer to each other) and confederations. and R4. This scales much better than configuring a multitude of IOS commands on several routers. that is. Example 6-69 displays the full working configuration on R1.108. setting the remote AS number to 1 (same on all IBGP peers). Example 6-68 Making R2. . R3. and R4 Members of the Peer Group Internal router bgp 1 neighbor 131.108. apply these settings to all the remote peers.255.255. and ensuring that community 2000 is sent to R2. R3. Example 6-68 shows how to make R2. You can configure BGP peers to override configuration options if required. advertising the next-hop-self attribute. namely route reflectors (you might notice this network is fully meshed.2 peer-group internal neighbor 131.

13 255. Notice R2 is not configured for peer groups.255.2 peer-group internal neighbor 131.255.5 255.1 255.255.255.1 255.108.255.255. Example 6-70 R2's Full Working Configuration hostname R2 ! enable password cisco ! interface Ethernet0/0 ip address 131.221 - .1.2 255.1.255.255.255.108.255.108.252 clockrate 128000 ! interface Serial1/1 Description Link to Internet ip address 141.108.252 neighbor internal peer-group neighbor internal remote-as 1 neighbor internal distribute-list 1 in neighbor internal route-map setattributes in neighbor 131.255.2.6 peer-group internal neighbor 131.255.255.255.199.0 access-list 1 permit any route-map setcommuntiy permit 10 set community no-export ! route-map setattributes permit 10 match ip address 2 set weight 1000 set community 1000 line con 0 line aux 0 line vty 0 4 end Example 6-70 displays the full working configuration on R2.108.255.1.0 interface Serial1/0 bandwidth 128 .199.108.4 mask 255.108.0 ! interface Serial1/0 ip address 131.1 remote-as 1001 neighbor 141.199.255.199.12 mask 255.1.108.252 ! interface Serial1/2 ip address 131.255.252 no ip directed-broadcast ! router bgp 1 no synchronization network 131.255.1.0.255.1 send-community neighbor 141.1.255.1 route-map setcommunity out access-list 1 deny 0.CCNP Practical Studies: Routing Example 6-69 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Ethernet0/0 ip address 131.252 network 131.108.14 peer-group internal neighbor 141.0.

108.255.108.255.1.255.255.0 mask 255.10 255.108.1 255.255.255.108.1 255.CCNP Practical Studies: Routing ip address 131.108.255.0 mask 255.0 ! interface Serial0 ip address 131.108.255.255.108. Notice R3 is not configured for peer groups.1 send-community neighbor 151.100.108.255.255.255.255.255.255.108.108.255.252 network 131.255.255.252 no ip directed-broadcast no ip mroute-cache ! interface Serial1/1 Description Link to Internet ip address 151.100.252 neighbor 131.100.1.255.255.1 remote-as 1002 neighbor 151.252 ! interface Serial1/2 ip address 131.255.255.9 255.1 remote-as 1 neighbor 131.1.2 remote-as 1 neighbor 131.108.108.255.8 mask 255.1.255.100.5 remote-as 1 neighbor 131.108.10 remote-as 1 neighbor 151.255.108.9 remote-as 1 ! no ip classless route-map setweight permit 10 match ip address 1 .222 - .2.252 ! router bgp 1 no synchronization network 141.255.0 network 131.1 255.108.6 255. Example 6-71 R3's Full Working Configuration hostname R3 ! enable password cisco ! interface Ethernet0 ip address 141.252 ! interface Serial1 ip address 131.4 mask 255.252 clockrate 128000 ! router bgp 1 no synchronization network 131.255.1.255.1.255.252 network 131.255.252 neighbor 131.1 route-map setcommunity out ! route-map setcommunity permit 10 set community no-export ! line con 0 line aux 0 line vty 0 4 ! end Example 6-71 displays the full working configuration on R3.8 mask 255.255.255.255.255.

255.255.0 ! interface Serial0 ip address 131. but also during your certification exams.2 255.252 clockrate 125000 ! interface Serial3 ip address 131. .12 mask 255.255.255.13 remote-as 1 ! line con 0 line aux 0 line vty 0 4 end Scenario 6-5: Verifying BGP Operation This final scenario looks at Cisco IOS mechanisms for monitoring and verifying BGP routing within a Cisco router network.255.255.255.252 network 151.108.255.255. not only in the real-life networks you come across.108.223 - .255.1.108.108.1 255. Example 6-72 R4's Full Working Configuration hostname R4 ! enable password cisco ! interface Ethernet0 ip address 151.255.CCNP Practical Studies: Routing set weight 1 ! route-map setweight permit 20 match ip address 2 ! line con 0 line aux 0 line vty 0 4 end Example 6-72 displays the full working configuration on R4.255.252 network 131.108.108.252 clockrate 125000 ! interface Serial1 ip address 131.255.0 neighbor 131.255.255. Notice R4 is not configured for peer groups.255.252 clockrate 125000 ! router bgp 1 no synchronization network 131.255.0 mask 255.10 255.108.0 mask 255.14 255. Refer to Figure 6-4 and the BGP topology to see how to use some common show commands to verify that BGP is operating correctly.255.1.255. Show and debug commands can be valuable.255.108.1 remote-as 1 neighbor 131.108.255.

* valid.108. The BGP table is not an IP routing table.1. Most engineers are familiar with a standard Cisco IOS IP routing table and mistakenly apply the same principles to the BGP table.108.255. d damped. such as neighbor state changes Example 6-73 displays a sample output taken from R1 in Figure 6-4 using the IOS show ip bgp summary command.108.108. including the local router identifier 131.0.255. part of the origin codes. this number remains the same.255.1.) It also shows six network paths on R1. memory can be a limiting factor. Example 6-73 show ip bgp summary on R1 R1#show ip bgp summary BGP router identifier 131.255. local preference (Locpref). Example 6-74 displays the BGP table on R1 in Figure 6-4.4/30 0.1.13.255.108.255.255.0 0 32768 i * i 131. main routing table version 11 6 network entries and 10 paths using 854 bytes of memory 3 BGP path attribute entries using 280 bytes of memory BGP activity 50/44 prefixes.0. and the path. (An increasing version number indicates a network change is occurring.2 0 100 1000 i * i 131. i . more memory is required. metric (MED). if no changes occur.0/30 131.108.1 4 1001 0 0 0 0 0 Up/Down State/PfxRcd 00:03:22 2 00:03:23 3 00:03:23 3 never Idle Example 6-73 displays a lot of useful information.0.199.255.108.224 - . The various networks are listed along with the next hop address. the BGP table version is displayed as 11 and the local router ID is 131.internal Origin codes: i .108. Notice the show ip bgp command can be performed in executive mode.2 0 100 1000 i * i 131.108.108. such as the Internet. As more BGP entries populate the IP routing table. weight.108. and the BGP table version of 11.) The BGP table is one that confuses most people.2 4 1 194 195 11 0 0 131.0/24 131.108.14 0 100 1000 i *> 131. 73/63 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ 131.6 0 100 1000 i *>i151. and the up/down time displays this connection was never established.0.incomplete Network Next Hop Metric LocPrf Weight Path *>i131. ? .108. e . such as remote and local network entries. Memory is important in BGP because in a large network.255. using 854 bytes of memory.255. Example 6-73 displays four configured remote peers: the first three are IBGP (because the AS is 1 and the same as the local AS) and one remote peer that has never been active.IGP.108.255.12/30 0. h history.108. and selected paths.14 0 100 1000 i Again.13 Status codes: s suppressed. the local AS of 1.1.255.EGP.255.108.108. BGP attributes.0 0 32768 i * i 131. local AS number 1 BGP table version is 11.8/30 131.CCNP Practical Studies: Routing This scenario covers the following commands: • • • • • show ip bgp summary— Displays BGP neighbors in summary mode show ip bgp— Displays the BGP topology table clear ip bgp *— Clears all BGP TCP sessions show tcp brief— Displays all TCP sessions (BGP uses TCP) debug ip bgp events— Displays any BGP events. (i is for IGP.255.0/24 131.1.13.14 0 100 1000 i *>i141. Example 6-74 show ip bgp R1>show ip bgp BGP table version is 11. The i on the left side (part of the status codes) indicates an internal BGP route and the i on the right side of Example 6-74 indicates the origin.1.6 4 1 84 83 11 0 0 131. > best.108.255.108.6 0 100 1000 i *>i131.108.255.14 4 1 152 152 11 0 0 141.) . The BGP table displays information. (The output indicates an idle session. local router ID is 131.6 0 100 1000 i *> 131. Entries are then inserted into the IP routing table.108.13.

0.11041 Foreign Address 131.108.2 0 1000 1000 i * i 131.108. for example. the BGP peer session must be cleared. The TCP port numbers are also listed.1. resulting in no downtime.179 131.255. This command is useful because you need to be certain that TCP is active at Layer 4 of the OSI model when troubleshooting to discover why two BGP peers are not sending updates.108. .108.1.108.14.225 - . Example 6-75 clears all BGP sessions on R1 after a configuration change to set all IBGP peer localpref attributes to 1000.EGP.108.4/30 0.108. configure soft configurations with the neighbor peer address soft-reconfiguration inbound command. h history. d damped.13.0/24 131.13 Status codes: s suppressed. has three TCP sessions in an established state.255. The most widely used tool when establishing why BGP is or is not peering is the debug ip bgp events command.108.255.incomplete Network Next Hop Metric LocPrf Weight Path *>i131.255. as displayed in Example 6-76.0/30 131. and the local address is a number TCP generates. Debugging BGP is useful.108.0.CCNP Practical Studies: Routing If a BGP configuration change is completed on Cisco IOS routers. e .14 0 100 1000 i The ? tool displays a number of options.0/24 131.5. clear all BGP sessions on R1 with this debug command turned on to discover the session you activated. including clearing BGP sessions based on AS numbers or remote peer address.8/30 131.255.0.108. you must clear the BGP sessions if you want a change to take place because BGP does not update changes after a BGP session is established.14 0 1000 1000 i *>i141. Also.1.C. Example 6-75 displays the BGP table after the change is configured and you clear all BGP peers sessions on R1.108.2. notice that the clear and debug commands are performed in privileged mode.0 0 32768 i * i 131.108.1. You would never use this command during normal working hours. ? .255.255.internal Origin codes: i .255. The foreign addresses list the TCP port as 179. Example 6-76 show tcp brief R1#show tcp brief TCB Local Address 812CC228 131.6 0 1000 1000 i *> 131.0 0 32768 i * i 131.108.255.108.B. On Cisco IOS routers. Next. Example 6-77 displays the sample output taken from R1 when the BGP sessions are cleared for demonstration purposes. which enables you to make changes and not have to clear the TCP peer.255.14 0 1000 1000 i *> 131.108.12/30 0. * valid.D BGP neighbor address to clear dampening Clear route flap dampening information flap-statistics Clear route flap statistics peer-group Clear BGP connections of peer-group R1#clear ip bgp * R1#show ip bgp BGP table version is 11.6 0 1000 1000 i *>i131.255.255. local router ID is 131. however.1. because BGP loses peering to any remote peers.108.179 (state) ESTAB ESTAB ESTAB Router R1.108. > best.108. To clear a single peer router. and you can expect BGP to send updates and keepalives across each TCP session.108.6. You can.255.179 131.2 0 1000 1000 i * i 131. use the clear ip bgp peer-ip-address command. i .1. Example 6-75 clear ip bgp * and show ip bgp on R1 R1#clear ip bgp ? * Clear all connections <1-65535> AS number of the peers A.0.1.108. This tells you that R1 has three TCP sessions active.108.11039 812D0054 131.IGP.6 0 1000 1000 i *>i151.255.255.11040 812CF508 131. instead of the default value of 100. The command to clear all sessions is clear ip bgp *. Example 6-76 displays the output from the show tcp brief command on R1.

0.255.14. neighbor version 1.6 computing updates.108.255.6 computing updates.108. check point net 0.0.2 update run completed.2 went from Idle to Active 4d01h: BGP: 131.108.0.0 4d01h: BGP: 131.1.108. ran for 0ms.2 computing updates.0.0 4d01h: BGP: 131.14 went from Idle to Active 4d01h: BGP: 131.255.6 went from Established to Idle 4d01h: BGP: 131. start version 1.2 went from Active to OpenSent 4d01h: BGP: 131.108.108.2. check point net 0.14 went from OpenSent to OpenConfirm 4d01h: BGP: 131.1. starting at 0.0.108.1.255.108.14. Example 6-78 debug ip bgp keepalives on R1 R1#debug ip bgp keepalives BGP keepalives debugging is on 4d01h: BGP: 131. After the sessions are active. starting at 0.255.255.6 went from OpenSent to OpenConfirm 4d01h: BGP: 131. neighbor version 0. neighbor version 1. throttled to 1.226 - .0 4d01h: BGP: scanning routing tables 4d01h: BGP: scanning routing tables 4d01h: BGP: scanning routing tables The sample output from Example 6-77 displays the BGP session's teardown state (reset by user) and the re-establishing of TCP sessions to the three peers: 131.14 sending KEEPALIVE 4d01h: BGP: 131. starting at 0.1.108. neighbor version 0.255.6 update run completed. ran for 0ms.108.108.2 sending KEEPALIVE 4d01h: BGP: 131.108.0 4d01h: BGP: 131. start version 9. neighbor version 0.108.255.108. throttled to 9. You can view keepalives with the debug ip bgp keepalives command.108.255.14 KEEPALIVE rcvd 4d01h: BGP: 131.108.0.255. table version 9.0 4d01h: BGP: 131.255. start version 1. .255.0.6 sending KEEPALIVE 4d01h: BGP: 131.1.255. table version 1.2 KEEPALIVE rcvd R1 is sending and receiving keepalives to the three remote peers to ensure that the remote routers are still active.108. starting at 0.108.6 update run completed.108. check point net 0.255.255.108.0 4d01h: BGP: 131.1.14 computing updates. throttled to 1.14 went from Active to OpenSent 4d01h: BGP: 131.0.2 went from OpenSent to OpenConfirm 4d01h: BGP: 131.108.0.108.255. table version 1.6 KEEPALIVE rcvd 4d01h: BGP: 131. throttled to 1.108.108.255.1. only changes are sent across the TCP peers. neighbor version 0.0. Example 6-78 displays a sample output taken from R1 after the TCP peers are established.108.6 went from Active to OpenSent 4d01h: BGP: 131.1.14 went from OpenConfirm to Established 4d01h: BGP: 131. neighbor version 0. ran for 0ms.108.14 went from Established to Idle 4d01h: BGP: 131.0. Assume that R1 is reloaded. start version 1. ran for 0ms.6 went from OpenConfirm to Established 4d01h: BGP: 131.0 4d01h: BGP: 131.108. 131.255. and 131.255.108. table version 1.2 went from Established to Idle 4d01h: BGP: 131.108.CCNP Practical Studies: Routing Example 6-77 debug ip bgp events and clear ip bgp *on R1 R1#debug ip bgp events BGP events debugging is on R1#clear ip bgp * 4d01h: BGP: reset all neighbors due to User reset 4d01h: BGP: 131. check point net 0.108.0.14 update run completed.255. neighbor version 0.255.0.2 went from OpenConfirm to Established 4d01h: BGP: 131.0.0.108.0.255.1.6 went from Idle to Active 4d01h: BGP: 131.1.108.0 4d01h: BGP: 131.

179 131.227 - . All odd routes have weight set to 200.1. Example 6-79 displays the TCP sessions on R1.108. You must use BGP4 as your dynamic routing protocol.108. Ensure that both Routers R1 and R2 have full connectivity to each other. All even routes have MED set to 100.255.179 131. configure the network in Figure 6-6 for IP routing. Use the ping command to ensure that all networks are reachable. Example 6-79 show tcp brief on R1 R1#sh tcp TCB 812CF984 812CCB20 812CC6A4 brief Local Address 131.11043 Foreign Address 131.2.13. you will discover three TCP sessions using a new local TCP port number because the sessions have been re-established and a new random local TCP port number has been chosen by TCP.6.255.108.1.11042 131.5.CCNP Practical Studies: Routing If you display the TCP sessions now.1.108. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. . All odd routes have MED set to 200. EBGP Topology • • • • All even routes have weight set to 100. Using the IP addressing scheme provided and BGP4 as your routing protocol. Ensure that all routes received by R2 are tagged as follows: Figure 6-6.108.255.108.11044 131.179 (state) ESTAB ESTAB ESTAB Practical Exercise: EBGP and Attributes NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter.255. The solution can be found at the end.14.

255.1 ! interface Loopback2 ip address 131.0 .255. BGP has no issues with VLSM.1 ! interface Loopback5 ip address 131.107.0 255.101.103.112.1 ! interface Loopback12 ip address 131.255.255.1 ! interface Loopback10 ip address 131.255.108.255.108.108.0 255.0 255.255.255.108.255.228 - . The no-auto summary command ensures that R2 sees all 16 individual routes. The 16 loopbacks on R1 are advertised to R2 using the redistribute connected command. respectively. Take note of the shaded sections.0 255.104.252 or /30.108.0 255.CCNP Practical Studies: Routing Practical Exercise Solution You will notice that all the IP addressing schemes are /24. 255.255. The dual-path connections between R1 and R2 allow redundancy.255.1 ! interface Loopback8 ip address 131. the route map on R2 is applied to both EBGP peers in case of link failure.0 255.111.105.1 ! interface Loopback3 ip address 131.255. Examples 6-80 and 6-81 display the full working configuration on R1 and R2.0 255. The serial link contains a mask.110.255.255.113.1 ! interface Loopback13 255.1 ! interface Loopback9 ip address 131.255.108.108.255.108.1 ! interface Loopback6 ip address 131.106.255.1 ! interface Loopback1 ip address 131.255.0. as they contain critical IOS commands that ensure the desired solution is achieved.108.108.0 255.255.0 255.108. The access list on R2 must be set with a mask of 0.255.255.0 255.108.255. therefore. or all even networks match these criteria.255.109.255.254.108.1 ! interface Loopback4 ip address 131.255.255.255.255.255.108.0 255.102. There are two EBGP sessions between R1 and R2. except for the serial link between R1 and R2. Example 6-80 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.0 255.1 ! interface Loopback11 ip address 131.1 ! interface Loopback7 ip address 131.

6 255.0 ! interface Loopback14 ip address 131.108.108.1.255.255.2 remote-as 2 neighbor 131.255.1 255.1 255.108.255.108.252 clockrate 128000 ! .252 clockrate 128000 ! interface Serial1/3 ip address 131.1 255.255.255.255.114.108.108.108.108.2 255.255.252 ! router bgp 1 redistribute connected metric 100 neighbor 131.255.0 ! interface Ethernet0/0 ip address 131.229 - .255.1 255.255.108.115.108.1 255.255.108.255. Example 6-81 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0/0 ip address 161.1 255.255.0 ! interface Loopback15 ip address 131.252 ! interface Serial1/3 ip address 131.255.255.6 remote-as 2 no auto-summary line con 0 line aux 0 line vty 0 4 ! end Example 6-81 shows the R2's full working configuration.255.255.255.255.255.116.1.255.255.5 255.255.0 interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 ip address 131.CCNP Practical Studies: Routing ip address 131.0 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 ip address 131.

230 - .108.254.108. Example 6-83 show ip bgp R2>show ip bgp BGP table version is 21.255.255.5 route-map setweight in no auto-summary ! access-list 1 permit 131.1.108.255.255.108.255.255.1.0.1 100 200 200 1 ? * 131.0/24 131.2.5 remote-as 1 neighbor 131.108.1. The answers to these question can be found in Appendix C. d damped.255.0 neighbor 131.0 0.0/24 in Example 6-83? Use Example 6-83 to answer questions 4-6. local router ID is 161.0.255.1.108.108.108.23 4: Foreign Address 131.1. h history. How many BGP sessions are in use? Example 6-82 show tcp brief R2>show tcp brief TCB Local Address 613EE508 131.IGP.11008 611654BC 161.1 100 200 200 1 ? .108.108. i .255.108.108.EGP. ? .255.1.6.0 ! route-map setweight permit 10 match ip address 1 set local-preference 100 set weight 100 ! route-map setweight permit 20 set local-preference 200 set weight 200 ! line con 0 line aux 0 line vty 0 4 ! end Review Questions The following questions are based on material covered in this chapter.1 route-map setweight in neighbor 131.5. > best.internal Origin codes: i .255.0/24 131." 1: 2: 3: Which IOS command clears all BGP sessions on a Cisco router? Which IOS command is used to enable BGP4 on a Cisco router? Example 6-82 displays the output from the show tcp brief command.108.179 131. e .1 Status codes: s suppressed.255.108.255.1 remote-as 1 neighbor 131.101.incomplete Network Next Hop Metric LocPrf Weight Path * 131.11051 (state) ESTAB ESTAB ESTAB Which path is chosen to the remote network 131.5 100 200 200 1 ? *> 131.5 100 200 200 1 ? *> 131.255.108.108.108.1.11009 613ED584 131.108. "Answers to Review Questions.255.0 mask 255.CCNP Practical Studies: Routing router bgp 2 network 161. Example 6-83 displays the BGP table on a Cisco BGP router.108.179 131.1.108. * valid.

1. Table 6-3.1 4 1 2755 2699 21 0 0 1d20h 131.108.101. main routing table version 21 20 network entries and 39 paths using 3028 bytes of memory 4 BGP path attribute entries using 432 bytes of memory BGP activity 61/41 prefixes. along with techniques used to load balance BGP using static routes. higher or lower weight. local AS number 2 BGP table version is 21.0/24 originate from? What is the metric and local preference for the remote network 131.0.0.101.108.255.5 4 1 2755 2699 21 0 0 1d20h 8: 9: 10: On a Cisco router. You learned how to successfully configure IBGP and EBGP. 119/80 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131. Summary of IOS Commands Command router bgp number neighbor remote IP address remote-as as show ip bgp {no} synchronization show ip bgp neighbors show ip bgp summary Purpose Enables BGP routing protocol Configures a BGP TCP peer Displays BGP table Enables or disables (no) BGP synchronization Displays the status of BGP TCP peer sessions Displays status of BGP TCP peer sessions in summary format . what value is preferred.255. and what is the range of values for weight? What are the terms peer or neighbor used to describe in BGP? What is the BGP table? 19 19 Summary You can now begin to apply this knowledge to the more complex scenarios found in the next chapter.1.108. The BGP principles presented in this chapter's Practical Exercise will benefit you in the next chapter's advanced BGP scenarios.108.108.CCNP Practical Studies: Routing *> 161.0/24? Example 6-84 displays the output from the show ip bgp summary command for a Cisco BGP-enabled router.108.1.231 - .0/24 5: 6: 7: 0. What is the BGP autonomous system that R2 resides in? How many BGP sessions are active. Table 6-3 summarizes the BGP commands used in this chapter.0 0 32768 i Which autonomous system does the network 131. and what version of BGP is configured on the router named R2? Example 6-84 show ip bgp summary on R2 R2>show ip bgp summary BGP router identifier 161.

.

Route reflectors are not used in External BGP (EBGP) sessions. A route reflector is a BGP router configured to forward routing updates to BGP peers within the same autonomous system (AS). BGP deals with large BGP networks using two methods: • • Route reflectors Confederations (advanced form of route reflectors. "Basic Border Gateway Protocol. BGP only propagates updates learned from IBGP connections to other IBGP sessions that are fully meshed.CCNP Practical Studies: Routing Chapter 7.) Route reflectors are used to address the scalability issues in large IBGP networks. To maintain accurate and up-to-date information in IBGP networks." This chapter covers BGP4 in even greater detail than the CCNP Routing Exam does in order to ensure that you have a good appreciation for how networks are connected to the Internet. The five practical scenarios in this chapter complete your understanding and ensure that you have advanced BGP networking knowledge to complement your understanding of today's most widely used networking protocol. In fact. you can easily calculate the number of peers by using the formula n(n-1)/2. Scalability with Border Gateway Protocol (BGP4) BGP is a complex routing protocol that requires that all routers be fully meshed in an Internal BGP (IBGP) network.233 - . the scalability and administration of BGP becomes a task you must carefully consider. Fully meshed networks contain a BGP peer to every BGP speaker in the network. Advanced BGP This chapter focuses on the advanced features of Border Gateway Protocol Version 4 (BGP4) and builds on the material presented in Chapter 6. there are 100(100-1)/2 = 100(99)/2 = 4950 TCP peers. NOTE To avoid routing loops. all routers must peer to one another. IP. Consider a network consisting of 100 routers. where n is the number of BGP routers. Having this many routers leads to a large number of TCP BGP peers. confederations are beyond the scope of this chapter. . BGP is a routing protocol designed for use in large IP networks. and as the network grows even to just 100 routers. For a 100-router network. IBGP works well in small networks. Figure 7-1 displays a simple four-router network running IBGP.

R1 Configured as Route Reflector Similarly. for a network consisting of 100 routers. R3.CCNP Practical Studies: Routing Figure 7-1. The routers on the edge are termed the router reflector clients (or just clients). using route reflectors can reduce this number to 99 IBGP sessions (a 98 percent reduction).234 - . Figure 7-2. and these routers are called route reflectors. instead of 4950 IBGP TCP sessions (fully meshed). and R4. In reality. Four-Router IBGP Network The number of IBGP sessions required to maintain full connectivity in the network in Figure 7-1 is 4(3)/2 = 6 IBGP sessions. . Figure 7-2 displays R1 reflecting (route reflector) BGP routing information to R2. By using route reflectors. you can reduce the number of IBGP sessions from six to three (a 50 percent reduction). what happens is that a router or routers running BGP become the focal point for disseminating routing information.

to R2 (peer address 131.2 ! Connection to R4 neighbor 131. In any cluster. and scalability concerns in a large BGP network can be overcome by specifying a core router(s).108. as you would normally configure an IBGP network.2. The following are the characteristics of router reflectors: • • • • • • • • Route reflector configuration is enabled only on the route reflector. apply the following IOS command to all IBGP peers: neighbor ip-address route-reflector-client Next. Example 7-1 displays the configuration on R1. R3. R3 (peer address (131.2 neighbor 131. R1 is configured as an IBGP peer to all clients.2. and R4.2). Example 7-1 Configuration on R1 for Route Reflection router bgp 1 ! Connection to R2 neighbor 131. .3.2).108. such as routing updates to all edge routers.3. Confederations are another way of dealing with the explosion of an IBGP network and are typically used in networks that contain thousands of IBGP peers. you must still configure the IBGP session indicating the IBGP peer to R2. which ensures a loop-free topology.2 ! connection to R3 neighbor 131. Clients receive all updates from the route reflector only. whenever you configure route reflectors. Hence. in which the route reflector ignores any update it receives with its own originator-ID.2. to perform core routing functions.108. The usual BGP routing algorithm is applied to all BGP routes to ensure a loop-free topology.CCNP Practical Studies: Routing The level of complexity.235 - . manageability. Nonclients (not part of a cluster) must still be fully meshed to maintain full connectivity. For example. Route reflectors preserve all BGP attributes.2 neighbor 131. the four routers in Figure 7-2 form a BGP cluster. and R4 (peer address 131. All updates contain the originator-ID attribute.108. also known as a route reflector. Configuring Route Reflectors Configuring route reflectors is a relatively straightforward exercise.108. Updates are sent from the route reflector to all clients.108. On the route reflector.4.2).2 remote-as 1 route-reflector-client remote-as 1 route-reflector-client remote-as 1 route-reflector-client Example 7-1 displays the route reflector IOS command pointing to R2.4.108.108.3. R3. there must be at least one route reflector. clients are configured normally as IBGP peers. configure the four routers in Figure 7-2 for route reflectors with R1 configured as the route reflector. Also. Route reflectors reduce the need to configure IBGP (full-mesh) large networks.4.108. and R4.2 neighbor 131. TIP Cluster is a term used to describe a route reflector and the clients. The concept of confederations is based on multiple subautonomous systems. which is configured as the route reflector.

but in practice.108. routing involves knowing only the next hop and not the full path to a remote destination. When a company connects two or more connections to the Internet.0/0 ip prefix-list ccnp permit 30. and the BGP network designer must ensure that the ISPs do not use the company's network as a transit.CCNP Practical Studies: Routing The benefits of using route reflectors include the following: • • • • • Addressing of scalability issues Enables a hierarchical design Reduces the number of TCP peers and. use the show ip prefix-list command in exec mode. Table 7-1. as long as a next hop router exists.0/0 ge 8 le 24 Multihoming Connections to the Internet Today. It is not uncommon to accept a full BGP routing table.0/8 ge 25 ip prefix-list ccnp permit 0. For example.0. you might want to accept all networks in the range 4. traffic transverses the Internet. specific routing information is not received through their Internet connection. all networks starting with 131.255. Prefix lists are efficient because BGP routers perform lookups on only the prefix (beginning) address and can make faster routing decisions. and to allow the network designer flexibility. BGP can be filtered using the following methods: • • • Access lists— Used when configuring route maps and filtering networks based on IP networks using filter-based lists Distribute lists— Filter incoming or outgoing IP networks Prefix lists— Filter information based on the prefix of any address.255. in practice.0. Remember.0.0. they are connected to two different ISPs.0 to 4. Table 7-1 displays some common prefix list examples used in today's large BGP networks.236 - .0. Connections can be to the same ISP. and only a default route is accepted.0/8 Deny mask lengths greater than 25 bits in routes with a prefix of 131/8 Permit mask lengths from 8 to 24 bits in all address spaces Example IOS command ip prefix-list ccnp deny 0.0.0/0 ip prefix-list ccnp permit 0.0.0. the following IOS command syntax is required: neighbor {ip address | peer-group} prefix-list prefix-list-name {in | out} To verify prefix list configuration. typically.0 Prefix lists are a new and a more efficient way of identifying routes for matching and filtering BGP information. however. two or more connections provide the same BGP routing information. the amount of traffic across WAN circuits Fast convergence in propagation of information Provides easier troubleshooting as the information is typically sent from one source Filtering is vital to any large BGP network.0.0. the BGP connection between the company and the ISP is termed a multihomed connection. This presents a problem because. for redundancy. for example. Use the following IOS command to enable a prefix list: ip prefix-list list-name [seq seq value] {deny | permit} network | len [ge ge-value] [le le-value] To apply a prefix list to a BGP peer.0. this has little or no value because all traffic to a default route is sent through the ISP connection. .0.0/8 ip prefix-list ccnp deny 131. In this case.255 and reject all other networks. therefore.0.0. most organizations have one or more connections to the Internet. Prefix List Examples Using the Prefix Name CCNP Filtering required Deny default routes Permit a default route Permit exact prefix 30.0. a prefix list accomplishes this task efficiently and easily.

1. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs. on the other hand.0. Route maps are typically used to ensure that only the correct networks are sent to the ISP and vice versa. The five scenarios presented in this chapter are based on complex BGP technologies so that you become fully aware of the powerful nature of BGP in large IP networks. R1 is configured as the route reflector. Typically. . There is no one right way to accomplish many of the tasks presented.237 - . the network command enables you to advertise networks to other BGP routers. R3. First.08. static routes are used to send all traffic to unknown destinations through the ISP connection. Also. use a 30-bit subnet mask. Four-Router Topology with Route Reflectors Figure 7-3 displays a simple four-router topology in AS 333. in a well-designed IP network. Example 7-2 displays the IBGP configuration on R1. ensure that the minimum number of peers exist. the designer applies a hierarchical IP address design to ensure that all IP address space is used efficiently.CCNP Practical Studies: Routing Another primary concern of a multihomed connection is redistributing interior routing protocols into BGP. Static routes— Typically. R3. you must be careful when you configure redistribution from one interior protocol to and from BGP . You can use three basic methods to accomplish this task: • • • network command— As you saw in Chapter 6. notice that the Class B address 131. and R2. allowing for only two hosts. so traffic from the Internet can be directed to the correct outgoing interface.0 is used throughout this network. The WAN links between R1 and R2. you must configure IBGP on Router R1. To reduce TCP traffic among all BGP-speaking routers. and the ability to use good practice and define your end goal are important in any real-life design or solution. for example. The ISP. and R4 as the clients. has the network in the BGP table. redistribution command— To avoid routing loops. and R4 are the clients. Scenario 7-1: Configuring Route Reflectors Configure the four-router topology in Figure 7-3 for IBGP using route reflectors with R1 as the route reflector and R2. Figure 7-3.

internal Origin codes: i . are established.1. however.1.1.2 remote-as 333 ! Peer to R3 R1(config-router)#neighbor 131.108.255.108.0.1. R3.0/30 131.108.108.2 0 100 0 i *>i131. The IP table on R1.108.2 0 100 0 i * i131.108.2). local router ID is 131.2 4 333 10 12 3 0 2 131.108.2).CCNP Practical Studies: Routing Example 7-2 R1 IBGP Configuration R1(config)#router bgp 333 ! Peer to R2 R1(config-router)#neighbor 131.2 4 333 15 13 1 0 0 131.238 - .108. and R4.4.108.0/24 0.0/24 131.108. h history.255.255.0/24 and 131. Example 7-6 displays the IP routing table on R1.5.1.6 remote-as 333 ! Peer to R4 R1(config-router)#neighbor 131. so you must configure R1 to reflect BGP information to R2. ? .0 0 32768 i * i 131. Example 7-4 show ip bgp summary Command on R1 R1#show ip bgp summary BGP router identifier 131. i .0. .incomplete Network Next Hop Metric LocPrf Weight Path *> 131. d damped.255. R3 (131.108.108. > best.255. Example 7-3 displays the configuration with R1 as a route reflector.3.0/24 131.6).255. main routing table version 3 3 network entries and 3 paths using 363 bytes of memory 1 BGP path attribute entries using 92 bytes of memory BGP activity 6/3 prefixes.4.255.0/24.108.3.EGP.6 0 100 0 i * i131.108.1.4/30 131.255.255. and R4 (131. * valid.108. Example 7-5 show ip bgp Command on R1 R1#show ip bgp BGP table version is 5. Example 7-5 displays the BGP table on R1.2 0 100 0 i *>i131.255.108.108.108.255.6 4 333 13 13 2 0 0 Up/Down State/PfxRcd 00:00:03 1 00:00:00 0 00:00:01 2 Example 7-4 shows that three remote peers.2 route-reflector-client Example 7-4 displays the BGP neighbors on R1 in summary format.108. 7/4 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ 131. to R2 (131.6 route-reflector-client ! RR to R4 R1(config-router)#neighbor 131. Example 7-3 R1 Route Reflector Configuration R1(config)#router bgp 333 ! RR to R2 R1(config-router)#neighbor 131.255.6 0 100 0 i R1 dynamically learns the remote networks 131.108.255.108. local AS number 333 BGP table version is 3.2 route-reflector-client ! RR to R3 R1(config-router)#neighbor 131.108. displays something quite different.108.255. e .2 remote-as 333 R1 is the route reflector.255.255.IGP.5 Status codes: s suppressed.108.108.108.

255.4/30 is directly connected.108. h history. Example 7-9 show ip route on R2 R2#show ip route C 131.2.IGP. To discover why.239 - .internal Origin codes: i .4.108. 2 masks C 131.255. Ethernet0/0 The R1 routing table contains no BGP entries because.0.0/24 0.3.255.0 is directly connected.CCNP Practical Studies: Routing Example 7-6 show ip route on R1 R1>show ip route 131.108.0/24 is directly connected. In this simple case.255.0/24 [200/0] via 131. 5 subnets.108.108.108.255.7. Serial1/1 C 131. ? .3.3.2 * i131.255. i . and R4.0/16 is variably subnetted.1.108. even though synchronization is disabled.BGP 131.4/30 131. local router ID is 131.108.108.6.1. the same command should be completed on all four routers in Figure 7-3.108. Example 7-10 show ip bgp and show ip route on R2 R2#show ip bgp BGP table version is 3.108. > best.108.2 % Subnet not in table Metric LocPrf Weight Path 0 32768 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i .108.108.0/24 is directly connected.108.0/30 is directly connected. Ethernet0/0 R1 can now reach the two remote networks: 131. Verify that R2 can also reach these networks because R2 is a route reflector client. IBGP does not insert any network into the IP routing table due to synchronization.1. Example 7-7 displays disabling synchronization on Router R1.connected.incomplete Network Next Hop *> 131. Example 7-9 displays the IP routing table on R2.108.255.4. 00:00:32 B 131.0 * i 131.108.0. d damped.0/24 131. Ethernet0/0 R2.1 Status codes: s suppressed. R2. Example 7-8 show ip route on R1 R1#show ip route Codes: C .255.6 * i131.255. R3.1 * i131.2 * i131.108.108.4/30 is directly connected.255.EGP.108. 2 masks C 131.108. has no remote BGP entries.108.255.1. 00:00:32 C 131.108.0/30 is directly connected.108.0/24 [200/0] via 131.108. Serial1/0 C 131.0. B . Example 7-7 Disabling Synchronization on R1 R1(config)#router bgp 333 R1(config-router)#no synchronization The IP routing table on R1 is displayed in Example 7-8.255.6 % Subnet not in table R2#show ip route 131. 3 subnets.1. Serial1/0 B 131.255.108. Example 7-10 displays the BGP table on R2.0/24 (R3) and 131.6 R2#show ip route 131. so you must disable synchronization.0/30 131. * valid. with route reflectors. Disable synchronization on R1.0/24 131. e . view the BGP table on R2.0/16 is variably subnetted. Serial1/1 C 131.255.4.0/24 (R4).108.0. you have no other IGP configured.108.

1/24).1. 00:03:25 B 131.1. the route reflector.108.255.255.108. round-trip min/avg/max = 16/16/20 ms Example 7-12 displays the remote BGP entries on R2.255.252 clockrate 128000 ! interface Serial1/1 .108. the BGP table on R2 displays the remote BGP entries in its IP routing table. which contain critical commands.255.108.1. Example 7-11 Advertising WAN links on R1 R1(config)#router bgp 333 R1(config-router)#network 131. 2 masks B 131.108.108. Example 7-11 displays the configuration on R1. Sending 5.3.4/30 [200/0] via 131.108.108.255.4.108. and a reply to the remote networks attached to R3 and R4. Example 7-12 show ip bgp on R2 and ping on R2 R2#show ip route 131.0/24 is directly connected.6.108.108.240 - .255.0/24 [200/0] via 131.0/24 [200/0] via 131.3.0/16 is variably subnetted. Example 7-13 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0/0 ip address 131. a successful ping request.5 255. 00:03:20 C 131.108.4.252 R1(config-router)#network 131. 100-byte ICMP Echos to 131.1 255.1 Type escape sequence to abort.1. Sending 5.108.CCNP Practical Studies: Routing Example 7-10 displays the remote entries present in R2's BGP table with a next hop address that is not routable.255. 5 subnets.252 After you clear all the BGP sessions on R1 with the clear ip bgp * command. round-trip min/avg/max = 16/16/20 ms R2#ping 131. especially on R1. Ethernet0/0 R2#ping 131. Example 7-12 displays the IP routing table on R2 and some successful ping requests to R3 E0 (131. Before you consider a more complex route reflector scenario. 00:02:58 B 131.108.1/24) and R4 E0 (131.4 mask 255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). BGP does not insert any remote network when the next hop address is not routable.4.1. configure R1 to advertise the WAN links to R2 and R3.3.0 ! interface Serial1/0 ip address 131.1. Example 7-13 displays R1's full working configuration.1 Type escape sequence to abort.255. In other words.108.0/30 [200/0] via 131.3.255. To fix this. 100-byte ICMP Echos to 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0.255. 00:02:58 B 131. here are the full working configurations on all four routers.108.255.108.255.108.255.0 mask 255.108.1.255.4.108.1.255. Take particular note of the shaded sections.2.

255.4 mask 255.0 mask 255.108.255.255.1.255. Example 7-14 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.255.255.255. Example 7-15 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.255.108.1.108.108.2 route-reflector-client neighbor 131.108.255.108.2 remote-as 333 neighbor 131.6 route-reflector-client line con 0 line aux 0 line vty 0 4 end Example 7-14 displays R2's full working configuration.252 bandwidth 125 ! interface Serial1 shutdown router bgp 333 .0 mask 255.108.255.255.255.108.252 network 131.108.3.255.0 ! R2 is a RR client to R1 router bgp 333 no synchronization network 131.108.2 255.255.252 ! router bgp 333 no synchronization network 131.255.255.255.255.0 neighbor 131.6 255.108.108.255.1.1 255.255.2 remote-as 333 neighbor 131.1.0 ! interface Serial0 ip address 131.108.108.0 network 131.CCNP Practical Studies: Routing ip address 131.255.6 remote-as 333 neighbor 131.0 mask 255.241 - .255.1.255.108.1 255.2 route-reflector-client neighbor 131.1.255.252 neighbor 131.1 remote-as 333 line con 0 line aux 0 line vty 0 4 end Example 7-15 displays R3's full working configuration.

255. 131.255.108. Figure 7-4. and 131.1 255.3. and each router is assigned a loopback address of the form 131.254. Example 7-16 R4's Full Working Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.108.255.4.252 clockrate 125000 ! interface Serial1 shutdown ! router bgp 333 no synchronization network 131.0 network 131.108.0 network 131.255.108.252 neighbor 131.4 for R4.255.1 remote-as 333 line con 0 line aux 0 line vty 0 4 ! end Scenario 7-2: Configuring Advanced BGP Route Reflectors Figure 7-4 displays a typical dual-homed BGP network and expands upon the network in Scenario 7-1.108.4. 131.108.CCNP Practical Studies: Routing no synchronization network 131.0 ! interface Serial0 bandwidth 125 ip address 131.254.108.255.255.4 mask 255.254. Scenario 7-2 Physical Topology .0 mask 255.255.255.255.108.253.255.108.255.5 for R5.0 mask 255.252 neighbor 131.255.242 - .2 for R2.254.1 for R1.108.5 remote-as 333 ! line con 0 line aux 0 line vty 0 4 end Example 7-16 displays R4's full working configuration.255.108.255.2 255.3 for R3.108.255. OSPF is the interior routing protocol used on routers R1–R5. 131.108.0 mask 255.255.

BGP Logical Connections The primary path for the edge routers R3. Figure 7-5 displays the IBGP and EBGP connections logically. Enable OSPF on the IGP routers by enabling all interfaces in area 0. and R5 is through R1. R1 and R2 are both configured as router reflectors to provide redundancy. if R1 fails.243 - . Hence. Assume the Routers R1–R5 are part of a large company and route reflectors are configured on R1 and R2 for redundancy purposes. .CCNP Practical Studies: Routing Ensure that as long as there is IP connectivity. R1 and R2. The two routers. R4. the IBGP sessions are established to R1 and R2. have one connection to the Internet through Serial 1/0. Figure 7-5. so you can take advantage of loopbacks for the source and destination address for all IBGP peer sessions. Figure 7-4 displays the physical topology. the primary path is through R2.

108.0 255.108.2 remote-as 333 neighbor 131.4 update-source Loopback0 neighbor 131.5 update-source Loopback0 neighbor 131.1. BGP is established. R4. Example 7-17 R1 OSPF Configuration R1(config)#router ospf 1 R1(config-router)# network 0. .254.4 remote-as 333 neighbor 131. R2 is configured to peer to the loopback interfaces to ensure that as long as there is IP connectivity.0 mask 255.108. R1 is configured to peer to the loopback interfaces to ensure that as long as there is IP connectivity. OSPF is used as the IGP to ensure IP connectivity among all loopback interfaces.254.1. IBGP is established.255.2 update-source Loopback0 neighbor 131.255.108. BGP should remain active.108.0.5 update-source Loopback0 neighbor 131. R4.108. and R5.3 route-reflector-client neighbor 131. Example 7-19 displays the configuration of R2 as a backup route reflector to R3. R4. and R5 using the loopback interfaces as the source and peer addresses.0 on R1 and displays the enabling of R1 to reflect BGP information to R3.4 remote-as 333 neighbor 131.108. R4.254.108.255.254.2 update-source Loopback0 Example 7-19 displays the local advertisement of the network 131.108.5 remote-as 333 neighbor 131.108. and R5.0 on R2 and the enabling of R2 to reflect BGP information to R3.3 remote-as 333 neighbor 131.255.108.1. In fact.255 area 0 Configure the same two commands on R2–R5 to enable OSPF as the IGP. For redundancy purposes.5 route-reflector-client neighbor 131.108.254.254.255.0.1 remote-as 333 neighbor 131.3 remote-as 333 neighbor 131.254.244 - . and R5.254.108.254.108.3 update-source Loopback0 neighbor 131.254.254.5 remote-as 333 neighbor 131.108.108.108. Next.0 neighbor 131.254.108. R3.254. Next.108. R1 is configured to peer to R2 but not as a route reflector.4 update-source Loopback0 neighbor 131.CCNP Practical Studies: Routing Example 7-17 configures all IP-enabled interfaces on R1 in area 0. Example 7-18 configures IBGP on R1 to act as a route reflector to R3.2 remote-as 333 neighbor 131.108.0 mask 255.254.108. Example 7-18 IBGP on R1 router bgp 333 network 131.0 neighbor 131. configure one of the edge routers.254.254.254.108.254.1.254.108. good IBGP design always uses loopbacks so that one routing failure does not result in loss (TCP fails) of IBGP connectivity.255.254.254. for IBGP.108.108.255.4 route-reflector-client neighbor 131.108. configure IBGP on R1 and use the loopback addresses as the next hop addresses because as long as you have IP connectivity.5 route-reflector-client Example 7-18 displays the local advertisement of the network 131.4 route-reflector-client neighbor 131.3 update-source Loopback0 neighbor 131.3 route-reflector-client neighbor 131.254.108.255. Example 7-19 IBGP on R2 router bgp 333 network 131.108.1 update-source Loopback0 neighbor 131.

5 131.2 remote-as 333 neighbor 131.108.1 0.5.255.0.4.108. R4 advertises 131. Example 7-23 displays the BGP table on the client router R3.0.254.0/24.1 update-source Loopback0 neighbor 131.0/24.254.108.254.254.3.108.2 remote-as 333 neighbor 131. After the BGP peer sessions are established on routers R4 and R5. Because R3 is locally connected to 131.0/24 *>i131. Example 7-21 IBGP on R4 router bgp 333 network 131.108.108.254.0 mask 255.108.2 update-source Loopback0 R3 is configured normally for IBGP to R1 and R2.0/24 * i Next Hop 131.108.254.108.5. view the IP routing table on R3.5.1 remote-as 333 neighbor 131.3.255.108.1 update-source Loopback0 neighbor 131.108.254.0 neighbor 131.255.0 mask 255.108.1 update-source Loopback0 neighbor 131.254.CCNP Practical Studies: Routing Example 7-20 displays the IBGP configuration on R3 pointing to R1 and R2.0/24 (indicated with the next of 0.1. use the network command to advertise this network to R1 and R2. .108. 131.0 neighbor 131.108.1 remote-as 333 neighbor 131.0.254. Example 7-24 displays the IP routing table on R3. Example 7-21 and Example 7-22 display the IBGP configuration on R4 and R5.108.254.2 update-source Loopback0 All the routers in Figure 7-5 have IBGP peers configured.2 update-source Loopback0 Example 7-22 IBGP on R5 router bgp 333 network 131.254.0 mask 255.108.255.0/24 * i *>i131.108.245 - .254.108.108.108. Example 7-23 show ip bgp on R3 R3#show ip bgp Network *>i131.108.108.254.108.254.2 remote-as 333 neighbor 131.0. advertised by R1 and R2. you can take a look at the BGP tables.3.255.0).1.5 Metric LocPrf Weight Path 0 100 0 i 0 100 0 i 0 32768 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i R3's BGP table has the local network 131. To confirm IP connectivity.0 neighbor 131.254.0.3.0/24 * i *> 131.108.108.4. remember that you have OSPF configured as the IGP. respectively.0.4 131.4.4 131.0 131.254.254.1 remote-as 333 neighbor 131.254. and R5 advertises 131. Also present in the BGP table is the remote network.108.255. Example 7-20 IBGP on R3 router bgp 333 network 131.108.108.108.108.2 131.

