You are on page 1of 421

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

i

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)

ii

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

iii

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

iv

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.

v

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.

vi

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

.

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

.

Passing the Routing 2.0 exam is one of the exams that you must pass to become a CCNP. This is a great skill and demonstrates to any employer that you are ready for any challenges that might be asked of you. 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. NOTE The Routing 2. Detailed solutions and tips are provided to guide you through the configurations. without too much coverage of topics not on the exam.0 exam-related topics. to configure an entire network consisting of various topologies. "CCNP Routing Self-Study Lab. and the only way to provide you with those skills is to demonstrate them in a working environment that uses common Cisco-defined techniques. and list-in-order style questions. all this book's features. which are outlined in this introduction. Chapter 9.com). 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. such as CCNP. open the door to many career opportunities. By demonstrating the determination to prepare for and pass the extensive CCNP exam process. You can assess your mastery of the subjects by looking over the Practical Exercise solution. The bulk of each chapter contains five scenarios. Having read many books. The second goal of this book is to provide you with comprehensive coverage of Routing 2. so be sure to check the latest updates from Cisco at www. CCNPs today are valuable compared to even CCIEs. where you have a knowledge deficiency in these topics. The Routing 2. are geared toward helping you discover the IP routing challenges and configuration scenarios that are on the Routing exam. Ultimately.0 exam is a computer-based exam with multiple-choice. fill-in-the-blank. By working through these various elements. 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. A Practical Exercise. CCNPs also demonstrate a strong desire to succeed.2test. This book is designed to allow a reader. The exam takes approximately 75 minutes and has approximately 60 questions. lets you test yourself by applying your knowledge without the benefit of the inline explanations that are provided in the scenarios. Each chapter starts by briefly describing the technology that is covered in the practical portion of the chapter. Most Cisco certifications require practical skills. through the examinations required. demonstrate a large knowledge base that can be built upon with almost any company running any technology. and what you need to know to master those topics. The exam is constantly under review.0 exam means that you have mastered the concepts and implementation skills necessary to build a complex IP network of Cisco routers. Audience CCNP Practical Studies: Routing is targeted to networking professionals. This technology background is brief and assumes the reader has a strong technical background and now desires a practical environment to apply this knowledge. xi - . which provide you with an opportunity to apply the material at hand practically with the aid of complete explanations. and routing protocols from start to finish. in a structured manner.CCNP Practical Studies: Routing Introduction The Cisco Certified Network Professional (CCNP) certification on the Routing and Switching career track is becoming increasingly popular. you will not only gain more confidence navigating within the Cisco IOS but also an understanding of how these various networking concepts relate. Finally. The best method to accomplish this is to demonstrate these topics and provide a step-by-step practical studies guide. 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. You should have CCNA-level knowledge to use this book to its full extent.com/warp/public/10/wwtraining/. Professional-level certifications. I know that technical content alone will probably not allow you to attain the skills necessary to pass a Cisco examination. technologies. 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. The exam can be taken at any Sylvan Prometric testing center (1-800-829-NETS. CCNP certification builds on your foundation established from the Cisco Certified Network Associate (CCNA) certification. CCNP Practical Studies: Routing is intended to help you move concepts and theories into practical experience on Cisco routers. CCNPs. each chapter ends with a series of review questions designed to allow you to further assess your knowledge of the technology covered. 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.cisco. You should check with Sylvan Prometric for the exact length of the exam. www. at the end of each chapter. familiar with networking concepts and the principles of routing theory." 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.0 examination. who desire a hands-on approach to applying their knowledge.0 exam. Therefore.

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

Scalability issues are presented. How Best to Use This Book This book provides a practical approach to learning networking concepts. visit www. If you want to purchase equipment. Of course. most readers will appreciate that Cisco routers are not easy to come by. If your place of employment has spare equipment that you can use. and some great tips are provided in the explanations to show you how to ensure network connectivity. Having your own equipment or access to the equipment is the ideal way to use this book but is not required. "Study Tips" Appendix A describes some useful study tips for CCNP candidates. "CCNP Routing Self-Study Lab" Chapter 9 is designed to assist you in your final preparation for the Routing 2. "Route Redistribution and Optimization" Chapter 8 covers the issues and challenges facing networks when information from one routing algorithm is redistributed into another. 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. There are five practical scenarios to complete your understanding of BGP to help you appreciate its complexity. Getting Equipment You can obtain reasonably priced equipment from various places. Appendix A. Appendix D. NOTE xiii - . for example. and ways to overcome large BGP networks are covered and configured on Cisco routers.0 exam by providing you a lab scenario that incorporates many of the technologies and concepts covered in this book. Common exam techniques and the best study practices are provided to ensure that you are fully prepared on the day of the examination. This chapter also covers how information can be controlled to ensure that the network is routing IP as correctly and efficiently as possible. Appendix B. numerous places exist on the Internet. "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.com. Sample displays are provided to demonstrate the working solutions. namely CCIE (Routing and Switching).ciscopress. Cisco. search Cisco partners or auction sites for cheap devices to help you. There are also simulators that offer a cheap solution to purchasing equipment. the chapter covers how BGP deals with large networks. "Advanced BGP" Chapter 7 describes BGP in greater detail.CCNP Practical Studies: Routing The basics terms and configuration options are described to help you appreciate the powerful nature of BGP. contact Cisco Systems for second-hand or used routers at very competitive prices. in particular. "What to Do After CCNP?" Appendix B describes what a CCNP can achieve after becoming CCNP certified. Full working configurations and sample displays are presented. this may be your first option. Chapter 9. The exercises presented are a combination of all the most critical topics found in this book into one scenario. For more details on CIM. "Answers to Review Questions" Appendix C provides answers to all of the review questions. Alternatively. so full working solutions and sample displays are presented to ensure that you understand and fully appreciate all concepts. Chapter 8. offers a product called Cisco Interactive Mentor (CIM) that enables candidates to simulate real-life networks. Chapter 7. Appendix C.

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

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

255. Understanding basic Internet Protocol (IP) networking not only applies to the CCNP certification but all Cisco-based certification. which is a task force consisting of over 80 working groups responsible for developing Internet standards.0 255. The Internet Engineering Task Force (IETF) standards body. determine how many hosts are available on a particular subnet.255. IP. segment to allow a hierarchical routing topology. D.255 Soon after these ranges were defined and the Internet's popularity extended beyond the Department of Defense in the United States. An IP address is configured on end systems to allow communication between hosts that are geographically dispersed.168. 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. 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.CCNP Practical Studies: Routing Chapter 1. Internet Protocol This chapter focuses on a number of objectives falling under the CCNP routing principles. 127[*] 128–191 192–223 224–239 240–255 Default Subnet Mask 255. or even how to best utilize an IP address space. defined five classes of addresses and the appropriate address ranges.255 192.0 255.240 Reserved 127. consider the following example.255. You are given the IP address 131. To best illustrate an IP address and subnet portion. Table 1-1.0. 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. C. A subnet is a network that you. and what the broadcast address is.108.0.255. It then briefly explains how to efficiently configure IP to ensure full use of address space. 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.255.0 is reserved for loopbacks purposes. Routing allows communication between these subnets. B. You can deduce the subnet for any IP address by performing a logical AND operation along with the subnet mask.255.0.16. Class A.255 172.255. Next.255.255.0. The host address is a logical unique address that resides on a subnet. -1- . This example helps you determine what the subnet is.56 and the subnet mask is 255.255. 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. how many hosts can reside on this subnet.0-172.0.0.0 255.1.16.0-10.0.0. Other reserved addresses for private use as defined by RFC 1918 are 10. This chapter starts by covering basic IP concepts.0-192. this chapter covers when and how IP routing tables can be minimized using summarization techniques with various routing protocols.0.168. Subnetting allows an administrator to extend the boundary for any given subnet.0. as network administrator. Table 1-1 displays the five ranges.255. 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.