108.255.108.4.0/24.108.255.108.108. 12 subnets.108.0/24 [110/1591] via 131. Serial0 C 131.108. 12 subnets.254.108.5.255. O .108.1/32 [110/801] via 131. Example 7-26 show ip route on R3 R3#show ip route 131.255. 00:21:51. Serial0 C 131.255.0.4/30 is directly connected. Serial0 O 131.5.0/16 is variably subnetted.255.108.108. 00:38:44. 00:29:59. Serial0 C 131.255.255.108. .0/24 [110/810] via 131.3/32 is directly connected.0/24.254. Serial0 O 131. Serial0 O 131.0/24 discovered by OSPF (indicated by the O on the left side of the IP routing table).4/32 [110/1582] via 131. Even though BGP (view the BGP table in Example 7-23) has inserted the remote networks. Loopback0 O 131.108. Serial0 O 131. 00:21:53.5.1.255.108.108.108. 00:04:10.255.8/30 [110/1581] via 131.0.5.0/24 and 131. Ethernet0 O 131. 01:04:33. 131.0/24 [110/1591] via 131.BGP.5.108. Serial0 O 131. Serial0 C 131.3.5.108.255.254.108. 00:29:59.5.108.108.108. 00:29:59.108. 01:04:33.5. Loopback0 O 131.1.0/24 [110/810] via 131. compared to 200 for IBGP. you can expect to see BGP routing entries in the IP routing table on R3.5.4. 01:04:33.5. 00:29:59.108.108.0/24.108.255. Serial0 The reason that OSPF is chosen for the preferred path is that OSPF has a lower administrative distance of 110.5.0/30 [110/1581] via 131.108. Example 7-25 Disabling Synchronization on R1–R5 R1(config)#router bgp 333 R1(config-router)#no synchronization R2(config)#router bgp 333 R2(config-router)#no synchronization R3(config)#router bgp 333 R3(config-router)#no synchronization R4(config)#router bgp 333 R4(config-router)#no synchronization R5(config)#router bgp 333 R5(config-router)#no synchronization After you clear all IBGP sessions on R1 and R2 with the clear ip bgp * command.3.5.255.5/32 [110/1582] via 131. 00:29:59.255. and 131.OSPF 131. as OSPF discovered routes.108.254.108.255.246 - .255.0/24 is directly connected.0/30 [110/1581] via 131. Serial0 O 131.5.5.255.5. 00:04:22.255.254.255.108.108.108.CCNP Practical Studies: Routing Example 7-24 show ip route on R3 R3#show ip route Codes: C .254. Example 7-25 displays the disabling of synchronization on all five routers. Serial0 C 131. Serial0 O 131.108.255.8/30 [110/1581] via 131.108.0/16 is variably subnetted. Serial0 O 131. 131.5. 01:04:33.254. 01:04:33.4/30 is directly connected.255. B . 01:04:33. Serial0 O 131.108.4.4.5.108.108.108.2/32 [110/811] via 131. 00:04:22. Serial0 O 131.254.108.254.108.108. Serial0 O 131.5. Ethernet0 O 131. 3 masks O 131. Serial0 C 131.108.255.5.254.5.2/32 [110/811] via 131.108. Change the default administrative distance on all five routers so that internal BGP is the preferred path in this five-router network.3/32 is directly connected.0/24 [110/1591] via 131.5.4/32 [110/1582] via 131. Serial0 O 131.108. Example 7-26 displays the IP routing table on R3.0/24 [110/1591] via 131.0/24 is directly connected.255.1/32 [110/801] via 131.108. 3 masks O 131.1.5/32 [110/1582] via 131. you need to disable synchronization on all the IBGP routers so that BGP entries are inserted into the IP routing table to see whether this solves the problem.108.108.108.5. Serial0 R3's IP routing table displays the remote networks 131.108.connected. 00:29:59.255.

Example 7-28 displays the IP routing table on R3 after the TCP peers are cleared. 3 masks O 131. EBGP administrative distance is 20. 01:18:33. as in this scenario. use the network <network subnet-mask> backdoor command. Example 7-27 displays the distance configuration on R1 and is configured on all five routers.254.254. and the local distance is also changed to 109.5. therefore.108.108. Serial0 C 131.108.5.0. Serial0 C 131. You use the ? tool to display the options as you enter the values.255. .108.5.5.108.5/32 [110/1582] via 131. if EBGP is configured between two routers and OSPF is the interior routing protocol. 12 subnets. Serial0 O 131. The IOS command to change the default BGP distance is as follows: distance bgp external-distance internal-distance local-distance The external distance is for EBGP routes (default is 20). Specifying the network allows the router to choose OSPF as the preferred path rather than the EBGP discovered path.108.2/32 [110/811] via 131.1. Serial0 O 131.254.0/24 [109/0] via 131.254.108. 01:18:33.108. Serial0 O 131. the internal distance is for IBGP routes (default is 200). and R5. Example 7-28 show ip route on R3 R3#sh ip route 131. a lower AD is always preferred.108.254.2.0/24 [109/0] via 131.108.108.108. For example. you use the concept of a backdoor to ensure that your IGP is the preferred routing method.1.3. 00:01:37 C 131.255.108.255.CCNP Practical Studies: Routing NOTE The same scenario can be duplicated using EBGP. By default.4/32 [110/1582] via 131. Serial0 B 131.255.5.254.0/30 [110/1581] via 131.254.5.108. far lower than OSPF (AD is 110). 01:18:33.255.255. 01:18:33. the external distance is unchanged at 20. and the local distance defines the AD for locally connected routes (default is 200).108. 01:18:33.255.0/16 is variably subnetted. To change this default behavior without the changing AD values.3/32 is directly connected.108.108. 00:00:50 R1 now uses BGP with an AD of 109 as the preferred path to the remote networks connected to R1/R2.255.0/24 [109/0] via 131. Example 7-27 Changing Default Distance R1(config)#router bgp 333 R1(config-router)#distance ? <1-255> Administrative distance bgp BGP distance R1(config-router)#distance bgp ? <1-255> Distance for routes external to the AS R1(config-router)#distance bgp 20 ? <1-255> Distance for routes internal to the AS R1(config-router)#distance bgp 20 109 ? <1-255> Distance for local routes R1(config-router)#distance bgp 20 109 109 The internal distance is set to 109 (less than OSPF 110).108.4.247 - . 01:18:33. Ethernet0 B 131. Serial0 O 131.5.108. in which case.255.0/24 is directly connected. R4.4/30 is directly connected.108. the next hop address is the EBGP connection. Changing the administrative distance is not always the most desirable method because all routers typically need modification.108. Loopback0 O 131.5. 00:01:38 B 131.108.255.8/30 [110/1581] via 131.1/32 [110/801] via 131.

internal Origin codes: i .254.1 255.0/24 131.108.0 131. Next.108.254.108.4.0/24 * i Next Hop 131. local router ID is 131. view the full working configurations of R1–R5.5.0/24 131.1.1.5 0 100 0 i The path to 131.108. Example 7-30 show ip bgp on R3 after R1 Failure R3#show ip bgp BGP table version is 86.EGP.0.2 131.254. h history.5 131.2 0 100 0 i *> 131. d damped.108. d damped.1.0/24 *>i131.254.CCNP Practical Studies: Routing This scenario built a redundant IBGP network. i .4.0/24 is through R1. Example 7-29 show ip bgp on R3 R3#show ip bgp BGP table version is 84. local router ID is 131.108.incomplete Network Next Hop Metric LocPrf Weight Path *>i131.3.0. * valid.254. Example 7-30 displays the BGP table on R3 after the BGP failure.255.108.108.108.108.108.4 0 100 0 i *>i131.3. > best. When the TCP peer to R1 fails on R3.254.108.254.0.4 131.255.108. i .255.0 ! interface Serial1/0 . Example 7-31 displays R1's full working configuration.IGP.0/24 *>i *> 131.0/24 * i *>i131.254.108.248 - .108. e .1.5.0 0 32768 i *>i131.108.254.incomplete Network * i131.4 131. Example 7-29 displays the current BGP table on R3.108.108.internal Origin codes: i .108.108.254.108.3 Status codes: s suppressed.0/24 0.IGP. Example 7-31 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131. ? . Before you build upon this scenario and add the EBGP connections to the two different ISP routers.0/24 is now through R2.1 255. ? .3 Status codes: s suppressed.108. simulate a routing BGP failure to R1 and ensure that R2 becomes the preferred path on all route reflector clients.108.1 0.EGP. the preferred path is through R2 (a route reflector).255 ! interface Ethernet0/0 ip address 131.0/24 131. > best. * valid. the peer address is 131. e .254.1.254.108. h history.255.0.1 (R1's loopback address).5 Metric LocPrf Weight Path 0 100 0 i 0 100 0 i 0 32768 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i The preferred path on R3 to 131.254.

255.254.0 mask 255.1.108.254.255.1 remote-as 333 .254.254.0 neighbor 131.254.255.255.5 255.5 remote-as 333 neighbor 131.254. Example 7-32 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.255.1.108.255.255.255 ! interface Ethernet0/0 ip address 131.4 route-reflector-client neighbor 131.0 255.0.3 route-reflector-client neighbor 131.108.5 update-source Loopback0 neighbor 131.0 mask 255.4 update-source Loopback0 neighbor 131.254.254.255.0 255.255 area 0 ! router bgp 333 no synchronization network 131.255.0.0.255.9 255.108.254.0 ! router ospf 1 network 0.252 clockrate 128000 ! interface Serial1/1 ip address 131.255.CCNP Practical Studies: Routing ip address 131.252 clockrate 128000 ! interface Serial1/3 shutdown ! router ospf 1 network 0.254.2 255.255.3 update-source Loopback0 neighbor 131.108.108.255.4 remote-as 333 neighbor 131.255.254.2 255.255.3 remote-as 333 neighbor 131.249 - .108.108.255.2 remote-as 333 neighbor 131.255.108.108.108.254.1 255.2 update-source Loopback0 neighbor 131.108.108.255.108.255.108.108.5 route-reflector-client distance bgp 20 109 109 ! line con 0 line aux 0 line vty 0 4 end Example 7-32 displays R2's full working configuration.252 ! interface Serial1/2 ip address 131.255.108.108.1.255.255 area 0 ! router bgp 333 no synchronization network 131.0.0 neighbor 131.254.108.

5 update-source Loopback0 neighbor 131.108.250 - .2 remote-as 333 neighbor 131.3.3 remote-as 333 neighbor 131.254.108.2 update-source Loopback0 distance bgp 20 109 109 ! line con 0 line aux 0 line vty 0 4 ! end .108.254. Example 7-33 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.108.255.4 update-source Loopback0 neighbor 131.254.108.1 255.255.5 route-reflector-client neighbor 131.108.108.254.108.6 255.255.254.0.255.255.255.4 remote-as 333 neighbor 131.3 route-reflector-client neighbor 131.108.1 update-source Loopback0 neighbor 131.5 remote-as 333 neighbor 131.255 area 0 ! router bgp 333 no synchronization network 131.254.3 update-source Loopback0 neighbor 131.254.108.254.255.255.254.254.0 neighbor 131.254.255.3 255.108.108.255.2 update-source Loopback0 distance bgp 20 109 109 ! line con 0 line aux 0 line vty 0 4 ! end Example 7-33 displays R3's full working configuration.108.108.2 remote-as 333 neighbor 131.254.255.0.108.108.0 mask 255.4 route-reflector-client neighbor 131.254.254.108.255.3.1 update-source Loopback0 neighbor 131.108.254.0 255.255 ! interface Ethernet0 ip address 131.1 remote-as 333 neighbor 131.0 ! interface Serial0 ip address 131.255.108.CCNP Practical Studies: Routing neighbor 131.108.252 bandwidth 125 ! interface Serial1 shutdown ! router ospf 1 network 0.

254.255. Example 7-35 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 131.254.255.251 - .108.108.255.255 ! interface Ethernet0 ip address 131.255.2 remote-as 333 neighbor 131.255.108.254.255.10 255.1 remote-as 333 neighbor 131.1 update-source Loopback0 neighbor 131.108.2 255.255.2 update-source Loopback0 distance bgp 20 109 109 line con 0 line aux 0 line vty 0 4 ! end Example 7-35 displays R5's full working configuration.255.5.255.0 ! interface Serial0 ip address 131.0 ! interface Serial0 ip address 131.1 255.0.255.252 ! interface Serial1 shutdown ! .255.255 area 0 ! router bgp 333 no synchronization network 131.255.255.255 ! interface Ethernet0 ip address 131.255.255.108.254.252 clockrate 125000 ! interface Serial1 shutdown ! router ospf 1 network 0.254.108.4.255.0 neighbor 131.4 255.254.0 255.CCNP Practical Studies: Routing Example 7-34 displays R4's full working configuration.1 255.108.108.0.4.255.108.0 mask 255.5 255.108.108. Example 7-34 R4's Full Working Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.255.

1 remote-as 333 neighbor 131.0.0 neighbor 131.108.0 255. . you build upon the IBGP network in Figure 7-4 and configure EBGP on R1 and R2 and simulate a dual-homing ISP connection.252 - . Example 7-36 configures ISP1 for EBGP and allows a default route to be advertised to the EBGP peer to R1.254. Figure 7-6.255.255.0.CCNP Practical Studies: Routing router ospf 1 network 0.5.108. Figure 7-6 displays the EBGP connections on R1 and R2 and the IP addressing.108. you configure two routers and inject default routes along with a large IP routing table to simulate an ISP router.255 area 0 ! router bgp 333 no synchronization network 131. Because most CCNP candidates do not have two ISP connections to configure in a lab environment. EBGP Connections Configure the routers ISP1 and ISP2 for EBGP and advertise a default route to the internal BGP network along with some routes that simulate an Internet environment.255.255.2 remote-as 333 neighbor 131.108.254.254.254.1 update-source Loopback0 neighbor 131.108.2 update-source Loopback0 distance bgp 20 109 109 line con 0 line aux 0 line vty 0 4 ! end Scenario 7-3: Configuring Dual-Homing ISP Connections In this scenario.0 mask 255.

1.EGP. i .0. ? .108.5 Metric LocPrf Weight Path 100 0 50001 i 0 4000 i 0 100 0 i 0 32768 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i 0 100 0 i .0 131.108.108.108. are providing default routes to R1 and R2.100.108.0/24 *>i * i131.108.1.254. h history.108.108.1 0. e . Example 7-39 R2's BGP table R2#show ip bgp BGP table version is 12.1.1.4 131. h history.108.1.108.254.108.0.108.0 131.4 131.108.254. Remember that both Internet routers.0/24 *> * i131.108.1.3.5 Metric LocPrf Weight 0 100 0 0 32768 0 100 0 0 100 0 0 100 0 0 100 0 0 100 0 0 100 0 0 100 0 Path 50001 i 4000 i i i i i i i i i R1.254.0/24 *>i Next Hop 171.3 131.254.254.3 131.2 default-originate Example 7-37 displays the EBGP configuration on ISP2.0/24 *>i Next Hop 171.254.0/24 *>i * i131.254.1 160.5 131.IGP.108.253 - .108.1.0 * i *> 131. d damped.100. ISP1 and ISP2.IGP. > best.254.254.108.0/24 * i * i131.108.incomplete Network * i0.4 131. e .108.108.254.5 131.0/24 *>i * i131.108.254.1. d damped.incomplete Network *> 0.0.108.0 *> * i131.0/24 *>i * i131. Example 7-37 EBGP on ISP2 router bgp 4000 neighbor 160.EGP.2 remote-as 333 neighbor 160.4.108. because it has a direct connection to the EBGP peer to ISP1.108. ? .2 remote-as 333 neighbor 171.CCNP Practical Studies: Routing Example 7-36 EBGP on ISP1 router bgp 50001 neighbor 171. Example 7-38 R1's BGP table R1#show ip bgp BGP table version is 8.254.254.1 0.internal Origin codes: i .254.108.108.0.0. local router ID is 131.100.1 131. * valid.1 Status codes: s suppressed.5.3 131.1.0.2 default-originate View the BGP tables on R1 and R2 and ensure that the BGP table contains a default route.100. > best. Example 7-38 displays R1's BGP table. Example 7-39 displays R2's BGP table.1 160.3. selects ISP1 for default-based traffic.4.254.108. local router ID is 131.3 131.0.4 131.2 Status codes: s suppressed.2 131. * valid.5.0. respectively.108.1. i .internal Origin codes: i .

4 0 100 0 i * i 131. To demonstrate another method.254.4.0 160. so to enable BGP to compare MED in different autonomous systems. you must enable the bgp always-compare-med command.0/0 through R1.0. e .108. d damped. i .108.1 200 0 4000 i * i 171.1 100 100 0 50001 i * i131.1. This traffic pattern is undesirable because IP packets might take different paths and not reach the destination in a timely manner. even though the MED is lower. and MED influences only EBGP connections.108.3 0 100 0 i * i 131.incomplete Network Next Hop Metric LocPrf Weight Path *> 0.0/24 131.IGP.100. Example 7-40 displays the MED configuration on R2. h history.CCNP Practical Studies: Routing Similarly.108.1 100 100 0 i *> 0. a dual-home connection is for redundancy purposes only. as shown in Example 7-41. R1 (in AS 333) and ISP2 (in AS 4000) are in different autonomous systems.internal Origin codes: i .1. Ideally.1 route-map setmedr1 in R2(config-router)#neighbor 160. R1 and R2. R2 selects ISP2 for all default-based traffic.108. the preferred path to the next hop 160. Example 7-40 MED Modification on R2 R2(config)#router bgp 333 R2(config-router)#neighbor 131.0/24 131. > best.100.254 - . the BGP table on R2 is displayed.3.108.108.254.108.0/24 131.1.5 100 100 0 i *>i 131. Lower MED values are preferred. . because R2 has a direct connection to the EBGP peer to ISP2.0.1. the BGP table on R2 displays the preferred default route 0. To accomplish this task.1 route-map setmedisp2 in R2(config)#route-map setmedr1 R2(config-route-map)#match ip address 1 R2(config-route-map)#set metric 100 R2(config-route-map)#exit R2(config)#route-map setmedisp2 R2(config-route-map)#match ip address 1 R2(config-route-map)#set metric 200 After you clear the BGP sessions to R1 and ISP2 on R2. you modify the MED value on R2 to ensure that all default traffic is sent through R1.254. The MED attribute is compared only for paths from neighbors in the same AS.0.108. local router ID is 131.0/24 131. Example 7-42 displays the configuration on R2 to allow MED to be compared between R1 and ISP2.254.4 100 100 0 i * i131. and BGP decisions are even though the two routers.0. are in different autonomous systems.108.108.254.5.100. ? . * valid. such as HTTP traffic.254. unless R1 loses the connection to ISP1.1. an example using AS_Path manipulation follows.108. resulting in loss or slow user-data transfer.0 0 32768 i *>i131.EGP.108.2 Status codes: s suppressed.254.0.0.1. This means that traffic is sent to different ISP routers for any traffic to the Internet.108. Example 7-41 show ip bgp on R2 R2#show ip bgp BGP table version is 9.254.3 100 100 0 i *>i131.254. Example 7-42 bgp always-compare-med Command on R2 R2(config)#router bgp 333 R2(config-router)#bgp always-compare-med After you clear the BGP sessions on R2. Configure R2 to send all default traffic through the connection on R1 to ISP1. The bgp always-compare-med command allows the MED values to be compared.5 0 100 0 i As displayed in Example 7-41. is through ISP2.

255.254.254.0 255.254.255.254.2 255.108.1 100 100 0 50001 i * i131.1 200 0 4000 i *>i 171.4 route-reflector-client .254. h history.108.1 100 100 0 i *> 0.4.255.108.1. Example 7-44 R2's Full Working Configuration Using MED hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.254.254.3 update-source Loopback0 neighbor 131.0 mask 255. d damped.255.0. > best.0 neighbor 131.100.255.254.4 update-source Loopback0 neighbor 131.255.1.108.1 route-map setmedr1 in neighbor 131.0 160.1.254.5.3 remote-as 333 neighbor 131. ? .254.0.255.4 remote-as 333 neighbor 131.108.5 100 100 0 i Example 7-43 shows that the new preferred path is through R1 because the MED is lower.108.254.255.255 area 0 ! router bgp 333 no synchronization bgp always-compare-med network 131.255.252 clockrate 128000 ! router ospf 1 network 0.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.108. Example 7-43 show ip bgp on R2 R2#show ip bgp BGP table version is 9.108.4 0 100 0 i * i 131.254.108.0.IGP.0.1 update-source Loopback0 neighbor 131.EGP.3 route-reflector-client neighbor 131.2 255.254.3.108.0/24 131.108. local router ID is 131.254.255.internal Origin codes: i .0 0 32768 i *>i131.100.2 Status codes: s suppressed.1.1. e .254.255 - .incomplete Network Next Hop Metric LocPrf Weight Path * 0.0/24 131.108.254.1.0/24 131.CCNP Practical Studies: Routing Example 7-43 displays the BGP table on R2.108.108.108.254.108.108.254. i .108.3 100 100 0 i *>i131.0.0.108.108.1 remote-as 333 neighbor 131. Example 7-44 displays R2's full working configuration.108.0/24 131.108.108.4 100 100 0 i *>i131.5 0 100 0 i * i 131. * valid.0 ! interface Serial1/3 ip address 160.2 255. Before removing the configuration comparing MED on R2 and demonstrating how the AS_Path attribute can also be used to accomplish the task.3 0 100 0 i * i 131.108.

1.5 remote-as 333 neighbor 131.1 route-map setmedisp2 in distance bgp 20 109 109 access-list 1 permit 0.108. Example 7-46 displays the BGP table on R2.1.0.108.1 route-map setmedisp2 in R2(config-router)#no neighbor 131.108.254.0.100.1. Next.1 remote-as 4000 neighbor 160.5 update-source Loopback0 neighbor 131. Example 7-45 AS_Path Manipulation of R2 R2(config)#router bgp 333 R2(config-router)#no neighbor 160.0 ! route-map setmedr1 permit 10 match ip address 1 set metric 100 ! route-map setmedisp2 permit 10 match ip address 1 set metric 200 ! line con 0 line aux 0 line vty 0 4 ! end In Chapter 6.1.254.256 - . Configure R2 to prepend AS_Paths (add AS_Paths) from ISP2 so that R1's connection to ISP1 is the preferred path for default routing.1 route-map aspath in R2(config)#route-map aspath R2(config-route-map)#set ? as-path Prepend string for a BGP AS-path attribute automatic-tag Automatically compute TAG value clns OSI summary address comm-list set BGP community list (for deletion) community BGP community attribute dampening Set BGP route flap dampening parameters default Set default information interface Output interface ip IP specific information level Where to import route local-preference BGP local preference path attribute metric Metric value for destination routing protocol metric-type Type of metric for destination routing protocol origin BGP origin code tag Tag value for destination routing protocol weight BGP weight for routing table R2(config-route-map)#set as-path ? prepend Prepend to the as-path tag Set the tag as an AS-path attribute R2(config-route-map)#set as-path prepend 4000 3999 3998 The? tool in Example 7-45 displays the options for prepending AS_Paths on R2.100.CCNP Practical Studies: Routing neighbor 131.108.5 route-reflector-client neighbor 160.1 route-map setmedr1 in R2(config-router)#neighbor 160.254.100.254. configure the AS_Path to 4000 3999 3998 on R2 for all incoming routes from ISP2. .100. you learned the BGP routing decisions and one of the decisions are based on shortest AS_Path.

1 filter R1(config-router)#neighbor 171.1 route-map noexport ? R1(config-router)#neighbor 171.100.108.0 Example 7-47 displays the configuration on R2 to allow only default routes and setting the no export community to ISP1.108. or a lower hop count away compared to 4000 3999 3998 (three hops).257 - .108.1.0.254.0.1.5 0 100 0 i *>i 131.1 filter-list 1 in R1(config-router)#neighbor 171.1 send-community R1(config-router)#neighbor 171.0/24 131.254. ISP1 and ISP2.254.108.1. e . .1 route-map noexport out R1(config)#route-map no-export R1(config-route-map)#set community no-export R1(config)#access-list 1 permit 0. Example 7-48 also shows the use of a well-known community value: no-export.0/24 0.1.254.108. Some other common configurations completed on routers connected to the Internet include the following: • • Ensuring that only a default route is accepted Ensuring that you are not a transit path for any Internet traffic Next.0.1. * valid.4.254.1 0 4000 3999 3998 4000 i *>i 171.108.0.1 (R1's link to ISP1) because the AS_Path is only 50001 (one hop). You can use a filter list along with a route map to permit a default route. i . The no-export community attribute advises a BGP router carrying this attribute that the route advertised should not be advertised to any peers outside the AS.254.108.108.254.5.0. Example 7-47 displays the configuration on R1 to allow only default routes and displays setting the no-export community to ISP1.IGP. local router ID is 131.1. In the next scenario. do not use the network between R1 and R2 as a transit path.108.108.108.internal Origin codes: i .254.1.108.2 Status codes: s suppressed.1.CCNP Practical Studies: Routing Example 7-46 show ip bgp on R2 R2#show ip bgp BGP table version is 7.incomplete Network Next Hop Metric LocPrf Weight Path * 0.0.4 0 100 0 i * i131. ? .108.0/24 131.1 0 100 0 i * i131.1.EGP.3 0 100 0 i * i131. d damped.0 160.108. Example 7-48 configures R2 (because R2 is also connected to an ISP router) using a route map to set the community and allowing only a default route using a filter list on inbound updates.108.3.0 0 32768 i * i 131.4 0 100 0 i *>i 131. > best. Example 7-47 R1 Allowing Only Default Routes (Filter List) and Setting Community R1(config)#router bgp 333 R1(config-router)#neighbor 171.108. You have seen two methods used on R2 and discovered how powerful BGP can be in allowing the network administrator to manipulate BGP and achieve any routing path desired.1 filter-list 1 R1(config-router)#neighbor 171.108.108.5 0 100 0 i R2 now prefers the path through the next hop address 171. configure R1 and R2 to accept only a default route and ensure that the service providers. h history.1 100 0 50001 i *> 131.0/24 131. you use prefix lists to accomplish the same task.108.3 0 100 0 i *>i 131.108.1.

1 255. view the full working configurations of the four main routers in this scenario. Example 7-50 ISP2's Full Working Configuration hostname ISP2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Serial0 ip address 160. Example 7-49 displays ISP1's full working configuration.100.1 route-map setcommuntiy out R2(config-router)#neighbor 160.1 255.0.0 R2(config)#route-map setcommuntiy R2(config-route-map)#set community no-export Before looking at how to use prefix lists to achieve complex routing filters.1.100.108.2 remote-as 333 neighbor 160.252 interface Serial1 shutdown ! router bgp 50001 neighbor 171.255.108.1.255.1.252 ! interface Serial1 shutdown ! router bgp 4000 neighbor 160.100.1 filter-list 1 in R2(config)#access 1 permit 0.1.1.100.1 send-community R2(config-router)#neighbor 160.2 default-originate line con 0 line aux 0 line vty 0 4 ! .1.108.2 remote-as 333 neighbor 171.1.2 default-originate ! line con 0 line aux 0 line vty 0 4 ! end Example 7-50 displays ISP2's full working configuration.0.CCNP Practical Studies: Routing Example 7-48 R2 Allowing Only Default Routes (Filter List) and Setting Community R2(config)#router bgp 333 R2(config-router)#neighbor 160.255.258 - .255.1.100.100.1. Example 7-49 ISP1's Full Working Configuration hostname ISP1 ! enable password cisco ! ip subnet-zero ! interface Serial0 ip address 171.

255.255.252 ! interface Serial1/2 ip address 131.108.259 - .1.254.1 remote-as 50001 neighbor 171.254.108.4 update-source Loopback0 neighbor 131.108.9 255.108.108.1 255.1 filter-list 1 in distance bgp 20 109 109 ! route-map noexport permit 10 .1.108.3 route-reflector-client neighbor 131.1.2 255.254.4 remote-as 333 neighbor 131.3 update-source Loopback0 neighbor 131.255.5 255.108.255.254.5 route-reflector-client neighbor 171.4 route-reflector-client neighbor 131.255.255 area 0 ! router bgp 333 no synchronization network 131.1.255.108.255.255.3 remote-as 333 neighbor 131.108.255.1 send-community neighbor 171.0 neighbor 131.254.252 clockrate 128000 ! interface Serial1/1 ip address 131.254.255.1.108.0.254.108.254.0 255.0 mask 255.1.5 update-source Loopback0 neighbor 131.255.108.108.1 255.252 clockrate 128000 ! router ospf 1 network 0.108.2 remote-as 333 neighbor 131.1 route-map noexport out neighbor 171.1 255.255.108.108.0 no ip directed-broadcast ! interface Serial1/0 ip address 131. Example 7-51 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.5 remote-as 333 neighbor 131.255.108.252 clockrate 128000 ! interface Serial1/3 ip address 171.255.254.255.255.254.255.254.254.1.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.2 update-source Loopback0 neighbor 131.CCNP Practical Studies: Routing end Example 7-51 displays R1's full working configuration.255.108.255.108.108.108.0.108.

254.254.108.255.108.0.252 clockrate 128000 ! router ospf 1 network 0.254.1 route-map aspath in neighbor 160.255.1.0.1 send-community neighbor 160.255.1.108.2 255.CCNP Practical Studies: Routing set ! line line line end community no-export con 0 aux 0 vty 0 4 Example 7-52 displays R2's full working configuration.255.108.100.254.254.1.254.255 area 0 ! router bgp 333 no synchronization bgp always-compare-med network 131.108.254.255.254.1 remote-as 333 neighbor 131.3 remote-as 333 neighbor 131.1.254.1 filter-list 1 in distance bgp 20 109 109 ! access-list 1 permit 0.1 update-source Loopback0 neighbor 131.254.4 update-source Loopback0 neighbor 131.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.1 remote-as 4000 neighbor 160.100.3 route-reflector-client neighbor 131.255.5 update-source Loopback0 neighbor 131.1.1. Example 7-52 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.0.254.100.2 255.108.1.108.255.108.1.5 route-reflector-client neighbor 160.108.108.100.0 neighbor 131.255.4 remote-as 333 neighbor 131.0 route-map setcommunity permit 10 set community no-export ! route-map setcommuntiy permit 10 set community no-export ! .0 ! interface Serial1/3 ip address 160.254.5 remote-as 333 neighbor 131.255.100.0.4 route-reflector-client neighbor 131.2 255.108.108.1 route-map setcommuntiy out neighbor 160.108.260 - .100.0 mask 255.0 255.3 update-source Loopback0 neighbor 131.255.

CCNP Practical Studies: Routing route-map aspath permit 10 set as-path prepend 4000 3999 3998 ! route-map setmedr1 permit 10 match ip address 1 set metric 100 ! route-map setmedisp2 permit 10 match ip address 1 set metric 200 ! line con 0 line aux 0 line vty 0 4 ! end .261 - .

262 - . you build upon the network in Figure 7-6. This scenario encompasses only two routers to demonstrate the power of BGP. . Two-Router ISP Simulation First. you remove all the IBGP sessions on R1 and advertise these static routes to R1. To make things simpler. Figure 7-7 displays the two-router topology with the router named ISP1 simulating an ISP environment. route maps. Example 7-53 displays the static route configuration of 25 networks on ISP1 and the advertisement of these static routes to R1.CCNP Practical Studies: Routing Scenario 7-4: Configuring Prefix Lists In this scenario. NOTE All filtering. configure some routes on ISP1 pointing to Null0 (a bit bucket. commonly used in BGP to advertise routes statically for entries in the IP routing table). Figure 7-7. You use the redistribute static command to inject networks into R1. You use some handy configuration tips to simulate an ISP environment and use prefix lists on R1 to ensure that you receive only necessary information to save bandwidth and IP and BGP table sizes. and IBGP peers configured in the previous scenario have been removed from Router R1 for clarity.

0 Null0 148.0.0.0.0 255.255.100.255.0.0.100.255. In a real-world BGP environment.0.0.255.255.0.0 0.0.0. The origin AS is 1000.0/16.0. and finally the Class B networks ranging from 141.255. and 200.0 Null0 5.255.263 - .0.0.0 255.0.255.255. the router ISP1 would have more specific entries to all these networks.0 Null0 150.0.0.0.0 255.0.108.0 Null0 141.0 Null0 6. Null routes and loopbacks are great learning tools.0.255. Example 7-54 Prepending Routes on ISP1 router bgp 50001 neighbor 171.0.0.0.0 255. the Class A networks 100.0.0.0.0.0.0. The last entry.0.0.0.0.1.0.0.255.0 Null0 8.255 access-list 1 permit 7.0. 300.0 255.0.0 Null0 3.0.255.0.0. is a default route advertisement. 101.0.0.255.255.0.0.255.0.0.0.255.0.0.0–11.0.0 Null0 2.255.255.255.0.0.0 255.0 0.0.0.0.0 0.0 0.0/0.0 Null0 149.0.0.255 access-list 1 permit 6. Example 7-54 configures all networks in the range 1.255.0.255 access-list 1 permit 11.0.0. and a static route would be configured so that information can be sent over the EBGP peers without the need for dynamic routing advertisements.255.0.0.0 Null0 142.0.0 255.0.255 access-list 1 permit 4.0 255.1.0.0 255.0.0.255.0.0 Null0 101.0 255.2 route-map prepend out access-list 1 permit 1.0 Null0 146.255 access-list 1 permit 3.0 0.0.255.0 Null0 147.0.0 255.0. 0.255 access-list 1 permit 5.0 Null0 0.255.0 255.0 0.100.0.0.0.0.0.0.0.0.0 255.255.0 0.100.100.0 255.255.0.0 Null0 100.0.255.0.0.0 Null0 141.0 Null0 4.255.0.0.0.0.0.0.100.0 255.0 0.0.0.0.100.0.0.0.0–150.0.0 Null0 144.255.255 access-list 1 permit 2.0 0.0 0.0 255.0.0 255.0 255.100.255 access-list 1 permit 9.255.0.0 255.100.0 0.255 access-list 1 permit 8. To simulate a real environment.0 255.100.0 255.0.0.255.0.0.100.CCNP Practical Studies: Routing Example 7-53 Static Route Configuration on ISP1 ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip route route route route route route route route route route route route route route route route route route route route route route route route route 1.255.0 null0 Example 7-53 displays the static route configuration of Class A networks ranging from 1.0 Null0 102.0.255 access-list 1 permit 10.0–11.0.0.0 Null0 145.0.0.0.255.0 255.0 Null0 11.0.0.0 255.0.0 0. with the path through 998 999.0.255 access-list 2 permit any route-map prepend permit 10 match ip address 1 set origin igp set as-path prepend 998 999 ! route-map prepend permit 20 match ip address 2 set origin igp .0.0 255.0 Null0 10.0.0.108. The route map name is set to prepend.0. All other networks are prepended with the autonomous systems 400.0.0.100.0. configure ISP1 to prepend some of the static routes with varying autonomous systems.0 Null0 143.0.255. and 102.0.0.0 Null0 7.

0.1.1.108.108.1.254.1 171. by viewing the BGP table on R1.1 171.0 146.0.100.100.0.0 11.1 Status codes: s suppressed.1 171. and 200 or {400 300 200}.0 142.100.0. The networks defined in access list 2 are prepended with an AS of 400.1.108.1 171.CCNP Practical Studies: Routing set as-path prepend 400 300 200 The route map also configures the BGP origin attribute to IGP (as advertised by the network command).0.1 171.108.0 148.108.0.1.264 - .0.108.108.1 171.1.108.100.0. ? . .0 102.0.0 149.0 100.0.0 2.0/24 141.108.0 5.0.0.100.1.0.1.108.internal Origin codes: i .0 147.108. Example 7-55 confirms that the attributes are set correctly.108.1 0.1.1.0.1 171.1 171. > best.100.1.0.108.0.1.0. local router ID is 131.0.1 Metric LocPrf Weight Path 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 32768 i 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 0 0 50001 400 300 200 i i i i i i i i i i i i i The first eleven networks in Example 7-55 match access list 1 configured on ISP1. e .108.108.108.0 144.1 171.1.0 3. All subnets allowed by access list 1 prepend all networks to 998 999 and set the origin to IGP.IGP.1.108.1 171.108.0.0 145.1 171.1.0 141.0. * valid.0.0.0.108.0.108.1 171. d damped.108.0.0 131.0.0 Next Hop 171.0.1 171. Example 7-55 show ip bgp on R1 R1#show ip bgp BGP table version is 25.0 10.EGP.100.0.0.1.108. h history.0. 300.incomplete *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> Network 1.1.108.108. To demonstrate full IP connectivity. i . view the IP routing table on R1.1.0 101.1.0.0. Similarly.1 171. line 20 in the route map (route-map prepend permit 20) statement configures all networks in access list 2 with an IGP origin attribute.1.0 7.0 4.1.108.100.1 171.0.0.0 171.1.108.1 171.1.1 171.1 171.0.0 8.100.0 6.0 143.0.1 171.1 171. Example 7-56 displays the IP (BGP routes only) routing table on R1.1 171.1.0.0.

0.108. where a virtual private network might be configured for extranets. 00:04:03 B 11.0/16 [20/0] via 171. matching the following criteria: • • • • NOTE Permit the default route 0.0.0.0/8 [20/0] via 171.1. Allow all routes 141.0/8 [20/0] via 171.108.1. 00:04:03 Example 7-56 displays all the networks advertised through ISP1. 00:04:03 B 7.0.0/16 [20/0] via 171.0.0–11.0.0 network.0.0. Manually generating routes to null0 using static routes is a great learning tool to deploy in any practice lab.108.0.1. (Next hop address is 171.108.1.108.0/8 [20/0] via 171.1.0/16 [20/0] via 171. 00:04:02 B 141.1. You do not need to specify the sequence.1.1.0.108. 00:04:03 B 145. Configure a prefix list on R1 to stop unnecessary routing traffic.108.0.1. but not 10.1.0.1.1. Cisco IOS (internal only) allows a router to generate as many routes as you could ever need to simulate the Internet.0.1.0. to be fully aware of all the entries advertised from ISP1 because you already have a default route.0/24. 00:04:03 B 148. 00:04:02 B 4.108.0. 00:04:03 B 8.0.1.0/8 [20/0] via 171.108.0.0.1. the initial number is 5 and is incremented by 5 each time.108.1.1.1.1.0.0/8 [20/0] via 171.0.1. the packets are dropped on ISP1.0. Allow any routes in the range 1.1.100.108.1. or an internal network running an IGP.1. you configure a prefix list on R1 to stop any BGP routes.0/16 [20/0] via 171.0/16 [20/0] via 171.1. 00:04:03 B 10.108.100.1. although this is not a recommended exercise.100.0. 00:04:02 B 101. For the purposes of this exercise. When you view the final configuration.1.1.100.0.100.1.0. 00:04:03 B 143.0/16 only.0.1. 00:04:03 B 149.108.1.1. 00:04:03 B 146.) NOTE If you try to ping any of these networks from R1.108.1.0/8 [20/0] via 171.108. 00:04:02 B 3. (This might be a network.0. Alternatively.0.0.0.0.1.100.108.) Deny all other routes.0/8 [20/0] via 171. but because you have configured a null0 route. 00:04:02 B 1.1.0. This is especially true because ISP1 is advertising the nonroutable 10.1.1.108.1.1.100. the EBGP peer address of ISP1.0.0.0/8 [20/0] via 171. Next.0. 00:04:03 B 144.1.108. There are other methods to generate BGP routes.0.108.1. Example 7-56 shows many BGP entries.0.0/8 [20/0] via 171.0/8 [20/0] via 171.0.100. 00:04:02 B 6.0/16 [20/0] via 171.1. . 00:04:02 B 2.108. you will discover the IOS has inserted the sequence numbers for you.0.1.100.0.0. so you might want specific routing information such as this.CCNP Practical Studies: Routing Example 7-56 show ip route bgp on R1 R1#show ip route bgp B 102. 00:04:02 B 100.108. As you can determine. the ping request reaches ISP1.0. There is no need for R1. you could peer to your corporate Internet gateway and receive the full BGP table.0.0.1.1. 00:04:02 B 5.108.0/8 [20/0] via 171.1.0/16 [20/0] via 171.0. or the IBGP network.265 - .0.108.0.0.0/16 [20/0] via 171.1. 00:04:03 B 142.0/8 [20/0] via 171.0/16 [20/0] via 171. all you need to be interested in is generating routes.1. 00:04:03 B 147.1. for example.0.108.0/16 [20/0] via 171. which might be in use on Router R1.1. such as BGP generators.0/8 [20/0] via 171. such as OSPF. 00:04:02 B 141. Prefix lists follow sequence numbers just as route maps do.108.0.

0.0.0.0. 35.1. .1.0/8 R1(config)#ip prefix-list ccnp permit 3.266 - . Example 7-59 displays the configuration on R1 when the show running-config command is entered in privilege mode on R1 (truncated). Example 7-57 Initial Prefix List Configuration on R1 Pointing to ISP1 R1(config-router)#neighbor 171. by default.0/8 R1(config)#no ip prefix-list ccnp permit 45.0.0.D IP prefix <network>/<length>.0.0. Example 7-58 Prefix List Configuration on R1 R1(config)#ip prefix-list ? WORD Name of a prefix list sequence-number Include/exclude sequence numbers in NVGEN R1(config)#ip prefix-list ccnp ? deny Specify packets to reject description Prefix-list specific descriptin permit Specify packets to forward seq sequence number of an entry R1(config)#ip prefix-list ccnp permit ? A.0. e.D IP prefix <network>/<length>.0/8 R1(config)#ip prefix-list ccnp permit 0.0/8 R1(config)#ip prefix-list ccnp permit 8.B.0.0.1 prefix-list ccnp in R1 is configured to apply a prefix list to all inbound traffic from the router ISP1.0.108.108.0/0 R1(config)#ip prefix-list ccnp permit ? A.0. named ccnp in Example 7-58.0. implicitly deny all other networks. you need to configure the options for the prefix list to perform any filtering.0/8 R1(config)#ip prefix-list ccnp permit 11.0.1.0.1 prefix-list ccnp ? in Filter incoming updates out Filter outgoing updates R1(config-router)#neighbor 171. e.C.108.0.0.1 prefix-list ? WORD Name of a prefix list R1(config-router)#neighbor 171.0/8 R1(config)#ip prefix-list ccnp permit 6. 35.0. configure a prefix list on inbound traffic from ISP1 on R1. you have not defined the prefix list.g.0.0.1.B..0.0. Example 7-57 displays the filter list configuration in BGP configuration mode.0.C.0.g.0/8 R1(config)#ip prefix-list ccnp permit 141.0/8 R1(config)#ip prefix-list ccnp permit 5. You do not need to deny any other networks because the Cisco IOS automatically denies all networks not specifically permitted in the prefix list.0.0/8 R1(config)#ip prefix-list ccnp permit 4. Example 7-57 uses the ? to guide you through the various options.0/16 Prefix lists.0/8 R1(config)#ip prefix-list ccnp permit 2..0.0.0. As yet. Example 7-58 displays the prefix list configuration in global configuration mode.0/8 R1(config)#ip prefix-list ccnp permit 1.0/8 R1(config)#ip prefix-list ccnp permit 9.0.0/8 R1(config)#ip prefix-list ccnp permit 7.0.0/8 R1(config)#ip prefix-list ccnp permit 2. First.0.0. As with an access list.CCNP Practical Studies: Routing Configure a prefix list on R1 to obtain the preceding objectives.0/8 R1(config)#ip prefix-list ccnp permit 45.

0.0.0.1.0.1 0 0 50001 998 999 i *> 2.internal Origin codes: i .0 171.1 0 0 50001 998 999 i *> 131.0.1.0.108.0..CCNP Practical Studies: Routing Example 7-59 show running-config on R1 R1#show running-config Building configuration.0.108. .0 neighbor 171.108.0.108.0.0 0 32768 i R1 defines only the networks in the prefix list named ccnp.0.0.0 171.1 0 0 50001 998 999 i *> 3.0/8 ip prefix-list ccnp seq 45 permit 8.htm#xtocid798074..0.1. > best.1.0/8 ip prefix-list ccnp seq 20 permit 3.0 171.0.0.0 171.0/0 ip prefix-list ccnp seq 10 permit 1. Cisco recommends that prefix lists be used in preference to route maps because prefix lists are hard coded in software (complied in code terms) and take less time to process.0.1.0/8 ip prefix-list ccnp seq 15 permit 2.0.0 171..108.0 171.0/16 The Cisco IOS automatically configures sequence numbering starting from 5–60.1 0 0 50001 998 999 i *> 6.0. ? .0/24 0.108.0.1.108.incomplete Network Next Hop Metric LocPrf Weight Path *> 0. e .IGP.0.0.0.108.0/8 ip prefix-list ccnp seq 60 permit 141.0.0.108.267 - .0/8 ip prefix-list ccnp seq 55 permit 11.0.1 remote-as 50001 neighbor 171.0.cisco.1 0 0 50001 998 999 i *> 4.0. Example 7-60 displays the BGP table on R1 after the BGP peer is cleared and re-established on R1. i .108.1. Example 7-60 show ip bgp on R1 R1#show ip bgp BGP table version is 12. NOTE The examples of prefix lists are practically endless.0/8 ip prefix-list ccnp seq 25 permit 4.0.0/8 ip prefix-list ccnp seq 50 permit 9.0.0.1 0 0 50001 998 999 i *> 7.108.255.108.108. h history.1.108.1.1..1.0 171.0 mask 255.255.0.0 171.0/8 ip prefix-list ccnp seq 30 permit 5.1.1 0 50001 i *> 1.0/8 ip prefix-list ccnp seq 35 permit 6.0.1 0 0 50001 998 999 i *> 11.1.0.0.0.0. d damped. Current configuration: !.EGP.0.0.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfbgp.0 171. visit www.0.108. local router ID is 171.1.truncated ! router bgp 333 network 131.1.0.1.0.0.0.1 0 0 50001 998 999 i *> 8.1 0 0 50001 998 999 i *> 5.0/8 ip prefix-list ccnp seq 40 permit 7. For more great examples.0.1 prefix-list ccnp in ! ip prefix-list ccnp seq 5 permit 0.2 Status codes: s suppressed.0. * valid.0 171.