255.1.224. perform a logical AND.2 = 30 hosts. Figure 1-1. you must examine the subnet mask in binary. and the second is that negative and positive or negative is negative.10.1.10.108. This is best explained with examples.255.224 (or 11100000.2 where n is the number of borrowed bits.224. Figure 1-1 displays the logical AND operation used to determine the subnet address.67 and the subnet mask of 255.224. you simply apply the formula 2n . AND Logic Operation The result of the logical AND operation reveals the subnet address is 131. the last eight bits represent the borrowed bits. -2- .2 = 32 . The number of hosts that can reside on this network with a subnet mask of 255.255.2 = 256 . To determine the subnet. this example shows you how to determine the subnet and the number of hosts that can reside on this network. The subnet address is reserved and cannot be assigned to end devices. in binary (positive is 1 and negative is 0). Figure 1-2. (You subtract two host addresses for the subnet address and the broadcast address.CCNP Practical Studies: Routing NOTE A logical AND operation follows two basic rules.) In IP. To determine the number of borrowed bits.255.1.) Now consider another example. or C address. 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. 0 AND 0 is 0. B.2 = 254 hosts. (255 in binary is 11111111. 5 borrow bits) is 25 . To determine the number of hosts available in any given subnet. So. 1 AND 0 is 0. Figure 1-2 displays the operation.0 is 131.64.0.108.108. 0 AND 1 is 0. So. which are not permitted to be used by host devices. for a Class C network. For a default Class C network mask of 255. Logical AND Operation The subnet is 171. the broadcast address for the subnet 131. You can apply the technique used in this simple example to any Class A. Given the host address 171. a broadcast address consists of all binary 1s.255. One is that positive and positive equal positive. and so forth.255. 1 AND 1 is 1. so for this example. the number of hosts that can reside are 28 .0.255.

Apply the formula to determine the best subnet to use to cater to two hosts on any given subnet and class of address. take CPU cycles on routers. or 2n = 4. Remember that you must subtract two host addresses for the subnet address and broadcast address. The subnet mask is 30 bits in length or 255. which is represented as 11111111.252 in binary. NOTE Loopback interfaces configured on Cisco routers are typically configured with a host address using a 32-bit subnet mask. most importantly.11111111. To give network designers the ability to manage large networks. 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. For a link that never uses more than two hosts.111111100. To demonstrate the use of VLSM. 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. require memory. and BGP4. Only two devices host systems are needed. Summarization and How to Configure Summarization Summarization. and the broadcast address is 11. The last two bits (00) are available for host addresses.255. 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. EIGRP. you get 2n . the subnet is 00. -3- . and. this wastes a vast amount of space. or n = 2 borrowed bits.2 = 2. Applying the formula. Table 1-2. 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. it would be wise to use the lowest possible number of subnet bits and lowest possible number of host bits. OSPF. the second is 10. consider the example of connecting two Cisco routers through a wide-area link. To allow a greater number of devices to connect to the Internet and intranets. summarization is important for limiting or reducing IP routing tables. NOTE The following routing algorithms support VLSM: RIP Version 2. a Class C network with 255 hosts among 255 different routers and conserves valuable IP address space. the first host address is 01. You could use a Class C mask or a mask that allows for 254 hosts. 252 addresses in fact.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. which allows. for example. IS-IS. put simply.11111111. To use any IP address space effectively. You need to borrow only two bits from the subnet mask to allow for two host addresses. The most important consideration to make when summarizing any IP address space is to ensure a hierarchical design.255.

it is important to understand that if a range of addresses is not contiguous (that is. you must first disable automatic summarization with the following command: router eigrp 1 no auto-summary Then. Automatic summarization simply announces a Class A network with an 8-bit mask. from 131. you can apply the mask 248 (11111 000) on the third octet and send an advertisement encompassing all seven routes.0. To illustrate the capabilities of summarization consider the following IP address ranges in Table 1-3. as seven different IP route entries. Before looking at how to complete this summarization using RIP.108. 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.1–7. EIGRP also applies automatic summaries but it also enables the manual configuration of summary addresses. automatic summarization occurs. In other words.108. Because the first five bits are the same.0/24 and 131. EIGRP. Also. which is not an ideal solution for management purposes and also provides extra overhead on a router. Class B with 16-bit mask. you can perform summarization. Table 1-3. 255.108.108.0. 255.108.0.1.7.4. and a Class C mask with a 24-bit mask.2.108.107.255. IP address space is configured across any given router so that it can be easily summarized. you apply the manual summarization on the interface to which you want to send the advertised summary.3. they do not start from a range that can be easily summarized. -4- .1.6. 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.5. Because the high-order bits are common in Table 1-3 (0000 0) and all seven routes are contiguous (binary 001 to 111). otherwise a default mask is assumed.255. To disable automatic summaries with RIPv2.0/24 131. 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. but they might reside in other parts of your network and cause IP routing problems. With RIPv2. such as the range of addresses 131.10. IP Address Range IP Subnet 131. summarization may be enabled by default.0/24 131. The following example shows you how to summarize the networks in Table 1-3 using EIGRP.0/24 131.0/24). Depending on the routing protocols in use. To configure summarization with EIGRP.0/24 131.0.0/24 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. You could still summarize the first seven networks.CCNP Practical Studies: Routing In a hierarchical design.0/24 131. summarization is impossible.108.0/24 131.108. or OSPF. Example 1-1 displays the command you use to summarize the seven networks in Table 1-3.108. The most important fact is that these seven networks are contiguous or in a range that you can easily summarize. for example. The binary examination of the subnets 1 to 7 in Table 1-3 displays that the first five bits (shaded) are unchanged. and this includes renumbering an IP network or using secondary addressing on Cisco routers. you must disable automatic summarization to allow the more specific routes to be advertised.

IP Helper Address As in any network. broadcasts are used to find and discover end systems. 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. BGP and IS-IS. covered in Chapters 4.255.1." 6. you use broadcasts to find an end system's MAC address. 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- .0/24 with one simple route. "Advanced BGP.0 255.1. An ABR resides in more than one OSPF area. Broadcasts on any network consume CPU and bandwidth to reduce this even more. In an IP network.1. "Advanced OSPF and Integrated Intermediate System-to-Intermediate System. The actual summary is 131.248. Assume the area-id for now is 1.108. 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 1-3.255. IP also uses broadcasts for such services as sending IP datagrams to all hosts on a particular network. To save on bandwidth.255.108. assume the Cisco router is an ABR. In a Layer 2 environment. "Basic Border Gateway Protocol" and 7. Also note that the EIGRP autonomous system number is 1.0 255.CCNP Practical Studies: Routing Example 1-1 Summary with EIGRP interface serial 0 ip summary-address eigrp 1 131.0.248. Layer 3 of the TCP/IP model. matching the configuration on the router because you can have more than one EIGRP process running.1-7.0 Example 1-1 applies a summary on the serial interface.0 255. For this example. Now look at how to configure the seven networks in Table 1-3 with an OSPF summary.248. 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. you can use the IP helper address command to convert a broadcast into a more specific destination address. So to allow the ability to forward packets wisely. which conserves bandwidth. Example 1-2 OSPF summary router ospf 1 area 1 range 131. you can correctly configure summarization only on area border routers (ABRs). OSPF allows summarization manually under the OSPF process ID.0 NOTE OSPF also enables you to summarize external OSPF routes redistributed from such protocols as IGRP or RIP. which replaces the seven individual routers numbered 131." also provide complex summarization techniques.108. 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. NOTE With OSPF.108.

by default.255. you see how to configure one Cisco router for IP routing using a Class B (/16) network 161. "Routing Principles. Readers who are familiar with these basics may want to skip this chapter and move on to Chapter 2. the IOS message tells you the Ethernet interface and the line protocol are up. and using good practice and defining your end goal are important in any real-life design or solution. Also. 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. 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.255. There is no one right way to accomplish many of the tasks presented. with one Ethernet interface.1. enable terminal monitor on any VTY lines." Scenario 1-1: Configuring a Cisco Router for IP In this scenario. all Cisco routers are enabled for IP routing with the command ip routing.255. -6- . Figure 1-3 displays the one router.CCNP Practical Studies: Routing NOTE The most common use for the helper address is for clients running DHCP. changed state to up NOTE When you enable the Ethernet interface with the command [no] shutdown.1. Example 1-3 IP Configuration on R1 R1(config)#int e 0/0 R1(config-if)#ip address 161.255. Figure 1-3.0 R1(config-if)#no shutdown 4w1d: %LINK-3-UPDOWN: Interface Ethernet0/0.108. named R1. changed state to up 4w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0.108. You can disable IP routing with the command [no] ip routing.1 255.0 with a Class C subnet mask (255. IP Routing on Cisco Routers Example 1-3 displays the IP configuration performed on R1's Ethernet interface.0 or /24 mask). which remote servers assign IP addresses and subnet masks usually performed locally through a broadcast to be served remotely with a unicast (one) packet.