255.0/8 ip prefix-list ccnp seq 30 permit 5.108.1.252 clockrate 128000 ! router bgp 333 network 131.0/8 ip prefix-list ccnp seq 20 permit 3.0/16 ! line con 0 line aux 0 line vty 0 4 end Example 7-62 displays ISP1's full working configuration.255. use the Class A 10. Example 7-61 displays R1's full working configuration.1 remote-as 50001 neighbor 171.255.1.0.108.255.0. Example 7-61 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.0.2 255.0 private address for network-layer addressing on all network devices and.1.0.0 ! interface Serial1/3 ip address 171.255.0.0.0.108.0/8 ip prefix-list ccnp seq 15 permit 2.0.0/8 ip prefix-list ccnp seq 45 permit 8.0.0/8 ip prefix-list ccnp seq 60 permit 141. Example 7-62 ISP1's Full Working Configuration hostname ISP1 ! enable password cisco ! interface Serial0 ip address 171.1 255.1 prefix-list ccnp in ! ip prefix-list ccnp seq 5 permit 0.252 ! router bgp 50001 redistribute static .0 neighbor 171.1 255.0/8 ip prefix-list ccnp seq 40 permit 7.0.0.0.0.0/0 ip prefix-list ccnp seq 10 permit 1.255.255.0.0.0. for example.108.268 - .CCNP Practical Studies: Routing Typically.0 mask 255.0.0/8 ip prefix-list ccnp seq 55 permit 11. therefore.1.0.1.1.0.108. block this network from all BGP sessions using prefix lists.0. Some ISPs. The best method you can apply to fully appreciate prefix lists is to set up a simple two-router topology and configure prefix lists to see the effect on the BGP table.1.108.0.0/8 ip prefix-list ccnp seq 50 permit 9.255.0.0/8 ip prefix-list ccnp seq 25 permit 4.0.0.0. prefix lists are used by large ISPs networks and are used to ensure that only routes permitted into an ISP are routed into the Internet.0/8 ip prefix-list ccnp seq 35 permit 6.

0 Null0 ip route 102.0.0.CCNP Practical Studies: Routing neighbor 171.0.0.255.0 Null0 ! access-list 1 permit 1.255.0.0 Null0 ip route 100.255.0 Null0 ip route 141.0.0 0.0.0 Null0 ip route 101.255.255.255.0 0.0 255.100.255.255.0.255.0 Null0 ip route 142.0.0.2 default-originate neighbor 171.255.0.0 255.255.0.0.0 255.0.255.0.255 access-list 1 permit 11.255.255.108.0.0.0 0.0 255.255.255.255 access-list 1 permit 7.0 Null0 ip route 148.255 access-list 1 permit 3.0 Null0 ip route 8.0.0.255.0.0.0.255.0.100.0.0.0.0.255 access-list 1 permit 5.0 255.0.255.0 Null0 ip route 4.0.0 Null0 ip route 2.0.0.255 access-list 2 permit any route-map prepend permit 10 match ip address 1 set origin igp set as-path prepend 998 999 ! route-map prepend permit 20 match ip address 2 set origin igp set as-path prepend 400 300 200 ! line con 0 line aux 0 line vty 0 4 end .0.100.0 255.0.0.0.0 Null0 ip route 146.0.0.100.0.0 Null0 ip route 5.0 Null0 ip route 3.0 Null0 ip route 143.0.0.0 255.0.255.255 access-list 1 permit 9.0 Null0 ip route 7.255 access-list 1 permit 2.255.0 255.0.0 255.108.0 Null0 ip route 1.255 access-list 1 permit 6.0.1.0 255.0.0.0.255.0 Null0 ip route 145.0 Null0 ip route 149.100.0 0.0.0.0 0.2 remote-as 333 neighbor 171.0.0 Null0 ip route 141.255.269 - .0.255.255.108.255 access-list 1 permit 4.0.0 Null0 ip route 6.0 255.0.0.0 Null0 ip route 11.0 0.0.0 Null0 ip route 10.0.0.0 0.0.0.255.0 0.0 0.0.0.2 route-map prepend out ! ip classless ip route 0.100.0 0.0.0.0.0.0.255 access-list 1 permit 10.0.0.0.0 255.0.0.255.0.1.0.0.0 Null0 ip route 144.0.0.100.0 255.0.0 Null0 ip route 147.0.0 255.0.0.0 255.0.1.0.0.255.0 255.0.0.255.0.0.255.108.0 0.0.0.255 access-list 1 permit 8.0.100.0.0 0.0.100.0 255.0.0.255.0 255.0 255.0.0 255.255.0.0 255.0 255.0.0.0 255.0.

0/8 is not advertised to any peer because R1 has only one EBGP peer to ISP1.0/8 command.C. Example 7-64 show ip bgp 1.0.0/8.108.0. The full list of available show commands used in BGP is displayed in Example 7-63.1.0.0.htm. Suppose you want Router R1 to detail information about the remote network 1. .0. The path traversed to reach 1.0.1. best.0/8 R1#show ip bgp 1. metric 0..0/8 is through the AS paths 50001 (ISP1).270 - .108. valid.C. The network 1.1) Origin IGP.B.1.0.D cidr-only community community-list dampened-paths filter-list flap-statistics inconsistent-as neighbors paths peer-group regexp summary <cr> IP prefix <network>/<length>.108. the origin attribute is set to IGP (meaning that BGP advertised this network through the network command).0/8 BGP routing table entry for 1.0. e.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprrp_r/bgp_r/1rfbgp2. This IOS command is typically used to determine which AS path is taken to reach a remote network and the advertised peer.1 from 171.1 (ISP1). external. For more examples of the full IOS command set. and finally originates from 999.0. ref 2 Example 7-64 shows that the remote entry is reachable through the next hop address 171.108. localpref 100.1 (171. 35.D A.0. visit www.g.0.0.CCNP Practical Studies: Routing Scenario 7-5: Monitoring BGP and Verifying Correct Operation Chapter 6 covered common BGP show commands.0.0. Table 7-2 summarizes all the fields from Example 7-64.0.0. Example 7-64 displays the output of the IOS show ip bgp 1. version 3 Paths: (1 available. then 998. best #1) Not advertised to any peer 50001 998 999 171.B.0/8 Network in the BGP routing table to display Display only routes with non-natural netmasks Display routes matching the communities Display routes matching the community-list Display paths suppressed due to dampening Display routes conforming to the filter-list Display flap statistics of routes Display only routes with inconsistent origin ASs Detailed information on TCP and BGP neighbor connections Path information Display information on peer-groups Display routes matching the AS path regular expression Summary of BGP neighbor status This scenario covers the highlighted options in Example 7-63. Example 7-63 Full show ip bgp Command List R1#show ip bgp ? A.0/8.1. NOTE The following sample IOS displays are taken from the two-router topology in Figure 7-7. This scenario covers some of the more advanced BGP monitoring commands.cisco.

0/24 Next Hop 0.0. i . Status of the table entry.EGP. Origin codes Network Next Hop Metric LocPrf Weight Path To display routes with unnatural network masks (that is.2 Status codes: s suppressed.incomplete Network *> 131. this is a router that is redistributed into BGP from an IGP. Local preference value as set with the set local-preference route-map configuration command. IP address of a network entity.0. use the show ip bgp cidr-only command. Autonomous system paths to the destination network.0/8. You should expect the network 131. Example 7-65 displays the output from the show ip bgp cidr-only command on R1. IP address of the next system that is used when forwarding a packet to the destination network. The default value is 100. In Example 7-66. e—Entry originated from Exterior Gateway Protocol (EGP). The origin code is placed at the end of each line in the table. e .IGP. > best. for example. Every network change results in a new table version number incremented by 1 for every change.271 - .0 (Class B subnetted or /24 network mask). ?—Origin of the path is not clear. the AS path is 50001 998 999. Usually.1. MED. Weight of the route. This number is incremented whenever the table changes.0. i—Entry was learned through an internal BGP (IBGP). Origin of the entry. Cisco-specific only. show ip bgp 1.0.internal Origin codes: i .1. d damped. .108. local router ID is 171. The status is displayed at the beginning of each line in the table.1.0. 1. Example 7-65 show ip bgp cidr-only on R1 R1#show ip bgp cidr-only BGP table version is 12. * valid.108. h history. It can be one of the following values: s—Entry suppressed. *—Entry is valid. It can be one of the following values: i—Entry originated from Interior Gateway Protocol (IGP) and was advertised with a network router configuration command.0/8 Explained Field BGP table version Status codes Description Internal version number of the table. ? .CCNP Practical Studies: Routing Table 7-2.108. classless interdomain routing [CIDR]). >—Entry is the best entry.0.0 Metric LocPrf Weight Path 0 32768 i Table 7-3 displays the field descriptions for the show ip bgp cidr-only command.

There can be one entry in this field for each autonomous system in the path. Regular expressions are patterns that match input strings.108.108. For example. the ^ matches the beginning of an input string. This number is incremented whenever the table changes. NOTE Regular expressions (REGEXP) are not defined as part of the CCNP certification exam but are so useful they are covered here for readers developing expert-level skills.108. This command is used to discover which networks match certain paths. and $ matches the end of an input string. you would use the show ip bgp regexp ^$ command. MED. This IOS command is used to match networks meeting certain path descriptions. ?—Origin of the path is not clear. The origin code is placed at the end of each line in the table. show ip bgp cidr-only Descriptions Field BGP table version is 12 local router ID 171. It can be one of the following values: s—The table entry is suppressed. character matches any single character. Example 7-66 displays the output taken from R1 matching all networks originating locally. Usually. Hence.1) Metric LocPrf Weight Path .1. ?—The origin of the path is not clear. Weight of the route.CCNP Practical Studies: Routing Table 7-3.2 Status codes Description Internal version number for the table. as set with the set local-preference route-map configuration command. as set through autonomous system filters.108. At the end of the path is the origin code for the path: i—The entry was originated with the IGP and advertised with a network router configuration command. I is displayed. IP address of the next system to use when forwarding a packet to the destination network.0/24) Next Hop (171.) i—Entry originated from Interior Gateway Protocol (IGP) and was advertised with a network router configuration command. the . IP address of the router. Internet address of the network the entry describes. Local preference value. *—The table entry is valid. e—The route originated with EGP. Usually this is a path that is redistributed into BGP from an IGP The final command most network designers use is the show ip bgp regexp command.1. The status is displayed at the beginning of each line in the table. this is a router that is redistributed into BGP from an IGP. Origin of the entry.0 is advertised using the network command. e—Entry originated from Exterior Gateway Protocol (EGP). if you want to discover all the paths originating locally.272 - . Status of the table entry. It can be one of the following values: Origin codes (131.1. Autonomous system paths to the destination network. Network (131. >—The table entry is the best entry to use for that network. i—The table entry was learned through an internal BGP (IBGP) session. For example.1.

1 171.0.0.1 171.1 171.0 Metric LocPrf Weight Path 0 32768 i Because R1 is advertising the network 131.0 (connected to E0).0 2.1.IGP.0/24 Next Hop 0.0.1 Metric LocPrf Weight Path 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i 0 0 50001 998 999 i After you ascertain which networks are encompassed in path AS 998.1 171.0.1 171.1 171.273 - . the output from the show ip bgp regexp ^$ command displays all locally connected originating routes. local router ID is 171.1 171. > best.internal Origin codes: i .1 171. h history.108. Example 7-67 show ip bgp regexp_998_ R1#show ip bgp regexp _998_ BGP table version is 12.incomplete *> *> *> *> *> *> *> *> *> Network 1.108.IGP.108.0.0 11. ? . e .1.0.0 4. as seen on R1. local router ID is 171.0.0.108.0.0 5.108.1.1.internal Origin codes: i .1. * valid. i . you could implement a route map that sets the MED to 100 and weight to 1000 for only those paths passing through 998.108.0 7.2 Status codes: s suppressed.CCNP Practical Studies: Routing Example 7-66 show ip bgp regexp ^$ R1#show ip bgp regexp ^$ BGP table version is 12.0 8.0 3. h history.1.0.1.1. You can easily discover the power of BGP—even by using only the most basic show commands described in this book. * valid.0.0.0.108.108. d damped. you might want to implement a route map. i . ? .0.incomplete Network *> 131. e .0.EGP.108.0.1.1.0 Next Hop 171. .1.2 Status codes: s suppressed.0 6.108.108. For example. Example 7-67 displays all networks coming through AS 998.0.EGP. > best.0. REGEXPs are used prior to making changes to BGP neighbors to ensure that the correct networks are tagged for further processing.1.0.0. d damped.108.1.108.

Practical Exercise Solution You have a lot to accomplish and you should begin by ensuring Layer 1. .108. or the physical layer between all routers. Five-Router Topology R1 has an EBGP peer to R5 and an IBGP peer to R2.108. set the weight to 2000 and the metric (MED) to 200. Ensure that R1 advertises a default route to R5 and that R2 advertises a default route to R4. is running. The solution can be found at the end. R3 runs only OSPF. Ensure that the 15 loopbacks on R1 (131. (That is.0 but does accept a default route only. Figure 7-8. Ensure that IP addressing is accurate.0–131. R2 has an EBGP peer to R4 and IBGP peer to R1. For all odd networks.0.0/24) are advertised to R5 and that R5 modifies all even networks with a local weight to 1000 and metric (MED) to 100.274 - . R1 and R2 run BGP and OSPF.108. Ensure that R3 can reach all BGP-advertised networks using OSPF as the only routing protocol. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. redistribution is required on R1/R2). Configure the five-router topology in Figure 7-8 for IP routing.16. Use a prefix list to accomplish this task.CCNP Practical Studies: Routing Practical Exercise: Advanced BGP NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. Ensure that R4 does not accept any networks in the range 131.2. All other networks must be denied on R4.

6. The shaded portions call your attention to critical commands required for full IP connectivity.255.255.4.1 255.108.108.0 ! interface Loopback9 ip address 131.0 ! interface Loopback3 ip address 131.255. 141.255.0 ! interface Loopback1 ip address 131. Redistribution is required on R1/R2 so that R3 can dynamically learn the remote BGP networks on R4/R5 through OSPF (external routes Type 2).255.16.108.108.1 255. Example 7-68 displays the full working configuration on R1.10.1 255.255.255. for example.0 ! interface Loopback5 ip address 131.255.108. Synchronization is disabled.0 ! interface Loopback4 ip address 131.108.14.255.108.108.255.255. perform some simple pings.1 255.9.1 255.1 255.0 ! interface Loopback6 ip address 131.255.108.1.255.255.0 ! interface Loopback14 ip address 131. After Layer 1 is up.255.255.0 ! interface Loopback12 ip address 131.13.11.CCNP Practical Studies: Routing Then.1 255.255.255.0/24.108. R1 has OSPF and BGP enabled.255.0 ! interface Loopback13 ip address 131.15.0 ! interface Loopback7 ip address 131. followed by EBGP between R1/R5 and R2/R4.108. start by configuring OSPF between R1/R2 and R3.108. and the next hop self-attribute is set to R5 so that R5 is able to reach R4's Ethernet network.0 .108.1 255.255. from R1 to R5 and R2 to R4. Example 7-68 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.2.255.8.1 255.3.0 ! interface Loopback2 ip address 131.255.1 255.255.7.108.255.255.255.1 255.0 ! interface Loopback11 ip address 131.255.255.255.108. Then configure IBGP between R1 and R2.1 255.12.0 ! interface Loopback10 ip address 131.275 - .255.0 ! interface Loopback8 ip address 131.1 255.5.1 255.1 255.

108.0.255.255.14.108. R2 has OSPF and BGP enabled.255.0 mask 255.11. and the next-hop-self attribute is set to R4 so that R4 can reach R5's Ethernet network.0 network 131.9.0 mask 255.1 255.0 network 131.5.1.1.0 network 131.255.0 ! interface Serial1/0 ip address 171.255.2 default-originate ! ip classless ip route 0.1 255.255.255.1.108.255.0 mask 255. Synchronization is disabled.0 network 131.2 next-hop-self neighbor 171.108.255.108.0 network 131.1.255.108.108.0/24.0.0 mask 255.1.255.255.0 255.255.255.255.255.2 remote-as 100 neighbor 171.0 network 131.255. 151.13.108.108.255 area 0 ! router bgp 100 no synchronization network 131.255.0 mask 255.CCNP Practical Studies: Routing ! interface Ethernet0/0 ip address 131. .0 network 131.108.0 network 131.0 mask 255.12.0 neighbor 131.2 remote-as 200 neighbor 171.0 mask 255.255.15.255.108.108.10.0 network 131.1.255.0.1.0 mask 255.255.255.255.0 network 131.0.255.255.0 network 131.0 mask 255.4. The shaded portions call your attention to critical commands required for full IP connectivity.255.0 mask 255.276 - .108.255.0 mask 255.255.108.7.108.0 network 131.16.8.0.2.0 mask 255.255.252 ! clockrate 128000 ! router ospf 1 redistribute connected metric 100 subnets redistribute bgp 100 metric 100 subnets network 0.0 network 131.255.108.108.6.0 mask 255.255.0 mask 255.108.108.1.0 Null0 ! line con 0 line aux 0 line vty 0 4 end Example 7-69 displays the full working configuration on R2.108.0.0 mask 255.108.255.108.255.108.255.255.0 network 131.255.3.255.0 network 131.0 0.0 mask 255.

255 area 0 ! router bgp 100 no synchronization network 131.1.108. R3 is running only OSPF.1.108.0 Null0 line con 0 line aux 0 line vty 0 4 ! end Example 7-70 displays the full working configuration on R3.1.0 redistribute ospf 1 metric 100 neighbor 131.255.0.0.6 next-hop-self neighbor 171.255.0.255.1.255.0 mask 255.1.1.255.0.255.0 ! Places all interfaces in OSPPD area 0 router ospf 1 network 0. The shaded portions call your attention to critical commands required for full IP connectivity.108.3 255.255.2 255.1.255.0.0. Example 7-70 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.277 - .252 clockrate 128000 ! router ospf 1 redistribute connected metric 100 subnets redistribute bgp 100 metric 100 subnets network 0.255.108.1 remote-as 100 neighbor 171.6 default-originate ! ip classless ip route 0.1.255 area 0 ! line con 0 line aux 0 line vty 0 4 end .0 255.108.0 0.0.108.0 255.0 ! interface Serial1/0 ip address 171.5 255.CCNP Practical Studies: Routing Example 7-69 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.108.255.255.255.0.108.6 remote-as 300 neighbor 171.

255.278 - .255.0 ! interface Serial0 ip address 171.0 neighbor 171.108.1.1 255.254.1.255.108.255.255 route-map changeattributes permit 10 match ip address 1 .108.6 255.255.0 0.1.1.2 255.255. The shaded portions call your attention to critical commands required for full IP connectivity.0/0 ! line con 0 line aux 0 line vty 0 4 end Example 7-72 displays the full working configuration on R5.255.CCNP Practical Studies: Routing Example 7-71 displays the full working configuration on R4.1.254.108.0 mask 255. The shaded portions call your attention to critical commands required for full IP connectivity. Example 7-72 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 151.1 remote-as 100 neighbor 171.1. Example 7-71 R4's Full Working Configuration R4 hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! cns event-service server ! interface Loopback0 ip address 131.0.108.108.108.0 ! interface Serial0 ip address 171.0.255.252 router bgp 300 network 141.1.108.4 255.0.108.0 mask 255.1 255.252 ! router bgp 200 network 151.255.255 no ip directed-broadcast ! interface Ethernet0 ip address 141.1.255.1.1 route-map changeattributes in no auto-summary ! ip classless !This ACL permits all even networks access-list 1 permit 131.108.5 remote-as 100 neighbor 171.255.108.108.5 prefix-list default in ip prefix-list default seq 5 permit 0.0 neighbor 171.255.0.1.255.255.

108." 1: 2: 3: 4: What does a route reflector do to nonclient IBGP peer? What is a BGP cluster? How is a route reflector client configured for IBGP? Which IOS command is used to display the following output? BGP table version is 61.0/24 *> 151.5 0.0.incomplete Network *> 0. > best. which IOS command sets the weight and local preference attribute to 100. d damped.0.IGP.108.108.0. ? .0.CCNP Practical Studies: Routing set metric 100 set weight 1000 ! This statement matches all odd statements as ACL matches even networks route-map changeattributes permit 20 set metric 200 set weight 2000 ! line con 0 line aux 0 line vty 0 4 ! end Review Questions The answers to these question can be found in Appendix C.1.incomplete Network *> 141.1 0.108.1.0 Metric LocPrf Weight Path 0 100 i 0 32768 i How many TCP peers are required in a 1000 IBGP network? Provide the IOS command syntax to enable a default route to be sent to a remote peer. which show command(s) can you use. ? . i .0.1 Metric LocPrf Weight Path 200 2000 100 300 i 0 32768 i 200 2000 100 ? Using a route map. > best.254.279 - .1. What is the originating AS for the remote preferred path to the remote network 141.0/24 *> 171. local router ID is 131. Can you set the BGP attribute next-hop-self to both EBGP and IBGP peers? .2 Status codes: s suppressed.0. i . h history.EGP. e .0/24? R5#show ip bgp BGP table version is 22.IGP.0/24 5: 6: 7: 8: Next Hop 171. To display route reflector clients. local router ID is 171. d damped.1.0. * valid.108.0 *> 141.108.108.EGP.internal Origin codes: i .1. if any? View the following BGP table.0 171.108.1. h history. e .0 9: 10: Next Hop 171.108.1. "Answers to Review Questions.4 Status codes: s suppressed.108.1.internal Origin codes: i . * valid.

CCNP Practical Studies: Routing Summary After configuring many of the advanced features deployed in today's large IP environments and the Internet community. how BGP can be modified using BGP attributes. Summary of IOS BGP Commands Command router bgp number neighbor remote IP address remote-as as show ip bgp [no] synchronization show ip bgp neighbors show ip bgp summary neighbor ip-address route-reflector-client ip prefix-list name permit | deny show ip bgp route show ip bgp cidr-only show ip bgp regexp word Purpose Enables BGP routing protocol Configures a BGP TCP peer Displays a BGP table Enables or disables (no) BGP synchronization Displays status of BGP TCP peer sessions Displays status of BGP TCP peer sessions in summary format Configures a remote router as a route reflector client Configures a prefix list in global configuration mode. and you saw how to monitor BGP. Table 7-4. Displays the BGP table Displays CIDR networks (classless networks) Finds matching networks based on a regular expression . BGP is a favorite topic on many Cisco certification examinations.280 - . you can now understand and appreciate the level of complexity of BGP. and the resulting routing decisions that are made based on the configuration. Table 7-4 summarizes the BGP commands used in this chapter. You discovered how BGP is enabled efficiently in large IBGP networks. The alternative methods used to change the routing decision made by BGP were also configured.

Routing using a single routing algorithm is usually more desirable than running multiple IP and non-IP routing protocols. However. This chapter contains five practical scenarios to complete your understanding of route redistribution and optimization and ensure that you have all the practical knowledge you need for understanding routing optimization. and the packet or user data is dropped. Distribution lists require that you configure access lists to define which networks are permitted or denied. information can be controlled to ensure that the network is routing Internet Protocol (IP) as correctly and efficiently as possible. such as OSPF or RIP. Hence. or routes to null0 (routing black hole or bit bucket) to ensure that network paths to nonexisting destinations are dropped. Route Redistribution and Optimization This chapter covers the issues and challenges facing networks when information from one routing algorithm is redistributed into another. The CCNP Routing exam devotes approximately 25 percent of its test questions to route optimization. with today's changing networks. you can also use static routes. as you discover in this chapter. default routes. Controlling Routing Updates By now. more than one IP routing protocol is often in use. for example. A routing loop is a path to a remote network that alternates between two routers. Routing with one particular algorithm is difficult enough. resulting in the loss of network connectivity. and acquisitions. Route maps— Route maps can also be used to define which networks are permitted or denied. mergers. . Cisco IOS Software allows the following methods to control route filtering: • • • Passive interfaces— A passive interface is a Cisco interface configured for routing. you must always be mindful of possible routing loops. you must convert the metric from hop count (RIP) to OSPF cost. policy routing. Route maps can also be used along with access lists to define which networks are permitted or denied when applying match statements under any route map configuration options.CCNP Practical Studies: Routing Chapter 8. Every routing protocol in use today can support redistribution. This is the only form of automatic redistribution that the Cisco IOS Software performs. especially from a configuration and troubleshooting perspective. Along with passive interfaces and filtering. is redistributed into Internet Gateway Routing Protocol (IGRP). In such a situation. when you perform any redistribution you must convert the metric. Because protocols. NOTE The Cisco IOS Software automatically redistributes between IGRP and Extended Internet Gateway Routing Protocol (EIGRP) when the same autonomous system (AS) is defined. You can use several methods to control information sent from one protocol to another to ensure that you avoid a routing loop.281 - . Distribution lists— Distribution lists define which networks are permitted or denied when receiving or sending routing updates. the time to live present in every IP packet expires. when redistributing from RIP to OSPF. but it does not send any routing information on the outbound interface. department politics. each of which assumes the path is reachable through the other. All other methods must be manually configured. and managing and controlling many different routing algorithms that might be used in a network is a considerable challenge. have defined metrics. you have discovered that minimizing routing table size and simplifying how routers choose the next hop destination path are critical for a well-tuned IP network. Redistribution Defined Redistribution is defined as the exchange of routing updates from one routing protocol to another. Routing information (if any exists) is still received and processed normally. A thorough knowledge of how routing information can be shared across different routing domains not only aids you on the CCNP Routing exam but also in the more difficult scenarios you might experience in real-life networks. When routing information from one routing protocol. such as Open shortest Path First (OSPF). For example.

Political reasons within an organization or department can impact routing algorithm decisions. Table 8-1. An organization might be transitioning from one protocol to another. Instead of reconfiguring potentially thousands of routers. to be configured on the edge of the network. nor do they send updates with the subnet mask. Redistributing from Classless to Classful Protocols Any form of redistribution from classless or classful IP routing protocols must be carefully configured. There are two primary concerns when redistributing from one protocol to another: • • Metric conversion Administrative distances You have seen already in this guide the various metrics used by OSPF or RIP. it is easier to configure redistribution on one router and allow immediate communication. Here are some reasons why a network administrator might configure more than one routing algorithm: • • • • An organization might have purchased another company that runs another routing protocol. RIP is fine for a LAN-based network. for example. consider the simple design rules when configuring between classless protocols and classful protocols. payroll might have specific needs or an engineer might prefer a different routing algorithm to ensure that only certain networks are propagated between each other. you must be careful when changing administrative distances. Some business units within an organization might have host-based routing and require RIP. The number of reasons is countless.282 - . Examples of classful protocols are IGRP and RIP. Classless protocols understand VLSM and examples include IS-IS. from legacy RIP to OSPF. For example. hence. OSPF. To understand. . for example.CCNP Practical Studies: Routing The reasons that multiple IP routing protocols might be configured in any one network are numerous. Cisco IOS routers always choose administrative distance over any metric. What is definite is that you need to understand redistribution and how it is configured and controlled on Cisco IOS-based routers. TIP Classful protocols do not understand variable-length subnet masks (VLSM). for example. Cisco Default Administrative Distances Default Administrative Distances Route Source Connected interface Static route Enhanced IGRP summary route External BGP Internal Enhanced IGRP IGRP OSPF IS-IS RIP EGP External Enhanced IGRP Internal BGP Unknown Default Distance 0 1 5 20 90 100 110 115 120 140 170 200 255 Table 8-1 shows that a Cisco router always prefers an EIGRP route (AD is 100) over an OSPF (AD is 110) or RIP (AD is 120). and BGP. Table 8-1 displays the administrative distances Cisco routers use by default.

0. R1 Is Redistributing OSPF Routes to RIP (to R2) Figure 8-1 displays R1 configured for redistribution to R2.283 - . The 141.1. Figure 8-1.255.2.0. Cisco IOS Command Syntax for Redistribution To configure redistribution among routing protocols.0. the subnetted routes on R1 are not passed to R2. or C network.0). is running RIP and has two local interfaces configured in the Class B network with Class C routers: 131.0/24. In other words.0. Consider the example in Figure 8-1.0. .0/24 and 131.108.0).0 have a 24-bit subnet mask because of the local attached interfaces. assumes the subnet mask is at the bit boundary: 8 bits for Class A (255. and 24 bits for Class C (255.255. R1 has a number of local interfaces subnetted using the Class B network 131. 16 bits for Class B (255.108. the following rules apply: • • The router configured as a classless router has one or more interfaces attached to a major network. B. Hence. on the other hand.CCNP Practical Studies: Routing For every router configured in a classful network.1/8 configured locally and assumes the same Class A mask on any networks received on any given interface. this chapter covers the Cisco IOS command required for enabling redistribution.1.0). and hence. To solve this problem and others you encounter. The router does not have any interfaces attached to the major network being advertised. R2. the following command is used under the routing process configuration: redistribute protocol [process-id] {level-1 | level-1-2 | level-2} [as-number] [metric metric-value] [metric-type type-value] [match {internal | external 1 | external 2}] [tag tag-value] [route-map map-tag] [weight number-value] [subnets] The redistribution command syntax is further explained in Table 8-2.1. such as a Class A.108. 141.0.108.0. R2 assumes the entire Class B network.0 network on R1 is advertised to R2 as a Class B network. the local router might have the Class A network 9.0.255. The RIP process on R2 assumes all networks in the Class B network 131.108. is reachable through R1 for networks not locally connected.0.108. For example.

It can be one of two values: 1—Type 1 external route 2—Type 2 external route If a metric-type is not specified. no routes are imported. For routing protocols. external 2— Routes that are external to the autonomous system. which is a 16-bit decimal number. such as OSPF and IS-IS. the remote AS number is used for routes from Border Gateway Protocol (BGP) and Exterior Gateway Protocol (EGP). or rip. AS number for the redistributed route. Specifies that for IS-IS. For the ospf keyword. isis. An integer from 0 to 65. this is an appropriate OSPF process ID from which routes are to be redistributed. but are imported into OSPF as Type 2 external routes. If this keyword is specified. Specifies that for IS-IS. level 1 routes are redistributed into other IP routing protocols independently. the default metric value is 0. static [ip]. ospf. The optional ip keyword is used when redistributing into the Intermediate System-to-Intermediate System (IS-IS) protocol.(Optional) Network weight when redistributing into BGP. For IS-IS. this is an autonomous system number. Use a value consistent with the destination protocol. route-map (Optional) Allows you to indicate a route map that should be interrogated to filter the importation of routes from this source routing protocol to the current routing protocol. connected. The static [ip] keyword is used to redistribute IP static routes. or igrp keyword. If not specified. the external link type associated with the default route advertised into the OSPF routing domain. This is not used by OSPF itself. and no value is specified using the default-metric command. (Optional) For OSPF. It can be one of the following keywords: bgp.535. but no route map tags are listed. the Cisco IOS software adopts a Type 2 external route. Command Syntax for Redistribution Syntax Protocol Description Source protocol from which routes are being redistributed. match {internal | (Optional) For the criteria by which OSPF routes are redistributed into other routing domains. external 1— Routes that are external to the autonomous system. zero (0) is used. If a value is not specified for this option. (Optional) Identifier of a configured route map.CCNP Practical Studies: Routing Table 8-2. these routes are redistributed as external to the autonomous system (AS). It can be one of the following: external 1 | external 2} internal— Routes that are internal to a specific autonomous system. If none is specified. level 2 routes are redistributed into other IP routing protocols independently. (Optional) For the bgp.284 - . tag tag-value process-id level-1 level-1-2 level-2 as-number metric metricvalue metric-type type-value . (Optional) Metric used for the redistributed route. both level 1 and level 2 routes are redistributed into other IP routing protocols. It can be used to communicate information between autonomous system boundary routers (ASBRs). all routes are redistributed. map-tag weight number. egp. but are imported into OSPF as Type 1 external routes. for other protocols. (Optional) 32-bit decimal value attached to each external route. mobile. Specifies that for IS-IS. The connected keyword refers to routes that are established automatically by virtue of having enabled IP on an interface. egp. igrp. it can be one of two values: internal— IS-IS metric that is < 63 external— IS-IS metric that is > 64 < 128 The default is internal.

285 - . You have already encountered some redistribution in previous scenarios. Start by configuring the edge devices for IGRP on R3 and RIP on R2.0 subnetted with a Class C mask. Command Syntax for Redistribution Syntax value subnets Description (Optional) For redistributing routes into OSPF. There is no one right way to accomplish many of the tasks presented. Example 8-1 displays the IP address configuration on R1 and the enabling of IGRP in AS 100. Figure 8-2.0. and the following five scenarios are designed to enhance your knowledge of why. The five scenarios presented in this chapter are based on complex redistribution technologies so that you become fully aware of the powerful nature of redistribution in large IP networks. Router R1 is running both RIP and IGRP.0/24 network configured locally on the Ethernet interface. RIP/IGRP Redistribution Figure 8-2 displays a simple scenario with the Class A network 9. and the abilities to use good practice and define your end goal are important in any real-life design or solution. when.CCNP Practical Studies: Routing Table 8-2.0. you configure three routers running RIP and IGRP. Routing redistribution is best described by examples. . Scenario 8-1: Redistributing Between RIP and IGRP In this scenario. Scenarios The following scenarios are designed to draw together some of the content described in this chapter and some of the content you have seen in your own networks or practice labs. and you configure it for redistribution. the scope of redistribution for the specified protocol. and how to successfully and efficiently redistribute routing protocols. so the five practical scenarios in this chapter concentrate on how redistribution is configured on Cisco IOS routers. Notice that R2 has the Class 10.1. Figure 8-2 displays the three-router topology with the Router R1 running RIP and IGRP.1.

0.0 R1(config-if)#interface S1/1 R1(config-if)#ip address 9.1.0. the network command used is network 9.255.1 255. R2 is configured for RIP and IGRP. Example 8-4 configures passive interfaces to ensure that only RIP updates are sent to R2 and IGRP updates are sent to R3. and you must ensure the metrics are converted from RIP (hop count) to IGRP (composite metric). when defining networks under the RIP process. and hence.0.2 255.0 R2(config-router)#network 10. .0 because IGRP is classful and automatically summarizes at the Class A network boundary.0.0 R1(config-if)#exit R1(config)#router rip R1(config-router)#network 9. you need to identify only the major network boundary.1.0 R1(config-router)#exit R1(config)#router igrp 10 R1(config-router)#network 9.1. Therefore.0. Example 8-4 Passive Interfaces on R1 R1(config)#router rip !Ensure RIP updates are not sent to R3 R1(config-router)#passive-interface s1/1 R1(config-router)#router igrp 10 !Ensure IGRP updates are not sent to R2 R1(config-router)#passive-interface s1/0 Example 8-5 displays the IP routing table on R1.0 R1 is configured locally for the Class A subnet network 9.0.255.0.0 R2 is running another classful IP routing protocol: RIP. when enabling IGRP in AS 10. which is running only IGRP. which is running only IGRP.1.0 R2(config-if)#interface serial 1/0 R2(config-if)#ip address 9.255.0.0.0.255. and ensure IGRP updates are not sent to R2.1.2.0 R2(config)#router rip R2(config-router)#network 9.255.0.0.0.1 255.0.255.0 R3(config-if)#interface serial0 R3(config-if)#ip address 9.0 and 10.0.0 for both RIP and IGRP.0.255. Therefore.255.0.1. in this case 9. on R3.0.0 R3(config-if)#exit R3(config)#router igrp 10 R3(config-router)#network 9. Example 8-2 IP Address Configuration and Enabling RIP R2(config)#interface ethernet 0/0 R2(config-if)#ip address 10.1.1. Example 8-2 configures R2 for IP addressing and enables RIP. Example 8-3 displays the IP address configuration on R1 along with enabling IGRP and RIP.2.0.CCNP Practical Studies: Routing Example 8-1 IP Address Configuration and Enabling IGRP on R3 R3(config)#interface ethernet 0 R3(config-if)#ip address 9.0 Notice. requires redistribution. Example 8-3 Enable IP and RIP/IGRP on R1 R1(config)#interface S1/0 R1(config-if)#ip address 9.3. you must ensure that RIP updates are not sent to R3.2 255.255.255. No redistribution is configured at this time.255.255.2 255.1 255.1.286 - .

0 network.0.1.0.0/24 is subnetted.1. you must perform the following tasks on R1: Step 1.2. Serial1/0 R 9.0.1. Example 8-7 Redistributing IGRP into RIP on R1 R1(config)#router rip R1(config-router)#redistribute igrp 10 metric 1 At this stage.1.0/8 [120/1] via 9.1. notice that R1 assumes that the entire Class A network 10.0. Specify the metric to be assigned to any redistributed routes.0.0/24 is subnetted.2. You set the metric for redistributing IGRP to RIP to a hop count of 1.287 - .1. R1 has full IP connectivity to R2 and R3.1. 00:00:27.3. The ? tool is used to displays IGRP metrics.0 [120/1] via 9. Serial1/1 I 9. the IP routing table on R1 displays network connectivity to R2 and R3. To configure redistribution.0. Example 8-6 displays the IP routing table on R2. Example 8-8 displays redistribution from RIP to IGRP.0 is directly connected. Typically. Also. 1 subnets C 10.2.0 [100/80225] via 9. you haven't configured redistribution from RIP into IGRP so that R3 has full connectivity to R2.CCNP Practical Studies: Routing Example 8-5 IP Routing Table on R1 R1#show ip route 9.1.0.1.1.3.0/24 is subnetted.1. Serial1/1 R 10.1. Use the redistribute command on R1 to specify the routes to be redistributed.2.0. Serial1/0 Currently.2. Step 2.1. 00:00:15. in 10 microsecond units R1(config-router)#redistribute rip metric 128 20000 ? <0-255> IGRP reliability metric where 255 is 100% reliable R1(config-router)#redistribute rip metric 128 20000 255 ? <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded R1(config-router)#redistribute rip metric 128 20000 255 1 ? <1-4294967295> IGRP MTU of the path R1(config-router)#redistribute rip metric 128 20000 255 1 1500 . the metrics used match those on the link from R1 to R2 (using the show interfaces serial 1/0 command and using the values output from this display).1. Ethernet0/0 The routing table on R2 in Example 8-6 displays no network connectivity to the LAN segment 9. Example 8-8 Redistribution from RIP to IGRP on R1 R1(config)#router igrp 10 R1(config-router)#redistribute rip ? metric Metric for redistributed routes route-map Route map reference <cr> R1(config-router)#redistribute rip metric ? <1-4294967295> Bandwidth metric in Kbits per second R1(config-router)#redistribute rip metric 128 ? <0-4294967295> IGRP delay metric.0. Example 8-7 displays the redistribution command on R1. Example 8-6 show ip route on R2 R2#show ip route 9.1.0 is directly connected. 2 subnets C 9. Serial1/0 C 9.0.0. 00:00:31.0 is directly connected.0.0/24 because you have yet to configure redistribution on R1.1. 3 subnets C 9.0/8 is reachable through R2 because R1 does not have any locally connected routes in the 10.0 is directly connected. Serial1/0 10.

0.0 [100/84000] via 9. round-trip min/avg/max = 28/29/32 ms Example 8-9 displays the remote network 9. Example 8-12 displays the IP routing table on R1 after an IGRP update is sent from R3 to R1.3. Serial1/1 .0/24 is subnetted.0. R1 had seen the 10.0. you configure a new subnet on R3 to make the networks a little more complex.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Ethernet0 I 10.255.1.2.0.1.0.0/24 is subnetted.0/8 [100/80625] via 9.0. Serial1/1 I 10. Example 8-9 IP Routing Table and Ping Request to 9. Serial0 C 9.2. 3 subnets C 9.288 - . 00:00:58.1. 3 subnets I 9. and enable IGRP on R3 to advertise the 10. and the metric is 1.2. A ping to the remote address 10.3. Serial1/0 R 9.1.1.1.0 [120/1] via 9.1. 100-byte ICMP Echos to 9.2.0.1.1/24 on R3 is successful because the remote network 10.1.1.1.1. Next.1.3. 100-byte ICMP Echos to 10.1.3. 00:00:23.1/24 on R3 is successful. Serial1/0 C 9.0 R3(config-if)#router igrp 10 R3(config-router)#network 10.1.2.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0 reachable through the next hop address 9.1 255.0.3.1 Type escape sequence to abort. 00:00:09.1/24 on R2 R2#show ip route 9.1.2.0/8 is reachable through the next hop address 9. Remember from Example 8-5. Serial0 C 9.0. Example 8-11 displays the loopback creation on R3 and the enabling of IGRP to advertise the loopback under IGRP.1.1.2.0.0/24 is subnetted.0.0.1 or through R1. 00:00:23.1.0.1.2. Sending 5.1. Serial0 R3#ping 10.1.0 network to R1.2.0/8 [100/102000] via 9. Ethernet0/0 R2#ping 9. as well as a ping request and reply to the remote network 9.0 is directly connected. round-trip min/avg/max = 28/29/32 ms A ping to the remote address 10.CCNP Practical Studies: Routing Examine the IP routing tables on R2 and R3 to ensure IP connectivity by pinging the remote network 9.1.1.3. Serial1/0 R 9. Example 8-10 displays the IP routing table on R3.1. Configure the address 10. 00:00:09.1.1 as displayed in Example 8-9.0. 00:00:58.3.1.0/8 network advertised through RIP with an AD of 120 through R2 (RIP).0 is directly connected.1/24.0.1.0.3.0 is directly connected.1.1.0 is directly connected.1.0.0 network.0 R3 does not advertise the 10.0 [120/1] via 9. as defined by the redistribution command in Example 8-7.1 as a loopback interface on R3 using a 24-bit subnet mask.1.1.0 [100/80225] via 9.1.1.0.2.0.1.1.1.3. Sending 5.1. Example 8-11 Loopback Creation on R3 R3(config-if)#interface loopback 0 R3(config-if)#ip address 10.1.2.0 is directly connected. Example 8-12 show ip route on R1 R1#show ip route 9. Serial1/1 I 9.0 is directly connected.255.0. 1 subnets C 10.1.0/24 is subnetted. Serial1/0 10.1 Type escape sequence to abort. Example 8-10 IP Routing Table and Ping Request on R3 R3#show ip route 9.2.1.1.1.0.0. 3 subnets C 9.1.1.

0 C 9.0.0.0/24 C 9. R1 does not accept the 10.0 network through R3.1.0.2.1.0.CCNP Practical Studies: Routing R1 changes the path to 10.2. Example 8-13 Ping Request on R1 R1#ping 10.0. 3 subnets is directly connected.0. NOTE Another method to overcome network connectivity problems is to configure static routes on R1 or enable an interface in the 10. Example 8-14 Distribution List on R1 R1(config)#router igrp 10 R1(config-router)#distribute-list 1 in R1(config-router)#exit R1(config)#access-list 1 deny 10. Example 8-15 confirms the installation on the RIP-discovered route through R2. Example 8-13 displays a ping request to the IP address 10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24.. R1 has lost connectivity to the 10. as displayed in Example 8-14.0.1 (R3's loopback interface). Serial1/0 Any form of redistribution requires careful filtering. There are a number of different solutions to this.2.0 R1(config)#access-list 1 permit any The distribute-list command. Of course.0 through R3 because the AD of IGRP is 100. Serial1/1 [100/80225] via 9.1.1.3. compared to RIP. Serial1/1 [120/1] via 9. round-trip min/avg/max = 12/14/16 ms All packets are sent to R3 because the IP routing table selects IGRP as the preferred path to all networks in the Class A range 10.0.1. R1 sends all traffic for the 10. when configured on R1.1.0 network. configure a static route on R1 with a more specific destination pointing to R3. At this point..1. Example 8-15 show ip route on R1 R1#sh ip route 9.2.1.1.1 Type escape sequence to abort. In effect.1.0..0 Serial1/1 . but in this case. Success rate is 0 percent (0/5) R1#ping 10. Example 8-16 displays the static route configuration on R1.2.1. when 10.0 networks configured on R2 and R3.289 - .1 (R3's Ethernet interface) and 10.0 is advertised by R3 to R1. Therefore.0.1.0 range because the only trusted information for this Class A network is from the RIP domain. Sending 5. does not permit the 10.0. Serial1/0 is directly connected.1.1.0 255. and accepts all other networks.0.1.255.2.0 range. configure R1 to reject any networks in the 10.0. 00:00:07.0/24 range on R1. Example 8-14 configures a distribution list on R1.0. Example 8-16 Static IP Route on R1 R1(config)#ip route 10.2.1. which is 120.2.0.1. Sending 5. this is not the desired solution because you have 10.0 R 10.0.0.0.0 network.0 I 9. 100-byte ICMP Echos to 10.2..1.0.0.0.1 Type escape sequence to abort.0.0.0.0/8 is subnetted. 100-byte ICMP Echos to 10. timeout is 2 seconds: . 00:00:07.255.0.1.1.0.0. To solve this problem. rejects all networks in the 10.

because the AD of static routes is 1 and is lower then RIP at 120. Example 8-18 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Serial1/0 ip address 9.0 ! router igrp 10 redistribute rip metric 128 20000 255 1 1500 passive-interface Serial1/0 network 9. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). send traffic for the more specific route through Serial 1/1 for hosts in the range 10.1–254/24.0.255.1 Type escape sequence to abort.0 distribute-list 1 in ip route 10.1.2.1. Sending 5. 00:00:54.0.1.1.1.0.0 access-list 1 permit any . Example 8-18 displays R1's full working configuration.0 is directly connected.1.0.1.1. you can determine that with even a few networks. In the scenarios that follow.255.0 is directly connected.2. redistribution causes routers to misinterpret information based on network configuration and classful behavior of routing protocols.1.2.2.0.255.CCNP Practical Studies: Routing Cisco IOS routers.2.0.0.0 [100/80225] via 9. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0 clockrate 128000 ! router rip redistribute igrp 10 metric 1 passive-interface Serial1/1 network 9. such as RIP and IGRP. 2 subnets.1.1.0/8 [120/1] via 9.2.0.1 (to R3) Example 8-17 show ip route and Ping Request on R1 R1#show ip ro 9.1.1.2.1 Type escape sequence to abort. Serial1/0 C 9.1.0/24 is directly connected.2.1 (to R2) and 10. 100-byte ICMP Echos to 10.1.1.0.255.0.2.290 - .2.1.1 255.255.0.1. Sending 5. 2 masks S 10.1.1 255. Serial1/1 10. 100-byte ICMP Echos to 10. round-trip min/avg/max = 12/14/16 ms In a simple three router network.0. you apply route maps instead of distribution lists to learn to use other filtering methods.0 clockrate 128000 ! interface Serial1/1 ip address 9. 3 subnets C 9. round-trip min/avg/max = 16/16/16 ms R1#ping 10. Serial1/1 R 10.255. Example 8-17 displays the IP routing table on R1 and a successful ping request to 10.1. Serial1/0 R1#ping 10. Serial1/1 I 9.1.3.0/8 is variably subnetted.1.2.1.0/24 is subnetted.0 Serial1/1 ! access-list 1 deny 10.1. 00:00:36.0 255. You also use the passive-interface command to ensure that a network running route redistribution is configured as efficiently as possible.