line protocol is up Interface is up and active Hardware is AmdP2. Example 1-5 Secondary Address Configuration on R1 R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131.1/24 and 131.1/24.108.1 255. BW 10000 Kbit. loopback not set. 45 interface resets 0 babbles. 0 drops.108.9645.108. line protocol is up Hardware is AmdP2.ff40 (bia 0001.255.1.1/24 configure IP address MTU 1500 bytes.0 secondary ip address 161. 43588385 bytes.9645. 0 no carrier 0 output buffer failures. 0 CRC. 0 throttles 0 input errors. 0 underruns 0 output errors.1. and the only way to view any secondary addressing is to view the configuration.1.ff40) Internet address is 161. Example 1-5 displays the secondary IP address assignment.1/24. DLY 1000 usec.1 255. Example 1-7 displays the full working configuration on R1 along with the secondary IP address. output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40. the Cisco IOS does not display IP secondary addressing.1. 30894958 bytes. input queue 0/75. keepalive set (10 sec) . load 1/255 Encapsulation ARPA.1. 0 no buffer Received 315628 broadcasts.1.108. ARP Timeout 04:00:00 Last input 00:00:21.108.9645.255. 0 giants.1. 0 overrun.0 ! interface Serial0/0 shutdown -7- .1.9645. load 1/255 Encapsulation ARPA. Example 1-6 show interfaces ethernet 0/0 R1#show interfaces ethernet 0/0 Ethernet0/0 is up. BW 10000 Kbit.255.CCNP Practical Studies: Routing Example 1-4 displays the active Ethernet interface up and the current IP address configuration. address is 0001.ff40 (bia 0001.108. you see how to configure a secondary address on R1 using the IP address 131.1 255.ff40) Internet address is 161.255. 0 late collision.. rely 255/255.1. address is 0001.108. 0 packets/sec 315871 packets input. 0 runts.108. 0 ignored. 0 abort 0 input packets with dribble condition detected 470705 packets output.truncated Example 1-6 does not show the secondary addressing on R1. Example 1-6 displays the Ethernet statistics on R1 and is truncated for clarity. Unfortunately.1/24 MTU 1500 bytes.255. Confirm the IP address assignment by displaying the interface statistics with the command show interfaces Ethernet 0/0. 22 deferred 0 lost carrier. Example 1-7 Full working configuration on R1 hostname R1 ! interface Ethernet0/0 ip address 131. 3 collisions.0 secondary R1 now has two IP address assignments: 161.1. 0 packets/sec 5 minute output rate 0 bits/sec. DLY 1000 usec. output 00:00:02. Example 1-4 show interface ethernet e0/0 on R1 R1#show interfaces ethernet 0/0 Ethernet0/0 is up. 0 drops 5 minute input rate 0 bits/sec. rely 255/255. 0 output buffers swapped out Next. keepalive set (10 sec) ARP type: ARPA. 131. 0 frame.. loopback not set.108.255.

This is only half the job. you must use the subnet mask of 255. you use the formula 2n . you must use the address space 131. where 192 in binary is 11000000. n. The network architect has also asked you to document all WAN addresses for future use. so count from binary 0 to all 1s.1. To determine the four subnets you must count in binary. Count only from the last octet. IP Address Configuration Requirements Start by breaking up the subnet 131. -8- . Figure 1-4 displays the network topology graphically. examine the subnet in binary.0. The last eight bits are used for host addresses.108. You know the broadcast address ends in all 1s.255.108.0/24 for all wide-area network (WAN) connections that use no more than two hosts per subnet. The host devices use the last six bits. you must also configure the four different subnets on R1 in Figure 1-4. which is the borrowed amount of bits.255.192.1. Figure 1-4. In addition to this. so by default you have 254 IP address available. The first subnet starts from 131.0/24 into four equal subnets. Table 1-4 displays the binary calculation.108. which becomes 2n = 64. becomes six bits.108. So to allow at most 62 hosts. To allow at most 62 hosts.1.2.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. To do this.2 = 62.0/24 into four equal subnets that can be used to allow at most 62 hosts per subnet.