255.1 255.291 - .0.255.2.1.0 network 10.0.0 network 10.0 ! no ip classless line con 0 line aux 0 line vty 0 4 ! end .0 bandwidth 125 router igrp 10 network 9.0.0 ! interface Ethernet0 ip address 9. Example 8-19 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 10.1.255.0. Example 8-20 R3's Full Working Configuration hostname R3 ! enable password cisco ! interface Loopback0 ip address 10.0 line con 0 line aux 0 line vty 0 4 end Example 8-20 displays R3's full working configuration.1.255.255.1.255.3.255.0.1.255.0.0 ! interface Serial1/0 bandwidth 128 ip address 9.0.CCNP Practical Studies: Routing line con 0 line aux 0 line vty 0 4 end Example 8-19 displays R2's full working configuration.0 ! router rip network 9.2 255.2.0.0 interface Serial0 ip address 9.1.255.1 255.255.2 255.1 255.1.

Because all RIP-enabled routers have a local interface configured using a Class C mask. and R3 to populate the IP routing tables. has been subnetted using a Class C mask throughout. The Class B network. you migrate a typical RIP network to OSPF in the core of the network and leave RIP on the edge of the network. Figure 8-3 displays the current RIP network that you migrate to OSPF. RIP Topology Loopbacks have been configured in R1. Figure 8-3. 141. The current IP routing table on R1 is displayed in Example 8-21. IP addressing and loopback address assignments have already been completed.292 - .CCNP Practical Studies: Routing Scenario 8-2: Migrating from RIP to OSPF in the Core In this scenario. network connectivity is maintained.0. on LAN-based segments.0. R2. bandwidth is not a major concern. .108. where typically.

108.108.108.0 [120/1] via 141.7.255. 26 subnets R 141.108. 00:00:13.0 [120/1] via 141.0 255.108.108.15.254. Serial1/0 R 141.254.255.0 is directly connected. Loopback3 C 141.0 .108.255.108.6.14.4. Loopback2 C 141.2.108.0 255. Serial1/0 [120/1] via 141.254. Loopback1 C 141.2.255.255. Example 8-22 displays the current working configuration on R1 running RIP as the primary routing algorithm. Serial1/0 R 141.255.108.108.108.108.0 [120/1] via 141.2. 00:00:13. Serial1/1 R 141.0 [120/1] via 141. 00:00:16.0 is directly connected.12.13.5.3.1 ! interface Loopback2 ip address 141. Serial1/0 R 141.20.108.108. Ethernet0/0 C 141.2.254.108. 00:00:12. Loopback5 C 141.108.19.0 255.108.255. Serial1/0 R 141. 00:00:17.2.255.108.0.1 ! interface Loopback3 ip address 141.0 [120/1] via 141.0 is directly connected.108. Loopback0 C 141.108.2.0/24 is subnetted.108.108. Serial1/1 R 141.108.CCNP Practical Studies: Routing Example 8-21 show ip route on R1 R3#show ip route 141.4.2.108.3.108.21. 00:00:16.22.255.0 [120/1] via 141. 00:00:12.0 is directly connected.108.1.108.2.0 [120/1] via 141.0 [120/1] via 141.0 [120/1] via 141.255.108.255.108. Serial1/0 R 141.108.2.0 [120/1] via 141.108.108. 00:00:16. Serial1/1 R 141. Example 8-22 R1's RIP Configuration hostname R1 ! enable password cisco ! ip subnet-zero ! interface Loopback0 ip address 141. 00:00:16.0 [120/1] via 141.2. Serial1/0 R 141.108.108.2.253.108.0 [120/1] via 141. Serial1/0 R 141. The main aim of converting the routing algorithm from RIP to OSPF is to enable VLSM in the WAN and summarization among routers to reduce IP routing table sizes.2.108. Serial1/0 C 141.2.0 [120/1] via 141. 00:00:15.108.1 ! interface Loopback1 ip address 141. 00:00:12.0 [120/1] via 141.9. Serial1/1 C 141.108. 00:00:11.108.1 ! interface Loopback4 ip address 141.255. 00:00:13.254. 00:00:16.108.0 is directly connected.254.0 255.2.108.8.108.255.108.0 is directly connected.108.255. Serial1/1 R 141.255. Serial1/1 R 141.0 is directly connected.1 ! interface Loopback5 255.255. Serial1/1 R 141.2.108.0 [120/1] via 141.2.2.0 [120/1] via 141.293 - .254.255. Serial1/1 Example 8-21 displays over 25 different networks. Serial1/0 R 141.16.2. Serial1/1 R 141. 00:00:17.108.0 is directly connected.2.10.255.0 is directly connected.255. Loopback4 R 141. 00:00:16.6.108.17.2. Serial1/1 C 141.108.254.254.5.254.23. 00:00:12. 00:00:12.255.0 [120/1] via 141.18.108.11.

255.255.8.108.108.108.255.1 255.0 ! interface Ethernet0/0 ip address 141.255.1 255.11.108.1 255.255.1 255.1 255.0 ! ip classless ! .1 255.255.255.255.255.2 255.0 ! interface Loopback1 ip address 141.1 255.108.255.0 ! line con 0 end Example 8-23 displays R2's current working configuration.10.255.108.108.1.0 ! interface Serial1/0 bandwidth 128 ip address 141.255.1 255.13.294 - .9.0.0 router rip network 141.254.255.255.255.CCNP Practical Studies: Routing ip address 141.255.255.0 ! interface Loopback5 ip address 141.108.1 255.0 ! interface Ethernet0/0 ip address 141.0 clockrate 128000 ! interface Serial1/1 ip address 141.255.255.14.1 255.255.255.0 ! interface Loopback6 ip address 141.255.108.0 ! interface Loopback2 ip address 141.255.2 255.15. Example 8-23 R2's RIP Configuration hostname R2 ! enable password cisco interface Loopback0 ip address 141.0.0 ! interface Loopback4 ip address 141.0 clockrate 128000 ! router rip network 141.0 interface Serial1/0 ip address 141.12.255.255.255.108.7.253.108.255.1 255.108.108.1 255.0 ! interface Serial1/1 ip address 141.108.108.108.255.255.255.0 ! interface Loopback3 ip address 141.

0 ! interface Loopback5 ip address 141.2 255.1 255.108.0 bandwidth 125 ! interface Serial1 ip address 141. .108.108.255.20.0 ! interface Serial0 ip address 141.255.255.22.253.0 ! interface Loopback1 ip address 141.1 255.108.295 - .255.254.255.255.255.1 255.CCNP Practical Studies: Routing end Example 8-24 displays R3's current working configuration.1 255.0 ! interface Ethernet0 ip address 141.255.255.108.255.1 255.0 ! interface Loopback3 ip address 141.108.17.18.255. Example 8-24 R3's RIP Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 141.255. Example 8-25 configures R1 for OSPF across the WAN to R1 and R2.255.16.255.108.255.108.255.21.0.108.19.0 ! interface Loopback2 ip address 141.0 ! end To start.108.0 bandwidth 125 clockrate 125000 ! router rip network 141.1 255.23.108.255. add OSPF to the center of the network. Maintain the Class C mask for now to make redistribution relativity easy to configure. You take the same configuration steps on R2 and R3.1 255. and place all the WAN interfaces in area 0.0 ! interface Loopback4 ip address 141. This step is common when migrating from one protocol to another.0 ! interface Loopback6 ip address 141.1 255.1 255.255.255.255.

6.0 is directly connected. Example 8-26 show ip route on R1 R1#show ip route 141.CCNP Practical Studies: Routing Example 8-25 OSPF Configuration on R1 R1(config)#router ospf1 R1(config-router)#network 141. Serial1/1 C 141.108. 10 subnets O 141.255.108. Loopback3 C 141.254.0 [110/1562] via 141.0.7.108.0 0.108.255 R1(config)#access-list 1 permit any .255 area 0 R1(config-router)#router rip R1(config-router)#passive-interface serial 1/0 R1(config-router)#passive-interface serial 1/1 R1 is configured not to send any RIP updates to Serial 1/0 (to R2) and Serial 1/1 (to R3).108. which.108.0.3.0 is directly connected. Next. you have not configured any redistribution. Loopback4 The only visible route on R1 is the locally connected routes and the WAN circuit between R2 and R3. Loopback5 C 141.0 0.0 is directly connected.0.0 is directly connected.0 is directly connected.0.3.0 is directly connected.0.0/24 is subnetted.108.108. Example 8-27 also displays redistribution from OSPF to RIP to allow communication from R2/R3 Ethernet segments to R1's locally connected network.0 0.255 R1(config)#access-list 1 deny 141.108.108.2.0 0.0.108.0.255 R1(config)#access-list 1 deny 141. R2.255. The ? tool is used to display the available options.108.0 is directly connected.0.0. Example 8-27 displays the RIP to OSPF redistribution on R1.108.0 0. Loopback1 C 141.108.0. Loopback2 C 141. is advertised by only RIP.4. so there is no connectivity among the Ethernet and loopback interfaces.1.0.0.2.0 is directly connected. Ethernet0/0 C 141. 00:00:04.255.7.108.0. this configuration stops the sending of unnecessary updates across WAN links. Serial1/0 C 141.255 R1(config)#access-list 1 deny 141. at the moment.0 0.255 area 0 R1(config-router)#network 141.0.0.0 0.0 0.0.108.254. Loopback0 C 141.0.255 R1(config)#access-list 1 deny 141.5.4.253.2.0.255 R1(config)#access-list 1 deny 141.108.6. and R3 to advertise the RIP networks to the OSPF backbone. Example 8-26 confirms the status of IP connectivity after the show ip route command is entered on R1.1.0 is directly connected.296 - .108.0 0.0.108. configure redistribution on routers R1. At this stage. Serial1/0 C 141.108. Example 8-27 Redistribution on R1 R1(config)#router ospf 1 R1(config-router)#redistribute rip metric ? <0-16777214> OSPF default metric R1(config-router)#redistribute rip metric 100 subnets R1(config-router)#exit R1(config)#router rip R1(config-router)#redistribute ospf 1 metric ? <0-4294967295> Default metric R1(config-router)#redistribute ospf 1 metric 3 R1(config-router)#distribute-list 1 out R1(config-router)#exit R1(config)#access-list 1 deny 141.255 R1(config)#access-list 1 deny 141.5.108.

108.) Also.108.108. can be replaced with the configuration in Example 8-28 to deny the range of networks 141.OSPF external type 1. the metrics have been set to 100 for all RIP-to-OSPF networks.0. E2 .0.0 has been subnetted across the network. networks have some other paths or back doors between any given routing topologies. E .255. Typically.108.108. Serial1/0 C 141. Loopback2 .0.connected. The access list 1.0 is directly connected.0 is directly connected.0 is directly connected.7. Without this keyword.108.23.253.2.108. previously defined with seven statements. Example 8-27 displays the keyword subnets because the Class B network 141. Loopback3 C 141.254.0 is directly connected.255 R2(config)#access-list 1 permit any Example 8-30 displays the redistribution and filtering on R3.0 [110/1562] via 141.2.OSPF external type 2.108.1. and the hop count for all redistributed OSPF networks into RIP is set to 3.0. 00:00:51.108.0 is directly connected.108.CCNP Practical Studies: Routing R1 is now configured to redistribute from RIP to OSPF and vice versa. Ethernet0/0 C 141.5. Example 8-29 Redistribution on R2 R2(config)#router rip R2(config-router)#distribute-list 1 out R2(config-router)#redistribute ospf 1 metric 3 R2(config-router)#router ospf 1 R2(config-router)#redistribute rip metric 10 subnets R2(config)#access-list 1 deny 141.0/24 is subnetted. Example 8-28 replaces the seven-line access list with two lines of IOS configuration.108.108. 26 subnets O 141.8.EGP 141.0.0 0.0 and permit all other networks.0 is directly connected. Serial1/0 C 141.255 from being advertised from OSPF to RIP.4.0 is directly connected.255 R3(config)#access-list 1 permit any Confirm IP routing connectivity from R1. you are using classless networks on all routers.0–141.E1 . the distribution list on R1 denies any networks residing in 141. Serial1/1 C 141.108.7.108.0.108.0–141. only classful networks would not be advertised. Loopback1 C 141. Example 8-31 show ip route and Pings on R1 R1#show ip route Codes: C .255 R1(config)#access-list 1 permit any Example 8-29 displays the redistribution and filtering required on R2.) Example 8-28 Access List Configuration on R1 R1(config)#no access-list 1 R1(config)#access-list 1 deny 141. Example 8-30 Redistribution on R3 R3(config)#router rip R3(config-router)#redistribute ospf 1 metric 3 R3(config-router)#distribute-list 1 out R3(config-router)#router ospf 1 R3(config-router)#redistribute rip metric 10 subnets R3(config-router)#exit R3(config)#access-list 1 deny 141. (In this case.297 - .255.108.7.108. Example 8-31 displays the IP routing table on R1 and some sample ping requests that conform IP connectivity.0 0. Loopback0 C 141. (The no access-list 1 command removes the configuration currently present for access list 1.0.1. This ensures that a routing loop cannot occur.108. To ensure that networks residing on R1 are never advertised by the OSPF backbone.7.7.3.0 0.

23. Sending 5.0.108. 00:00:52.2.254. 00:00:52. Serial1/0 O E2 141. Serial1/0 O E2 141. Sending 5.255.0.108. 00:00:51.108. and R3.2. Loopback5 C 141.0 [110/10] via 141. Serial1/0 O E2 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0 [110/10] via 141.0.10. 00:00:51. round-trip min/avg/max = 12/14/16 ms The next step in migration is to remove RIP and enable OSPF across all interfaces in the networks. 00:00:51. Serial1/0 O E2 141.108.108.108.0 [110/10] via 141.108.0 [110/10] via 141. Before you complete this migration.0 [110/10] via 141.0 distribute-list 1 out access-list 1 deny 141.255.108.19.2.0 [110/10] via 141.9.254.0 [110/10] via 141.108.108.254. Serial1/1 R1#ping 141.1 Type escape sequence to abort. 00:00:51.108.108.2. 00:00:51.2.15. Serial1/0 O E2 141. Serial1/1 O E2 141.255.0 [110/10] via 141.8.21.108.CCNP Practical Studies: Routing C 141.108.0 0. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).20.108.17.108. 00:00:52.108.108.0 [110/10] via 141.108.254.108.108.9. Example 8-32 displays the IP routing configuration on R1.254.108.255 area 0 network 141. Serial1/1 O E2 141.2. 00:00:52.108.1 Type escape sequence to abort.2. Serial1/0 O E2 141. 00:00:52.0 [110/10] via 141.254.0. 00:00:52.6.254.254.108.0 is directly connected.108.2. Serial1/1 O E2 141.2.255.0.0.7.108.22.0 [110/10] via 141.298 - .254.0 [110/10] via 141.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.108.108. Loopback4 O E2 141.255. Example 8-32 show running-config (Truncated) on R1 router ospf 1 redistribute rip metric 100 subnets network 141.108. .0 0.108.108. round-trip min/avg/max = 16/16/16 ms R1#ping 141. R2.2. Serial1/0 O E2 141.1. 00:00:52.7.18.0 [110/10] via 141. Serial1/1 O E2 141. 100-byte ICMP Echos to 141.255.0.2.9.255 access-list 1 permit any Example 8-33 displays the IP routing configuration on R2.108.22.0 [110/10] via 141.108.108.0 [110/10] via 141.2.108.16.0 0. 00:00:51.12.22. 00:00:51.108. Serial1/1 O E2 141. look at the routing configurations on Routers R1.11.255.108.108. 00:00:52. Serial1/1 O E2 141.108.2.255. Serial1/0 O E2 141. 100-byte ICMP Echos to 141.108.108. Serial1/1 O E2 141. 00:00:52.13.2.1.255.0 [110/10] via 141.0 is directly connected.14.2.108.2.

255 area 0 network 141.299 - .255 access-list 1 permit any Figure 8-4 displays the OSPF area assignment to complete the RIP to OSPF migration.108.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial0 passive-interface Serial1 network 141.0 distribute-list 1 out ! ip classless ! access-list 1 deny 141.0.255.255 area 0 network 141.0.0 distribute-list 1 out ! access-list 1 deny 141.CCNP Practical Studies: Routing Example 8-33 show running-config (Truncated) on R2 router ospf 1 redistribute rip metric 10 subnets network 141.0.0 0.0 0.0.16.108.7.0.0.0 0.108.8.0.0 0.108.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.255 access-list 1 permit any Example 8-34 displays the IP routing configuration on R3.0.0.108.0.253.0.254. .108.0 0.253.0 0. Example 8-34 show running-config (Truncated) on R3 router ospf 1 redistribute rip metric 10 subnets network 141.108.7.108.0.

255 area 0 R1(config-router)#network 141.108.0.0.252 R2(config-if)#interface s1/1 R2(config-if)#ip address 141.7.252 Example 8-36 displays the removal of RIP on R2 and the OSPF and IP address assignment on R2.255 area 1 R1(config)#interface s1/0 R1(config-if)#ip address 141. note the new IP address assignment for the WAN links with /30 subnets.108.8.252 .2 255.255.1 255.108.0.108.108.0 0.0.108.255. Example 8-35 displays the removal of RIP on R1 and the OSPF and IP address assignment on R1.255. Example 8-35 Removal of RIP on R1 and OSPF/IP Address Assignment R1(config)#no router rip R1(config)#router ospf 1 R1(config-router)#network 141.0 0.255.0.255.255.255 area 2 R2(config-router)#exit R2(config)#interface s1/0 R2(config-if)#ip address 141.5 255.CCNP Practical Studies: Routing Figure 8-4.300 - .10 255. OSPF Area Assignments Figure 8-4 displays the OSPF area assignment along with the ability to re-address the WAN circuit to /30 subnets because OSPF understands VLSM.108.255 area 0 R2(config-router)#network 141.7.255.255.108.0 0.255.255. Also.252 R1(config-if)#interface s1/1 R1(config-if)#ip address 141.0.0 0.255. Example 8-36 Removal of RIP on R2 and OSPF/IP Address Assignment R2(config)#no router rip R2(config)#router ospf 1 R2(config-router)#network 141.255.255.0.255.

0/24 is directly connected.16.255.108.108.255 area 0 R3(config-router)#exit R3(config)#interface serial0 R3(config-if)#ip address 141.0.0 0. view the IP routing table on R1.108. Serial1/0 C 141. Loopback2 C 141. Serial1/0 O IA 141.8.0. Serial1/0 O IA 141.19.301 - .108.1/32 [110/782] via 141. 00:00:28.108.3. Serial1/1 O IA 141.108.108.0/16 is variably subnetted. 00:00:28.108.108.2.255.255.1/32 [110/782] via 141. 00:00:28.2.1/32 [110/782] via 141.0 0.OSPF.108.108.108.108.9 255.255. 00:00:28.108.108. R2.255.2.255. Serial1/1 In Example 8-32.255.1/32 [110/782] via 141.108. and R3.255. Now that OSPF is configured across all routers.108. Example 8-38 displays R1's IP routing table. Serial1/0 O IA 141.0/24 is directly connected. 3 masks O 141. 00:00:27. 00:00:28.) Example 8-39 displays the summarization for .108.108.6. Serial1/1 O IA 141.255. Example 8-38 R1's IP Routing Table R1#show ip route Codes: C .108.17.255. Serial1/0 C 141. 00:00:28.10.108.6.0/24 [110/791] via 141. Serial1/0 O IA 141.1/32 [110/782] via 141. 00:00:27. (All routers are ABRs because each router resides in areas 0.255.255.0/24 is directly connected. 1.connected. so configure each router in Figure 8-4 to summarize locally connected routes.23.255.255.108. Serial1/1 C 141.2. 00:00:27.6 255. The OSPF type route is displayed as O IA in Example 8-38.0/24 is directly connected.0/24 is directly connected.0.CCNP Practical Studies: Routing Example 8-37 displays the removal of RIP on R3 and the OSPF and IP address assignment on R3. Serial1/1 O IA 141. and R3 causes the Cisco IOS to remove any redistribution between RIP and OSPF automatically.4. 00:00:27. .0/24 [110/791] via 141.18. 26 subnets.255. Therefore.1/32 [110/782] via 141.11. Serial1/0 O IA 141.2.108.1/32 [110/782] via 141.255.1/32 [110/782] via 141. 00:00:27.252 R3(config-if)#interface serial1 R3(config-if)#ip address 141. the redistributed routes appear as E2 (External Type 2) and OSPF is configured across all three routers.1/32 [110/782] via 141. Serial1/1 O IA 141.2.8/30 [110/1562] via 141.108.22.108. Serial1/1 O IA 141.4/30 is directly connected.20.15. Ethernet0/0 C 141. 00:00:28. which are contiguous.108.108. Serial1/1 O IA 141.252 NOTE Removing RIP from Routers R1.1/32 [110/782] via 141. IA . 00:00:28.108.255. Loopback1 C 141. 00:00:28. Serial1/0 O IA 141.255 area 3 R3(config-router)#network 141.108.7.6. R2.255.5.14.1/32 [110/782] via 141.6.2.OSPF inter area 141.255.108.1/32 [110/782] via 141.1/32 [110/782] via 141.6.255.12. Loopback0 C 141. Serial1/0 O IA 141.255.108.108.0/24 is directly connected. Example 8-37 Removal of RIP on R3 and OSPF/IP Address Assignment R3(config)#router ospf 1 R3(config-router)#network 141. manual removal of redistribution is not required on Routers R1.255.108.23.255.108.108.108.0/30 is directly connected. Loopback5 C 141.2.6.2.6. 00:00:28.1.108.1/32 [110/782] via 141.108.7.108.255.108.6. 00:00:28.6. Serial1/0 O IA 141.255.2.108. Loopback4 O IA 141. 2.108.108. 00:00:27.0.13.0/24 is directly connected. OSPF can support VLSM and network summarization.255.9.108.108.108. O .21. Serial1/1 O IA 141. or 3. Loopback3 C 141.108.108.255.

0.108.302 - . Serial1/0 O IA 141.0. as displayed in Example 8-21.0. To summarize internal OSPF routes.16.255.0 Example 8-43 displays the OSPF IP routing table on R1. Example 8-40 enables the use of zero subnets on R1.15. 00:01:13.255.0–141.0–141.7.108.255. subnet zero is a perfect example.16.248.1 255.0.108. 3 masks O 141.0.255.248.B.108.0 255. Example 8-39 displays the area summary command on R1.7.108.255.0 255. (These networks reside in area 3. the network IP designer should always use all the address space available.255.108. Serial1/0 O IA 141. 255.C. when RIP was the primary routing algorithm.D IP address to match R1(config-router)#area 1 range 141.108.16. 00:04:57.0. Example 8-39 Area Summary on R1 R1(config)#router ospf 1 R1(config-router)#area 1 ? authentication Enable authentication default-cost Set the summary default-cost of a NSSA/stub area nssa Specify a NSSA area range Summarize routes matching address/mask (border routers only) stub Specify a stub area virtual-link Define a virtual link and its parameters R1(config-router)#area 1 range ? A.0 Example 8-42 displays the summarization required on R3 to encompass the networks 141. To enable subnet zero.2.0 on R1 or subnet zero.0.0 Example 8-41 displays the summarization required on R2 to encompass the networks 141.108.108. With large IP networks.108.0– 141.8/30 [110/1562] via 141.248.C.108.B.0–141.CCNP Practical Studies: Routing networks 141. Serial1/1 .23. encompasses the seven networks ranging from 141.255.2.248.) Example 8-43 show ip route ospf on R1 R1#show ip route ospf 141. Example 8-40 Subnet Zero Enabling on R1 R1(config)#ip subnet-zero R1(config-if)#interface loopback 6 R1(config-if)#ip address 141.0 The ? tool is used to display the various options. You may ask yourself why you are not using 141.0. (These networks reside in area 2.108. The mask.108. you must configure the global ip subnet-zero command on R1.255.0/16 is variably subnetted.108. The loopback addresses on R1 reside in OSPF area 1.8. (Initially.255.0 ? A.108. the area area-id range network subnet mask IOS command is required. 13 subnets.108.0. 00:04:57.255.255.8.) Example 8-41 Area Summary on R2 R2(config)#router ospf 1 R2(config-router)#area 2 range 141.D IP mask for address R1(config-router)#area 1 range 141.108.0 255.0/21 [110/782] via 141.108.108.) Example 8-42 Area Summary on R2 R3(config)#router ospf 1 R3(config-router)#area 3 range 141.0/21 [110/791] via 141.8.108.0.255. you had 17 RIP entries.108.6.

1 255.0.1 255.1 255. Example 8-44 displays R1's full working configuration.108. to classless protocols.108.255.0. Now.0 ! interface Loopback2 ip address 141.255.0 ! interface Serial1/0 ip address 141.255.108.1. such as RIP. such as OSPF.255.0 ! interface Loopback5 ip address 141.255 area 1 network 141.255.7.108.255.255.0 0.0.108.255.252 clockrate 128000 ! router ospf 1 area 1 range 141.255 area 0 ! ip classless end Example 8-45 displays R2's full working configuration.255.255. .108.255.255.255.0. The migration in this scenario demonstrates the powerful use of redistribution and what you should be aware of when configuring metrics.1 255.5.1 255.255.255.CCNP Practical Studies: Routing R1 has 3 OSPF network entries as opposed to 17 using RIP.7.108.0.108.0 ! interface Loopback6 ip address 141.255.248.303 - .0 ! interface Loopback4 ip address 141.0 ! interface Ethernet0/0 ip address 141.255.108.1 255. Before looking at another scenario.0 ! interface Loopback3 ip address 141.108.0 network 141.0 255.6.0 ! interface Loopback1 ip address 141.2.255.255.252 no ip mroute-cache no fair-queue clockrate 128000 ! interface Serial1/1 ip address 141.255.3.1 255.1 255.5 255.255.108.0 0. Example 8-44 R1's Full Working Configuration Hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.108.108. you can see why networks are converted from classful routing protocols. view the full working configurations of all three routers in Figure 8-4.4.0.255.255.255.1 255.

1 255.255.1 255.108.255.108.255.255.255.255.1 255.255.0 ! interface Loopback5 ip address 141.255.255.11.0 ! interface Loopback6 ip address 141.2 255.0 network 141.10 255.255.108.255 area 0 ! ip classless ! end Example 8-46 displays R3's full working configuration.CCNP Practical Studies: Routing Example 8-45 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 141.14.15.1 255.255.108.255.0.108.7.304 - .108.255.255.0 255.255.108.255.1 255.10.8.0 ! interface TokenRing0/0 no ip address shutdown ring-speed 16 ! interface Serial1/0 bandwidth 128 ip address 141.0 ! interface Loopback4 ip address 141.255.108.0 0.255.108.8.108.1 255.0.1 255.108.108.255.12.255.13.248.0 0.8.255.0 ! interface Loopback2 ip address 141.0 ! interface Loopback1 ip address 141. .255 area 2 network 141.255.0 ! interface Ethernet0/0 ip address 141.1 255.0.255.252 ! interface Serial1/1 ip address 141.255.9.0 ! interface Loopback3 ip address 141.252 ! router ospf 1 area 2 range 141.108.

108.255.0.0.1 255.1 255.21.1 255.255.108.108.108. The end design goal of this scenario is to ensure full IP connectivity among all interfaces.305 - .255.255. you configure a five-router topology with four different autonomous systems using two IP routing algorithms: OSPF and EIGRP.108.0 media-type 10BaseT ! interface Ethernet1 no ip address ! interface Serial0 ip address 141.108.255.17.255.108.0 255.7.108.255.22.255.255.9 255.108. .0 ! interface Loopback6 ip address 141.255.108.255 area 3 network 141.255.255.0 ! interface Loopback1 ip address 141.252 bandwidth 125 ! interface Serial1 ip address 141.255.248.18.0 ! interface Loopback5 ip address 141.0.16.23.0 ! interface Loopback2 ip address 141.1 255.255 area 0 area 3 range 141.1 255.108.255.6 255.16.255.0 ! interface Loopback4 ip address 141.255.1 255.255.CCNP Practical Studies: Routing Example 8-46 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 141.255.1 255.0 ! end Scenario 8-3: Redistributing Between EIGRP and OSPF In this scenario.255.255.255.108.0 0.0 0.255.19.252 bandwidth 125 clockrate 125000 ! router ospf 1 network 141.1 255.0 ! interface Ethernet0 ip address 141.255.20.0 ! interface Loopback3 ip address 141.108. The internetwork in Figure 8-5 has an OSPF domain and three EIGRP domains.16.255.

0.0.255. notice that a redundant path exists between R4 and R5.0.255. namely OSPF on Routers R1–R3. (Remember that OSPF has a process ID that is only locally significant.255. you can use one IOS command to place all R1's interfaces in OSPF area 0 or the backbone. the backbone. Figure 8-5 displays the OSPF area assignments required for this topology.255.0. hence.108. Example 8-47 R1's OSPF Configuration R1(config)#router ospf 1 R1(config-router)#network 0. you must carefully consider any route redistribution to avoid routing loops. OSPF and EIGRP Domains Routers R1.306 - .0.255 area 0 Routers R2 and R3 reside in OSPF and EIGRP domains. configures the IP address 141. The WAN link between R4 and R5 resides in EIGRP domain 3. Start by enabling the routing protocols in use. Also. Therefore. Figure 8-5 depicts a simple OSPF network with one area. the backbone network in OSPF.0. and R3 are configured in OSPF process 1.2 into area 0.) R4 is configured in EIGRP domain 1.CCNP Practical Studies: Routing Figure 8-5. and R5 is configured in EIGRP domain 2. . R2.2 0. 0. Example 8-48 configures R2's serial link to R1 to reside in area 0.0 255.0. All of Router R1's interfaces reside in area 0. Example 8-48 R2's OSPF Configuration R2(config)#router ospf 1 R2(config-router)#network 141.0 area 0 The inverse mask. Example 8-47 places all interfaces on R1 in area 0.108. Figure 8-5 details the IP address assignment.

0.108.0.0 R4(config-router)#network 161.13 Pri 1 1 State FULL/ FULL/ Dead Time 00:00:38 00:00:38 Address 141. Also on R4. Example 8-49 R3's OSPF Configuration R3config)#router ospf 1 R3config-router)#network 141. Example 8-52 show ip eigrp interfaces on R4 R4#show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Interface Peers Un/Reliable SRTT Se0 1 0/0 7 Et0 0 0/0 0 IP-EIGRP interfaces for process 3 Xmit Queue Mean Interface Peers Un/Reliable SRTT Se1 0 0/0 0 Pacing Time Un/Reliable 5/194 0/10 Pacing Time Un/Reliable 0/10 Multicast Flow Timer 226 0 Multicast Flow Timer 0 Pending Routes 0 0 Pending Routes 0 Example 8-52 confirms that the Ethernet interface and link to R3 reside in EIGRP 1 and the WAN link to R5 resides in EIGRP 3.0 R4(config-router)# no auto-summary R4(config-router)#! R4(config-router)#router eigrp 3 R4(config-router)# passive-interface Ethernet0 R4(config-router)# passive-interface Serial0 R4(config-router)# network 141.CCNP Practical Studies: Routing Example 8-49 configures R3's serial link to R1 to reside in area 0. Before you configure redistribution. Similarly. for interfaces in EIGRP domain 1. There is no EIGRP peer to R5 because EIGRP is not enabled on R5 yet. and no designated router (DR) or backup designated router (BDR) is selected over a point-to-point (in this case back-to-back serial connected Cisco routers).6 0.255. Example 8-50 confirms that OSPF has formed a full relationship to R2 and R3.108. configure the EIGRP domains on R4 and R5.108. Example 8-52 confirms the EIGRP interfaces in domains 1 and 3.255.307 - . Example 8-51 EIGRP Configuration on R4 R4(config)#router eigrp 1 R4(config-router)# passive-interface Serial1 R4(config-router)# network 141.255. you need to apply the passive interface command to ensure that no routing updates are sent. Example 8-51 configures R4 in EIGRP domains 1 and 3.0 area 0 R1 should now have full OSPF adjacency to R2 and R3.255.0 R4(config-router)# no auto-summary Automatic summarization is disabled on R4.100. Example 8-53 configures R5 in EIGRP 2 and EIGRP 3. in EIGRP domain 3. so you can apply some summary commands later. the WAN link to R5.255.6 Interface Serial1/0 Serial1/1 R1 is fully adjacent (Full) to R2 and R3.108. The peers on R4 confirm that EIGRP is configured on R3.0.108. Example 8-50 shows ip ospf neighbor on R1 R1#show ip ospf neighbor Neighbor ID 141.2 141.108.108. only one network resides in EIGRP 3.0.0.17 141. .

100.18. Therefore. The second summary route redistributed from domain 3 to 2 appears as an external EIGRP (D EX) route. display the IP routing tables on R2 and R3. 00:01:26.100.0. 00:01:26.308 - .0 R5(config-if)#exit R5(config)#router eigrp 3 R5(config-router)# redistribute eigrp 2 R5(config-router)#router eigrp 2 R5(config-router)# redistribute eigrp 3 To ensure IP connectivity.0.100. the core routers in the network. Redistributing from one EIGRP AS to another does not require you to define a metric because EIGRP conserves the metric.255.100. Example 8-54 configures redistribution from EIGRP domain 1 to 3 on Router R4 and also configures a summary route on R4.108. advertising the subnet 160.0. Serial1/1 R2 has the summary route from R4 appearing as an internal EIGRP route (D) because the network resides in the same AS.0 R5(config-router)# no auto-summary At this stage.108.100. 13 subnets. 2 subnets D 160.0.0/17.255.108. advertising the subnet 160.128.128. Example 8-54 Redistribution on R4 R4(config)#interface s0 R4(config-if)#ip summary-address eigrp 1 160.255. 2. you have not configured any redistribution.100. You configure route maps on R2 and R3.12/30 [170/22016000] via 141.0 [170/21049600] via 141.108.108.20/30 [90/21024000] via 141. Example 8-55 Redistribution on R5 R5(config-router)#interface Serial0 R5(config-if)# ip summary-address eigrp 2 160.255. 00:01:26. Start by configuring redistribution in the EIGRP domains 1.108. 00:01:26.0/17 is subnetted.18. you redistribute only networks using the metric from the original AS or domain.128.0.108.CCNP Practical Studies: Routing Example 8-53 EIGRP Configuration on R5 R5(config)#router eigrp 3 R5(config-router)# passive-interface Ethernet0 R5(config-router)# passive-interface Serial0 R5(config-router)# network 141. later in this chapter.0/17.128. . Example 8-56 show ip route eigrp on R2 R2#sh ip route eigrp 141. and 3.255. 2 masks D 141.255. You do have to ensure that route maps or distribution lists are used to avoid loops.18. Serial1/1 160. Serial1/1 D EX 160.0.0.108.0.0 R5(config-router)# no auto-summary R5(config-router)#! R5(config-router)#router eigrp 2 R5(config-router)# passive-interface Serial1 R5(config-router)# network 141.255.108. Serial1/1 D EX 141.18.100.0/16 is variably subnetted.0 R5(config-router)# network 160.0 [90/20537600] via 141.128.0 255.255.0 R4(config)#router eigrp 1 R4(config-router)#redistribute eigrp 3 R4(config-router)#exit R4(config)#router eigrp 3 R4(config-router)#redistribute eigrp 1 Example 8-55 configures redistribution from EIGRP domain 2 to 3 on Router R5 and also configures a summary route on R4.100. Example 8-56 displays the IP routing table (EIGRP only) on R2.0 255.

0. Example 8-57 show ip route eigrp on R3 R3#show ip route eigrp 160.108.108.0. 00:10:12.108.108. respectively.0. Serial1 D EX 141.0.0.7.255. Similarly. as shaded in Example 8-58. R3 has an internal (D 160.14.108.108.4/30 (Link R1/R3).14.3 access-list 2 deny 141.255 and also the WAN subnets 141. .255. 00:07:27.100. you must assign metrics when redistributing and ensure.108.255. Serial1 Similarly.16/30 [170/22016000] via 141.309 - .0 0.0. Because OSPF and EIGRP use different metrics for routing.108. Serial1 141. 00:06:21. Serial1 D 160.255.0) for the remote Ethernet segments on R4 and R5.20/30 [90/21504000] via 141.7.255.0.14.100.0) and external summary route (D EX 160.108. by using route maps.0.255. Example 8-58 configures R2 for redistributing OSPF routes into EIGRP and EIGRP routes into OSPF.0 0. that no redistributed information causes a routing loop.0 0.128. the route map named allowintoospf permits all networks matching access-list 2. Example 8-59 displays the OSPF to EIGRP redistribution on Router R3 with a route map configured to ensure that erroneous information is not sent from either routing domain.4 0. this prevents erroneous routing information and routing loops from occurring.108.255 access-list 2 deny 141.255.0.14.0.108.100.0/17 is subnetted.255. 2 masks D 141. R1's IP routing table does not contain the EIGRP networks because the OSPF routers R2 and R3 (ABRs and ASBRs) have yet to enable redistribution from EIGRP (composite metric) to OSPF (cost metric).0/30 (Link R1/R2) and 141.CCNP Practical Studies: Routing Example 8-57 displays the IP routing table (EIGRP) in R3.100.108.100.128.0. Example 8-58 Retribution on R2 router eigrp 2 redistribute ospf 1 metric 1500 2000 255 1 1500 route-map allowintoeigrp ! router ospf 1 redistribute eigrp 2 metric 100 subnets route-map allowintoospf ! route-map allowintoeigrp permit 10 match ip address 1 ! route-map allowintoospf permit 10 match ip address 2 ! Networks in Access list 1 reside in the EIGRP domain access-list 1 deny 160.0 [90/21017600] via 141. R2 is configured not to permit any routes from R4 advertising networks in the range 141. indicating that only networks matching access list 1 are allowed into OSPF.108.255 access-list 1 permit any ! Networks in Access-list 2 reside in the OSPF domain access-list 2 deny 141.255. 00:10:12.255. 13 subnets.0–141. 2 subnets D EX 160.108.255.0.3 access-list 2 permit any R2 is configured to redistribute OSPF networks with a route map named allowintoeigrp.0.0 [170/21529600] via 141.0/16 is variably subnetted.100. when redistributing EIGRP networks into OSPF.

0. In other words.1.0.100.1/25 and 150.100. Example 8-60 displays the IP routing table (OSPF routes only) on R1 and some sample pings to the remote EIGRP networks 160.0 [110/100] via 141.108.0 0.0/17 is subnetted.100.255.1.0/16 is variably subnetted.255.3 access-list 2 permit any route-map allowintoeigrp permit 10 match ip address 1 ! route-map allowintoospf permit 10 match ip address 2 NOTE If the WAN link between R4 and R5 goes down. 100-byte ICMP Echos to 160.0.1.0. R4 won't be able to get to the networks connected to R5 because the 160. A common technique to ensure network connectivity is to ping IP interfaces.100.7. 01:16:02. 01:16:11.16/30 [110/100] via 141.255. round-trip min/avg/max = 28/30/32 ms R1#ping 160.128. For the purposes of this exercise.108.108. 2 masks O E2 141.255 access-list 2 deny 141.0 0. you can add the network 160.1.255.255.3 access-list 2 deny 141.0.CCNP Practical Studies: Routing Example 8-59 Redistribution on R3 router eigrp 1 redistribute ospf 1 metric 1500 20000 255 1 1500 route-map allowintoeigrp ! router ospf 1 redistribute eigrp 1 metric 100 subnets route-map allowintoospf ! Networks in Access list 1 reside in the EIGRP domain access-list 1 deny 160.100.0.108.108.108.12/30 [110/100] via 141.108.255. .255 access-list 1 permit any ! Networks in Access-list 2 reside in the OSPF domain access-list 2 deny 141. examine some IP routing tables starting from the core router R1 in OSPF area 0. To fix this.20/30 [110/100] via 141.108.100.1 Type escape sequence to abort. Serial1/1 O E2 141.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).100. assume the back-to-back serial connections between R4 and R5 never fail. Example 8-60 show ip route ospf and Pings on R1 R1#show ip route ospf 141.6. Sending 5.100.1. 01:16:02.0. round-trip min/avg/max = 28/31/32 ms R1# Example 8-61 displays the IP routing table on R4.1.255.0. EIGRP domain 3 is isolated. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Serial1/1 O E2 141.129/25.100. Serial1/1 R1#ping 160.6.0 network is denied from being redistributed into EIGRP from OSPF.108.255.100. 01:16:02.4 0.255. Serial1/0 O E2 160. 2 subnets O E2 160.0 as part of the access list. Now that redistribution is completed and filtered on core routers. or the backbone.108. 13 subnets. 01:16:02.0.6.6.310 - .0.128.0.2. Serial1/1 160.255.100.100.108. Sending 5.0. 100-byte ICMP Echos to 160.0 [110/100] via 141.0.108.128.255.0 0.

255.108.1.100.108.4.6.CCNP Practical Studies: Routing Example 8-61 show ip route on R4 R4#show ip route C D C D D D D D D D D D D 141. round-trip min/avg/max R4#ping 141.2.100.0.108.1 Type escape sequence to abort.108.108. timeout is !!!!! Success rate is 100 percent (5/5). Serial1 160.108.0/30 [170/22016000] via 141.4.311 - . 01:42:25.0 is directly connected.255.0/24 [170/22016000] via 141.1.22.108.1 Type escape sequence to abort.108.108.108. 01:21:46.2. 100-byte ICMP Echos to 141.0/24 [170/22016000] via 141. Sending 5. Example 8-62 Pinging Loopbacks from R4 R4#ping 141.22.108.108.128.108.108.20/30 is directly connected.0.255. 01:42:51. Sending 5.108. round-trip min/avg/max R4#ping 141.22. Serial1 141.5.1 2 seconds: = 36/37/44 ms 2 seconds: = 36/37/40 ms 2 seconds: = 36/36/40 ms 2 seconds: = 36/37/40 ms 2 seconds: = 36/38/40 ms 2 seconds: = 36/50/100 ms . 13 subnets.255.108. 01:21:46.7.5.108.255. round-trip min/avg/max R4#ping 141. Serial0 141. and notice that the shaded routes in Example 8-61 encompass all the routes from 141. Serial1 141. 01:21:46.0/16 is variably subnetted.1.108.108.6. Serial1 141.255.108.255.255.108. 01:21:46.108. Serial1 141.3. 01:42:27. 100-byte ICMP Echos to 141. Serial1 141.108. Sending 5. 01:21:46.108. Serial1 141.108.0/24 [170/22016000] via 141.255.108. Serial1 141.108.3.0/24 [170/22016000] via 141.108.255. round-trip min/avg/max R4#ping 141.1.255. (These routes are the loopback interfaces on R1.108.108.108.108. 100-byte ICMP Echos to 141.108.255.108.255. 100-byte ICMP Echos to 141.108.108. Sending 5.13. timeout is !!!!! Success rate is 100 percent (5/5).255.4/30 [90/21504000] via 141. timeout is !!!!! Success rate is 100 percent (5/5). timeout is !!!!! Success rate is 100 percent (5/5).255.1 Type escape sequence to abort.0/24 [170/22016000] via 141.2.108. Serial1 141. Sending 5. round-trip min/avg/max R4#ping 141. 01:21:46.1.1 Type escape sequence to abort.108.16/30 [90/21504000] via 141.5.) Example 8-62 displays a successful ping from R4 to all the remote loopbacks on R1 to ensure that you have network connectivity from the EIGRP domain.0.0/24 [170/22016000] via 141.100. round-trip min/avg/max R4#ping 141.1 Type escape sequence to abort. 2 masks 141.22. 100-byte ICMP Echos to 141.1.22. Serial0 141. 01:21:46.0.108.0/24 [170/22016000] via 141.1.22.0– 141. timeout is !!!!! Success rate is 100 percent (5/5).255.108.22.255. Serial1 160.1 Type escape sequence to abort.12/30 is directly connected. 01:21:47. Sending 5. Ethernet0 EX EX EX EX EX EX EX EX EX D EX C Full connectivity is displayed on R4.22.0. 01:42:25.255. Serial1 141.3.4.0.0 [170/21017600] via 141.1.7. 2 subnets 160.22.0/17 is subnetted. 100-byte ICMP Echos to 141. timeout is !!!!! Success rate is 100 percent (5/5).22.0/24 [170/22016000] via 141.0.108.1. Serial1 141.22.

6.255.0/24.255.20/30. Ethernet0 P 141. U .4/30.0/24.128.0/24. 1 successors.0/24.1.108.255.4.Reply.108. A . FD is 21504000 via 141.7.255.1.3.1. Serial0 P 141. 1 successors.0/24.255.108. Example 8-63 displays the output from the show ip eigrp topology command on R4.13 (26112000/6826496). FD is 22016000 via Redistributed (22016000/0) via 141.22 (21504000/2169856). round-trip min/avg/max = 36/38/40 ms Because R4 and R5 have a redundant path to the OSPF backbone.0/24. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0. 1 successors.255.13 (21504000/20992000).13 (26112000/6826496).108.1. FD is 22016000 via Redistributed (22016000/0) via 141. FD is 21504000 via 141. Serial1 . 1 successors.0/17.0/17. 1 successors.16/30. FD is 281600 via Connected. FD is 20992000 via Connected. Sending 5. Serial0 P 141.108.100.108.16/30. 100-byte ICMP Echos to 141.108. Serial0 P 141.13 (26112000/6826496).Passive.312 - .108.108.255. FD is 21017600 via Redistributed (21017600/0) via 141.255.108.108.2.13 (26112000/6826496).108. Q .CCNP Practical Studies: Routing Type escape sequence to abort.108. FD is 22016000 via Redistributed (22016000/0) via 141.1) P 141. Serial0 P 141.0/30.108.108.108.5. the EIGRP topology table on R4 and R5 displays feasible successors. FD is 22016000 via Redistributed (22016000/0) via 141.108. Serial0 IP-EIGRP Topology Table for AS(3)/ID(160.13 (26112000/6826496). Serial0 P 141.6. Serial1 via Reconnected (20992000/0) P 141.100. Serial0 P 141. 1 successors.1) Codes: P . r .108. FD is 21504000 via Redistributed (21504000/0) P 141. 1 successors. Serial0 P 160.108.108. 1 successors.108. FD is 20992000 via Connected. FD is 22016000 via Redistributed (22016000/0) via 141. FD is 20992000 via Connected. Example 8-63 show ip eigrp topology on R4 R4#show ip eigrp topology IP-EIGRP Topology Table for AS(1)/ID(160.255.255.0/24. 1 successors. Serial0 P 141.108.100.Active.255. 1 successors.Reply status P 141. Serial0 P 141.13 (26112000/6826496). 1 successors.108. FD is 22016000 via Redistributed (22016000/0) via 141.108.255.13 (26112000/6826496). Serial1 P 141.0. R .255. 1 successors.100.255.12/30. 1 successors. 1 successors.108.255.108.255.13 (26112000/6826496).20/30. FD is 22016000 via Redistributed (22016000/0) via 141.108.Query.13 (26112000/6826496). 1 successors.Update. Serial0 P 141.255. 1 successors.13 (26112000/6826496).255. FD is 22016000 via Redistributed (22016000/0) via 141.108.255.0/24. 1 successors. Serial0 P 160. FD is 22016000 via Redistributed (22016000/0) via 141.