108.108. Table 1-6 displays the third subnet calculation starting from the next available decimal number of 128. Table 1-5 performs the same calculation in binary without the intermediate steps to demonstrate the broadcast address for the second subnet. 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 131.191. Table 1-6.1. Notice that the last six bits are all 1s.108.1.127.64 and the broadcast of 131. which indicates the broadcast address.1.0 to 131.1.CCNP Practical Studies: Routing Table 1-4.108.1. 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. and the broadcast address as 131.128.1. Table 1-5.63. so the first subnet ranges from 131. and the broadcast address is 131.108.1.108.108. which in binary is 001111111.108. The subnet is 131.63.0. 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. -9- .1.

255. Example 1-8 displays the IP configuration on the four interfaces on R1. The mask or subnet mask is derived from the six bits you borrowed to extend the Class B address 131.255.108.255.192 The mask is 255.255.193 255.1.2.1.255. Binary 1100000 is 192.255.108.1. Now that you have the four broken subnets.CCNP Practical Studies: Routing Finally. you need two bits per subnet. Binary Addition Subnet 4 Decimal 192 193 194 195 … 253 255 NOTE If you are confused about how to convert binary from decimal.0.255. you have to break up the network 131.1.129 255. To complete this scenario.65 255. where n = 2. . so you can quickly break up any type of subnet in various design situations or examination scenarios.10 - .192 in Example 1-8.255.108.192 R1(config)#interface ethernet 0/1 R1(config-if)#ip address 131. and you have already discovered that the mask is 255. you can deduce the last subnet available in exactly the same way. simply use a Windows-based calculator to perform the calculation to assist in your first few calculations.108. Once more.255.192 R1(config)#interface ethernet 0/2 R1(config-if)#ip address 131.252.255. or 2n = 4.108. configure the Router R1 in Figure 1-4 for IP routing. Table 1-7 displays the final binary addition. It is vital that you can perform these steps without much thought.1. Example 1-8 IP Configuration on R1 with Four Subnets R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131. So.108.108. Table 1-7.2 = 2.1 255. 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 131.255.192 and the broadcast address for the final subnet as 131.192 R1(config)#interface ethernet 0/3 R1(config-if)#ip address 131.255.108.0/24 into 30-bit sized subnets so that they can be used on WAN circuits that contain no more than two hosts.1.1.255. use the simple formula 2n .

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

- 11 -

CCNP Practical Studies: Routing
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.

- 12 -

CCNP Practical Studies: Routing

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.

- 13 -

CCNP Practical Studies: Routing
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.

- 14 -

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

- 15 -

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.

- 16 -

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

- 17 -

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."

- 18 -

You can use static routing to minimize large routing tables and can manually configure it to override dynamic information. you assign each routing method. AD is defined as the trustworthiness of a routing information source. IGRP. Table 2-1 displays the default AD values on a Cisco router. an administrative distance (AD). To overcome this problem. the less trusted the source.19 - . When you configure multiple routing algorithms on a Cisco router. deciding which path to take is vital. 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. AD is important because routers cannot compare. 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). Intermediate System-to-Intermediate System (IS-IS) Protocol. Cisco IOS enables the network designer to change the AD with the distance command. The higher the value (between 0–255). OSPF. and RIP are dynamic routing protocols and are all covered in this book. this section looks at the two main types of routing methods that routers use to detect remote destinations dynamically. Distance Vector and Link-State Routing Protocols Now that you are aware of the routing methods available.CCNP Practical Studies: Routing Cisco IOS-Based Routers All Cisco routers support IP routing. for example. Using AD ensures that the Cisco routers can compare the remote destinations they learn through various routing algorithms. the router selects the IGRP path because of the lower AD. Table 2-1. EIGRP. . Example 2-2 shows a full list of the protocols that Cisco IOS-based routers support. 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). RIP's metric to OSPF's metric because hop count means nothing in OSPF and cost means nothing in a RIP domain. whether dynamic or static.