Serial1 via Redistributed (26112000/0) P 141. 1 successors.108. 1 successors. FD is 22016000 via 141.22 (22016000/21024000).22 (22016000/2730496).3. Example 8-64 Shut Down S1 on R4 R4(config)#interface serial 1 R4(config-if)#shutdown 04:02:11: %LINK-5-CHANGED: Interface Serial1. . as shaded in the output.255.0/24.22 (22016000/2730496).108.0.0/24 is through Serial 1.108.255. 1 successors. 1 successors. for example.255. FD is 22016000 via 141.108.255.100.22 (22016000/2730496).6.0/17.255.108. FD is 22016000 via 141.108.128. FD is 21504000 via Redistributed (21504000/0) via 141.313 - . which is higher than through Serial 1 to R5 (22016000 compared to 26112000).108.108.255.0/24.4/30.108.CCNP Practical Studies: Routing P 141. 1 successors.12/30. R4 has a number of dual paths to remote networks. Next.108. changed state to down The IP routing table on R4 displays the path to the remote loopbacks and OSPF network through Serial 0.108.22 (22016000/2730496).108. FD is 281600 via Redistributed (281600/0) P 141. 1 successors. Serial1 via Redistributed (26112000/0) In Example 8-63.108. 1 successors. 1 successors.0/24. 1 successors. Example 8-64 disables the link to R5. Serial1 P 160.108. FD is 22016000 via 141.0/24.0/24.22 (22016000/2730496).1. Serial1 via Redistributed (26112000/0) P 141.255.255.0/24.108. Serial1 via Redistributed (26112000/0) P 141. simulate a network failure by shutting down the serial link to R5 on R4.0/24.22 (22016000/2730496).5.255. Example 8-65 confirms the IP routing table.255. note the EIGRP composite metric. 1 successors. FD is 22016000 via 141.0/24.7. Serial1 via Redistributed (26112000/0) P 141.100.4. FD is 20992000 via Connected.255.0/17. 1 successors. Serial1 via Redistributed (26112000/0) P 141. Serial1 P 141. 1 successors.2. FD is 22016000 via 141.108. FD is 22016000 via 141. changed state to administratively down 04:02:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1. FD is 22016000 via 141.108. 1 successors.108.22 (21017600/281600). Because the metric is lower through Serial 1.255.108.6.108.0. Serial1 via Redistributed (26112000/0) P 160.22 (22016000/2730496). Serial0 via Reconnected (20992000/0) P 141. Serial1 via Redistributed (26112000/0) P 141. FD is 22016000 via 141. the chosen path to the remote network 141.22 (22016000/2730496).0/30.22 (22016000/2730496).108.255.255. Serial1 via Redistributed (26112000/0) P 141.108.108. FD is 21017600 via 141.

0 ip ospf network point-to-point ! interface Loopback5 ip address 141. 00:02:08.108.0 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.0 [170/26112000] via 141.6.108.13. Example 8-66 displays R1's full working configuration.CCNP Practical Studies: Routing Example 8-65 show ip route eigrp on R4 R4#show ip route eigrp 141.0/24 [170/26112000] via 141.255. 00:02:07.6.255. 2 masks D 141.108.0 ip ospf network point-to-point ! interface Loopback4 ip address 141.1 255. Serial0 D EX 141.255.1 255.255.13.7.255.0/24 [170/26112000] via 141. Serial0 D EX 141.108.108.2.5.0. 00:02:07.255.1.255.13. You must pay particular attention to the metric and avoid any routing loops.1 255.255.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 141.108.108.108.0 ip ospf network point-to-point ! interface Loopback3 ip address 141.0/30 [170/26112000] via 141.255. 11 subnets.108. Serial0 D EX 141.1 255. Serial0 D EX 141.1 255.255.100.108.108. Example 8-66 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Loopback0 ip address 141.0.0/24 [170/26112000] via 141. 00:02:08.0 ! interface Serial1/0 ip address 141. Serial0 160.255.5.255.255.0/24 [170/26112000] via 141.3.13.4.0/24 [170/26112000] via 141.255.1 255. Serial0 D EX 141.255.255.13.13.7.108.1.13. 00:02:08.0/17 is subnetted.255.13.108.108.0.3. 00:02:07.0.108.108.100. 00:02:08.108.255.108.314 - .108.4.0/24 [170/26112000] via 141.108.255.255.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 141.108.255. 00:02:07. 00:02:07. Serial0 D EX 141.255.255.255. Serial0 This scenario demonstrates the metric and filtering techniques common in today's large IP networks and the care that you must take when sending networks from one routing algorithm to another.0/24 [170/26112000] via 141.108.108.13.108.128.0/16 is variably subnetted.255.108.108.255. Serial0 D EX 141.108.0 ip ospf network point-to-point ! interface Loopback2 ip address 141. 02:53:02.0/24 [170/26112000] via 141. 2 subnets D EX 160.2.13.1 255. 00:02:08. Serial0 D EX 141.252 .108.255.4/30 [90/21504000] via 141.255.108.1 255.1 255.255.108.255.13. Serial0 D EX 141.255.

0 0.255.0.0.108.3 access-list 2 deny 141.0.255.255 area 0 ! end Example 8-67 displays R2's full working configuration.2 255.0 255.0.0 255.255.3 access-list 2 permit any route-map allowintoeigrp permit 10 match ip address 1 ! route-map allowintoospf permit 10 match ip address 2 ! end Example 8-68 displays R3's full working configuration.0 area 0 access-list 1 deny 160.0.255.255.252 clockrate 128000 ! router ospf 1 redistribute connected subnets network 0.255.0 0.0.0 0.255.0.5 255.0.0.0 redistribute eigrp 2 metric 100 subnets route-map allowintoospf redistribute eigrp 1 network 141.255. Example 8-67 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Serial1/0 bandwidth 128 ip address 141.255 access-list 1 permit any access-list 2 deny 141.255.108.108.2 0.0 no auto-summary ! router ospf 1 summary-address 141.255.255.255.108.252 ! router eigrp 2 redistribute ospf 1 metric 1500 2000 255 1 1500 route-map allowintoeigrp passive-interface Serial1/0 network 141.108.17 255. .0.0.255.100.108.248.0.255.108.CCNP Practical Studies: Routing clockrate 128000 ! interface Serial1/1 ip address 141.255.7.255 access-list 2 deny 141.0.4 0.108.108.315 - .255.252 no ip mroute-cache ! interface Serial1/1 ip address 141.0.

108.0 0.6 0.0.255.108.108.4 0.0 area 0 access-list 1 deny 160.0 255.0 0.255.1 255.100.0.255.100.0.1.0 5 ! interface Serial1 bandwidth 125 ip address 141.CCNP Practical Studies: Routing Example 8-68 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Serial0 ip address 141.0.255.252 ip summary-address eigrp 1 160.0 no auto-summary ! router ospf 1 redistribute eigrp 1 metric 100 subnets route-map allowintoospf network 141.255.108.0.108.255 access-list 1 permit any access-list 2 deny 141.255.0.13 255.128.255.7.316 - .128.6 255.0 0.0 ! interface Serial0 bandwidth 125 ip address 141.0.108.252 clockrate 125000 ! .255.255 access-list 2 deny 141.255.108.255.255.0.255.21 255. Example 8-69 R4's Full Working Configuration hostname R4 ! enable password cisco ! interface Ethernet0 ip address 160.3 access-list 2 deny 141.100.255.252 bandwidth 125 clockrate 125000 ! router eigrp 1 redistribute ospf 1 metric 1500 20000 255 1 1500 route-map allowintoeigrp passive-interface Serial0 network 141.0.0.108.3 access-list 2 permit any route-map allowintoeigrp permit 10 match ip address 1 ! route-map allowintoospf permit 10 match ip address 2 ! end Example 8-69 displays R4's full working configuration.255.255.255.252 bandwidth 125 ! interface Serial1 ip address 141.255.0.14 255.108.255.0.

0.108.255.108.100.CCNP Practical Studies: Routing router eigrp 1 redistribute eigrp 3 passive-interface Serial1 network 141.255.1 255.0 network 160.128.0 clockrate 125000 ! interface Serial1 ip address 141.0.108.0 255.255.255.255.317 - .0.0.108.128.0 no auto-summary access-list 1 permit 160.0.0 ! interface Serial0 ip address 141.0.127.0.0 0.0 no auto-summary ! router eigrp 3 redistribute eigrp 1 passive-interface Ethernet0 passive-interface Serial0 network 141.252 no ip directed-broadcast ! router eigrp 3 redistribute eigrp 2 passive-interface Ethernet0 passive-interface Serial0 network 141.108.255.100.0.255 access-list 2 permit 160.255 route-map allowtoR3 permit 10 match ip address 1 ! route-map allowtoR5 permit 10 match ip address 2 end Example 8-70 displays R5's full working configuration.0 0.100.0 network 160.100.252 ip summary-address eigrp 2 160.108.128.22 255.100.255.0.18 255.0.100.128.127.0 no auto-summary ! ip classless ! end . Example 8-70 R5's Full Working Configuration hostname R5 ! enable password cisco interface Ethernet0 ip address 160.255.0 no auto-summary ! router eigrp 2 redistribute eigrp 3 passive-interface Serial1 network 141.

0 area 333 . This scenario uses static routes to ensure connectivity between the classless (RIP) domain to the classful (OSPF) domain.108.255.255.3.255.1 0. This scenario contains only two routers.4. you apply passive interfaces where required.128 R1(config-if)#interface Loopback3 R1(config-if)# ip address 131.128 R1(config-if)#interface Loopback2 R1(config-if)# ip address 131.0 area 333 R1(config-router)#network 131.2. Example 8-71 R1 Configuration R1(config)#interface Loopback0 R1(config-if)# ip address 131.3.129 0.0.108.5.0.2. even on the loopbacks.3.4.1 255. Ensure that RIP updates are sent to only the Ethernet interfaces on R1 by configuring R1 with passive interfaces.129 255.3. allow only one routing algorithm to advertise each interface.0.255.108.255. To ensure that routing resources are not wasted.255.108.0.108.255.1 0.0 area 333 R1(config-router)#network 131.108.0. and R2 is running RIP only.248 R1(config)#router ospf 1 R1(config-router)#network 131. Router R1 has a number of interfaces in OSPF area 333.1 255. This scenario is designed to ensure that you are fully aware of all the potential problems when routing between OSPF (classless routing protocol) and RIP (classful routing protocol).248 R1(config-if)#interface Loopback4 R1(config-if)# ip address 131. Example 8-71 configures R1 for IP addressing and enables OSPF and RIP. The ability to configure networks from a classless and classful domain and vice versa is critical.1 255.1 255. Routing IP Between RIP and OSPF The end goal of this scenario is to ensure full IP connectivity between the two different IP networks.255.255.0. so you can easily replicate this network with your own set of Cisco IOS routers.255.318 - . because OSPF advertises these routes.0 area 333 R1(config-router)#network 131.108.108. To do this.0.108. You configure R1 for redistribution between RIP and OSPF. Figure 8-6.0 R1(config-if)#interface Loopback1 R1(config-if)# ip address 131.CCNP Practical Studies: Routing Scenario 8-4: Route Summarization Using Static Routes The internetwork in Figure 8-6 displays a simple two-router topology with two routing algorithms in use.0.1 0.

1.0.255. Example 8-75 Static Route Configuration on R2 R2(config)#ip R2(config)#ip R2(config)#ip R2(config)#ip route route route route 131.255.0 To enable R2 to learn the OSPF loopback interfaces on R1 dynamically.108. Example 8-73 displays the redistribution on R1 from RIP to OSPF.108.2 255. by setting the metric to 1 (hop count).0 is directly connected.108.5.108. enable RIP-to-OSPF redistribution on R1.108.1 131.1.CCNP Practical Studies: Routing R1(config-router)#network 131.319 - .0 R2(config-if)#exit R2(config)#router rip R2(config-router)#network 131.128 255.108.108.255.1. 00:00:06.1.108.0.1 131. Confirm network connectivity by viewing the IP routing table on R2 and pinging all remote loopback interfaces on R1.3.0 255.128 131.108.108. Ethernet0/0 C 131.255.4. only 24-bit networks are advertised by R1 and accepted by R2.255.255.0.108.1.108.108. .1.1.0 [120/1] via 131.1.1. The first is to use static routes. and the second method uses summarization techniques on R1. Ethernet0/0 The only IP network in Example 8-74 is the subnet 131.255. Configure R2 with static routes and ensure network connectivity to R1 loopback interfaces.108. Example 8-72 RIP Configuration on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip address 131. Example 8-75 configures R2 with four static routes pointing to the next hop destination to R1's Ethernet IP address of 131. which is a Class C subnetted route.0. Example 8-74 show ip route R1 R2#show ip route 131.248 131.1 0.0 area 333 R1(config-router)#router rip R1(config-router)#network 131.0 255.0 255.1 R2 is configured with static routing information.108.128 131.3.108. You can use two methods to solve this scenario.2.1 131. Example 8-76 displays R2's IP routing table and five ping requests to all R1's loopback interfaces.0/24 is subnetted.5.255. Example 8-74 displays the IP routing table on R1.255.248 131.0.0 R1(config-router)#pass R1(config-router)#passive-interface lo0 R1(config-router)#passive-interface lo1 R1(config-router)#passive-interface lo2 R1(config-router)#passive-interface lo3 R1(config-router)#passive-interface lo4 Example 8-72 enables IP RIP on R2.2. even though the remote networks are not Class C subnets.108.1. Example 8-73 Redistribution on R1 from RIP to OSPF R1(config)#router rip R1(config-router)#redistribute ospf 1 metric 1 View the IP routing table on R2 to determine which RIP networks R1 advertises to R2.255. 2 subnets R 131.0.108. Because R2 is configured with a classful routing protocol.

1 Type escape sequence to abort.3.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.1. round-trip min/avg/max = 1/3/4 ms R2#ping 131. S .static.108. you configure routing between VLSM and FLSM networks without using static routing.108.2.108.108.108.255.108. Sending 5.5.3.4.1 Type escape sequence to abort.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).5.1.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.0 ! interface Loopback1 ip address 131.255.1 Type escape sequence to abort. Sending 5.108.129 255. Sending 5. you can use static routes to overcome the limitations of routing between VLSM networks or fixed-length subnet mask (FLSM) networks. 100-byte ICMP Echos to 131.108.128/25 [1/0] via 131. 100-byte ICMP Echos to 131. round-trip min/avg/max = 1/3/4 ms R2#ping 131.1.108. 100-byte ICMP Echos to 131.R .0/29 [1/0] via 131.3.connected.108.2. Example 8-77 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 131.5.108.129 Type escape sequence to abort. round-trip min/avg/max = 1/2/4 ms R2#ping 131.108.108.RIP 131. Example 8-77 displays R1's full working configuration.1.128 interface Loopback3 ip address 131.255.1 255.1.3. 6 subnets.129.0/25 [1/0] via 131.255.3.1 R 131. round-trip min/avg/max = 1/2/4 ms R2# Example 8-76 displays IP networks installed in the routing table.0/16 is variably subnetted.108.1.108.128 interface Loopback2 ip address 131.1. 3 masks S 131.2.0.108.248 . round-trip min/avg/max = 1/3/4 ms R2#ping 131.255.1 Type escape sequence to abort.4.1.3.108.2. Sending 5. Even though RIP is classful.108.108.0/29 [1/0] via 131.108.1. 100-byte ICMP Echos to 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).320 - . Ethernet0/0 C 131.3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).3.1 255. Sending 5.108.1 S 131.4.1 255.1 S 131.4.108.108. 00:00:13. In the next scenario.255.CCNP Practical Studies: Routing Example 8-76 show ip route and ping on R2 R2#show ip route Codes: C .1.108.1 S 131. Ethernet0/0 R2#ping 131.0/24 is directly connected.0/24 [120/1] via 131. 100-byte ICMP Echos to 131.

108.108.1 0.255.108.1.0.255.0.0.0.255.2 255.1 ip route 131.0 255.1 .321 - .128 131.108.255.248 131.1.0.108.0 255.0 ! router rip network 131.1 255.108.1.3.3.0 router ospf 1 network 131.2.108.255.255.1 131.108.128 131.129 0. Example 8-78 R2's Full Working Configuration (Truncated) hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.248 131.255.0 255.1 131.108.CCNP Practical Studies: Routing ! interface Loopback4 ip address 131.5.108.0.108.108.108.255.0 255.108.5.5.255.0.3.1.128 255.0 area 333 ! router rip redistribute ospf 1 metric 1 passive-interface Loopback0 passive-interface Loopback1 passive-interface Loopback2 passive-interface Loopback3 passive-interface Loopback4 network 131.1.1 255. Example 8-79 removes the static route configuration on R2.128 131.1 ip route 131.1.3.108.5.255.3.248 ! interface Ethernet0/0 ip address 131.0.108.108.108. you revisit the topology in Figure 8-6 and use dynamic routing to insert the non-class C networks into R2's routing table.0.1 131.4.0 area 333 network 131.108.1 end Scenario 8-5: Route Summarization Without Using Static Routes In this scenario.0 ! ip route 131.248 131.1.1 0.0.108.255.108.1.255.1.1 0.255.1 0.255.255.1.108.0 area 333 network 131.128 255.4.0 255.108.255.108.4.128 131.255.0 ! end Example 8-78 displays R2's full working configuration.108.0.255.108. Example 8-79 Removing the Static Route Configuration on R2 R2(config)#no R2(config)#no R2(config)#no R2(config)#no ip ip ip ip route route route route 131.0 255.0.0 area 333 network 131.3.0 area 333 network 131.255.255.255.248 131.1 ip route 131.255.

0 255.108.108. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 R2 assumes all 131. R1 sends only the loopbacks interfaces and R2 accepts only routes that are not locally connected.1. you can advertise all loopbacks on R1 as Class C subnets to R2.0 R1(config-router)#summary-address 131. [120/1] via 131.108. 00:00:06. Because all Cisco IOS routers always choose a path with a more specific route.0/24 network.108.1. as displayed in Example 8-74.2.3 Loopback Loopback interface Null Null interface Serial Serial <cr> R1(config-route-map)#match interface loopback 1 R1(config-route-map)#match interface loopback 2 R1(config-route-map)#match interface loopback 3 R1(config-route-map)#match interface loopback 4 R1 is configured to permit only the loopback interfaces 1–4 to be redistributed into RIP.0.255.0 R 131.4.108.0 R1(config-router)#summary-address 131.255.108. the loopbacks on R1) are redistributed to R2.0/24 R 131.0.0 R 131.0 C 131.108.5. Example 8-80 summary-address Command on R1 R1(config)#router ospf 1 R1(config-router)#summary-address 131. as displayed in Example 8-81. 00:00:06.CCNP Practical Studies: Routing The IP routing table on R2 now contains only the 131.108.108.5.255. configure a distribution list that allows only the loopbacks configured on R1.0 255.255. is directly connected. To redistribute the networks in R1's network.0 is subnetted. Example 8-81 displays the IP routing table on R2.1. [120/1] via 131. [120/1] via 131.1. To ensure that routing loops cannot occur.108.0 networks are subnetted as 24-bit networks.1. 00:00:06. Example 8-80 configures summarization on R1 for the four loopbacks. called allowout.108.1.1. 5 subnets [120/1] via 131. .108. To ensure that R1 never accepts routes that are locally reachable. 00:00:06.0 R1(config-router)#redistribute connected subnets The last command in Example 8-80 ensures that all connected routes (in this case. that permits only the non-class C networks to be advertised to R2. so you do not need to add this interface.108. you can apply the summary-address network-mask command. Example 8-82 configures a route map.255.3.1.322 - .2.0 R 131. Example 8-81 show ip route on R2 R2#show ip route 131.0 255. Example 8-82 Route Map Configuration on R1 R1(config)#router ospf 1 R1(config-router)#redistribute connected subnets route-map allowout R1(config-router)#exit R1(config)#route-map R1(config)#route-map allowout R1(config-route-map)#match in R1(config-route-map)#match interface ? Ethernet IEEE 802.4. R1 is an ASBR.108. so you can use the summary command to send an update to RIP with any mask you need.3. Loopback 0 is a Class C subnet route.255.1.108.

0 R2(config)#access-list 1 permit 131.4.0 R2(config)#access-list 1 permit 131.108.3.0 [120/1] via 131.0.1.128 ! interface Loopback2 ip address 131. Example 8-84 show ip route rip on R2 R2#show ip route rip 131.108.255.0 ! router ospf 1 summary-address 131.255. 5 subnets R 131.0 summary-address 131.5.0 redistribute connected subnets route-map allowout network 131.248 interface Ethernet0/0 ip address 131.0.108.108.108.0.255.1 0.CCNP Practical Studies: Routing Example 8-83 configures a distribution list on R2 permitting only loopbacks 0–4 into R2's IP routing table.108.108.1 0.1.108. Example 8-85 displays R1's full working configuration.255.108.2.0 area 333 network 131.255.108.1.3.4.3.255.0.108.108.1.108.1 255.108.129 255.0.3.2.108.129 0.0 [120/1] via 131.255.255.5.255.3.0 area 333 network 131.108.108.108. R 131.1 255.0 [120/1] via 131.0.5.2.108.108.1 0.3.108.1 255.4.128 ! interface Loopback3 ip address 131.4.248 ! interface Loopback4 ip address 131. the network should be free of routing loops and maintain full network connectivity.108.0 255.2.108.0/24 is subnetted.108.0 ! interface Loopback1 ip address 131.1.0 R2(config)#access-list 1 permit 131. all other networks are rejected.0 [120/1] via 131.0 Example 8-84 confirms the IP routing table on R2.108.0.0 area 333 . R 131.0 area 333 network 131.0.323 - . 00:00:00.1 0.0 255.255. and as long as route maps and filtering are applied.255. 00:00:00. Example 8-85 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Loopback0 ip address 131. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 The same principles applied here can be applied to any number of routers.255.0 255.108. 00:00:00.1 255. 00:00:00.255.0.255.1.108.255.1.255.5. R 131.1.0 area 333 network 131.255.1.255.0.0 summary-address 131.1 255.4.0.5. Example 8-83 Distribution List Configuration on R2 R2(config)#router rip R2(config-router)#distribute-list 1 in R2(config-router)#exit R2(config)#access-list 1 permit 131.3.

0.5.0.0 ! route-map allowout permit 10 match interface Loopback1 Loopback2 Loopback3 Loopback4 ! end Example 8-86 displays R2's full working configuration.0 distribute-list 1 in access-list 1 permit 131.CCNP Practical Studies: Routing ! router rip redistribute ospf 1 metric 1 passive-interface Loopback0 passive-interface Loopback1 passive-interface Loopback2 passive-interface Loopback3 passive-interface Loopback4 network 131.108.0 access-list 1 permit 131.0 access-list 1 permit 131.108.0.255. Example 8-86 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.255.324 - .108.3.108.2 255.0.0 access-list 1 deny 160.108.255.0 ! router rip network 131.108.0 0.0 access-list 1 permit 131.1.108.4.100.2.255 end .

Loopbacks are used on Routers R1–R3 to populate the network with IP routing entries. The solution can be found at the end. Each router is configured for local loopbacks and an interior routing protocol. Figure 8-7. One common troubleshooting scenario is to create a loop by disabling split horizon and then configuring route maps and/or filtering to stop the routing loop—great fun. So the main issue to be aware of is filtering. .325 - . Figure 8-7 displays a three-router topology running four routing algorithms. Practical Exercise Topology Configure all three routers. Then configure redistribution by using filtering wherever required to avoid routing loops. After you configure the loopbacks and WAN links are operational. of course. all using /24-bit subnet masks. is configured across the WAN. Use filtering and make extensive use of passive interfaces to avoid routing loops. you start by enabling the local LAN interfaces.CCNP Practical Studies: Routing Practical Exercise: Redistribution NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. EIGRP. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. Practical Exercise Solution The issue of FLSM and VLSM is not paramount in this topology because all subnets are /24. Ensure that routing updates are sent to only the relevant interfaces. but only in a practice lab.

108.1 255.0.0 ! interface Loopback1 ip address 141.108.108.326 - .1 255.0 ! ip classless .108.CCNP Practical Studies: Routing The following configurations provide a sample working solution to the network topology in Figure 8-7.0 ! interface Serial1/0 bandwidth 128 ip address 151.255.108.3.255.255.255.108.108.1 255.0 distribute-list 1 in ! router rip passive-interface Serial1/0 passive-interface Serial1/1 network 141. The shaded portions in Example 8-87 are key configuration commands for filtering.255.255. Example 8-87 displays R1's full working configuration.0 clockrate 128000 ! router eigrp 1 redistribute rip metric 128 20000 255 1 1500 network 151. All other networks are allowed into R1's IP routing table.0.255.255.0 ! interface Loopback2 ip address 141.0 ! interface Loopback3 ip address 141.255.6.108.0 ! interface Ethernet0/0 ip address 141.5.1 255.1 255.1 255.255. The redistribution on R1 is filtered to deny any locally sourced networks on R1.1 255.0 ! interface Loopback6 ip address 141.255.255. Static routes are not used in this design.0 ! interface Loopback5 ip address 141.0 ! interface Loopback4 ip address 141.255.255. Example 8-87 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.255.1.255.108.108.0.7.108.255.1 255.254. R1 is configured for RIP and EIGRP. however.1 255.255.255.4.0 clockrate 128000 ! interface Serial1/1 bandwidth 128 ip address 151.255. You can.2.1 255.108.255. configure this network many different ways.

11.255.255.108.108.0 ! interface Loopback6 ip address 141.1 255.0.1 255.255.1 255.0 0.13.255.2 255.255 access-list 1 permit any ! line con 0 line aux 0 line vty 0 4 end Example 8-88 displays R2's full working configuration.1 255.255.108.0 ! ip classless .0 ! router eigrp 1 network 151.255.108.108.255.255.15.327 - .8.108.108.0 ! interface Loopback3 ip address 141.255.1 255.0 distribute-list 1 in ! router igrp 1 passive-interface Serial1/0 passive-interface Serial1/1 network 141.255. Example 8-88 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero ! interface Loopback0 ip address 141.108.255.1 255.108.255.0 ! interface Ethernet0/0 ip address 141.0.255.0.255.255.253.7.0 interface Serial1/1 bandwidth 128 ip address 151.255.CCNP Practical Studies: Routing ! access-list 1 deny 141.108.108.10.14.0 ! interface Loopback2 ip address 141.1 255.1 255.255.108.255.2 255.0.12.0 ! interface Loopback1 ip address 141.255.255.0 ! interface Loopback5 ip address 141.108.0 ! interface Serial1/0 bandwidth 128 ip address 151.0 ! interface Loopback4 ip address 141.9.255.

0 media-type 10BaseT ! interface Ethernet1 no ip address ! interface Serial0 ip address 151.1 255.108.255.255.255.255.255.255 access-list 1 permit any ! line con 0 line aux 0 line vty 0 4 ! end Example 8-89 displays R3's full working configuration.0 ! interface Loopback3 ip address 141.0.328 - .22.255.0 0.CCNP Practical Studies: Routing ! access-list 1 deny 141.255.108.108.1 255.254.0 ! interface Ethernet0 ip address 141.108.108.108.20.0.1 255.0 ! interface Loopback1 ip address 141.19.255.255. Example 8-89 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 141.255.255.255.18.0 bandwidth 128 clockrate 128000 ! router eigrp 1 redistribute ospf 1 metric 128 20000 1 1 1500 network 151.108.255.1 255.17.255.1 255.108.108.23.0 bandwidth 128 ! interface Serial1 ip address 151.7.16.1 255.108.0 ! interface Loopback4 ip address 141.8.0 ! interface Loopback5 ip address 141.2 255.0 .255.255.255.108.21.0 ! interface Loopback2 ip address 141.108.255.255.0 ! interface Loopback6 ip address 141.253.1 255.255.1 255.1 255.

108.6.0 [170/25632000] via 151.0 [170/25632000] via 151. Example 8-91 displays the EIGRP topology table on R1.2.2. 00:06:20.108.7.108.108.2.255. Example 8-90 show ip route on R1 R1#show ip route 141.0 is directly connected. 24 subnets C 141.0 [170/20640000] via 151.9.0.253.108.2.2. Serial1/1 D EX 141. 00:06:21. Also.15.0 is directly connected.0 is directly connected.254.255 access-list 1 permit any ! line con 0 line aux 0 line vty 0 4 ! end Example 8-90 displays the IP routing table on R1.17.0 is directly connected.108.108.255.108.108.0/24 is the same.7. 00:06:21.108. 00:06:21. Serial1/1 D EX 141.0 [170/20640000] via 151.0/24 is subnetted. Serial1/0 D EX 141. Serial1/1 D EX 141.2.108.255.0 [170/20640000] via 151.254.CCNP Practical Studies: Routing distribute-list 1 in ! router ospf 1 network 141.108.108.108.255. demonstrating full network connectivity.23.2.0 [170/25632000] via 151. 00:06:21. 3 subnets C 151.7.0.108.22. 00:06:22.253.1. Loopback0 C 141.108.20.0 [170/25632000] via 151. The EIGRP topology table on R1 confirms the same composite metric.108.108. 00:06:22. Serial1/1 D EX 141. 00:06:22. Serial1/1 D EX 141.2.2.0 [170/20640000] via 151.108. Loopback4 D EX 141.254.254. Loopback2 C 141.108.108. 00:06:21.329 - . Serial1/1 D EX 141.0 [170/20640000] via 151. Ethernet0/0 C 141.108.10. .0 is directly connected.2. Serial1/1 151.4.108.12.108.108. Serial1/0 R1# The redistributed networks from R2 and R3 appear as external EIGRP routes (D EX).108.254.0 is directly connected.16.108.21. 00:06:22. 00:06:21.0 is directly connected.8.0 [170/25632000] via 151. 00:06:22.108.16.254.108.108. Loopback5 C 141.16.0 [90/21024000] via 151. 00:06:22. The shaded portions display the dual path to 151.254. Serial1/1 D EX 141.2.11. 00:06:21.108.3.14. 00:06:22.108.108.2.0. Serial1/0 D EX 141.255.0.108.13. 00:06:22. Loopback6 C 141.255. Serial1/0 C 151.108. Serial1/1 D 151.108.2.0 is directly connected.19.254.0/24 is subnetted. Serial1/0 D EX 141.2. Serial1/0 D EX 141.255 area 100 ! ip classless access-list 1 deny 141.0.255.255.0 [170/25632000] via 151.108.0 is directly connected. Serial1/0 D EX 141.108.0 [170/20537600] via 151.108. Serial1/1 [90/21024000] via 151.0 0.108.2.108. Serial1/0 D EX 141.0 [170/20640000] via 151. 00:06:22.2.0 [170/25632000] via 151.0 [170/25632000] via 151.254.2. Loopback3 C 141.108.18.253. because the composite metric to the WAN network 151.108.0.108. EIGRP is load balancing.2.5.255.108.0 [170/20640000] via 151.108.0 0.254. Serial1/0 D EX 141.108.255. Loopback1 C 141. 00:06:22.108.0 is directly connected.108.108.2. Serial1/0 D EX 141.108.

Q .0/24.253.108. FD is 20640000 via 151.108. FD is 25632000 via 151. FD is 25120000 via Redistributed (25120000/0) P 141.16.2 (25632000/25120000).0/24.108. FD is 25632000 via 151. 1 successors. r .12. 1 successors. FD is 25632000 via 151.108.108.108.108.108.108.Reply status P 151. Serial1/0 P 151.254.2 (21024000/20512000).0/24. 1 successors.254.5. FD is 25120000 via Redistributed (25120000/0) P 141.14.19. FD is 21024000 via 151. 1 successors.254.2 (21024000/20512000).0/24.21. 1 successors. Serial1/1 P 151.7.108. 1 successors.108.108. 1 successors.108.0/24.0/24.254. 1 successors. 1 successors.0/24.255. 1 successors.0/24. 1 successors. FD is 25120000 via Redistributed (25120000/0) P 141.3.254. FD is 25632000 via 151.15.108.2 (20640000/128256). 1 successors. 1 successors.108.22.108.108. 1 successors.0/24.108.108.2 (20640000/128256).108.20.108.Reply.11.108. A . Serial1/0 P 141.0/24. 1 successors. FD is 20640000 via 151.2 (20640000/128256).17. Serial1/1 P 141. 1 successors.108. Serial1/0 via 151. Serial1/0 P 141.108. FD is 25632000 via 151. FD is 25632000 via 151.0/24.254. FD is 25632000 via 151. 1 successors. Serial1/1 P 141.2 (20640000/128256).255. Serial1/1 P 141.255.1.Query.0/24.254.108. 1 successors. R .2 (20640000/128256). FD is 20640000 via 151.0/24.0/24. FD is 25120000 via Redistributed (25120000/0) P 141.108.108.108. FD is 20640000 via 151.2 (25632000/25120000).108. FD is 20512000 via Connected.108. FD is 25632000 via 151.0/24. Serial1/0 P 141.0/24.0/24. Serial1/0 P 141.23.255. Serial1/1 P 141. Serial1/0 P 141.Update. 1 successors.18. 1 successors.10.0. FD is 25120000 via Redistributed (25120000/0) P 141. FD is 25120000 via Redistributed (25120000/0) P 141.2 (25632000/25120000).0/24.108. 1 successors.2 (25632000/25120000). FD is 20640000 via 151.108.0/24. 1 successors.Active. Serial1/0 P 141.6.255.254.108. Serial1/1 P 141. 1 successors.108. Serial1/1 P 141.CCNP Practical Studies: Routing Example 8-91 show ip eigrp topology on R1 R1#show ip eigrp topology IP-EIGRP Topology Table for process 1 Codes: P . 1 successors.0/24.255.255.2 (25632000/25120000). 1 successors. Serial1/1 .13. 2 successors.108.108.2 (25632000/25120000).Passive.9.2 (20537600/281600).108.0/24.255.2 (20640000/128256).108.0/24. U .108. Serial1/1 P 141. FD is 20640000 via 151.2. Serial1/0 P 141. FD is 25120000 via Redistributed (25120000/0) P 141.108.2 (25632000/25120000).255.0/24.0/24.108.254. Serial1/1 P 141.8.2 (25632000/25120000).0/24.108.108.0/24.0/24.330 - .108.254. FD is 20512000 via Connected. FD is 20537600 via 151. FD is 25120000 via Redistributed (25120000/0) P 141.255. FD is 20640000 via 151.2 (20640000/128256).4.108. 1 successors. Serial1/0 P 141.

17. round-trip min/avg/max = 16/17/20 ms R1#ping 141. 100-byte ICMP Echos to 141.108. 100-byte ICMP Echos to 141. Sending 5.1 Type escape sequence to abort.1. Sending 5.1.1. Sending 5. round-trip min/avg/max = 12/14/16 ms R1#ping 141. 100-byte ICMP Echos to 141.1.108.1.11. Sending 5.1 Type escape sequence to abort.108.11.1.108.12. round-trip min/avg/max = 16/16/16 ms R1#ping 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).18.1 Type escape sequence to abort.108.108.12. Example 8-92 Pinging Remote Networks on R1 R1#ping 141. Sending 5. timeout is 2 seconds: !!!!! . 100-byte ICMP Echos to 141. 100-byte ICMP Echos to 141.1.1 Type escape sequence to abort.108.8. 100-byte ICMP Echos to 141. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.1 Type escape sequence to abort.108. round-trip min/avg/max = 12/14/16 ms R1#ping 141.15.108.CCNP Practical Studies: Routing R1# Example 8-92 confirms network IP connectivity by pinging all the remote networks from R1. round-trip min/avg/max = 16/16/16 ms R1#ping 141.14. round-trip min/avg/max = 16/16/16 ms R1#ping 141. Sending 5. 100-byte ICMP Echos to 141.1.108.17.13.15.1 Type escape sequence to abort.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.18.1.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. Sending 5.1 Type escape sequence to abort. Sending 5.10. Sending 5.108.108.108. round-trip min/avg/max = 16/16/16 ms R1#ping 141.13. 100-byte ICMP Echos to 141.1 Type escape sequence to abort.9. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/16 ms R1#ping 141.9.1.16. round-trip min/avg/max = 16/16/16 ms R1#ping 141.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10. 100-byte ICMP Echos to 141.108.1.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/17 ms R1#ping 141. Sending 5.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).8.1 Type escape sequence to abort. 100-byte ICMP Echos to 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort.331 - .108.14.16. 100-byte ICMP Echos to 141.

22.108. Sending 5.108.108. "Answers to Review Questions.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).20. round-trip min/avg/max = 12/14/17 ms R1#ping 141. 100-byte ICMP Echos to 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).21. round-trip min/avg/max = 16/16/16 ms R1#ping 141. round-trip min/avg/max = 16/16/16 ms R1#ping 141. Sending 5.108.19.1 Type escape sequence to abort. 100-byte ICMP Echos to 141.1." 1: 2: 3: 4: 5: 6: 7: 8: 9: 10: How many IP routing tables are there when more than one routing protocol is configured on a Cisco router? Which path is preferred if OSPF and EIGRP have dynamically discovered a remote network? What common methods are used to control routing updates and filtering? What is the metric used by OSPF. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.23. such as hop count or OSPF cost? Give two examples of classful protocols? Give two examples of classless protocols? What are the three methods commonly applied to avoid routing loops when redistribution is required? .332 - . round-trip min/avg/max = 12/15/17 ms R1#ping 141.108.CCNP Practical Studies: Routing Success rate is 100 percent (5/5). Sending 5. 100-byte ICMP Echos to 141. round-trip min/avg/max = 12/13/16 ms R1#ping 141.22.108.21.108.1. 100-byte ICMP Echos to 141. round-trip min/avg/max = 16/16/16 ms R1# Review Questions The answers to these question can be found in Appendix C.1 Type escape sequence to abort. 100-byte ICMP Echos to 141.1 Type escape sequence to abort.1 Type escape sequence to abort.1.23.19. Sending 5.1.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. and is the lower or higher metric the chosen path? Is a static route always preferred over a directly connected route? Which command stops updates from being sent out of any interface? Which parameter does the Cisco IOS always compare before looking at routing metrics.1 Type escape sequence to abort.20.

and you should now have the skills necessary to enable any form of route redistribution. and route maps enables you to avoid routing loops and ensure that full IP connectivity still exists. Enables OSPF routing. All hardware interfaces are shut down by default. In such a situation. Disables updates sent outbound but still listens to updates. . Summary of IOS Commands Command area area-id range address mask router ospf process id router eigrp autonomous domain ID no auto-summary show ip route show ip eigrp topology [no] shutdown ping ip-address redistribute options passive-interface Purpose Summarizes OSPF network ranges. You can have more than one OSPF process ID running. Routing between classless and classful domains is one of the major learning tools you must master quickly in any IP network. See Table 8-2 for a complete listing of available options. Useful for determining other paths available on an EIGRP router. Mastering distribution lists. Table 8-3. Enables or disables an interface." Table 8-3 summarizes the most important commands used in this chapter. information can be controlled to ensure that the network is routing IP as correctly and efficiently as possible.333 - . "CCNP Routing Self-Study Lab. Enables EIGRP routing under a common administrative control. Disables automatic summarization. The issues of routing loops and metric conversion from one routing protocol to another have been demonstrated. Displays the complete IP routing table. Enables redistribution. The process ID is local to the router. known as the autonomous domain. Displays the EIGRP topology table. static routing.CCNP Practical Studies: Routing Summary Redistribution from one routing protocol to another has been extensively covered in this chapter. Tests IP connectivity. You should now be ready to apply the information in this and all of the previous chapters to the self-study lab in Chapter 9.

.

CCNP Practical Studies: Routing

Chapter 9. CCNP Routing Self-Study Lab
This chapter is designed to assist you in your final preparation for the Routing exam by providing you an extensive lab scenario that incorporates many of the technologies and concepts covered in this book. The lab presented here requires a broad perspective and knowledge base. This means that any knowledge you have acquired through the practical examples presented in this guide and real-life network implementations will help you achieve the end goal—a routable network according to the set design criteria. This lab is presented in small sections and provides you a specific amount of time to complete the tasks so that you can ensure that all features are configured in a timely manner, allowing you the ability to tackle any similar Cisco-based certification or real-life network topology configuration. NOTE The following lab is designed to draw together some of the content described in this book and some of the content you have seen in your own networks or practice labs. There is no one right way to accomplish many of the tasks presented here. The abilities to use good practice and define your end goal are important in any real-life design or solution. The Ethernet interfaces on all routers are connected to a Catalyst 6509 switch. Hints are provided to ensure that you are aware of any issues or extra configuration commands required to complete a specific task.

How to Best Use This Chapter
The following self-study lab contains a six-router network with two Internet service provider (ISP) routers providing connections to the Internet. Although on the CCNP Routing exam you do not have to configure six routers running multiple protocols, this lab is designed to ensure that you have all the practical skills to achieve almost any IP routing requirements in real-life networks. More importantly, it tests your practical skill set so you can pass the CCNP Routing examination with confidence. Full working solutions are provided, along with the configuration of a Catalyst 6509 used to create the LAN-based networks, and the two ISP routers simulating an Internet service. Following the full configurations in the solution section, a section displays sample routing tables taken from each router, as well as some sample ping and telnet commands to demonstrate full IP connectivity. The IBGP and EBGP network connectivity is demonstrated displaying the BGP tables. Figure 9-1 displays the six-router topology used in this lab.

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CCNP Practical Studies: Routing
Figure 9-1. Router Topology

The Goal of the Lab
The end goal of this lab is to ensure that all devices in Figure 9-1 can route to all networks. This ensures, for example, that users on R5's Ethernet networks (E0 and E1) can reach all parts of the network.

Physical Connectivity (1 Hour)
Construct your network as shown on Figure 9-1. All back-to-back serial connections require a clock source. Use common Cisco defined techniques by using the IOS description name of link command to provide documentation for all serial links and virtual LANs.

Catalyst Switch Setup 6509 (0.25 Hours)
Configure the Ethernet switch for seven VLANs and cable a catalyst switch for the following VLAN number assignments:

• • • • • • •

VLAN 100 is connected to R1 E0/0. VLAN 200 is connected to R2 E0/0. VLAN 300 is connected to R3 E0. VLAN 400 is connected to R4 E0. VLAN 500 is connected to R5 E0. VLAN 550 is connected to R5 E1. VLAN 600 is connected to R6 E0.

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CCNP Practical Studies: Routing
Configure the management interface (or sc0) on the switch with the IP address 133.33.1.2/29, and ensure that all routers can Telnet to the switch after you have completed configuring your IGP protocols. Configure a default route pointing to R1's Ethernet interface, IP address 133.33.1.1/29 on Catalyst 6509.

IP Address Configuration (0.5 Hours)
Use the Class B IP address 130.33.0.0. Configure IP addressing as follows:

• • • • •

Use a 29-bit mask for VLAN 100 and a 25-bit mask for VLAN 200 and VLAN 300. Use a 27-bit mask for VLAN 400. Use a 24-bit mask for VLAN 500, VLAN 550, and VLAN 600. Use a 30-bit mask for all WAN connections on Routers R1, R2, R3, and R4. Use a 24-bit mask for the WAN connection between Routers R4/R5 and R4/R6.

After IP routing is completed, all interfaces should be pingable from any router. Table 9-1 displays the IP address assignment for Routers R1–R6.

Table 9-1. IP Address Assignment Router Interface R1 E0/0 R1 S0/0 R1 S1/0 R1 S1/1 R1 S1/3 R2 E0/0 R2 S1/0 R2 S1/1 R3 E0 R3 S0 R3 S1 R3 S2 R4 E0 R4 S1 R4 S2 R4 S3 R5 E0 R5 E1 R5 S0 R6 E0 R6 S1 ISP1 S0 ISP1 E0 ISP2 S0 ISP2 E0 133.33.1.1/29 171.108.1.6/30 (to ISP2) 133.33.7.1/30 133.33.7.5/30 171.108.1.2/30 (to ISP1) 133.33.3.1/25 133.33.7.2/30 133.33.7.9/30 133.33.4.1/25 133.33.7.10/30 133.33.7.13/30 133.33.7.6/30 133.33.5.1/27 133.33.7.14/30 133.33.10.2/24 133.33.11.2/24 133.33.8.1/24 133.33.9.1/24 133.33.10.1/24 133.33.6.1/24 133.33.11.1/24 171.108.1.1/30 141.108.1.1/24 171.108.1.5/30 141.108.1.2/24 IP Address

Loopback IP Addressing: Part I (0.25 Hours)
Configure each router with a loopback interface. Assign the loopbacks on each router using the range of addresses from 133.33.201.0– 133.33.206.0 and a Class C mask. It must be possible to ping and telnet to the loopbacks from any one router. Test IP connectivity by pinging from R1, and ensure that you can telnet to any router within your network after you complete all IGP routing protocol configurations.

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CCNP Practical Studies: Routing
Table 9-2 displays the loopback addresses you need to assign to all six routers.

Table 9-2. Loopback Address Assignments Router R1 R2 R3 R4 R5 R6 133.33.201.1/24 133.33.202.1/24 133.33.203.1/24 133.33.204.1/24 133.33.205.1/24 133.33.206.1/24 Loopback 0

Ensure that all loopbacks in Table 9-2 appear as 24-bit networks in all IP routing tables, by using the interface ip ospf network point-topoint command for all routers configured with OSPF.

Loopback IP Addressing: Part II (0.25 Hours)
Create seven loopback interfaces in R1 by using 24-bit network masks in major networks ranging from 133.33.16.0/24–133.33.23.0/24. Create seven loopback interfaces in R2 by using 24-bit network masks in major networks ranging from 133.33.24.0/24 to 133.33.31.0/24. Ensure that you perform network summarization of these loopbacks to reduce IP routing table size wherever possible. Configure a static route on R5 to ensure that all loopbacks ranging from 133.33.16.0 to 133.33.31.0 are encompassed by a single static routing entry. (Hint: The subnet mask for a static route is 255.255.240.0.)

IGP Routing (7 Hours)
This section requires you to configure OSPF, IGRP, and EIGRP across the six routers and ensure that redistribution is used to provide IP connectivity among all routing domains.

IGRP Configuration (1.0 Hour)
Configure IGRP (AS 1) on R4 and R5 to meet the following specifications:

• • • • •

Configure IGRP on R5 E0/E1 and for the serial link between R4 and R5. Ensure proper filtering is configured on R4 to send only networks that do not reside on R5. Redistribute the IGRP route into OSPF/EIGRP domain. View the OSPF section for details on redistribution. Make sure you can see distributed IGRP routes throughout the topology. By using the IOS passive-interface command, ensure that only the correct interfaces residing in the IGRP AS are configured to send and receive IGRP updates. This ensures that router resources are not unnecessarily consumed.

EIGRP Configuration (1.5 Hours)
Configure EIGRP on Routers R1, R4, and R6:

• • • • • •

Configure the link between R4 and R6 in EIGRP domain 1. Configure VLAN 600 to reside in domain 2. Redistribute between EIGRP 1 and 2 and ensure network connectivity. Ensure that the IGRP domain and OSPF domain have these networks present in their respective IP routing tables. Ensure that VLAN 600 (133.33.6.0/24) and the loopback subnet on R6 (133.33.206.0/24) OSPF cost metric are set to 1000. (Metric type 2 by default is configured when redistributing from any protocol into OSPF.) Hint: Use the route-map command to complete this task. Configure R6 to set all external EIGRP routes (D EX) in AS 1 with an administrative distance of 90 (the same AD as internal EIGRP routes).

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CCNP Practical Studies: Routing OSPF Configuration (2.5 Hours)
Configure OSPF on R1, R2, R3, and R4:

• • • • • • • • • •

Configure the serial back-to-back links between R1/R2, R2/R3, and R1/R3 in the backbone (area 0.0.0.0). Configure the serial link between R3 and R4 in OSPF area 350. Configure VLAN 100 in area 100. Configure VLAN 200 in area 200. Configure VLAN 300 in area 300. Configure VLAN 400 in area 350. Additional areas are not required. Ensure that any OSPF areas not connected to area 0 are configured with an OSPF virtual link to ensure IP connectivity. (Hint: No virtual links are required because no OSPF areas are partitioned from the backbone area, or 0.0.0.0.) Assign any loopbacks into already existing areas. Redistribute OSPF into EIGRP and IGRP to maintain full-network connectivity.

OSPF Modifications (2 Hours)
Configure OSPF to perform the following functions:

• • • • • • •

Ensure that R3 is always the DR on VLAN 300 by setting the OSPF priority to 255. Change the Hello interval between R1/R3 WAN link to 25 seconds. Configure MD5 authentication between R1/R3 WAN link setting the password to ccnp. (Hint: All routers in area 0 require authentication; hence, the serial link between R1/R2 requires MD5 authentication as well.) Configure the local names of Routers R1–R6 so that all OSPF-enabled routers can perform an OSPF name lookup (using the loopbacks in Table 9-2 as IP addresses) for all OSPF adjacencies. Ensure that the router ID on all OSPF enabled-routers (R1 to R4) match the loopbacks used in Table 9-2. (Hint: Use the routerid command under the OSPF process ID.) Configure area 200 as a stub area. Ensure that the OSPF cost as seen by R1 and R3 for VLAN 200 is 1000.

BGP Routing Configuration (5 Hours)
The aim of this exercise is to configure IBGP among the routers in your IGP network (Routers R1–R6) and minimize the number of IBGP peer sessions for easy configuration. R1 is the focal point for all IBGP peering sessions and has two EBGP connections to the same ISP provided for redundancy purposes. You will also be asked to configure BGP attributes to influence routing decisions made in your IBGP network and also influence which path the Internet ISP routers, ISP1 and ISP2, choose to use for networks residing in your routing domain.

IBGP Configuration (2 Hours)
Configure IBGP (your autonomous system number is 1) within your network to meet the following conditions:

• • • • •

All routers are configured with minimum number of IBGP peers for scalability; this means you must use route reflectors and configure R1 as the route reflector to R2, R3, R4, R5, and R6 (route reflector clients). Use BGP peer groups on R1 to minimize the BGP configuration code required on R1. Disable BGP synchronization on all IBGP routers. All IBGP routers should receive routing updates from R1 only. All IBGP connections must be active as long as there is an active path between the routers; hence, use the assigned loopback interfaces as your source and next hop peer address for establishing TCP sessions. (Hint: Because there are redundant paths, the best practice in an IBGP network is to use loopback interfaces as the source and destination addresses for all IBGP peer sessions.)

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CCNP Practical Studies: Routing EBGP Configuration (1 Hour)
• • • •
Router R1 has two EBGP connections to the same ISP for redundancy purposes. Configure R1-R6 to meet the following requirements: Configure EBGP between R1 (AS 1) and ISP1/ISP2 (AS 1024). The Routers ISP1/ISP2 are both connected to AS 1024. Configure ISP1 and ISP2 to provide a default route to R1, along with some specific routing destinations using static routes to Null0. Example 9-1 displays the static route configurations on ISP1 and ISP2.

Example 9-1 Static Routes on ISP1/ISP2

ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip ip

route route route route route route route route route route route route route route route route route route route route route route route route •

0.0.0.0 0.0.0.0 Null0 1.0.0.0 255.0.0.0 Null0 2.0.0.0 255.0.0.0 Null0 3.0.0.0 255.0.0.0 Null0 4.0.0.0 255.0.0.0 Null0 5.0.0.0 255.0.0.0 Null0 6.0.0.0 255.0.0.0 Null0 7.0.0.0 255.0.0.0 Null0 8.0.0.0 255.0.0.0 Null0 10.0.0.0 255.0.0.0 Null0 11.0.0.0 255.0.0.0 Null0 100.0.0.0 255.0.0.0 Null0 101.0.0.0 255.0.0.0 Null0 102.0.0.0 255.0.0.0 Null0 141.100.0.0 255.255.0.0 Null0 141.108.0.0 255.255.0.0 Null0 142.100.0.0 255.255.0.0 Null0 143.100.0.0 255.255.0.0 Null0 144.100.0.0 255.255.0.0 Null0 145.100.0.0 255.255.0.0 Null0 146.100.0.0 255.255.0.0 Null0 147.100.0.0 255.255.0.0 Null0 148.100.0.0 255.255.0.0 Null0 149.100.0.0 255.255.0.0 Null0

The ISP has provided you with the following next hop addresses and your local AS number: - The R1 S0/0 next hop address is 171.108.1.1/30, and the remote AS is 1024. - The R1 S1/3 next hop address is 171.108.1.5/30, and the remote AS is 1024.

Configure EBGP on R1 and ensure that all advertised routes from ISP1 and ISP2 are present in R1's BGP table.

Advanced BGP Configuration: Policy Routing (1 Hour)
Using policy-based routing, ensure that all traffic sent from R3 (from users on VLAN 300) meets the following criteria:

• • • •

All Internet traffic sent to the default route 0.0.0.0 is sent through R1. All ICMP traffic is sent through R2. All other traffic is sent through R1. Using the IOS debug ip policy command, ensure that IP traffic is sent over the correct interface.

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CCNP Practical Studies: Routing Advanced BGP Configuration: Attribute Modification (1 Hour)
Configure R1 to set the following attributes for networks from the ISP routers named ISP1/ISP2:

• •

Prepend all networks in the range 1.0.0.0 to 9.0.0.0 with the AS_Path 400 300 200 and set the origin attribute to incomplete. Set the weight of all networks received from ISP1 to 100 and ISP2 to 200.

Self-Study Lab Solution
The following sample configuration files achieve the desired design criteria. This is by no means the only possible solution. As you have discovered throughout this practical guide, there is not always one right way to accomplish the tasks presented. In fact, the best possible way to learn more is to change the questions to meet your own goals and use show and debug commands to verify IP connectivity. Presented here are nine configuration files. Example 9-2 displays R1's full working configuration. Example 9-2 R1's Full Working Configuration

hostname R1 ! enable password cisco ! ip subnet-zero ip host R6 133.33.206.1 ip host R5 133.33.205.1 ip host R4 133.33.204.1 ip host R3 133.33.203.1 ip host R2 133.33.202.1 ip host r1 133.33.201.1 ! interface Loopback0 ip address 133.33.201.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback1 ip address 133.33.16.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback2 ip address 133.33.18.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback3 ip address 133.33.17.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback4 ip address 133.33.19.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback5 ip address 133.33.20.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 133.33.21.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback7

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CCNP Practical Studies: Routing
ip address 133.33.22.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback8 ip address 133.33.23.1 255.255.255.0 ip ospf network point-to-point ! interface Ethernet0/0 description VLAN 100 (OSPF Area 100) ip address 133.33.1.1 255.255.255.248 ! interface Serial0/0 description Serial Link to ISP2 S0 ip address 171.108.1.6 255.255.255.252 no ip mroute-cache no fair-queue clockrate 125000 ! interface Serial1/0 description Serial Link to R2 S1/0 bandwidth 125 ip address 133.33.7.1 255.255.255.252 ip ospf authentication message-digest ip ospf authentication-key ccnp clockrate 128000 ! interface Serial1/1 description Serial Link to R3 S2 bandwidth 125 ip address 133.33.7.5 255.255.255.252 ip ospf authentication message-digest ip ospf authentication-key ccnp ip ospf hello-interval 25 ! interface Serial1/2 shutdown ! interface Serial1/3 description Serial Link to ISP1 S0 bandwidth 125 ip address 171.108.1.2 255.255.255.252 ! router ospf 1 router-id 133.33.201.1 area 0 authentication message-digest area 100 range 133.33.16.0 255.255.248.0 network 133.33.1.1 0.0.0.0 area 100 network 133.33.7.1 0.0.0.0 area 0 network 133.33.7.5 0.0.0.0 area 0 network 133.33.16.0 0.0.7.255 area 100 network 133.33.201.1 0.0.0.0 area 0 ! router bgp 1 no synchronization redistribute connected redistribute ospf 1 neighbor ibgpnetwork peer-group neighbor ibgpnetwork remote-as 1 neighbor ibgpnetwork update-source Loopback0 neighbor ibgpnetwork next-hop-self

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202.1 ip host R1 133.205.0 access-list 2 permit any route-map setattributes permit 10 match ip address 1 set origin incomplete set as-path prepend 400 300 200 ! route-map setattributes permit 20 match ip address 2 ! line con 0 line aux 0 line vty 0 4 ! end Example 9-3 displays R2's full working configuration.33.1 remote-as 1024 neighbor 171.0.1 weight 100 neighbor 171.0.1 peer-group ibgpnetwork neighbor 133.202.1 peer-group ibgpnetwork neighbor 133.1.0.0 access-list 1 permit 9.33.1 peer-group ibgpnetwork neighbor 133.33.108.0.0.5 remote-as 1024 neighbor 171.0 access-list 1 permit 7.1.33.0.33. Example 9-3 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.0.33.0 access-list 1 permit 5.204.33.1.1 ip host R3 133.0 access-list 1 permit 8.0 ip ospf network point-to-point .108.1 ip host R2 133.0.1.201.206.1 ip host R4 133.0.0.CCNP Practical Studies: Routing neighbor 133.1 255.1 route-map setattributes in neighbor 171.33.0.204.0 access-list 1 permit 6.0.0 access-list 1 permit 3.33.255.203.0.108.0.108.255.1.33.1 ip host R5 133.0.203.1 peer-group ibgpnetwork neighbor 133.202.343 - .0.0.0 access-list 1 permit 4.0 access-list 1 permit 2.1.5 route-map setattributes in neighbor 171.206.108.1 peer-group ibgpnetwork neighbor 171.33.5 weight 200 no auto-summary ! ip classless ip ospf name-lookup ! access-list 1 permit 1.0.1 ! interface Loopback0 ip address 133.33.205.108.

28.255.255.255.33.255.1 255.0 ip ospf network point-to-point ! interface Loopback8 ip address 133.1 255.33.1 255.255.128 ip ospf cost 200 ! interface TokenRing0/0 no ip address shutdown ring-speed 16 ! interface Serial1/0 description Serial Link to R1 S1/0 bandwidth 125 ip address 133.30.252 ! interface Serial1/2 no ip address shutdown .1 255.33.252 ip ospf authentication message-digest ip ospf authentication-key ccnp no ip mroute-cache no fair-queue ! interface Serial1/1 description Serial Link to R3 S0 bandwidth 125 ip address 133.CCNP Practical Studies: Routing ! interface Loopback1 ip address 133.255.7.255.33.9 255.33.33.24.1 255.1 255.27.255.255.0 ip ospf network point-to-point ! interface Loopback7 ip address 133.33.0 ip ospf network point-to-point ! interface Loopback5 ip address 133.1 255.33.255.255.255.255.2 255.344 - .255.1 255.0 ip ospf network point-to-point ! interface Loopback6 ip address 133.255.31.255.255.0 ip ospf network point-to-point ! interface Loopback4 ip address 133.7.255.255.33.255.0 ip ospf network point-to-point ! interface Loopback2 ip address 133.3.29.0 ip ospf network point-to-point ! interface Ethernet0/0 description VLAN 200 (OSPF Area 200) ip address 133.1 255.26.0 ip ospf network point-to-point ! interface Loopback3 ip address 133.33.33.25.255.255.

33.0.1 ip host r4 133.248.1 ip host R3 133.1 ip host R5 133.203.33.202.24.0.33.202.0 network 133.1 remote-as 1 neighbor 133.0.255.33.0 0.0.0.33.201.255.2 0.202.201.24.1 255.1 area 0 authentication message-digest area 200 stub area 200 range 133.0.0 area 0 ! router bgp 1 no synchronization neighbor 133.33.0 area 0 network 133.3.255.255 area 200 network 133.204.1 ip host r2 133.0 area 200 network 133. Example 9-4 R3's Full Working Configuration hostname R3 ! enable password cisco ip subnet-zero no ip domain-lookup ip host r1 133.9 0.1 0.201.0 area 0 network 133.33.33.205.33.0 ip ospf network point-to-point ! interface Ethernet0 description VLAN 300 (OSPF Areas 300) ip address 133.1 255.33.0 255.33.1 0.7.33.1 update-source Loopback0 ! ip classless ip ospf name-lookup ! line con 0 line aux 0 line vty 0 4 ! end Example 9-4 displays R3's full working configuration.33.1 ! interface Loopback0 ip address 133.0.0.4.1 ip host R6 133.206.7.33.33.33.345 - .33.203.0.255.7.128 no ip directed-broadcast ip ospf priority 255 ip policy route-map sendtraffic media-type 10BaseT ! interface Ethernet1 no ip address .255.CCNP Practical Studies: Routing ! interface Serial1/3 no ip address shutdown ! router ospf 1 router-id 133.

203.1 remote-as 1 neighbor 133.0.0 area 0 network 133.33.0.255.1 area 0 authentication message-digest network 133.252 ip ospf authentication-key ccnp ip ospf hello-interval 25 clockrate 125000 ! interface Serial3 shutdown ! router ospf 1 router-id 133.10 255.1 0.0.346 - .0 access-list 100 permit icmp any any access-list 101 permit ip any any route-map sendtraffic permit 10 match ip address 1 set interface Serial2 ! route-map sendtraffic permit 20 match ip address 100 set interface Serial0 ! route-map sendtraffic permit 30 match ip address 101 .CCNP Practical Studies: Routing no ip directed-broadcast shutdown ! interface Serial0 description Serial Link to R2 S1/1 bandwidth 125 ip address 133.255.0 area 300 network 133.252 no ip directed-broadcast fair-queue 64 256 0 clockrate 2000000 ! interface Serial2 description Serial Link to R1 S1/1 ip address 133.0.33.0.0 area 350 network 133.1 0.33.203.33.255.6 255.0.33.255.13 0.1 update-source Loopback0 ! ip local policy route-map sendtraffic ip ospf name-lookup ! access-list 1 permit 0.255.7.4.7.0.7.0.201.0 area 0 ! router bgp 1 no synchronization neighbor 133.6 0.33.0.33.7.7.0.0.0.201.13 255.33.7.10 0.33.0 area 0 network 133.33.255.252 no ip directed-broadcast ip ospf authentication-key ccnp fair-queue 64 256 0 clockrate 125000 ! interface Serial1 description Serial Link to R4 S1 bandwidth 125 ip address 133.33.

CCNP Practical Studies: Routing set ! line line line ! end interface Serial2 con 0 aux 0 vty 0 4 Example 9-5 displays R4's full working configuration.0 ip ospf network point-to-point ! interface Ethernet0 description VLAN 400 (OSPF Area 400) ip address 133.33.0 distribute-list 3 out ! .33.202.1 255.255.33.252 ! interface Serial2 description Serial Link to R5 S0 ip address 133.1 ip host R5 133.7.33.206.1 255.10. Example 9-5 R4's Full Working Configuration hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup ip host R6 133.0 clockrate 125000 ! router eigrp 1 redistribute ospf 1 metric 128 20000 255 1 1500 route-map allowospf passive-interface Ethernet0 passive-interface Loopback0 passive-interface Serial1 passive-interface Serial2 network 133.0 ! interface Serial3 description Serial Link to R6 S1 ip address 133.0.204.1 ip host R2 133.224 ! interface Serial0 no ip address shutdown ! interface Serial1 description Serial Link to R3 S1 ip address 133.33.33.203.255.1 ip host r3 133.2 255.33.205.2 255.14 255.1 ! cns event-service server ! interface Loopback0 ip address 133.347 - .33.1 ip host R1 133.33.1 ip host r4 133.204.33.33.201.255.255.5.33.255.255.255.11.255.255.255.

33.3.33.9.255.14 0.0 access-list 6 permit 133.0 255.204.33.33.6.0 access-list 2 permit 133.201.1 0.0 access-list 5 deny 133.0 access-list 3 deny 133.12 access-list 6 permit 133.0 access-list 1 deny 133.33.33.5.205.204.33.255.33.7.0 access-list 4 permit 133.255.0 access-list 3 deny 133.10.5.33.1 remote-as 1 neighbor 133.33.6.0 Null0 no ip http server ip ospf name-lookup ! access-list 1 deny 133.33.33.255.0 Null0 ip route 133.0.0 area 350 ! router igrp 1 redistribute static metric 128 20000 255 1 1500 redistribute ospf 1 metric 128 20000 255 1 1500 passive-interface Ethernet0 passive-interface Loopback0 passive-interface Serial1 passive-interface Serial3 network 133.33.0 access-list 5 permit any access-list 6 permit 133.0 255.33.0.8.33.0.33.0 access-list 2 permit 133.11.0 255.33.0 access-list 1 permit any access-list 2 permit 133.33.0 access-list 1 deny 133.33.33.255.0 access-list 3 deny 133.0 access-list 3 permit any access-list 4 permit 133.255.206.0 area 350 network 133.33.10.1 update-source Loopback0 ! ip classless ip route 133.0 access-list 5 deny 133.33.348 - .206.0 Null0 ip route 133.1 0.0.0 access-list 6 permit 133.5.1 redistribute connected subnets route-map connectedroutes redistribute eigrp 1 metric 100 subnets route-map eigrpnets redistribute igrp 1 metric 100 subnets route-map igrpnets network 133.255.0.33.1.33.33.33.33.0 Null0 ip route 133.33.0 access-list 2 permit 133.0 access-list 6 permit 133.201.4.0.205.255.0 Null0 ip route 133.255.7.204.6.0 255.8.33.CCNP Practical Studies: Routing router ospf 1 router-id 133.0 area 350 network 133.33.7.33.255.0 255.9.0 distribute-list 1 out ! router bgp 1 no synchronization neighbor 133.0.0 route-map igrpnets permit 10 match ip address 2 ! route-map eigrpnets permit 10 match ip address 4 .206.11.

0.33.255.33.0 ! interface Ethernet0 description VLAN 500 (EIGRP AS 1) ip address 133.0 ! interface Serial0 description Serial Link to R4 S2 ip address 133.255.255.1 255.206.201.255.33.33.1 update-source Loopback0 ! .255.1 ip host R3 133.349 - .201.205.1 ip host R2 133.33.33.33.0 ! interface Ethernet1 description VLAN 550 (EIGRP AS 1) ip address 133.CCNP Practical Studies: Routing set metric 1000 ! route-map allowospf permit 10 match ip address 5 ! route-map connectedroutes permit 10 match ip address 6 ! line con 0 transport input none line aux 0 line vty 0 4 no login ! end Example 9-6 displays R5's full working configuration.255.203.1 255.255.1 255.1 remote-as 1 neighbor 133.33.8.33.1 255. Example 9-6 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.33.0 ! router bgp 1 no synchronization neighbor 133.10.33.33.33.1 ip host R1 133.1 ip host R5 133.255.202.9.204.1 ! interface Loopback0 ip address 133.205.201.0 clockrate 125000 ! interface Serial1 shutdown ! router igrp 1 network 133.1 ip host R4 133.

205.33.255.33.206.0 .0 Serial0 ! line con 0 line aux 0 line vty 0 4 ! end Example 9-7 displays R6's full working configuration.0.33.1 255.1 255.0 ! router bgp 1 no synchronization neighbor 133.201.0 distance eigrp 90 90 ! router eigrp 2 passive-interface Serial1 network 133.6.CCNP Practical Studies: Routing ip classless ip route 133.16.0 ! interface Ethernet0 description VLAN 600 (EIGRP AS 2) ip address 133.255.33.255.240.33.203.1 ip host R4 133.255.206.0 255.0 ! router eigrp 1 redistribute eigrp 2 route-map allowout passive-interface Ethernet0 passive-interface Loopback0 passive-interface Serial0 network 133.350 - .255.33.1 ! interface Loopback0 ip address 133.33.33.204.206.0.33.0 ! interface Serial0 shutdown ! interface Serial1 description Serial Link to R4 S3 ip address 133.11.255.33.202. Example 9-7 R6's Full Working Configuration hostname R6 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.1 ip host R5 133.1 update-source Loopback0 ! ip classless ! access-list 2 permit 133.201.1 ip host R3 133.1 ip host R2 133.33.1 ip host R1 133.33.1 255.1 remote-as 1 neighbor 133.33.33.201.255.33.

0.0.0.0.33.0 Null0 ip route 8.0 255.0.0.CCNP Practical Studies: Routing access-list 2 permit 133.0.0.1.0.0.100.0 255.255.108.0 0.0 255.0.0 Null0 ip route 5.1.0.0 Null0 ip route 143.0.0 Null0 ip route 101.0 255.0.0 Null0 ip route 6.0 Null0 ip route 142.0.0 255.0.0 Null0 ip route 102.0.0.255.0.0.0.0 255.0 Null0 ip route 141.0.0.108.0.0.0 Null0 ip route 2.0.0 255.108.0.0.108.0 255.0 255.0.0.0 Null0 ip route 7.0.1 255.0 Null0 ip route 100.0.0.100.0.0 Null0 ip route 10.0.0.0.0.108.255. Example 9-8 ISP1's Full Working Configuration hostname ISP1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 description ISP LAN connection to ISP2 ip address 141.0 255.0.0 255.0.0.0 ! interface Serial0 description Serial Link to R1 S1/2 ip address 171.351 - .1.0.255.0.0 255.0.0.0.0 255.0 Null0 ip route 11.1.0.255.1.0.0 Null0 ip route 1.0 255.100.0.0.0.0.0.0 255.0.0.2 default-originate no auto-summary ! ip classless ip route 0.2 remote-as 1024 neighbor 171.0.255.255.0 Null0 .0.0 route-map allowout permit 10 match ip address 1 ! line con 0 line aux 0 line vty 0 4 ! end Example 9-8 displays ISP1's full working configuration.0 255.0 Null0 ip route 141.0.0.0.0.0 255.0.0.0 Null0 ip route 4.100.0.0 Null0 ip route 144.2 remote-as 1 neighbor 171.0.1 255.0 255.108.255.0.0 Null0 ip route 3.252 clockrate 125000 ! interface Serial1 shutdown ! router bgp 1024 redistribute static neighbor 141.255.6.

0.6 remote-as 1 neighbor 171.0 Null0 ip route 10.0 255.0 Null0 ip route 8.0.0.0.0.0.0 Null0 ip route 1.100.0.0.0.0.0 255.252 ! interface Serial0 description Serial Link to R1 S1/3 ip address 171.0.0 255.0.1.0.0.0.352 - .0.0 Null0 ip route 5.0 255.252 ! interface Serial1 shutdown ! interface Serial2 shutdown ! interface Serial3 shutdown ! router bgp 1024 bgp log-neighbor-changes redistribute static neighbor 141.0.0.0.0 255.0.0.0.5 255.0.CCNP Practical Studies: Routing ip route ip route ip route ip route ip route ! line con line aux line vty ! end 145.0.0.0 Null0 ip route 3.0.6 default-originate ! ip classless ip route 0.100.255.0 148.1.0.0 149.0.0.1 remote-as 1024 neighbor 171.1.1.0 Null0 ip route 11.108.0.0 255.108.0 255. Example 9-9 ISP2's Full Working Configuration hostname ISP2 ! enable password cisco ! ip subnet-zero no ip finger no ip domain-lookup ! interface Ethernet0 description ISP LAN connection to ISP1 ip address 141.0 0 0 0 4 255.108.0.0 Null0 ip route 7.255.0 255.255.0.0.0 147.0 Null0 Null0 Null0 Null0 Null0 Example 9-9 displays ISP2's full working configuration.255.0.0 255.100.0 Null0 ip route 4.108.0.0.0.0.0 255.0 Null0 .255.0 255.0.0.0.255.2 255.0.0 255.0.0.0 255.0.0.0 0.1.0.0.0 255.0.0 Null0 ip route 6.0.0.255.108.0.100.255.0.100.0 146.255.0.0 Null0 ip route 2.

0.0 Null0 145.255.0 255. (The following configuration is also truncated.0.2/255.0 Null0 102.0.1.108.100.100.255.0 255.0.100.0 Null0 146.255.0 Null0 101.0.0.33.0 255.0.0.255.0.0.0.100.0.0.0/0.0 133.0 255. the #s are comment lines in Catalyst 6500 series software placed by Catalyst IOS).0 255.0.0.255.0.0.0.0.255.0.255.0.0 255.0.0.0. Example 9-10 Full Working Configuration of Catalysts Switch 6509 #vtp set vtp domain ccnp set vlan 1 name default type ethernet mtu 1500 said 100001 state active set vlan 100 name VLAN_100_R1E0/0 type ethernet mtu 1500 said 100100 state active set vlan 200 name VLAN_200_R2E0/0 type ethernet mtu 1500 said 100200 state active set vlan 300 name VLAN_300_R3E0 type ethernet mtu 1500 said 100300 state active set vlan 400 name VLAN_400_R4E0 type ethernet mtu 1500 said 100400 state active set vlan 500 name VLAN_500_R5E0 type ethernet mtu 1500 said 100500 state active set vlan 550 name VLAN_550_R5E1 type ethernet mtu 1500 said 100550 state active set vlan 600 name VLAN_600_R6E0 type ethernet mtu 1500 said 100600 state active set vlan 700 name VLAN_700_ISP_BACKBONE_ETHERNET type ethernet mtu 1500 said 100700 state active set vlan 1002 name fddi-default type fddi mtu 1500 said 101002 state active set vlan 1004 name fddinet-default type fddinet mtu 1500 said 101004 state active stp ieee set vlan 1005 name trnet-default type trbrf mtu 1500 said 101005 state active stp ibm set vlan 1003 name token-ring-default type trcrf mtu 1500 said 101003 state active mode srb aremaxhop 7 stemaxhop 7 backupcrf off ! #ip set interface sc0 100 133.255.0.7 set ip route 0.0 Null0 148.255.0.255.100.100.0.0 255.0 255.0 Null0 149.100.0 Null0 143.0 255.255.0.0 Null0 141.33.0 255.1 ! #set boot command set boot config-register 0x102 set boot system flash bootflash:cat6000-sup.248 133.100.100.33.0.0 255.0 Null0 144.0 Null0 147.0.0 Null0 141.0 255.255.1.1.353 - .0 Null0 142.0.CCNP Practical Studies: Routing ip route ip route ip route ip route ip route ip route ip route ip route ip route ip route ip route ip route ip route ! line con line aux line vty end 100.5-5-4.0.0.bin ! #mls set mls enable ipx ! # default port status is enable ! #module 1 : 2-port 1000BaseX Supervisor .0.0.0 Null0 0 0 0 4 Example 9-10 displays the full working configuration of the Catalyst 6509 switch.0 255.0.

33. so even correct configurations do not always guarantee connectivity.5. 00:03:34.33. as displayed in Example 9-10.7. Serial1/0 O 133. is the most widely used command on Cisco IOS routers.4.6. show ip route.6.33. OSPF.33.0/27 [110/1610] via 133.0/25 [110/1000] via 133.33. Serial1/1 O E2 133. 00:03:35.7. 00:13:18.6.33.33.33. 00:13:17.0/24 [110/1000] via 133.0/24 [110/100] via 133.33.7.33.CCNP Practical Studies: Routing ! #module 2 empty ! #module 3 : 48-port 10/100BaseTX Ethernet set vlan 100 3/1 set vlan 200 3/2 set vlan 700 3/11.33. and telnet Commands The following displays are presented here to demonstrate IP connectivity among all six routers.3.2.6. The first command used. ping.6.2.7.0/24 [110/1000] via 133. Serial1/1 [110/1600] via 133. Cisco IOS contains bugs and caveats.0/24 [110/801] via 133.204.6. Serial1/1 O IA 133. 00:13:17.33.0/16 is variably subnetted.3/15 set port name 3/1 R1 E0/0 set port name 3/2 R2 E0/0 set port name 3/3 R3 E0 set port name 3/5 R4 E0 set port name 3/7 R5 E0 set port name 3/8 R5 E1 set port name 3/9 R6 E0 set port name 3/11 ISP2 E0 set port name 3/15 ISP1 E0 set spantree portfast 3/1-48 enable #module 4 empty #module 5 empty #module 6 empty #module 7 empty #module 8 empty #module 9 : 8-port 1000BaseX Ethernet #module 15 : 1-port Multilayer Switch Feature Card #module 16 empty end Cat6509> (enable) New catalyst software displays only nondefault configurations.7. This section starts by looking at the IGP network namely.0/24 [110/100] via 133. BGP tables are presented to display BGP attributes and next hop path taken from each router. EIGRP. 00:13:18.7.0/25 [110/810] via 133.7. Example 9-11 show ip route ospf on R1 R1#show ip route ospf 133.33.8. Serial1/0 O E2 133. and telnet commands. 00:03:35.33.33.33.6. 00:03:35.2.33.206. Some ping and telnet requests from each router are also shown. Serial1/1 O 133. 6 masks O IA 133. 28 subnets. Serial1/1 O E2 133. You should familiarize yourself thoroughly with the common show. 00:03:34.6.354 - . 00:03:34.0/24 [110/1601] via 133.6. Serial1/1 O IA 133. Finally.8/30 [110/1600] via 133. Serial1/0 O 133.7. Example 9-11 displays the IP (OSPF) routing table on R1. Serial1/1 O E2 133.7. Any network designer must use common verification tools to ensure that IP connectivity is achieved.33.7.33. and IGRP.33.33.7. Serial1/1 O IA 133. ping.203. debug.0/24 [110/801] via 133.33.6.7.7. Serial1/1 .0.205. 00:03:34. Sample show.33. 00:03:34.33.202.

206.6 Interface Serial1/0 Serial1/1 Because R1 is configured with the IOS ip ospf name-lookup command and there is a host entry for R2 and R3.33. 00:02:42.202.1.33. Serial1/1 133.10.33. Serial1/1 133.1 Type escape sequence to abort. round-trip min/avg/max = 16/16/20 ms R1#ping 133.33. Sending 5.1 Type escape sequence to abort.12/30 [110/1600] via 133. round-trip min/avg/max = 28/31/32 ms R1#ping 133.9.203.33. 133. Example 9-13 Pinging Local Loopbacks on R1 R1#ping 133.7.1 Type escape sequence to abort.1 Type escape sequence to abort.CCNP Practical Studies: Routing O O O O O E2 E2 E2 IA IA 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7. 100-byte ICMP Echos to 133. Sending 5.33.33.201. as required.206. Example 9-12 show ip ospf neighbor on R1 R1#show ip ospf neighbor Neighbor ID R2 R3 Pri 1 1 State FULL/ FULL/ Dead Time 00:00:36 00:01:37 Address 133.0/21 [110/801] via 133. Serial1/0 R1 has an OSPF cost metric to networks 133. Sending 5.33. 100-byte ICMP Echos to 133.204. 00:03:36. 00:03:36.33.6.33.33.33.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.7.2. Example 9-13 displays a ping request to all IP interfaces present in Figure 9-1's interior IP routing network to demonstrate IP connectivity.33. round-trip min/avg/max = 1/1/4 ms R1#ping 133. Serial1/1 133. Serial1/1 133.2 133. The OSPF adjacency on R1 is displayed in Example 9-12.33. Sending 5.205. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7.1 Type escape sequence to abort.7.203.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. round-trip min/avg/max = 32/32/32 ms Example 9-14 displays IP connectivity to the remaining IP interfaces as described in Table 9-1.33.6. 100-byte ICMP Echos to 133.0/24 [110/20] via 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24.205. 00:02:41. 00:03:35.6. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).24. the remote neighboring routers are listed as R2 and R3 in Example 9-12.33.7. (Note the local interfaces on R1 are not displayed or pinged from R1. and 133.33.33.0/24 as 1000.33.) . round-trip min/avg/max = 16/16/16 ms R1#ping 133. The loopbacks in Table 9-2 are used to ping from R1.1.1.355 - .33.1 Type escape sequence to abort. 100-byte ICMP Echos to 133.3.0/24 [110/20] via 133.0/24.204.201. round-trip min/avg/max = 32/32/36 ms R1#ping 133.33.206.202. 100-byte ICMP Echos to 133.7.0/24 [110/100] via 133.1.33.1. Sending 5.33.1. Sending 5. 100-byte ICMP Echos to 133.11.33.6.6.

33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).6. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.7.7.33.1 Type escape sequence to abort.1. Sending 5.33.11.10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.11. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7.33.1 Type escape sequence to abort. round-trip min/avg/max = 28/29/32 R1#ping 133. Sending 5.11.10.13.33.10.13 Type escape sequence to abort. round-trip min/avg/max = 32/32/36 R1#ping 133.1.33. 100-byte ICMP Echos to 133. round-trip min/avg/max = 28/30/32 R1#ping 133.2. Sending 5. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.2 Type escape sequence to abort. 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/20/28 R1#ping 133.7.14. 100-byte ICMP Echos to 133. 100-byte ICMP Echos to 133. Sending 5.9 Type escape sequence to abort.356 - . 100-byte ICMP Echos to 133.33.4.33. 100-byte ICMP Echos to 133.33.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 28/30/32 R1#ping 133.10. Sending 5.6 Type escape sequence to abort. Sending 5.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).2 Type escape sequence to abort. round-trip min/avg/max = 16/16/20 R1#ping 133.2.7.33. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).14 Type escape sequence to abort.9.10 Type escape sequence to abort. timeout is 2 seconds: !!!!! ms ms ms ms ms ms ms ms ms ms ms .1.33.33.33.CCNP Practical Studies: Routing Example 9-14 Pinging LAN/WAN Interfaces from R1 R1#ping 133. Sending 5. round-trip min/avg/max = 32/32/33 R1#ping 133. round-trip min/avg/max = 28/29/32 R1#ping 133. round-trip min/avg/max = 16/16/20 R1#ping 133.33.7. round-trip min/avg/max = 16/16/16 R1#ping 133.1.33.7.7.2 Type escape sequence to abort.33.3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7.33. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5. Sending 5. 100-byte ICMP Echos to 133. Sending 5. round-trip min/avg/max = 16/16/20 R1#ping 133.10.2.1 Type escape sequence to abort.3. 100-byte ICMP Echos to 133.7.33. Sending 5.33.33. Sending 5.11.4.33.

Sending 5.10. round-trip min/avg/max = 16/17/20 R1#ping 133. Dead 40.108. 100-byte ICMP Echos to 133. round-trip min/avg/max = 32/32/33 R1#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. Network Type BROADCAST.1 Type escape sequence to abort.1. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. Example 9-15 show ip ospf interface on R1 ms ms ms ms ms ms ms R1#show ip ospf interface Ethernet0/0 is up. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1/0 is up. timeout is 2 seconds: !!!!! Success rate is 0 percent (5/5) R1#ping 133.1.5 Type escape sequence to abort. 100-byte ICMP Echos to 171. Router ID 133.2 Type escape sequence to abort. Router ID 133. Sending 5.8.10.8. round-trip min/avg/max = 32/32/36 R1#ping 133. Hello 10.1.1.201.1/29.1.108.1.33. Area 100 Process ID 1.9.8.201. Adjacent neighbor count is 1 .33.33.1 Type escape sequence to abort. Retransmit 5 Hello due in 00:00:04 Neighbor Count is 1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Cost: 10 Transmit Delay is 1 sec. round-trip min/avg/max = 32/37/48 R1#ping 133. Priority 1 Designated Router (ID) r1.33. 100-byte ICMP Echos to 133. Retransmit 5 Hello due in 00:00:05 Neighbor Count is 0. 100-byte ICMP Echos to 133.33. Interface address 133.1 No backup designated router on this network Timer intervals configured.357 - . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).8.1 Type escape sequence to abort. Wait 40. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5.2 Type escape sequence to abort.10.1.1. Hello 10.33. Sending 5. round-trip min/avg/max = 16/16/20 R1#ping 171.1. 100-byte ICMP Echos to 171.10. Dead 40.33. 100-byte ICMP Echos to 133.CCNP Practical Studies: Routing Success rate is 100 percent (5/5). Network Type POINT_TO_POINT.33. round-trip min/avg/max = 16/16/16 R1# Example 9-15 displays output when the show ip ospf interface command is entered on R1.2. round-trip min/avg/max = 16/16/16 R1#ping 171. Wait 40.1. Sending 5.9.33. Timer intervals configured. State POINT_TO_POINT. Sending 5.33.1/30.1. line protocol is up Internet Address 133. Cost: 800 Transmit Delay is 1 sec.108. 100-byte ICMP Echos to 133.108.1.5.2.1 Type escape sequence to abort.7.33. Area 0 Process ID 1. State DR.33. line protocol is up Internet Address 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.

358 - .1. Network Type POINT_TO_POINT. Wait 40.1.17. Timer intervals configured. Hello 10. Cost: Transmit Delay is 1 sec. Cost: Transmit Delay is 1 sec.201.1/24. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. State POINT_TO_POINT. Router ID 133. Cost: Transmit Delay is 1 sec. Wait 40. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Area 100 Process ID 1. line protocol is up Internet Address 133. Network Type POINT_TO_POINT.201. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback3 is up.33. Wait 40.201. Network Type POINT_TO_POINT. Hello 10.33. Retransmit 5 Hello due in 00:00:18 Neighbor Count is 1. Router ID 133.5/30. Network Type POINT_TO_POINT. Dead 100.33. line protocol is up Internet Address 133.33.33. Router ID 133. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Cost: 800 1 1 1 1 1 1 . using default key id 0 Serial1/1 is up. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback5 is up.16. Network Type POINT_TO_POINT.18.201. Wait 40.1. Network Type POINT_TO_POINT. Dead 40.201.33. line protocol is up Internet Address 133. Dead 40. Dead 40.33.33.33. Router ID 133. line protocol is up Internet Address 133.1. Dead 40. State POINT_TO_POINT. using default key id 0 Loopback0 is up.33. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.7.1/24. Timer intervals configured. line protocol is up Internet Address 133.1. Wait 40. Area 0 Process ID 1.20. Router ID 133.201.1/24.33. Cost: Transmit Delay is 1 sec.33. Timer intervals configured. State POINT_TO_POINT. Wait 100.201. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.1/24. Hello 25. State POINT_TO_POINT. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback2 is up. State POINT_TO_POINT.1/24.1.33.33. Cost: Transmit Delay is 1 sec. Area 0 Process ID 1.CCNP Practical Studies: Routing Adjacent with neighbor r2 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Hello 10. Dead 40. using default key id 0 Loopback1 is up. line protocol is up Internet Address 133. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.1. Area 100 Process ID 1. Hello 10. line protocol is up Internet Address 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Area 100 Process ID 1.19. Cost: Transmit Delay is 1 sec. Timer intervals configured. Router ID 133.1/24.201. Area 100 Process ID 1. State POINT_TO_POINT. Timer intervals configured. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback4 is up. Timer intervals configured. Hello 10. Router ID 133. Network Type POINT_TO_POINT. Area 100 Process ID 1.

33. Timer intervals configured. Dead 40.33. Dead 40.7.1. and whether authentication is in use.7. Timer intervals configured.23.33. 00:06:22.0/24 [110/1000] via 133.33. Serial1/1 O E2 133. Retransmit Hello due in 00:00:00 Neighbor Count is 0.205. Serial1/0 O 133.33. 00:06:23.7.10.7.10. Serial1/1 O E2 133. 17:03:37. 00:06:22. Serial1/1 O E2 133.10.33.1.16.204. You can verify OSPF area assignments and other details.33.33. line protocol is up Internet Address 133. Network Type POINT_TO_POINT.10.33.33. line protocol is up Internet Address 133.0/24 [110/801] via 133. Router ID 133. Retransmit Hello due in 00:00:00 Neighbor Count is 0.33.7. 00:06:21. Wait 40. Timer intervals configured.9. 00:06:22. Serial1/1 O IA 133.33. Serial1/1 O E2 133. Transmit Delay is 1 sec.10. State POINT_TO_POINT. Example 9-16 displays the IP OSPF routing table on R2. 00:06:21.33.12/30 [110/1600] via 133.11. Area 100 Process ID 1. 6 masks O IA 133. 00:06:21.33.33.33. Serial1/1 O E2 133.1. Retransmit Hello due in 00:00:00 Neighbor Count is 0.0/25 [110/810] via 133.6.CCNP Practical Studies: Routing Transmit Delay is 1 sec.33.33.201.10.7.203. Serial1/1 O 133.33.7.1/24.201. Hello 10.10. line protocol is up Internet Address 133. Network Type POINT_TO_POINT. Wait 40. Dead 40.33.10. Hello 10.33.10.4/30 [110/864] via 133. . State POINT_TO_POINT.33.33. Serial1/1 O E2 133.1.22.8. 00:06:21. 37 subnets. Transmit Delay is 1 sec. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) R1# 5 Cost: 1 5 Cost: 1 5 Cost: 1 5 Example 9-15 displays the area assignments. Dead 40.1.0/21 [110/801] via 133.7.1.0/24 [110/20] via 133.33.33.0/24 [110/801] via 133. 00:05:29.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback6 is up. Wait 40. Router ID 133.0.0/24 [110/1601] via 133. State POINT_TO_POINT. 17:03:37.10.33.201.10.0/24 [110/1000] via 133.7. Transmit Delay is 1 sec.201. Serial1/0 O 133.359 - .33.1/24.7.206.1. Router ID 133.33.7. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback7 is up. Serial1/1 O IA 133. Serial1/1 O IA 133.0/24 [110/100] via 133.33.33.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Wait 40. Network Type POINT_TO_POINT. State POINT_TO_POINT. Area 100 Process ID 1.10.0/24 [110/20] via 133.4. 17:03:37.7.7.33.0/29 [110/810] via 133. with the same command (show ip ospf interface). Serial1/1 O IA 133. Serial1/1 O E2 133.7.7. such as Hello and dead intervals. Example 9-16 show ip route ospf on R2 R2#show ip route ospf 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback8 is up.7.7. Serial1/1 O IA 133.21. the OSPF neighbor states. 00:06:22.0/24 [110/100] via 133. Serial1/0 Example 9-17 displays a successful ping request to all six loopbacks interfaces demonstrating full IP connectivity among all six routers in Figure 9-1.33. Hello 10.1/24.0/24 [110/100] via 133.0/27 [110/1610] via 133. 00:06:22. Area 100 Process ID 1.7. 00:05:29.0/16 is variably subnetted.33. Timer intervals configured. 00:06:23.33.33.33. Hello 10.10.5.33.10.

33.1 Type escape sequence to abort.33. line protocol is up Internet Address 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133. Example 9-18 show ip ospf interface on R2 R2#show ip ospf interfac Ethernet0/0 is up.201.203. Adjacent neighbor count is 1 Adjacent with neighbor r1 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.3. Wait 40. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/20 ms R2#ping 133.205. Interface address 133. Network Type POINT_TO_POINT. Sending 5.7.1 Type escape sequence to abort.202. Cost: 800 Transmit Delay is 1 sec.204. Retransmit 5 Hello due in 00:00:09 Neighbor Count is 0. Cost: 200 Transmit Delay is 1 sec. Network Type BROADCAST.1.1. line protocol is up Internet Address 133.1. State DR.33. line protocol is up Internet Address 133.33.9/30.1 Type escape sequence to abort.1. Timer intervals configured.202.3. Priority 1 Designated Router (ID) 133.33. round-trip min/avg/max = 1/2/4 ms R2#ping 133. Dead 40. Sending 5. 100-byte ICMP Echos to 133.33.33. round-trip min/avg/max = 32/32/36 ms R2#ping 133. round-trip min/avg/max = 16/16/16 ms R2#ping 133.1 No backup designated router on this network Timer intervals configured.206.33.202. round-trip min/avg/max = 32/32/32 ms Example 9-18 displays the output from the IOS show ip ospf interface command. Router ID 133.1 Type escape sequence to abort.33.1 Type escape sequence to abort. Hello 10.33. 100-byte ICMP Echos to 133.33. Sending 5.204. Area 0 Process ID 1.1.CCNP Practical Studies: Routing Example 9-17 Ping Request on R2 to Remote Networks R2#ping 133.1.202.360 - . Area 200 Process ID 1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).206. Sending 5.1.33. 100-byte ICMP Echos to 133.202. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.1/25. 100-byte ICMP Echos to 133.33. Sending 5.205.1 Type escape sequence to abort.203.7.33.2.2/30. Area 0 . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). State POINT_TO_POINT. Sending 5. Retransmit 5 Hello due in 00:00:08 Neighbor Count is 1. Hello 10.33.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1/0 is up.1.201. round-trip min/avg/max = 16/16/20 ms R2#ping 133. 100-byte ICMP Echos to 133. Wait 40.33. Router ID 133.33. Dead 40. using default key id 0 Serial1/1 is up.

33. Hello 10.202. using default key id 0 Loopback0 is up. Hello 10. line protocol is up Internet Address 133. Wait 40.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback4 is up. Hello 10. Area 200 Process ID 1. Router ID 133. Transmit Delay is 1 sec. Wait 40. line protocol is up Cost: 800 5 Cost: 1 5 Cost: 1 5 Cost: 1 5 Cost: 1 5 Cost: 1 5 Cost: 1 5 . Wait 40.CCNP Practical Studies: Routing Process ID 1. Network Type POINT_TO_POINT. Wait 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback2 is up. Timer intervals configured. Retransmit Hello due in 00:00:00 Neighbor Count is 0. State POINT_TO_POINT. Transmit Delay is 1 sec. line protocol is up Internet Address 133. Network Type POINT_TO_POINT. Area 200 Process ID 1. Wait 40.25. Network Type POINT_TO_POINT.1/24. Dead 40.33.1/24.33. Area 200 Process ID 1. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Dead 40.33. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.202.202. Transmit Delay is 1 sec.1. using default key id 0 Loopback1 is up. Wait 40. Hello 10. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Wait 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback5 is up. Network Type POINT_TO_POINT.26.1. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. State POINT_TO_POINT. Network Type POINT_TO_POINT. line protocol is up Internet Address 133. Router ID 133.361 - . Retransmit Hello due in 00:00:00 Neighbor Count is 0.27. Hello 10.1/24. Transmit Delay is 1 sec. line protocol is up Internet Address 133.33.1/24.1/24. Hello 10. State POINT_TO_POINT.202. Hello 10. Area 0 Process ID 1. Timer intervals configured. Timer intervals configured.1. Dead 40.1. State POINT_TO_POINT. Router ID 133.33. Dead 40. Router ID 133.202.28. Router ID 133. State POINT_TO_POINT. Dead 40. Timer intervals configured.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback6 is up. line protocol is up Internet Address 133.24. line protocol is up Internet Address 133.202. State POINT_TO_POINT.1/24. Transmit Delay is 1 sec.202. Transmit Delay is 1 sec. Area 200 Process ID 1. Dead 40. Transmit Delay is 1 sec. Retransmit Hello due in 00:00:08 Neighbor Count is 1. Router ID 133.1.33. Timer intervals configured. Timer intervals configured.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback3 is up. Router ID 133.33.202.1. State POINT_TO_POINT. Network Type POINT_TO_POINT. Timer intervals configured. Area 200 Process ID 1. Dead 40. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Network Type POINT_TO_POINT.1.33.33.

33.3. Serial1 O E2 133.33.33.14.7. Network Type POINT_TO_POINT.1. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback8 is up. Serial1 O E2 133.33.206. Serial2 O IA 133.7. Area 200 Process ID 1.1 133. Router ID 133. 00:07:08. 00:07:08.0/30 [110/864] via 133. 00:07:08. State POINT_TO_POINT. Dead 40.7. 00:06:10. Serial2 O IA 133.33.202.33. 00:07:08.29.14. State POINT_TO_POINT.1. .33.33.33.33.33.6. Serial1 O E2 133. Wait 40.33. 00:07:08.7.0/24 [110/801] via 133. Transmit Delay is 1 sec.33. Serial1 O E2 133. 6 masks O 133. Serial1 O 133.7.33.201.16.0/16 is variably subnetted.33.0/27 [110/810] via 133. 17:04:09.14.33. Router ID 133.7.33. Router ID 133.33. Dead 40. Serial0 Example 9-21 displays a successful ping request to all routers by using the names configured on R3.33.31. 00:07:08.7.9. Hello 10.0/24 [110/100] via 133.5.0. Serial1 O E2 133.202. Serial0 O E2 133.0/24 [110/1000] via 133.5.5. 00:07:08. 29 subnets. 17:04:09. 00:06:10.7.11.9.24.33.7. 00:07:08.33.9.7.33. Timer intervals configured.0/24 [110/801] via 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback7 is up. Dead 40. Example 9-20 show ip route ospf on R3 R3#show ip route ospf 133. Serial2 O IA 133. Wait 40.1/24.33. Serial2 O 133.1. Example 9-19 show ip ospf neighbor on R2 Cost: 1 5 Cost: 1 5 Cost: 1 5 R2#show ip ospf neighbor Neighbor ID Pri State R1 1 FULL/ R3 1 FULL/ - Dead Time 00:00:35 00:00:36 Address 133.33.33.5. Serial0 O 133.14. 17:04:10.202.8.7.0/24 [110/20] via 133.33.33.CCNP Practical Studies: Routing Internet Address 133.30.7. Network Type POINT_TO_POINT.7. Area 200 Process ID 1. State POINT_TO_POINT.33. Serial1 O IA 133. (Refer to the full configuration in Example 9-4). Serial1 O E2 133.33. Transmit Delay is 1 sec.1/24.33.33.9. 00:07:08. 00:07:09.202.0/24 [110/100] via 133.7. Serial1 O 133.0/25 [110/1000] via 133.7.14. Retransmit Hello due in 00:00:00 Neighbor Count is 0.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0.0/24 [110/65] via 133. Timer intervals configured.14.5.7. Timer intervals configured.33. 00:07:09. Hello 10.33. line protocol is up Internet Address 133.10 Interface Serial1/0 Serial1/1 Example 9-20 displays the IP (OSPF) routing table on R3.0/21 [110/65] via 133.0/29 [110/74] via 133.7. Area 200 Process ID 1.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0.204.205. Transmit Delay is 1 sec.1/24.33. Network Type POINT_TO_POINT.0/24 [110/1000] via 133.10.33.14.14.1.7.0/24 [110/100] via 133.33.0/21 [110/801] via 133.33.0/24 [110/20] via 133. line protocol is up Internet Address 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) R2# Example 9-19 displays the OSPF neighbors on R2.33. Hello 10.7.33. Wait 40.14.362 - .

203.33. Area 300 Process ID 1. maximum is 0 msec Neighbor Count is 0.33. Network Type BROADCAST. State POINT_TO_POINT. Cost: 10 Transmit Delay is 1 sec.33.205.4. line protocol is up Internet Address 133. flood queue length 0 Next 0x0(0)/0x0(0) .33. Hello 10. Router ID 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5. 100-byte ICMP Echos to 133.363 - . Sending 5.33. round-trip min/avg/max = 16/17/20 ms R3#ping r5 Type escape sequence to abort.1/24.1.204. Timer intervals configured. 100-byte ICMP Echos to 133. line protocol is up Internet Address 133. Interface address 133.1. Dead 40. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Wait 40. Network Type POINT_TO_POINT. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0.201.1. Retransmit 5 Hello due in 00:00:04 Index 1/1. 100-byte ICMP Echos to 133.33. Retransmit 5 Hello due in 00:00:00 Index 3/5. round-trip min/avg/max = 32/33/36 ms R3#ping r6 Type escape sequence to abort.1. Sending 5. Cost: 1 Transmit Delay is 1 sec.CCNP Practical Studies: Routing Example 9-21 Pinging All Loopbacks Using Names on R3 R3#ping r1 Type escape sequence to abort.1. round-trip min/avg/max = 32/32/36 ms R3# Example 9-22 displays the output when the show ip ospf interface command is entered on R3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Router ID 133. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).202.33.33.1. Sending 5. State DR.1/25.1.4.33. Wait 40.206.33.33. Dead 40. Example 9-22 show ip ospf interface on R3 R3#show ip ospf interface Ethernet0 is up. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 20/22/24 ms R3#ping r2 Type escape sequence to abort. Sending 5. maximum is 0 Last flood scan time is 0 msec. round-trip min/avg/max = 16/16/16 ms R3#ping r3 Type escape sequence to abort.1. Area 0 Process ID 1. 100-byte ICMP Echos to 133. Priority 255 Designated Router (ID) r3. Hello 10.203. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up.203.1 No backup designated router on this network Timer intervals configured.203. Sending 5. 100-byte ICMP Echos to 133. round-trip min/avg/max = 1/2/4 ms R3#ping r4 Type escape sequence to abort.

Area 0 Process ID 1. Timer intervals configured. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1. Router ID 133. using default key id 0 Serial1 is up. Retransmit 5 Hello due in 00:00:01 Index 1/2. Timer intervals configured. maximum is 0 Last flood scan time is 0 msec. Adjacent neighbor count is 1 Adjacent with neighbor r2 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.33. Network Type POINT_TO_POINT. Timer intervals configured.7. Wait 100. Network Type POINT_TO_POINT.33.1. maximum is 0 msec Neighbor Count is 1.6/30. Router ID 133. IGRP. Cost: 64 Transmit Delay is 1 sec. Area 350 Process ID 1. using default key id 0 R4 is configured for three interior routing protocols: OSPF. maximum is 9 Last flood scan time is 0 msec.203. . flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1. Hello 25. maximum is 0 msec Neighbor Count is 1. Example 9-23 displays the full IP routing table on R4 including the BGP routes. Wait 40. maximum is 9 Last flood scan time is 0 msec. maximum is 9 Last flood scan time is 0 msec.33. Retransmit 5 Hello due in 00:00:02 Index 2/3.7.33. Wait 40. and EIGRP. Adjacent neighbor count is 1 Adjacent with neighbor r4 Suppress hello for 0 neighbor(s) Serial2 is up.203. line protocol is up Internet Address 133. State POINT_TO_POINT. maximum is 0 msec Neighbor Count is 1.CCNP Practical Studies: Routing Last flood scan length is 0. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1. Cost: 800 Transmit Delay is 1 sec. Cost: 800 Transmit Delay is 1 sec.1. State POINT_TO_POINT.33. line protocol is up Internet Address 133.13/30. Hello 10. Network Type POINT_TO_POINT. Dead 40. using default key id 0 Serial0 is up. maximum is 0 msec Neighbor Count is 0. line protocol is up Internet Address 133. Area 0 Process ID 1.1. Hello 10. Retransmit 5 Hello due in 00:00:02 Index 1/4.10/30. Router ID 133. Adjacent neighbor count is 1 Adjacent with neighbor r1 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.203.7. Dead 100. State POINT_TO_POINT. Dead 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.33.364 - .

33.33. 01:12:20 B 3.1.4.33. Serial2 I 133. L1 .0/24 is directly connected.1. R .0. Serial1 S 133.33.0.33.0.1.OSPF NSSA external type 1. S . 00:19:02.0. Serial3 O IA 133.33.7.0/24 [110/865] via 133.IGRP.0/8 [200/0] via 133.33.33.33.ODR P .7.OSPF.0. Serial2 C 133.0/8 [200/0] via 133. L2 . Serial2 C 133.33.OSPF NSSA external type 2 E1 . 01:12:20 B 141.33.0.108.0/27 is directly connected.0/8 [200/0] via 133. 01:12:20 B 4.206.0/24 [90/2195456] via 133.33.0/24 is directly connected.33.13. 01:12:04 B 2.201.201.201.per-user static route.1. 00:19:02. 01:12:20 B 142.201.0/8 [200/0] via 133.0/24 [110/129] via 133.6.33.7.mobile.OSPF inter area N1 .4 [200/0] via 133.33.13.0/24 [110/65] via 133.0/8 [200/0] via 133.108.33. 00:19:02.33.13.13.204.0/30 [110/928] via 133.0/16 [200/0] via 133.33.OSPF external type 2.0.1. 01:12:20 B 5.static. 01:12:20 B 1.33.0/16 [200/0] via 133.33.7.33.13.0.100.33.100.7. o .OSPF external type 1.33. Serial1 O IA 133.5.201. B .0.201.8/30 [110/864] via 133. O .108.0/16 [200/0] via 133.201.100.1. 00:19:02.100.201.100.1. Null0 S 133.0/24 [100/8976] via 133. 01:12:21 B 10.0. Null0 C 133.0.1.201.1.0 B 102.connected.0.33. 01:12:20 B 143.33.33.RIP.33.0/8 [200/0] via 133.1.33.0. 01:12:20 B 100.100.3.201. Serial3 O IA 133.33. 00:01:04.0.0/16 [200/0] via 133. 01:12:20 171.33.201.1.33. I .0/24 [100/8576] via 133. IA .201.13.7.10. Serial1 O IA 133.1.1.33.33.1 to network 0.0.0. ia .0/24 is directly connected.0/8 [200/0] via 133.0/25 [110/1064] via 133.7.33.0/16 [200/0] via 133.10.33.0.1. 00:19:02.0.201.33. 00:19:02.0.33. Serial1 S 133.201.7.0.0. Null0 O IA 133.1. 01:12:21 B 11.33.0 [200/0] via 133.4/30 [110/128] via 133. 34 subnets. Loopback0 I 133. 2 subnets B 171.1.periodic downloaded static route Gateway of last resort is 133.0.13.202.0/29 [110/138] via 133.EGP i .7.100.33.0.1.205.1. Serial1 S 133.365 - .0/8 [200/0] via 133.108.201.201.0/24 is directly connected.0.IS-IS.33.33.candidate default.1.10.33.1.1. 01:12:21 B 146.0.0. 00:19:03.0/24 is directly connected.201.0. EX . 01:12:21 133.33. 01:12:04 B 171.8.7.0/16 [200/0] via 133.0/24 [100/8576] via 133.EIGRP external.201.1.33.0/24 is directly connected.1.33. 00:19:02.201. 02:53:58.1.1.201.BGP D .0/8 [200/0] via 133.201.1. 01:12:20 B 144. 01:12:20 B 8.33.0/16 [200/0] via 133.1.1.10.12/30 is directly connected.33.33.IS-IS level-2. U .0. 00:19:02.0. Serial1 S 133.33. N2 .IS-IS inter area * .33. E2 .201.0/8 [200/0] via 133.33.1.0.5.0/30 is subnetted. 01:12:20 B 101.0.4.33.0/16 [200/0] via 133.3.0/8 [200/0] via 133.33.33. 01:12:20 B 7.33.33.0.201.7.1. Null0 O IA 133.0.0/24 is directly connected.33.0/16 [200/0] via 133.201. 00:01:05.203.11.33.33. E .1.CCNP Practical Studies: Routing Example 9-23 show ip route on R4 R4#show ip route Codes: C .0.1.33.13.0. 01:12:20 B 141.7.0/24 [90/2297856] via 133.100. Serial1 O IA 133. 01:12:20 B 145.0.0/16 [200/0] via 133. 00:01:05. Null0 O IA 133. 01:12:20 B 6. 6 masks C 133.EIGRP.0/8 [200/0] via 133.0.33. 01:12:21 B 149.100.0.7.33.33.IS-IS level-1.201.201.0. Serial1 . 01:12:21 B 148. Serial2 D 133.11. Serial1 O IA 133.7.0. 01:12:21 B 147. 02:53:59. Ethernet0 D 133.1.0/8 [200/0] via 133.0/25 [110/74] via 133.201.1.9. Serial1 I 133.13.33.0/16 is variably subnetted. M .

maximum is 10 Last flood scan time is 0 msec.1/27. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1.1. Router ID 133.22. State DR. BGP is supplied a default route from R1. Hello 10.201. Retransmit 5 Hello due in 00:00:03 Index 1/1.33.13. Cost: 10 Transmit Delay is 1 sec.5. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0. 01:12:07 [200/0] via 133. Network Type POINT_TO_POINT.0/24 B 133.21.33. Retransmit 5 Hello due in 00:00:00 Index 3/3. State POINT_TO_POINT.1.0/24 B 133. Serial1 via 133.0/24 B 133.204. 00:19:03. IGRP.201. 01:12:07 [200/0] via 133.1.33.1.204.0/24 B 133.33. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) . maximum is 4 msec Neighbor Count is 1.33.7.5.33.0/21 B 133.33.0/24 O IA 133.1. Area 350 Process ID 1.0/24 B 133.33. 01:12:07 [110/129] via 133. 01:12:07 [200/0] via 133.201. Interface address 133.14/30.33.33.0/0 [200/0] is directly connected. maximum is 0 msec Neighbor Count is 0.20. line protocol is up Internet Address 133. Wait 40. Router ID 133. Hello 10.CCNP Practical Studies: Routing C 133.1.1.33.1.201. line protocol is up Internet Address 133.16.18. Area 350 Process ID 1.204. Cost: 64 Transmit Delay is 1 sec.7.33.0/21 B* 0. Serial3 [200/0] via 133.201.0.33. Dead 40.204. and EIGRP. 01:12:07 [200/0] via 133.33.201.0. maximum is 0 Last flood scan time is 0 msec. 01:12:07 [110/865] via 133. Retransmit 5 Hello due in 00:00:02 Index 2/2. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1 is up. Dead 40.33. the gateway of last resort is set.33. 01:12:23 R4's IP routing table has entries for OSPF.1. 01:12:07 [200/0] via 133. Cost: 1 Transmit Delay is 1 sec.33.33. Priority 1 Designated Router (ID) r4. Router ID 133.1 No backup designated router on this network Timer intervals configured. Wait 40.33.16. Hello 10.33.33.33.17. Timer intervals configured.33.33.201.1/24. Dead 40.19.1.0/24 O IA 133.33.7.0/24 B 133.1. Wait 40.201.13. Example 9-24 displays the output from the IOS show ip ospf interface command.33. Serial1 [200/0] via 133. maximum is 0 msec Neighbor Count is 0.201. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up.33. 01:12:07 [200/0] via 133.11. Example 9-24 show ip ospf interface on R4 R4#show ip ospf interface Ethernet0 is up.366 - .23.33. and hence. Area 350 Process ID 1.1. maximum is 0 Last flood scan time is 0 msec. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0.33. Timer intervals configured. State POINT_TO_POINT. line protocol is up Internet Address 133. Network Type POINT_TO_POINT. 00:19:03. Network Type BROADCAST.24.0/24 B 133.

timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/17/20 ms R4#ping 133.33.7. Sending 5.33. round-trip min/avg/max = 1/2/4 ms R4#ping 133.CCNP Practical Studies: Routing Example 9-25 displays the output from the IOS show ip ospf neighbor command on R4. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.202. Example 9-25 show ip ospf neighbor on R4 R4#show ip ospf neighbor Neighbor ID Pri State r3 1 FULL/ - Dead Time 00:00:33 Address 133.206. Sending 5. round-trip min/avg/max = 16/16/20 ms R4#ping 133. 100-byte ICMP Echos to 133.1.33.33.205.1 Se3 Hold Uptime SRTT (sec) (ms) 12 02:58:28 33 RTO Q Seq Type Cnt Num 200 0 62 Example 9-28 displays a ping request from R4 to all IP addresses in Table 9-2 to demonstrate IP connectivity.33.201.203.11. Sending 5.33.204.206.367 - .203. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133.1 Type escape sequence to abort.1 Type escape sequence to abort. Sending 5. 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/16/20 ms R4#ping 133. Sending 5.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).201.1 Type escape sequence to abort. Example 9-27 show ip eigrp neighbors on R4 R4#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 0 133. 100-byte ICMP Echos to 133.33. Sending 5.33.13 Interface Serial1 Example 9-26 displays the output from the IOS show ip eigrp interfaces command.33.202.1 Type escape sequence to abort.205.33.1. Example 9-26 show ip eigrp interfaces on R4 R4#show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Interface Peers Un/Reliable SRTT Se3 1 0/0 33 Pacing Time Un/Reliable 0/15 Multicast Flow Timer 115 Pending Routes 0 Example 9-27 displays the output from the IOS show ip eigrp neighbors command on R4. round-trip min/avg/max = 16/16/20 ms R4#ping 133.1 Type escape sequence to abort.1.33.33.1.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/16/20 ms . Example 9-28 Pinging Loopbacks on R4 R4#ping 133.204.33.

Serial0 I 133. 00:00:45.33. Example 9-30 demonstrates full IP connectivity by pinging all the loopback interfaces in Table 9-2 and some of the non-Class C networks. round-trip min/avg/max = 32/32/32 ms R5#ping 133. round-trip min/avg/max = 28/32/36 ms R5#ping 133.1 Type escape sequence to abort.1.1.2.203.33. R4 has been configured to send all networks as /24. 100-byte ICMP Echos to 133.0/24 [100/10476] via 133. Sending 5.33.202.0/16 is variably subnetted.1.33.33.2. 100-byte ICMP Echos to 133.10.33.33.1 Type escape sequence to abort.0.33.33.0.3.7. Sending 5.0/29.10.0 with a Class C mask.0/24 [100/100125] via 133. as displayed in Example 9-29.33.0/24 [100/8976] via 133.33.33. Serial0 I 133.0/24 [100/100125] via 133.1.10.33.1 Type escape sequence to abort. Sending 5.33.2.33.10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 00:00:45.203.2.33.2.7. Serial0 I 133.2.33.33.1.33.0/24 [100/100125] via 133. Example 9-29 IGRP IP Routing Table on R5 R5#show ip route igrp 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.203. Serial0 I 133.2. .10.11.33.33.10. 00:00:44.33.201. round-trip min/avg/max = 1/2/4 ms R5#ping 133.10.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 00:00:45.33.201. Serial0 I 133.0/24 [100/100125] via 133.33.33.0/24 [100/100125] via 133.1 Type escape sequence to abort.4. 00:00:45.1 Type escape sequence to abort.0/24 [100/100125] via 133.10. Example 9-30 Pinging All Loopbacks on R5 R5#ping 133.33. 00:00:44. Serial0 I 133.10.33.0/24 [100/10976] via 133.10. round-trip min/avg/max = 32/32/32 ms R5#ping 133.6.33. such as the subnets 133. 100-byte ICMP Echos to 133. 00:00:44.33.2.33.33. and because the local interfaces are configured with the Class B network 133.1.1.1 Type escape sequence to abort.0/24 [100/100125] via 133. round-trip min/avg/max = 32/32/36 ms R5#ping 133. round-trip min/avg/max = 16/16/16 ms R5#ping 133.CCNP Practical Studies: Routing Example 9-29 displays the IGRP IP routing table on R5.10.33.1. 100-byte ICMP Echos to 133. Serial0 I 133.206. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5.201. 34 subnets. 00:00:44.204.0/24 [100/100125] via 133.10.2.0/24 [100/10576] via 133. 00:00:45.1 Type escape sequence to abort. Serial0 R5 is running only IGRP.1.33.2.202.2. Serial0 I 133.33. 100-byte ICMP Echos to 133. Serial0 I 133. 100-byte ICMP Echos to 133.0 and 133. 7 masks I 133. 00:00:44.205.2.205. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).204. Serial0 I 133. Sending 5.368 - .33.206.33.33.3. 00:00:45. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. Sending 5.204.5. 00:00:44.202.206. Serial0 I 133.

11.0/24 [90/2169856] via 133.CCNP Practical Studies: Routing Sending 5.7.33.11.2. 00:00:35.33.2.0/27 [90/2195456] via 133.7. Serial1 D 133.11.33.4. Serial1 D 133.11.33. round-trip R5#ping 133.7.16. Serial1 D EX 133. 00:02:35.0/16 is variably subnetted. Serial1 D EX 133.2.1 Type escape sequence to abort.11.0/24 [90/2809856] via 133. 00:02:35. 00:00:35.11.33.2.11. Serial1 D EX 133.33.7.7. Sending 5.33.7. 00:02:35. !!!!! Success rate is 100 percent (5/5).33. 00:02:35.11.0/24 [90/2169856] via 133.2.33.11. 00:00:35. round-trip timeout is 2 seconds: min/avg/max = 32/32/32 ms timeout is 2 seconds: min/avg/max = 32/33/36 ms timeout is 2 seconds: min/avg/max = 40/40/40 ms timeout is 2 seconds: min/avg/max = 32/32/36 ms Example 9-31 displays the EIGRP routing IP table on R6. 00:00:35.33.11.3. Serial1 Example 9-32 displays the interfaces configured in EIGRP 1 and 2.2. 00:02:35.33.1.2.11. . Serial1 D EX 133. 00:00:35.33.33.33. which is running EIGRP in two domains: 1 and 2.9.5. Serial1 D EX 133.0/24 [90/2169856] via 133.2.24.2. 00:02:35.11.8.0/24 [90/2707456] via 133.2. 00:02:34.11. 00:02:35.0/24 [90/25632000] via 133.11. 00:02:35. 00:00:37.0/21 [90/25632000] via 133.205.2.369 - . !!!!! Success rate is 100 percent (5/5).0/24 [90/2707456] via 133.2. 100-byte ICMP Echos to 133.2.33. Serial1 D 133.4. round-trip R5#ping 133.0/24 [90/25632000] via 133.2.33.0.33.33. Example 9-31 show ip route eigrp on R6 R6#show ip route eigrp 133.33.33.33.33. 6 masks D 133.12/30 [90/2681856] via 133. 100-byte ICMP Echos to 133.3.33.33.1.11. Serial1 D EX 133.33.33.33.7. 00:00:36.0/30 [90/25632000] via 133.0/25 [90/25632000] via 133.10. Serial1 D EX 133.2.5 Type escape sequence to abort.202. Serial1 D 133.0/21 [90/25632000] via 133. !!!!! Success rate is 100 percent (5/5).203.33.33.33.33.1. Serial1 D 133.7.2.33.33. 00:02:35.7.33. Sending 5.33.33.2. 00:00:35.2.201.33.0/25 [90/25632000] via 133.11. !!!!! Success rate is 100 percent (5/5). Serial1 D EX 133.33.33.2. Serial1 D 133.7. round-trip R5#ping 133.33.1.0/24 [90/2169856] via 133.33. 26 subnets.7.33.2. 100-byte ICMP Echos to 133.33.5. Serial1 D EX 133.33.33.2. 100-byte ICMP Echos to 133. Sending 5. Serial1 D EX 133.2. Serial1 D EX 133.33.33.11. Serial1 D EX 133.2.33.0/24 [90/2681856] via 133. Serial1 D EX 133.4/30 [90/25632000] via 133. 00:02:35.204.33.11.11. Serial1 D 133. 00:02:34. 00:00:36.2. 00:00:35.33.11.2 Type escape sequence to abort.33. Serial1 D EX 133.8/30 [90/25632000] via 133.11.0/24 [90/25632000] via 133.33.1. 00:00:36.11.33.11.33.0/29 [90/25632000] via 133.0/24 [90/2169856] via 133. Serial1 D 133.5.0/24 [90/2297856] via 133.

Sending 5. round-trip min/avg/max = 32/32/36 ms R6#ping 133.33.201. 100-byte ICMP Echos to 133.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort.206. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.33. round-trip min/avg/max = 16/16/16 ms R6#ping 133.201.33.1. 100-byte ICMP Echos to 133.33.202. round-trip min/avg/max = 32/32/32 ms R6#ping 133.1.11. No EIGRP routers exist in domain 2. 100-byte ICMP Echos to 133. Sending 5.204. round-trip min/avg/max = 32/32/36 ms R6#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.33. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5.204. Example 9-34 Pinging Loopbacks on R6 R6#ping 133. Sending 5. Sending 5.370 - . Example 9-34 displays a successful ping request to all loopback interfaces in Figure 9-1. Sending 5.203.33.1 Type escape sequence to abort. Example 9-33 EIGRP Neighbors on R6 Pacing Time Un/Reliable 0/15 Pacing Time Un/Reliable 0/10 0/10 Multicast Flow Timer 6287 Multicast Flow Timer 0 0 Pending Routes 0 Pending Routes 0 0 R6#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 0 133.2 Se1 IP-EIGRP neighbors for process 2 Hold Uptime SRTT (sec) (ms) 10 03:06:26 818 Q Seq Cnt Num 4908 0 8 RTO Note that only one neighbor is pointing to R4.1 Type escape sequence to abort. 100-byte ICMP Echos to 133.33.202. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. 100-byte ICMP Echos to 133. round-trip min/avg/max = 1/2/4 ms R6# .206.CCNP Practical Studies: Routing Example 9-32 show ip eigrp interfaces on R6 R6#show ip eigrp interfaces IP-EIGRP interfaces for process 1 Xmit Queue Mean Interface Peers Un/Reliable SRTT Se1 1 0/0 818 IP-EIGRP interfaces for process 2 Xmit Queue Mean Interface Peers Un/Reliable SRTT Et0 0 0/0 0 Lo0 0 0/0 0 Example 9-33 displays the EIGRP neighbors on R6. round-trip min/avg/max = 32/32/32 ms R6#ping 133.205.1 Type escape sequence to abort.33.1.1 Type escape sequence to abort.33.1.1 Type escape sequence to abort.205.203.

1 Trying 133. Example 9-36 displays the BGP table on R1. the BGP tables on R3–R6 are exactly the same as R2. R5>telnet 133.206.203. R4.33.203.33..204. .33. Open R6>quit [Connection to 133.204..371 - .33.1 .33.204.33.33.. and R6 from R5.33. Open R6>quit [Connection to 133. Therefore. Open R3>quit [Connection to 133.1 Trying 133.203. users on connected interfaces routed throughout this network also have full IP connectivity.1 Trying 133.1 .201.204.1 closed R5>telnet 133.206.1 .1 closed R5>telnet 133..33..33.204.33.1 closed R5>telnet 133.206.33.33.204. R3...206.33. Example 9-35 Telnet into R1.201.1 closed R5>telnet 133.202.33. Open R1>quit [Connection to 133.1 Trying 133.1 ...201.1 Trying 133. Because IBGP is running among R1 (route reflector) and route reflector client.CCNP Practical Studies: Routing Telnet from the classful domain on R5 and ensure that you can telnet to all five remote routers. View the BGP tables on R1 and R2.. R2. Routers R2–R6.1 .1 .33.1 Trying 133.206. Open R2>quit [Connection to 133. Open R4>quit [Connection to 133.1 ..1 Trying 133.33.33..206..33. Example 9-35 displays an executive user telneting from R5 to all remote routers using the loopback interfaces in Table 9-2.1 closed R5>telnet 133..33.1 closed R5>telnet 133. only R2's BGP table is presented here for your reference.33. Open R4>quit [Connection to 133.202.202. so if you can telnet from the router.1 closed R5> by foreign host] by foreign host] by foreign host] by foreign host] by foreign host] by foreign host] by foreign host] Telnet is an application layer protocol.

0.0.5 0 200 400 300 200 1024 ? * 171.0 0 32768 ? *> 133.7.7.1.7.5 0 200 400 300 200 1024 ? * 171. h history.108.33. i .1 0 100 400 300 200 1024 ? *> 3.108.1.108.0 171.0.1.33.0.1.108. local router ID is 133.0 0 32768 ? *> 133.108.1.0/24 0.0/24 133.7.0 171.0 0 32768 ? *> 133.33.16.33.0.1.1.1.0.33.0.0/27 133.0. > best.6 801 32768 ? *> 133.108.0.0.7.202.6 810 32768 ? *> 133.1.5.5 0 200 400 300 200 1024 ? * 171.0 0 32768 ? *> 133.24.0.1.21.1 0 100 400 300 200 1024 ? *> 6.5 0 200 1024 ? * 171.0.7.1.4/30 0.1.0.0/24 0.0.1 Status codes: s suppressed.0/24 133.1.0/24 0.0.1 0 100 400 300 200 1024 ? Network Next Hop Metric LocPrf Weight Path *> 10.108.0 171.5 0 200 1024 ? * 171.6 1601 32768 ? *> 141.0 0 32768 ? *> 133.IGP.1 0 100 400 300 200 1024 ? *> 5.108.33.108.0.33.7.203.108.19.0 171.0/25 133.0 0 32768 ? *> 133.incomplete Network Next Hop Metric LocPrf Weight Path *> 0.5 0 200 400 300 200 1024 ? * 171.0 171.1 0 100 400 300 200 1024 ? *> 4.0.0 171.33. ? .1.108.5 0 200 400 300 200 1024 ? * 171.0.1 0 100 400 300 200 1024 ? *> 8.0 0 32768 ? *> 133.1.0.372 - .204.33.1 0 100 1024 ? *> 102.0 171.33.108.5 0 200 1024 ? .33.33.0.33.18.0. * valid.33.33.0.5 200 1024 i * 171.108.33.0 0 32768 ? *> 133.33.5 0 200 400 300 200 1024 ? * 171.1 0 100 400 300 200 1024 ? *> 7.CCNP Practical Studies: Routing Example 9-36 show ip bgp on R1 R1#show ip bgp BGP table version is 77.33.0.17.0.1.3.108.0.5 0 200 400 300 200 1024 ? * 171.7.6 1600 32768 ? *> 133.0. e .33.0.0 171.0.0/24 133.201.1 0 100 400 300 200 1024 ? *> 2.0.0.33.108.12/30 133.2 1600 32768 ? *> 133.0/21 133.23.0/24 0.33.0.100.0.0.1 0 100 1024 ? *> 133.1 0 100 1024 ? *> 11.33.0.0/24 0.0/24 0.33.1.5 0 200 1024 ? * 171.8/30 133.0 0 32768 ? Network Next Hop Metric LocPrf Weight Path *> 133.108.33.0/30 0.108.1.7.0.0.0 171.0 0 32768 ? *> 133.4.0.108.108.0/29 0.0.108.108.1.5 0 200 1024 ? * 171.33.0.0.1.108.20.1 100 1024 i *> 1.0/25 133.108.1.5 0 200 1024 ? * 171.1.0.7.22.1.5 0 200 400 300 200 1024 ? * 171.2 1000 32768 ? *> 133.7.108.0.108.33.7.108.internal Origin codes: i .0 171.0.0.0.1.33.6 1610 32768 ? *> 133.0.1 0 100 1024 ? *> 100.5 0 200 1024 ? * 171.33.0/24 0.108.0.1.1.0.2 801 32768 ? *> 133.2 801 32768 ? *> 133.0 171.1.0.0.108.108.0 0 32768 ? *> 133.1.0 171.0.108.1.0.0 171.0.1.1 0 100 1024 ? *> 141.0/24 0.0/24 0.33.1.108.0 0 32768 ? *> 133.1.0 171.33.0.33.108.7.0 171.201.1 0 100 1024 ? *> 101.EGP. d damped.0 171.

33.1 133.1.5 Next Hop 171.33.201.4/30 171.0.0.201.0 *>i10.0 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? Metric LocPrf Weight Path 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 200 1024 ? 0 100 1024 ? 0 32768 ? 0 32768 ? Example 9-37 displays the BGP table on R2.5 171. > best.1.1 133.1 Next Hop 133.1 133.7.33.1 133.201.0.CCNP Practical Studies: Routing * *> * *> * *> * *> * *> * *> * *> * *> * *> *> 142.33.201.108.0 *>i5.0 *>i100.1 171.1 171.0.0.1 133.108.0 149.201.201.201.33.1.1 Status codes: s suppressed.1.108.0.1 171.201.5 171.33.0.201.0 *>i101.0.201.201.33.33.0.0.0.33.0/24 *>i133.EGP.0.108.0 *>i1.0/29 *>i133.0.0/24 Next Hop 133.33.373 - .0.33.1.33.33.100.0.0/25 *>i133.201.100.5 171.1 133.0 *>i2.1.1 171.33.0.1.0.1.33.108.0.33.1 133.0.201.100. Example 9-37 show ip bgp on R2 R2#show ip bgp BGP table version is 370.1 133.33.0/25 *>i133.4/30 *>i133.33.0/27 Network *>i133.0/30 171.1 133.1 133.0 *>i4.0.108.201.19. * valid.1 133.0.108.0/24 *>i133.33.0.202.incomplete Network *>i0.0.4.1.1 171.33.1 0.1.108. local router ID is 133.108.0 143.0 148.1 133.0.0.1.33.201.108.33.100. h history.1 133.7.33.0.108.201.33.201.108.18.21.0 *>i133.33.0.108. i .1.201.108.7.1 171.1 133.33.0.1 133.0 146.1 133.0 171.0.1.0 Network 147.1 Metric LocPrf Weight Path 100 0 1024 i 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 400 300 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 ? 1000 100 0 ? 810 100 0 ? 1610 100 0 ? Metric LocPrf Weight Path 0 100 0 ? 0 100 0 ? 1600 100 0 ? 1600 100 0 ? 0 100 0 ? 0 100 0 ? 0 100 0 ? 0 100 0 ? 0 100 0 ? 0 100 0 ? 200 200 200 200 200 200 200 200 1024 1024 1024 1024 1024 1024 1024 1024 ? ? ? ? ? ? ? ? .33.1 133.0/24 *>i133.201.33.20.0.201.0.1 171.0.100.1 133.0 *>i6.33.201.0/24 *>i133.1 133.0 *>i3.5 171.33.1 133.1.201.108.33.0 *>i102.1 133.0 144.33.108.1.33.12/30 *>i133.3.0.IGP.33.201.100.17.0/24 *>i133.5 171.1.33.1.33.0 *>i8.0 145.0.1 133.33.108.108.1.1 133.33.16.1 133.201.0/30 *>i133. d damped.0.201. e .108.1. ? .100.0.1 133.33.0 0.100.33.5 171.201.0.1.internal Origin codes: i .5 171.33.201.201.33.1 133.5.7.8/30 *>i133.33.1 171.0.0.0.0 *>i7.0 *>i11.

33.1.1.33.202.33.201.0.0 *>i144.100.33.23.1 171.33.1. main routing table version 77 47 network entries and 71 paths using 6455 bytes of memory 10 BGP path attribute entries using 1004 bytes of memory BGP activity 266/219 prefixes.33.108.33.201.108.11068 Foreign Address 171.33.0.33.1 133.201.0.1.201.100.11071 812F1F10 r1.201.0 *>i171.100.204.100.22.1 133.1 133.1 133.100.179 r3.205.2.0.1 133.1 Next Hop 133.33.201.0/24 *>i133.1 133. Example 9-38 show ip bgp summary on R1 R1#show ip bgp summary BGP router identifier 133.1 133.1.203.201.1.33.33.33.33.33.179 171.108.202.0.0/24 *>i141.206.11069 812F1A94 r1.33.0/21 *>i133.1.204.1 133.108.201.1 133.33. Example 9-39 displays the TCP sessions on R1 with the IOS show tcp brief command.0.179 R6.24.33.201.33. 533/462 paths Neighbor 133.0 *>i141.33.33.201.1 133.33.1 133.1.100.201.1 133.0/24 *>i133.33.1 133.108.201.33.1 133. local AS number 1 BGP table version is 77.1.108.203.0 *>i143.1 133.33.201.33.1 133. Example 9-39 show tcp brief on R1 R1#show tcp brief TCB Local Address 812F0240 171.0 *>i148.0/30 *>i171. (BGP uses TCP port 179.0 *>i147.0.11001 R5.11074 812EFDC4 171.1 133.CCNP Practical Studies: Routing *>i133.374 - .179 r2.0 Network *>i145.1 133.5 V 4 4 4 4 4 4 4 AS MsgRcvd MsgSent 1 182 274 1 182 274 1 182 274 1 182 274 1 146 255 1024 229 322 1024 217 317 TblVer 77 77 77 77 77 77 77 InQ OutQ Up/Down State/PfxRcd 0 0 01:48:26 0 0 0 01:48:27 0 0 0 01:48:31 0 0 0 01:48:30 0 0 0 00:18:14 0 0 0 01:48:17 24 0 0 01:48:14 24 The shaded peers in Example 9-38 are route reflector clients to R1.201.0 *>i146.11073 8130B85C r1.201.1 133.6.33.1 133.) .1 171.0.179 81308298 r1.11070 813029BC r1.1 133.108.0/24 *>i133.0/24 *>i133. and Example 9-39 confirms that BGP is configured with the TCP port number 179.108.33.179 R4.0 *>i149.0.179 (state) ESTAB ESTAB ESTAB ESTAB ESTAB ESTAB ESTAB R1 is configured with seven BGP TCP peers.201.108.0 *>i142.1 0 100 0 ? 0 100 0 ? 801 100 0 ? 0 100 0 ? 801 100 0 ? 801 100 0 ? 1601 100 0 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? Metric LocPrf Weight Path 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 1024 ? 0 100 0 ? 0 100 0 ? Example 9-38 displays the BGP peer sessions on R1 in summary format using the IOS show ip bgp summary command.0.33.33.33.100.4/30 R2# 133.201.1.201.33.0/24 *>i133.201.201.201.5.100.100.

not found in many engineers. as a further exercise. It is now up to you to take the skills you learned in this book and extend them further. you have discovered how to route IP with any routing protocol and subnet addressing. For example. and although it may not be a network you will ever need to configure. .CCNP Practical Studies: Routing Summary You have completed a complex routing topology. even into areas you thought you could never master.375 - . and the ability to configure OSPF or RIP correctly and ensure network connectivity is a rare skill. you could modify the topology in Figure 9-1 and change the routing algorithms in use to see whether you can maintain a fully routable network. IP routing algorithms are complex.

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com/warp/customer/10/wwtraining/training_over/) offers many training courses. if you don't attempt every question. so you can quickly eliminate two or three options.cisco. so you might not get the attention you require. self-study is where you will acquire most of your knowledge. so you do not want to attempt an exam more than once if you can help it. so if you come across a difficult question. so it's best to determine whether you need a training course to help lay the foundations. mark the question for later review and move on to the next question. are regarded as the most difficult and well-respected IT certification exams in the world. particularly if you're a beginner. including the most coveted CCIE examination. including free sample examination questions: www. This simple tool can be useful in determining weak areas before you even book the real examination. but it is by no means the only resource you should use to prepare for any Cisco certification. Training courses are always packed with other candidates and offer a particular learning style. Cisco certification exams are computer-based. If this is the case. As such. Cisco computer-based examinations contain all multiple-choice questions. CCNPs are highly regarded in the IT industry. the process of elimination is important. In any multiple-choice examination. removed. Ensure that you are always updated about exam changes through the Cisco Web site. Self-analysis is one of the most difficult tasks to undertake.CCNP Practical Studies: Routing Appendix A.) Typically. Be honest with yourself because the Cisco certification exams will be 100 percent honest with you. NOTE The following link provides all the information you need on the Routing exam. Provided here are some useful study tips. (See the previous note for a sample simulation program.com/warp/public/10/wwtraining/certprog/testing/current_exams/640-503. they are constantly evolving and questions are changed. Cisco certifications. The exams require self-study and maybe even classroom training. Study Tips This appendix is a short study guide.377 - . Typically. you give yourself a 50 percent chance of scoring the valuable points. Cisco (www. Becoming Cisco certified in one of the certification tracks requires much more than simply picking up a manual or book and cramming or learning. A typical computer-based exam costs approximately $250. you must practice with a simulation that places you in an exam situation. . you are provided four or five possible answers. Any incorrect answer you select results in zero points. This appendix provides some handy study tips. The tests always include easy and hard questions. is to determine your strengths and weaknesses. Taking any Cisco examination is not an exercise you want to do repeatedly. If you can narrow the options to two choices.html Download the free challenge test and grade yourself. or added at any time. the questions have two options that initially appear to be correct. you are at a severe disadvantage because you will not score any points for questions you do not attempt. Strategies for Cisco Exam Preparation The first step.cisco. and some questions require more than one answer. To achieve time-management proficiency and the skills required to answer questions correctly. Time management is crucial.

you can go in early. typically an erasable sheet. except a refreshment and the provided writing materials. Have a relaxing evening.) You can hire and actually configure Cisco IOS routers and switches for a set fee. so even if you are struggling. On the day before the exam. do the following things: • • • • Leave plenty of time to get to the testing center. Try to stay calm. write down the topics you were not comfortable with and the source materials you need to acquire that knowledge. park and take a few moments to relax before the exam. What makes you a CCNP is passing a couple of exams. If you work daily with routers in your present job. Typically. comfortable clothing and take a sweater in case the room is too cold. Leave all those heavy books at home. Wear loose. you can use the exam to your advantage by remembering the topics that are not your strengths. Point your search engine toward the keywords. Ensure that you have the correct directions for the testing center. Always attempt a question even if you are unsure of the correct answer. Use the materials provided to work out the logic of some questions. Various Internet sites. do the following things: • • • • Call Sylvan Prometrics or whomever is hosting your examination and confirm your seat. CIM is a virtual IOS simulator that enables you to configure a set number of IOS features without having to purchase expensive Cisco routers. By building a small practice lab. but what makes you a quality CCNP is the desire to extend your ability with every passing moment.CCNP Practical Studies: Routing Hands-On Experience Almost all CCIE. Confirm that your photo ID will be accepted. the time. even with just two routers. do the following things: • • • If you do not know the answer to a question. in fact. CCNP. so you need to be on your guard mentally. The testing center provides a pen and some form of writing paper. provide tuition and virtual labs. and CCNA engineers will tell you that hands-on experience with Cisco routers and switches is the most valuable learning tool.com/warp/public/710/cim/index. are real Cisco devices. too many to mention here. (These labs are called virtual but. try answering the question by a process of elimination. . Some candidates attempt to cram in too much learning the night before at the cost of a good night's sleep. Remember that you can take the exam multiple times. You are not allowed anything in the exam room. ensure that you utilize your daily access to view how the network is functioning using the techniques presented in this guide. Sometimes. you can study any routing algorithm using loopback interfaces. and the location of the exam. Cisco virtual labs. two answers will stand out. it's best to take your passport so you will not have any problems. The following link provides more details about this virtual lab program: www. Cisco provides an excellent product called Cisco Interactive Mentor (CIM).378 - . Mark questions you are unsure of or didn't answer so that you can return to them with a fresh perspective after you have worked through other questions.cisco. Cisco Systems even provides lab access at various Cisco sites around the world. as discussed in several scenarios in this book. Allow at least an extra hour for any traveling involved.html Strategies for the Exam This section covers some simple things you can do the day before and during the exam. so try and eliminate the two obviously incorrect answers as soon as you can. On the exam day. even if you passed. Immediately after the examination. The examination questions are written by folks who want you to pick the first answer that looks good. Contact your Cisco representative for more information. Take advantage of this free access to try new configurations and get expert advice from local Cisco engineers. so you can take advantage of your adrenaline rush if you arrive early. During the exam. so you can view the technology and spend time configuring Cisco IOS features for free.

CCNP Practical Studies: Routing Cisco Certification Status As soon as you pass all tests for a given Cisco certification. you attain that Cisco certification status. Cisco also generates transcripts that indicate which exams you have passed and your corresponding test scores. you receive a login ID and password. In addition. This Web site takes about seven days from your examination date to be updated.galton. and more (sometimes even a free shirt).com/~cisco/. Cisco sends these transcripts to you. You can also download Certification logos for use on your business cards. and you can keep your demographic information up to date so you are always informed of any changes. Cisco certification logos. . Tracking Cisco Certification Online Cisco also provides online tracking. so you can track your status of any certification path at www.379 - .

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The passing mark is approximately 70 percent. you need to be aware of the challenges in front of you.com/warp/customer/625/ccie/certifications/security. The majority of CCIEs are located in Europe and North America.CCNP Practical Studies: Routing Appendix B. Pass an eight-hour lab examination where the passing score is set at 80 percent. but varies according to statistics and may float between 65-75 percent. CCIE is regarded as the most sought-after certification in the industry today.cisco. What to Do After CCNP? This appendix covers some options for you after becoming a qualified Cisco Certified Network Professional. To obtain a guest account. there were approximately 6700 CCIEs. at least two years of internetworking experience is critical.cisco. For more information on the Communications and Services track. However.com/partner/training/course_channelpartners. that changed in October 2001.shtml You need an account to access some of the URLs presented in this chapter. SNA. You cannot hope to become a CCIE by simply buying a book or a series of books. as newer certifications generally take months or even years to become well established. Steps Required to Achieve CCIE Certification The CCIE program requires a candidate to perform two qualification steps: Step 1. gradually building path to the CCIE certification.html. four CCIE tracks were retired: ISP Dial. Step 2. This certification is aimed mainly at partners who supply the Cisco course material to the general public. Design. another difficult certification option is Cisco Certified Systems Instructor (CCSI).cisco. About 110 of these 6700 CCIEs hold more than one CCIE qualification. NOTE If you are interested in leading training courses. more and more vendors are devising their own certification programs and trying to catch up to the industry-leading Cisco Systems. As of September 30. visit www.381 - . . NOTE For more information on the Security track. You can pursue one more challenging step: the coveted Cisco Certified Internetwork Expert (CCIE) certification. The Security examination is one examination you should also consider. 2001. While working in the CCIE program every day for the past two years. Historically. Cisco introduced the CCNA and CCNP certifications so candidates can follow a preferred. and WAN Switching. go to www. Before you decide to take this step. especially considering today's climate of Internet firewall frailty and demand for security experts. and even then you must fully prepare for the difficult examination. CCNA and CCNP are not prerequisites to attempt the CCIE examination. go to www. Recently. The guest account also enables you to book a lab seat for the CCIE examination. Pass a two-hour. I have seen the many changes and challenges facing potential CCIEs. computer-based qualification examination consisting of 100 questions.html. For information. Hands-on experience is required. the lab examination was a full two-day lab. go to www.com/warp/customer/625/ccie/certifications/services. Three varieties of CCIE certification are currently available: • • • CCIE Routing and Switching (Released 1993) CCIE Security (Released August 2001) CCIE Communications and Services (Released August 2001) This discussion concentrates on the Routing and Switching (R&S) certification.cisco.com/pcgibin/register/main?page=start&relation=clnc.

cisco. You can view some sample questions at www.html CCIE Lab Exam Test Format Passing the qualification examination is the easier part of the CCIE exam journey. computer-based examination is similar to other Cisco certifications. You are no longer required to troubleshoot a network (regarded as the true method to test a CCIE's ability to restore a network back to full IP connectivity). What makes some of questions more difficult on the exam is that more than five answer choices are listed for all or most questions. your life needs to change dramatically. The topics tested include the following: • • • • • • • • • • • Cisco device operation General networking theory Bridging and LAN switching Internet Protocol IP routing protocols Desktop protocols Performance management WAN (addressing. you are now required to configure only a set number of features. You can book your lab examination online at the following address: http://tools. and if you book the test.cisco. Cisco announces a beta trial for the Routing and Switching qualification test. framing. The following link has more information: www. To pass the lab exam. After you pass the qualification test.382 - . signaling.html. and so on) LAN Security Multiservice The blueprint for this examination is located at www. although it is a little more difficult with many more indepth questions.com/warp/customer/625/ccie/ccie_program/whatsnew. you are eligible to sit for the lab examination.html.com/warp/customer/625/ccie/certifications/rsblueprint. and you need to study on routers full time for at least three to six months. This reduces the effectiveness of eliminating obviously incorrect answers and choosing from the remaining answers. NOTE Occasionally. you pay only a small fee compared to the standard fee of approximately $250. The good news is that the format of the lab examination has changed from two full days to one day only.CCNP Practical Studies: Routing CCIE Qualification Exam Test Format The CCIE Routing and Switching qualification exam uses the typical certification test format with multiple-choice questions that have one or more correct answers per question.com/warp/customer/625/ccie/certifications/sample_routing.jsp The lab examination contains the following devices: • • • • • • 2500 series routers 2600 series routers 3600 series routers 4000 and 4500 series routers 3900 series Token Ring switches Catalyst 5000 series switches . The two-hour.cisco.com/CCIE/Schedule_Labhttps://www.scribd.com/jsp/login.cisco.

5710 Fax: +86 10 8518 2096 E-mail: ccie_apt@cisco.CCNP Practical Studies: Routing Ensure that you practice with and understand these devices. Europe. North Carolina Halifax. Practice configuring almost every IOS feature. Canada Sao Paulo.383 - . and Africa San Jose. India Tel: +61 2 8446 6135 Fax: +61 2 8448 7980 E-mail: ccie_apt@cisco. Where can I take the lab examination? For locations and contact information. South America. Japan . Australia. Brazil Brussels.com • For lab locations in Tokyo. Anyone can configure a Cisco router. California Research Triangle Park.com • For lab locations in Chatswood. instead of relying on limited experience with certain commands. but the ability to understand the full consequence of a command is crucial to passing the CCIE Lab Examination. and fully understand what each IOS command actually enables. All CCIE certification labs around the world are testing candidates in the new one-day format. and Bangalore.com Tel: 1-800-829-6387 (select option 2) or 1-919-392-4525 Fax: 1-919-392-0166 • For lab locations in Beijing China. Belgium Johannesburg. and Singapore Tel: +86 10 6526 7777 Ext. CCIE Lab Exam Frequently Asked Questions The following are some frequently asked questions regarding the difficult one-day CCIE Lab Examination: 1: A: 2: A: When did the lab format change from two days to one day? October 2001. Nova Scotia. South Africa E-mail: ccie_ucsa@cisco. NSW. contact the following: • For lab locations in North America.

however.CCNP Practical Studies: Routing Tel: +81-3-5324-4111 Fax: +81-3-5324-4022 E-mail: ccie@cisco. You can.com. you are provided an electronic feedback form so that you can make any comment on the lab exam or proctor. you're provided only a brief score report through e-mail with your new grade.jsp. What if I have a question and cannot find the answer? E-mail your question to ccie@cisco.com/warp/customer/625/ccie/recertifications/ccie_information.jp 3: A: What are the maximum score and the passing score required? The total examination is worth 100 points and the passing grade is 80 percent. you can e-mail your concerns to ccie@cisco.com/kobayashi/chat/cciechat. Even with a regrade. you also gain access to an exclusive CCIE chat forum and CCIE merchandise. and you get a CCIE medallion and certificate.html 9: A: What happens if I fail? Am I told in which areas I scored poorly? Cisco will not tell you specific areas of weakness. pass or fail. You can cut and paste to and from Notepad. If you feel otherwise. so expect to take the examination more than once. The proctor may also make any changes required in case of network hardware failures or examination mistakes.cisco. The proctor is there to ensure that you have the best possible chance of success and should not hinder your ability to pass the test. What happens after the exam? You will be escorted outside the lab. pay a fee to have your lab routers re-examined for accuracy. no additional information is provided to you.co. You will receive an e-mail notification within 24 hours. Where can I find out more about CCIE and all the different certification tracks? 4: A: 5: A: 6: A: 7: A: 8: A: 10: A: 11: A: 12: .384 - . but you are not permitted to save any files.com/CCIE/Schedule_Labhttps://www.scribd.com/jsp/login. that is left to you to decipher from the brief score report.html.com. The calculator is useful for determining subnets and bit boundaries or converting hexadecimal to decimal.cisco. The proctor will not provide answers but will ensure you understand the question. Can I use Notepad and Windows calculator? Yes you can. What materials can I bring into the lab? You are permitted to bring only necessary medication and a dictionary. There is no limit on the number of lab attempts. How many times can I retake the lab examination? You must allow 30 days between lab attempts. The passing rate for first attempts is low. Cisco provides refreshments at all CCIE lab sites. however.cisco. which allows you to communicate with other CCIEs from anywhere around the world. What happens if I pass? In addition to becoming a CCIE. The following URL provides more details on CCIE benefits: www. What is the role of the proctor? You can seek clarification from a proctor if you do not understand a question or the objective of a question. Cisco also provides a forum accessible only by CCIE's at www. At the end of the day. Cisco will not release the passing rate. Lunch is also provided. No other materials are permitted. The e-mail notification will notify you that the result of your lab attempt is available online at tools. The CCIE team responds to all questions.

cisco.CCNP Practical Studies: Routing A: The following URL provides all the material required for any of the three main CCIE tracks: www.com/warp/customer/625/ccie/ .385 - .

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What is the purpose of the broadcast address in any given subnet? The main purpose of a broadcast address in the case of IP is to send out onto the wire a packet that all hosts common to the particular subnets will see and receive. Answers to Review Questions This appendix contains the answers to each chapter's review questions.224 161.00000000) What is the equivalent subnet mask for the notation 131.127 Subnet 171.255. and BGP. Cisco routers drop broadcasts unless you configure bridging.387 - .18.255.88.0 151. Chapter 1 1: Given the following host address and subnet mask combinations.252. Which routing protocols do not support VLSM? IGRP and RIP I.1. IS-IS.1.67 255.108.192 A: Performing a logical AND reveals the following: • • • • Subnet 131. the subnet mask 255. OSPF. or the subnet mask 255.1.0 and a subnet mask of 255.255.31 Subnet 161.254. The answers are in bold.00000000.255.108.255.24 255.40.88.128 171.199.100.CCNP Practical Studies: Routing Appendix C. Given the subnet in binary notation 1111111.0 and broadcast address 151.199.1. or 2n=1024.0 (1111111.145. The number of bits required in the subnet mask is 10 bits. These routing protocols support VLSM because the routing protocols send the subnet mask as part of any routing update.1.255. Which subnet mask provides approximately 1022 hosts? 2n-2 = 1022.11111111. The only way to overcome this is to use a combination of static IP routes or a default route.1.0 and broadcast address 161.199.108.255.255.1.255 Subnet 151.80.0.108.108.254.0.255.0 borrows nine (or n) bits from the subnet mask.40.0/24? The broadcast address is 131.100.100.0 and broadcast address 171. how many hosts are available on this subnet? Using the formula 2n-2 = 29-2 = 512 hosts.88.100. what is the decimal equivalent? The decimal equivalent is 255.0 and broadcast address 131.11111100.45.255.0/24? 5: A: 6: A: 7: A: 8: A: 9: . What is the broadcast address for the subnet 131.56. The original questions are included for your convenience.255 where 255 represents all binary 1s.100. EIGRP. determine the subnet address and broadcast addresses: • • • • 131.255.40. or a Class B address.10 255. Which routing protocols support VLSM and why? RIPv2.63 2: A: 3: A: 4: A: Given the network 141.00000000.108.255.54 255.11111111.0.

so RIPv2 has been enabled to cater to the 30-bit mask between the routers.0. a ping test is sent to three remote networks. Why is the command version 2 configured on each router? Because you are using two types of masks.255 It is common in large organizations to utilize the private Class A address and use public addresses only on the Internet connection using Network Address Translation (NAT). and 131. Chapter 2 1: A: 2: A: 3: A: 4: A: 5: A: What information is stored in an IP routing table as seen by R1? RIP routing entries and connected routes. 131.0-172. what other methods could you use to ensure connectivity to the remote networks? You can use the telnet application or the trace command to ensure connectivity.11111111.255. The following are the three private ranges: 10: A: • • • Class A: 10.16.255.255 Class C:192. or VLSM.255.108. Identify the private address ranges defined in RFC 1918? RFC 1918 defines three major classes for private use.0.108. and 1 represents the hop count to reach the remote network. Is the ping test successful or not? Explain why or why not? The ping tests to remote networks 131.0 (or /24) and 255.255.1-192.255 Class B: 172.16. RIPv1 does not understand VLSM.0/24.168.252 (or /30). 255. What does the 120 represent and what does the 1 represent? The 120 is the default administrative distance or trustworthiness of the information.0/16? There are nine subnets using two masks.0.0-10. the slash bit notation represents the number of bits assigned to the subnet mask: /24 means 24 bits.255. Which command do you use to view only RIP routes? show ip route rip or sh ip ro r.00000000 or 255.7. which are address ranges that are not routable in the Internet.255. Which command do you use to view only connected routes? show ip route connected or sh ip ro c.388 - . all the remote networks are 1 hop count away.0. In this case.255. Each remote routing entry is labeled with the following information: [120/1].255.255.0/24 are all successful because the 5 ICMP packets are all reachable as displayed by the five ! characters. In binary this is 11111111.108.8.CCNP Practical Studies: Routing A: The slash notation is common in today's documentation and on Cisco IOS. From R1.11111111. 6: A: 7: A: 8: A: .168.0.108. How many subnets are known by R1 using the Class B network 131.9. Besides a ping test.0/24.255.

255.108.33.108. The actual hop count is set by the ASBR (router Simon) in Figure 4-8. SanFran is also a backbone router. what is the hop count or metric to the remote network 141.0/24 take? Because this network is not listed in Sydney's IP routing table.1.4.2.108. Which command do you use to view only OSPF routes? show ip route ospf. What path does the packet sent to the IP subnet 171.0.0.0.0.108.4.108.1/24? R1's routing table has no entry for the network 141.108.108. In other words. Why is the remote network 141.CCNP Practical Studies: Routing Chapter 3 1: A: 2: A: 3: A: Which information is stored in an IP routing table as seen by R1? OSPF routing entries and connected routes. How many subnets are known by R1 using the Class B networks 131. What is the cost associated with the remote network 131.1.108. This is commonly referred to as the Gateway of Last Resort (GOLR). This is typically Internet-based traffic. Simon is configured to set all networks with a hop count of 2 by using the command redistribute ospf 1 metric 2.4 (router Simon).0/24 [110/74]? The cost is 74 and the administrative distance is 110.0/32 displayed as learned through the denotation: O IA? O IA indicates this remote network is learned through OSPF (O) and resides in an area not local to the router (IA). which can be truncated as sh ip ro os. What type of OSPF routers are the Routers Simon. packets to this network are dropped. as well as a router that performs route redistribution (an ASBR).1. the packet is sent to the default routing entry or the next hop address of 141. There are nine subnets using three different masks for the Class B network 131.0/16? There are eight subnets using three masks for the Class B address 141.108. and because there is no default network or gateway of last resort. and SanFran? Simon is a backbone OSPF router in area 0.0.389 - .1.6. Mel is contained within one area only and because that area is the backbone.108.0/16 and 141.100. 4: A: 5: A: 6: A: Chapter 4 1: A: What does the routing entry shaded in Example 4-64 display? The IP route labeled as R* means that any IP packet designated for a remote destination not specifically listed in the IP routing table is to be sent to the next hop address of 141.100.108. 2: A: 3: A: 4: A: . but it supplies a default router and can also be classed as an ASBR. this is an intra-area OSPF route.0. Mel is a backbone router. What path is taken to the remote network 141.0/24? The RIP metric is set to 2. In Example 4-64. Mel. The gateway of last resort is also set to 141.108.108.

Null0 141.108.2.108.0/16 is variably subnetted. Example 4-65 displays the IP routing table on Simon.2.0/24 is directly connected.390 - . reduces the topology table. Chapter 5 Example 5-79 displays the detailed paths to the three remote networks. Serial3 141.255. 171.3.0.CCNP Practical Studies: Routing 5: A: Why are static routes injected into the router named Simon? Static routes are configured on this ASBR to install them into the IP routing table.1. Configure the command ip ospf domain-lookup in global configuration mode to allow OSPF to assign a name to an IP address.108.108.1.2 Interface Serial2 Serial3 Two methods are used in OSPF to summarize IP networks.108. 00:12:23.108.108.0/24 is a summary.108.109. Serial3 141.4/30 is directly connected. Example 4-66 show ip ospf neighbor Command on Simo Simon#show ip ospf neighbor Neighbor ID mel sanfran 7: Pri 1 1 State FULL/ FULL/ - Dead Time 00:00:30 00:00:30 Address 141.0/30 is directly connected. in turn.108.0. Because Simon has more specific routing entries. Example 4-66 displays the OSPF neighbors on the router Simon. Null0 How many OSPF neighbor adjacencies do you expect to see on the router named Simon? There should be two OSPF neighbors: one to SanFran and one to Mel.109. External summarization with the IOS command summary network mask command.0. Null0 141.255. 5 masks 141.2. Ethernet1 141.109.2 to network 0. 00:31:47.3. 171.255.0/25 is directly connected.0. 00:12:23.6 141.4. namely 141.108.0/24 is a summary. Ethernet0 141. Serial2 141.255.108. What are they and what IOS command is used to provide summarization? Inter-area summarization with area area id range mask command.2. . 10 subnets.255.0/24 is directly connected. 00:31:46.0/24 is a summary.6.108.3.0. and 171. leading to fewer SPF calculations as well.108.4.0/24 is directly connected.255. Changes are less likely to occur within a small group of routers than in a large group.108.1/28.108.2.1/29 and 141. A: 8: A: Why does creating areas reduce the size of the OSPF database? Reducing the number of areas leads to the reduction of SPF calculations and.255.0/28 [110/74] via 141.0/24. the longest match rule is used to route packets to the remote networks. Serial2 141.3. as seen by the router SanFran along with a successful ping to the remote networks.4. Null0 141.108.0 C O C C S O C S O O O 6: A: 141.108. Example 4-65 Simon's IP Routing Table Simon#show ip route Gateway of last resort is 141. Null0 141.108.108.255. 00:12:23.0/29 [110/74] via 141.

0 Routing entry for 171.109.108. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171.108. traffic share count is 1 Total delay is 6000 microseconds. metric 409600. type internal Redistributing via eigrp 1 Last update from 131. you see the output displayed in Example 5-80.0. minimum MTU 1500 bytes Loading 1/255.3. metric 409600.109. Hops 1 SanFran#ping 171.0 Routing entry for 171. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).4. 00:13:26 ago. 100-byte ICMP Echos to 171. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).2. via Ethernet0/0 Route metric is 409600. 00:13:32 ago. type internal Redistributing via eigrp 1 Last update from 131. round-trip min/avg/max = 1/3/4 ms If you perform a show ip route of the network 171. traffic share count is 1 Total delay is 6000 microseconds. Example 5-80 show ip route 171. Sending 5.0 % Subnet not in table The reason that subnet 4 is not included in the IP routing table is that the summary address configured on the router Sydney includes only the subnets 1. 2.0/22 Known via "eigrp 1".0/22 Known via "eigrp 1". 00:13:38 ago Routing Descriptor Blocks: * 131. 00:13:38 ago.1 Type escape sequence to abort. 100-byte ICMP Echos to 171.391 - .0/24 on SanFran. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). minimum bandwidth is 10000 Kbit Reliability 255/255.109. minimum bandwidth is 10000 Kbit Reliability 255/255. via Ethernet0/0 Route metric is 409600.2.108.109. via Ethernet0/0 Route metric is 409600. 100-byte ICMP Echos to 171. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171.2 on Ethernet0/0.0.4. Sending 5.1.0 Routing entry for 171. minimum MTU 1500 bytes Loading 1/255.1 Type escape sequence to abort. distance 90.2.109.2.1.109.108. 00:13:32 ago Routing Descriptor Blocks: * 131.1. from 131.CCNP Practical Studies: Routing Example 5-79 show ip route and ping on SanFran SanFran#show ip route 171. and 3. Hops 1 SanFran#ping 171.1. minimum bandwidth is 10000 Kbit Reliability 255/255.1. Hops 1 SanFran#ping 171.1. 00:13:26 ago Routing Descriptor Blocks: * 131.1.1.0. minimum MTU 1500 bytes Loading 1/255.1.109.0/22 Known via "eigrp 1".109. traffic share count is 1 Total delay is 6000 microseconds.1.108.4. distance 90.2.109.109.109.2. Sending 5.3.109.3. .2. from 131.108.1.1. metric 409600.2 on Ethernet0/0.2 on Ethernet0/0.0 on SanFran SanFran#show ip route 171.1.2. distance 90.108. from 131.2.108.1.109.109.109.108.1. type internal Redistributing via eigrp 1 Last update from 131.1 Type escape sequence to abort.

2 Et0/0 Hold Uptime SRTT (sec) (ms) 11 00:18:37 4 RTO Q Seq Cnt N um 200 0 353 Example 5-81 displays adjacent EIGRP neighbors with the show ip eigrp neighbors command.0. Example 5-79 confirms connectivity by displaying detailed IP route entries for the remote networks 171.109.0/22 embrace? The /22 indicates a mask of 255. Manual redistribution is required between different autonomous systems or routing domains. When is the EIGRP topology table updated? Whenever a change occurs in the network.0 when applied to the Class B address 171. 171.255. Why does EIGRP need to be manually configured to redistribute into another autonomous system? EIGRP manually redistributes only between IGRP in the same AS. and 3 (00000011). What does the term Stuck in Active mean? Stuck in Active (SIA) is not a good network condition because the EIGRP router places the network in an active state (in the EIGRP topology table) and sends out a query to a neighbor.109.1.109.3. an industry standard. and 171. In binary.0. What is the default administrative distance for EIGRP internal routes? The default value is 90.0.109. Which IOS command is used to enable BGP4 on a Cisco router? router bgpas. the EIGRP neighbors are reset.2.1. a failure to reply leaves the router in an active state. the EIGRP topology table is updated by update packets sent to all EIGRP routers in the same AS.109. and it disables automatic summarization of subnet routes into network-level routes. What is the variance command used for? The variance command. 252 is 1111 11100.0/24. which is more trusted than OSPF at 110. Which IOS command is used to display the output in Example 5-81? Example 5-81 Neighbors Output 2: A: 3: IP-EIGRP neighbors for process 1 H Address Interface 0 A: 4: A: 131.392 - .0/24 on SanFran. under the EIGRP process. such as a network failure. resulting in network down times and the loss of IP data. What is the purpose of the command no auto-summary? The no auto-summary command enables you to transmit subprefix routing information across classful network boundaries.CCNP Practical Studies: Routing 1: A: Example 5-79 displays the IP routing table of the Router SanFran. 5: A: 6: A: 7: A: 8: A: Chapter 6 1: A: 2: A: Which IOS command clears all BGP sessions on a Cisco router? clear ip bgp *. Cisco IOS developers figure that their own routing protocol is more trustworthy than OSPF. In the end. . the last two are not the same. Notice.252.108. The last three bits includes the networks 1 (00000001). but the first six are (11111100 is 252). Which networks does the entry 171. 2 (00000010). is used to allow additional paths to a remote destination when the composite metric is not the same.0.

How many BGP sessions are in use? Example 6-82 show tcp brief R2>show tcp brief TCB Local Address 613EE508 131.108.108. The version of BGP in use is 4.1 100 200 200 1 ? *> 161.255.108.101.1.0/24 131.1.255.1 4 1 2755 2699 21 0 0 1d20h 19 131. Example 6-83 displays the BGP table on a Cisco BGP router. ? .255. h history.255. i internal Origin codes: i .1.0/24 131. the default setting. Port 23 (local port) is used by Telnet.1.255.0/24 0.5 100 200 200 1 ? *> 131. * valid.5 4 1 2755 2699 21 0 0 1d20h 19 A: [click here]R2's local AS number is 2 and the number of active BGP sessions is two because the state is blank. Which path is chosen to the remote network 131.1.108.EGP. main routing table version 21 20 network entries and 39 paths using 3028 bytes of memory 4 BGP path attribute entries using 432 bytes of memory BGP activity 61/41 prefixes.2.1 Status codes: s suppressed.0 0 32768 i A: 5: A: 6: A: 7: The path chosen is indicated by > on the left side of the BGP table. and what version of BGP is configured on the router named R2? Example 6-84 show ip bgp summary on R2 R2>show ip bgp summary BGP router identifier 161.11008 611654BC 161.101.255.108. which indicates the next hop address 131. Example 6-84 displays the output from the show ip bgp summary command for a Cisco BGP-enabled router.108.108.1.393 - . Example 6-83 show ip bgp R2>show ip bgp BGP table version is 21.0. local AS number 2 BGP table version is 21.108.179 131.255. 119/80 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131.108. .108.1.23 A: 4: Foreign Address 131.255.1.1. or AS 1.108.incomplete Network Next Hop Metric LocPrf Weight Path * 131.0/24 in Example 6-83? Use Example 6-83 to answer questions 4-6.255.1.11009 613ED584 131.255.0/24? The metric is set to 100 (lower is preferred) and the local preference is 200 (higher values preferred). What is the metric and local preference for the remote network 131.1.108.6.108.CCNP Practical Studies: Routing 3: Example 6-82 displays the output from the show tcp brief command. What is the BGP autonomous system that R2 resides in? How many BGP sessions are active.108.108. e .108.IGP.5. local router ID is 161.101.108.11051 (state) ESTAB ESTAB ESTAB There are two BGP TCP sessions (the foreign TCP port number is 179).255.179 131.108.5 100 200 200 1 ? *> 131. > best.108.108. Which autonomous system does the network 131.1 100 200 200 1 ? * 131.0/24 originate from? The path is indicated by 1 ?.255. d damped.108.0.

0 *> 141. e . and AS path. what value is preferred.CCNP Practical Studies: Routing 8: A: 9: A: 10: A: On a Cisco router. What is a BGP cluster? Cluster is a term used to describe a router reflector and the configured route reflector clients. you would only need 999 peers (use the formulae (n-1) where n is the number of routers). ? . Which IOS command is used to display the following output? 3: A: 4: BGP table version is 61. With the use of route reflectors.0. if any? To view route reflectors. Chapter 7 1: A: 2: A: What does a route reflector do to nonclient IBGP peers? A route reflector reflects information to only configured clients. How many TCP peers are required in a 1000 IBGP network? The number of peers without the use of route reflectors is n(n-1)/2. which is only 0.1. Based on these entries. For example. What is the originating AS for the remote preferred path to the remote network 6: A: 7: A: 8: . Route reflectors are used in IBGP networks only. The route reflector has additional commands to ensure that updates are reflected from one route reflector client to another. the number of peers is 1000(999)/2 = 499500. To display route reflector clients. How is a route reflector client configured for IBGP? Route reflector clients are configured for normal IBGP peering. What are the terms peer or neighbor used to describe in BGP? A peer or neighbor indicates a TCP session between two BGP routers.incomplete Network *> 0. and the range of values for weight is 0–294967295. d damped.EGP. where n is the number of BGP routers.1. local preference. The default value is 0.108. and the second is to view the running configuration with the IOS show running-config command.0. What is the BGP table? The BGP table is a collection of local and remote network entries describing the next hop address. All other peers must be fully meshed.IGP. which show command(s) can you use. weight. neighbor peer ip -address default-originate. you can use two methods on the route reflector: one is to use the IOS show ip bgp neighbors command.0/24 A: 5: A: Next Hop 171.5 0. networks are inserted into the IP routing table.4 Status codes: s suppressed.394 - . Provide the IOS command syntax to enable a default route to be sent to a remote peer. with 1000 BGP routers. h history. i internal Origin codes: i . local router ID is 131.2 percent of the same fully meshed network. * valid.0. and what is the range of values for weight? Higher weight values are preferred.0 Metric LocPrf Weight Path 0 100 i 0 32768 i This display is a BGP table and is output when the IOS show ip bgp command is used in exec or privileged mode. higher or lower weight.108.0.108. > best. View the following BGP table.254.

which IOS command sets the weight and local preference attribute to 100? First. Chapter 8 1: A: How many IP routing tables are there when more than one routing protocol is configured on a Cisco router? There is only one IP routing table. which can include routing information dynamically discovered using OSPF or RIP.IS-IS level-2. 10: A: Can you set the BGP attribute next-hop-self to both EBGP and IBGP peers? No.0 A: Next Hop 171.2 Status codes: s suppressed. o . R . E2 .0 171.108. L1 .RIP. and originating from AS 300. h history.108.1.108. I .OSPF inter area N1 . N2 .0.candidate default U . and in this example. i internal Origin codes: i .1.ODR 2: A: Which path is preferred if OSPF and EIGRP have dynamically discovered a remote network? The Cisco IOS gives administrative distance first priority given.EGP. the path traversed to reach the remote network 141.1.OSPF external type 1.0/24? R5#show ip bgp BGP table version is 22. > best. then 100.108.IGRP.108.EIGRP.1. e . .1. For example.static.108. * valid.EIGRP external.1 Metric LocPrf Weight Path 200 2000 100 300 i 0 32768 i 200 2000 100 ? Cisco IOS always displays the AS path taken.OSPF external type 2.0. Using a route map.0/24 *> 171.connected. d damped.0/24 *> 151. The next-hop-self attribute is used for IBGP peers only.IGP.108.0.108. local router ID is 171. B .mobile.incomplete Network *> 141.IS-IS level-1.1. you must apply it to remote BGP peers on the inbound or outbound direction required.BGP D .1 0.CCNP Practical Studies: Routing 141. You can change the default AD values by using the IOS distance command.per-user static route. you must define a route map with an arbitrary name (ccnp in this example) and then complete the following set of commands: 9: A: R5(config)#route-map ? WORD Route map tag R5(config)#route-map ccnp R5(config-route-map)#set weight 100 R5(config-route-map)#set local R5(config-route-map)#set local-preference 100 After defining the route map.OSPF. The lower AD is more trustworthy. * .0 is through the AS 2000.1.IS-IS. EX . IA . E . L2 . M .395 - . The IOS command to set this attribute to remote peers is neighbor ip-address next-hop-self.OSPF NSSA external type 2 E1 .OSPF NSSA external type 1. the following indicates all the possible routing methods on a Cisco router: Codes: C . EIGRP AD is 90 and OSPF is 110. O . ? . S .EGP i . so the Cisco IOS chooses EIGRP.

distribution lists. What are the three methods commonly applied to avoid routing loops when redistribution is required? The three methods are as follows: Passive interfaces— A passive interface is a Cisco interface configured for routing. updates are still received and processed. Which command stops updates from being sent out of any interface? passive-interface interface stops updates from being sent. The lower cost is always preferred to a remote destination. Distribution lists require that you configure access lists to define which networks are permitted or denied. and IS-IS are common examples. but it does not send any routing information on the outbound interface. Route maps can also be used along with access lists to define which networks are permitted or denied when you apply match statements under any route map configuration options. compared to 1 for static routes. Is a static route always preferred over a directly connected route? No. Give three examples of classful protocols. and route maps. What is the metric used by OSPF. 8: A: 9: A: 10: A: . Cisco IOS chooses any remote path by comparing administrative distance. Lower ADs are always preferred. such as hop count or OSPF cost? Before looking at routing protocol metrics. Route maps— Route maps can also be used to define which networks are permitted or denied.CCNP Practical Studies: Routing 3: A: 4: A: 5: A: 6: A: 7: A: What common methods are used to control routing updates and filtering? The main methods are passive interfaces. For example. Routing information (if any) is still received and processed normally. OSPF. Lower ADs are always preferred. directly connected interfaces have an AD of 0. although. Which parameter does the Cisco IOS always compare before looking at routing metrics.396 - . BGP. Give two examples of classless protocols? RIP and IGRP are classless protocols. and is the lower or higher metric the chosen path? OSPF's metric is cost (ranging from 1 to 65535). Distribution lists— Distribution lists define which networks are permitted or denied when receiving or sending routing updates. EIGRP (AD 90) is preferred over OSPF (AD 110) routers.

. Of course. Solutions are not provided in this book per a request from Cisco's CCIE department. but in reality. this sample lab asks you to physically cable the network. NOTE This sample lab incorporates many of the technologies and concepts covered in this guide. a sign indicates a possible action you must take. you'll know little about the lab content before your first attempt. in this guide.com/warp/customer/625/ccie/. The strict nondisclosure agreement policed by Cisco ensures that candidates do not share any information about the lab content.397 - . so you must research the various solutions on your own. it all comes down to your level of hands-on experience. Because this appendix covers a sample CCIE lab.cisco. CCIE Preparation—Sample Multiprotocol Lab This appendix is designed to assist you in your final preparation for the most widely sought after certification in the world today. In fact. and you are encouraged to read the most up-todate information on the Web at www. A CCIE candidate is no longer required to sit through a separate troubleshooting section but must configure a network in eight hours. My answer to them is to practice and configure every feature available and then practice even more. but often at an elevated level. The CCIE lab changed dramatically in format in October 2001 from a two-day lab to a one-day lab. One of the most critical skills in the new CCIE lab format is time management. The CCIE team has approved a sample CCIE multiprotocol lab for inclusion in this book so that you can be aware of the level of difficulty you must prepare to encounter when attempting the CCIE lab. CCIE (Routing and Switching). Therefore. the physical cabling is already completed for you. No time allocation is provided. because in the real CCIE lab. The end goal of any CCIE lab is a working network solution. no matter how many books you purchase. many published books describe how to achieve CCIE. If a section has no time allocation. Figures D-1 and D-2 show the topology and assignments for this sample lab. each section describes the time constraints within which you should complete that section. Therefore. as you will discover in this sample CCIE lab.CCNP Practical Studies: Routing Appendix D. Today. the exercises presented in this lab require a broad perspective and knowledge base and experience that goes beyond even the practical examples presented earlier in this guide. Imagine you are asked to drive down a 100-mile length of perfectly straight road. Candidates who prepare for the CCIE lab often ask me how to best prepare for the lab. You must be able to provide a working solution quickly and adhere to the guidelines stated in the lab. that section has already been completed for you in the real CCIE lab. This lab is designed to be completed within eight hours. not every feature is tested. and you must have a broad knowledge of all IOS features to configure challenging and difficult scenarios. A good analogy is a driving test. The exam designer does not necessarily ask about the best solution. the FBI has been involved in recent cases in which individuals have been jailed for selling information directly related to CCIE lab examinations. You might be restricted in the way you provide a working solution. For example. Imagine every 100 feet.

398 - . Frame Relay DLCI Assignment Basic Setup (1 Hour) Configure the network in Figure D-1 for basic physical connectivity. . CCIE Lab Topology Figure D-2. Communications Server (0.CCNP Practical Studies: Routing Figure D-1.25 Hours) NOTE Not all CCIE labs require a communication server to be configured.

R2. a CCIE candidate is not required to cable the lab network physically. named VLAN_D. Communication server port 9 connects to the Catalyst Ethernet switch. R4. VLAN 6. All serial links between routers are connected through a Frame Relay switch. Communication server ports 2 through 8 are connected to routers R2 through R8. Configure R1 as the communication server by using the ip host command. R5.CCNP Practical Studies: Routing Configure the communication server so that when you type the host name of a router on the server. R9 is a Catalyst 6509 switch with a Multilayer Switch Feature Card (MSFC) module installed. Catalyst Ethernet Switch Setup II (0. and R7 are connected to the Catalyst Ethernet switch (Catalyst 6509 series switch). R3. you are connected across the console port to that router: • • • • • • Set up the routers as shown in Figure D-1. and R8 are connected to the Catalyst Token Ring switch (Catalyst 3900 series switch).0. Physical Connectivity (No Time) NOTE From October 1. Routers R1 and R4 are connected to an ISDN service with the switch type defined as basic-5ess. Using VLAN_A.2/25. VLAN 7. R1 connects to number plan 0298017705. Set all Ethernet ports to forward data immediately after a device is plugged in or activated. Communication server port 10 connects to the Catalyst Token Ring switch. Ensure that all devices in your network can telnet to the switch even if R1 or R2 is down. is connected to R3. Routers R1. Therefore. Configure the following characteristics for the topology in Figure D-1: • • • • • All rings should be set to 16 Mbps and should have an MTU size of 1500. Catalyst Ethernet Switch Setup I (0. Ensure that the switch has the best possible chance of becoming the root bridge in VLAN_E. VLAN 3. named VLAN_C. R6.108. respectively. is connected to R1 and R2. This section is added for completeness only.399 - . VLAN 4. Set the hello time on VLAN_B to 10 seconds. Routers R1. is connected to R7. named VLAN_B.25 Hours) Configure the Ethernet switch for five VLANs: • • • • • VLAN 2. named VLAN_E. Ensure that the switch is configured in the VTP domain Cisc0_vTp and the switch can create and delete VLANs in the future. Construct your network as shown in Figure D-1.25 Hours) Configure the following spanning-tree parameters on the Catalyst 6509: • • • • Ensure that the switch never becomes the root bridge on VLAN_D. configure the management interface SC0 with the address 131. You network is already physically patched. . is connected to R4. 2001 onward. no time allocation is given to this section. is connected to R6 and R9. named VLAN_A. and R4 connects to number plan 0296307050.

Warn all Telnet clients that any "unauthorized access is not permitted" by displaying a warning message when any Telnet session is activated to the SC0 interface only.5(4) 4.---1 1 15 1 3 3 9 9 Mod --1 15 3 9 Mod 1 (enable) show module Ports Module-Type ----.CCNP Practical Studies: Routing Configure the following miscellaneous parameters: • • • • • • • Disable Cisco Discovery Protocol on ports 3/1-8.4 1. Therefore.3(1) 5. Example D-1 show module on R9 (MSFC) Cat6509> Mod Slot --. Ensure that the switches get a clock source from R1 using NTP.5(4) 12. 5. 12. Do not route between any other interfaces. no time is projected for this section.1 1. Catalyst Ethernet MSFC Setup (0.1(1)E. Example D-1 displays the hardware profile on the Catalyst 6509 switch. the subject is presented here to ensure potential CCIE candidates have a good understanding of IP address spaces and subnetting. Ensure that any IP phones installed or connected to Card 3 are supplied inline power. Disable power redundancy on the switch. ensure that the switch automatically enables the affected ports after 10 minutes.24)V 5.1 1 By using the information displayed in Example D-1.1 2. IP Configuration and IP Addressing (No Time) NOTE Because of recent changes to the CCIE exam.----------SAD0413022N SAD041501U6 SAD04270A8A SAD03479837 MAC-Address(es) 00-30-96-33-21-7e to 00-30-96-33-21-7f 00-30-96-33-21-7c to 00-30-96-33-21-7d 00-d0-01-b0-4c-00 to 00-d0-01-b0-4f-ff 15 00-30-96-33-24-84 to 00-30-96-33-24-c3 3 00-30-96-34-9b-48 to 00-30-96-34-9b-77 9 00-30-96-2b-e1-f4 to 00-30-96-2b-e1-fb Mod Sub-Type Sub-Model 1 L3 Switching Engine WS-F6K-PFC 3 Inline Power Module WS-F6K-VPWR Hw 3.5(4) Sub-Serial Sub-Hw SAD04150DYL 1. the candidate is not required to configure IP addressing.1(1)E. Ensure that the only MAC address permitted to access the switch on port 3/3 is the MAC address 2010-2010-2010 or 4000-00004000. configure the MSFC for IP routing in VLAN 6 using RIPv2 only.3(1) Sw 5. .3 Fw 5. If any ports become disabled because of hardware errors.2(0.25 Hours) Configure R9 (6509 with an MSFC card) for IP routing. however.400 - .------------------------2 1000BaseX Supervisor 1 Multilayer Switch Feature 48 10/100BaseTX Ethernet 8 1000BaseX Ethernet Model ------------------WS-X6K-SUP1A-2GE WS-F6K-MSFC WS-X6348-RJ-45 WS-X6408-GBIC Sub --yes no yes no Status -------ok ok ok ok Module-Name Serial-Num ------------------.

It must be possible to ping and telnet from any one router using the loopback address. RIP Configuration (0. and do not rely on autosensing the LMI type on any routers. Use a 26-bit mask for all Token Ring networks.5 Hours) Configure IP across your Frame Relay network as displayed in Figure D-2: • • • • • • • You have to use static maps for each protocol. Use LMI type to Cisco only. Use a subnet with the least number of hosts for the ISDN link. Use a 28-bit mask for VLAN D. Make sure you can see distributed RIP routes throughout your topology. IGRP Configuration (0. Authenticate any RIP packets. Ensure that only unicast updates are sent and received. Frame Relay Setup (0. Configure IP addresses on your remaining interfaces: • • • • • • • • Use a 25-bit mask for VLAN 2. IGP Routing (3 Hours) After this section is completed. The Frame port type is DCE. After your IP address space and IP routing are complete. Use a 29-bit mask for all Frame Relay connections running classless IP routing protocols. Use a most efficient subnetwork for IP addresses on the Frame cloud. You must use this address space for all addresses unless a different address space is specified in a particular question.108. Use a 24-bit mask for VLAN E. All router interface types are DTE.108. You may assign a subnet from your Class B range.5 Hours) Configure RIP on Routers R6 and R9 only: • • • • • Configure RIP on R6 E0 and R9 E0.255. all routers must have full IP connectivity between every routing domain. No subinterfaces are allowed on any router. including the ISDN backup interfaces when operational. Configure local IP host addresses on each router so that an exec or privilege user can type the router name to ping or telnet without having to type the full IP address.0.255 to design your network. Ensure that you read the entire paper before designing your IP address space. it must be possible to reach all your routers and switches. Set the enable password for all routers and switches to ccieToBe.CCNP Practical Studies: Routing Use the Class B subnetted IP address 131.5 Hours) Configure IGRP on Routers R6 and R7 only: . No dynamic mapping is permitted. Use a 24-bit mask for all Frame Relay connections running classful IP routing protocols. Do not use the keyword broadcast for the Frame Relay link between R6 and R7 when mapping IP. Ensure that you can also ping the local interface from each router configured for Frame Relay.401 - . Use a 27-bit mask for VLAN 3. Redistribute the RIP route into IGRP domain.0 to 131. Assign each router a 24-bit subnet for the loopback address to use.

The Ethernet segment on R4 resides in area 0. Make sure you can see distributed IGRP routes throughout your topology as Type 1 OSPF routes. acting as an IPX server. Ring 100 is in area 100. The Ethernet segment between R1 and R2 resides in area 1. Do not create any additional areas. except Router R3. Ring 500 is in area 500.0.0. Ensure that R3 never sends any updates across the Ethernet (E0) segment. and EIGRP domains.0. Ensure that all OSPF routes are redistributed and reachable in the IGRP.0. Summarize as much as possible to reduce the redistributed routes into OSPF. Configure NLSP between R6 and R7. Ensure that R1 will never be the DR on all segments.0. Do not create any unspecified OSPF areas: • • • • • • • • • • • • • • • • • Configure the OSPF backbone over the Frame Relay network between the three routers: R2. RIP. but ensure that all routes appear in the IGRP and RIP domains. Ensure that the router ID of all OSPF-enabled routers is the loopback address. Ensure that R4 is the DR in the OSPF backbone network. You cannot configure IPX addressing on the Frame Relay link. You can use IPX EIGRP as your routing protocol. and R7. R4. and R8 only: • • • • • Configure EIGRP in domain 333 between the serial link on R7 to R8. R3 to R8.0. Redistribute the IGRP routes into OSPF domain. The ISDN link between R1 and R4 resides in the area 0. Ensure that area 0. Ensure that the OSPF backbone in the Frame cloud is authenticated. Do not use the redistribute connected command on any router to accomplish this. All routers must be able to see all other IPX routes and must be able to IPX ping each router. Configure two IPX services on R1 named IPXServ1. and Ring 800. Disable IPX RIP wherever possible. Ensure that EIGRP is authenticated across the Frame Relay connections. Redistribute the OSPF and external EIGRP routes with an administrative distance of 199 in the EIGRP domain.0. EIGRP Configuration (0. and IPXPrn1. IGRP covers the link between R6 and R7 only. Ensure that all loopbacks appear as /24 bit networks on all IP routing tables. OSPF Configuration (1. Set the hello interval between the link R1 and R4 to 25 seconds. R7. Redistribute the EIGRP routes into OSPF domains with a cost metric of 1000 seen on all OSPF routers.5 Hours) Configure EIGRP on Routers R3.CCNP Practical Studies: Routing • • • • • Use 10 as the AS number for IGRP. You can assume no other areas or routers are attached to this segment. Between R6 and R7. Set the hello interval on R2 Ethernet segment to 20 seconds.40 is configured so that excessive CPU resources are not consumed on Router R4. IPX Configuration (1 Hour) Configure IPX and ensure that IPX connectivity exists on all routers: • • • • • • • Configure IPX directly on all interfaces except all WAN and loopback interfaces.402 - . Ensure that all IPX-enabled routers can reach these two server SAPs.40.5 Hours) Configure OSPF as described in Figure D-1. Ensure that you can IPX ping across your network. The link between R4 and R5 is in area 4. do not enable EIGRP IPX. acting as a printer server. .

Use PPP encapsulation and the strongest authentication available.403 - . Ensure that you never bring up more than one B channel to keep costs to a minimum.75 Hours) Configure DLSw+ on R1. DLSw+ Configuration (0.R1: 0298017705 . SNA hosts reside on Rings 100 and 500. R1 should place an outgoing call to R4. Ensure that the only SAPs enabled on R3 are null SAPs and SAP 08. ensure that all exec users can use the IOS clear in exec mode on Router R1 only. Configure the ISDN interfaces on R1 and R4 as follows: • • • • • • Only when S0 of R1 goes down. VTY Changes (0. . Permit all other NetBIOS traffic starting with the name Simonis?***. Flash Configuration (0.CCNP Practical Studies: Routing Basic ISDN Configuration (0. R1 and R2 are running the same IOS code and are the same router hardware type (Cisco 2503 routers). R3. and R8: • • • • • • • • • • • Rings 100. Ensure that remote DLSW+ peers do not send too many queries for the destination MAC address 0200. When the Frame Relay link is restored. They don't have Cisco IOS Software or an TFTP server on hand.5 Hours) ISDN switch information: • • ISDN switch type: basic-5ess ISDN numbering: .R4: 0296307050 • SPIDS are not required. To allow nonprivileged users access to R1 and the ability to clear terminal server lines. 500.20 Hours) Configure all VTY lines so that network administrators do not require local authentication.20 Hours) Your customers accidentally erased router R1's system image in Flash memory.0200.0200 on Ring 100 or VLAN 2. and 800 should have connectivity to VLAN 2 and 3. Administrators must still use the enable password ccieToBe on all routers to access privilege mode. They also have no Internet access. Ensure that all routers peer to R1 and only in a network failure do DLSw+ circuits terminate on R5. R5. Hosts on Ring 500 are used only when Ring 100 is not reachable. DLSw+ peers should be active only when user-based traffic (SNA/NetBIOS) is sent or received. When the ISDN is active. bring down the ISDN link after 25 minutes. Ensure that VLAN 2 can reach hosts on Ring 100. ensure that DLSw+ remains established. Configure a filter that blocks NetBIOS packets with the destination name SimonisaCCIE from leaving R5 and R8. Ensure that the IOS image is restored to the Flash on R1 and then reload R1. Use a different virtual ring group on each router. If IP connectivity exists. all routers must be able to ping and telnet the local ISDN interfaces on R1 and R4. R4 cannot call R1 under any circumstances.

20 Hours) Some users on VLAN_A have configured their PCs with the Class A addresses ranging from 10.404 - . Do not change the administrative distance on any interior routing protocol. R8's remote peer is 191. but only allow clients from Ring 500.1. Configure R5 and R8 as route reflectors. As long as there is IP connectivity in your network. Basic IBGP Configuration (0. Private Address Space Allocation (0. Assuming you have access to the switch using password recovery on the switch.1.108.110.0 to 121.1 to 10. and ensure that all traffic uses a preferred path through router R5. as your network is prone to failures across the Frame Relay cloud. Do not disable BGP synchronization. Ensure that the only route accepted is a default route and routes of the form 110.255. ensure that all networks are advertised to the route reflectors R5 and R3.10. Set the weight to 1000 for all even networks and 2000 for all odd networks. Minimize IBGP configurations as much as possible.20 Hours) Configure R1 to act as an HTTP server. Use AS 2002 on all IBGP routers. Ensure that the remaining network can access the host with the IP address 10. Ensure that all routers have entries in their IP routing tables. BGP Routing Configuration (0.200.0 to 121. EBGP Configuration (0.1. .10.20 Hours) The enable password on the 6509 switch has been modified.110. Ensure that the Class A address is never present in any routing table except R1.255/24.255. Set all routes in the range 110.5 Hours) Configure IBGP on all routers in your network: • • • • • • • • • • Do not use any WAN IP interfaces for IBGP sessions.25 Hours) Configure EBGP on R5 and R8 as follows: • • • • R5's remote peer is 171.0. Using the network command only.1.2/30 and remote AS is 4345.255 with the following attributes: • • • Ensure that BGP origin is set to IGP.2/24 and remote AS is 1024. Prepend with paths with the AS paths 1000 999 100. set the enable password to ccie and the access password to cisco.255.100/24.100. even in the event of network failure of any one router.10. make sure all configured interfaces/subnets are consistently visible on all pertinent routers.100. ISP1 and ISP2 are advertising the full Internet routing table. ensure BGP is active in all routers.0.75 Hours) After finishing each of the following sections. Catalyst 6509 Password Recovery (0. and allow the users to access the rest of the network.CCNP Practical Studies: Routing HTTP Server (0. Make sure your have full BGP connectivity.1.