Link-state routing protocols. also sends all summary information every 30 minutes by default.0. When an update is sent. it is 255. Table 2-2 describes the characteristics of distance vector protocols. You use this method to stop routing loops. create a topology of the network and place themselves at the root of the tree. the entire routing table is sent. Any new OSPF-enabled routers immediately transmit a multicast Hello packet by using the OSPF routers multicast address of 224.20 - . for example. Hello packets are used to establish and maintain neighbors. A hop count is defined as the number of times a packet needs to pass through a router to reach a remote destination.6 for all DRs and BDRs. such as RIP.0. The OSPF database is populated with link-state advertisements (LSAs) from neighboring routers. Therefore. This saves on bandwidth as well. Link-State Protocol Summary Characteristic Explanation Periodic updates Only when changes occur. Algorithm Dijkstra Algorithm for OSPF. For IP RIP. Updates are sent to a multicast address. Examples RIP and IGRP are examples of distance vector protocols. (For an IP datagram. Table 2-3 displays the characteristics of link-state protocols.0. Table 2-3.) NOTE Hello packets are used to discover neighboring routers.255.0. updates Database A database contains all topological information from which an IP routing table is assembled. such as RIP and IGRP. . DRs use the multicast address 224.5 for all OSPF routers and 224.0. determine the path to remote networks using hop count as the metric.0. A higher hop counts allows your network to scale larger. also known as Dijkstra's Algorithm) to determine the path to a remote destination. Updates are not sent out an outgoing interface from which the source network was received. IGRP is another example of a distance vector protocol with a higher hop count of 255 hops. so when changes occur updates can be sent immediately. the loopback interface with (numerically) the highest IP address is the router ID. For IP RIP.255.CCNP Practical Studies: Routing Distance vector protocols (a vector contains both distance and direction). which is the highest IP address configured on the local router. OSPF. it is 15 and for IGRP. (Loopback interfaces never fail unless you shut them down or manually delete them. Examples OSPF and IS-IS.) In the event that more than one loopback interface is configured on a Cisco router. such as Ethernet or Token Ring. For RIP. One of the drawbacks of protocols. Count to infinity This is the maximum hop count. Table 2-2. Typically. the maximum hop is 15. A hop count of 16 indicates an unreachable network.255. Two versions of RIP exist: version 1 and version 2.6 to send updates to all other OSPF routers. Only devices running routing algorithms listen to these updates.0 through 239. The two most important reserved addresses are 224. such as OSPF and IS-IS.0. these are sent when a change occurs outside the update interval. two reserved multicast addresses are vital for maintaining OSPF adjacencies across any broadcast media.255. OSPF administrators configure loopback interfaces to ensure that the OSPF process is not prone to failures. the maximum time to live ensures that loops are avoided. which is the time it takes for routing information changes to propagate through all your topology. this interval is 30 seconds. such as cost and the advertising router or the router ID.0. Updates are sent to the broadcast address 255.255. is convergence time.255. Linkstate protocols implement an algorithm called the shortest path first (SPF. CPU/memory Higher CPU and memory requirements to maintain link-state databases. Also known as Flash updates.0. The LSA packets contain information.5. OSPF uses the Class D multicast addresses in the range 224. Broadcast Only devices running routing algorithms listen to these updates. Algorithm One algorithm example is Bellman-Ford for RIP. 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. There is no hop count limit.0. Convergence Updates are faster and convergence times are reduced.

a Class A network ranges from 1–127 and uses a subnet mask of 255.0.0. the default mask of 255. and BGP.0.0.168. 1. B. Classful and Classless Routing Protocols Routing protocols can also be described as classful and classless. EIGRP. whereas RIP is considered the easiest. 0 1.0.0–192.255.0–126. 1. and the vector indicates the direction and path to a remote network. BGP is considered the most complex routing protocol to configure. BGP is considered a path vector protocol because autonomous system numbers are carried in all updates. Also note distance vector protocols are simpler to implement.0.255.255 172.0–10.1. and Class C uses 255.254.255.255 192. 0 1.255.0–172. and E network. and Class C addresses. 1 Address Range 1. 0 1.0.108.255 240.0.0. you can use a Class B network. (Class D is reserved for multicasts. such as 131.0. B. mask).0. and when designing networks. For example.255. At last count (October 2001).0.0–254. and C addresses define a set number of binary bits for the subnet portion.0–239.255.255. D.0 192. Classful addressing is the use of Class A.0.254.255. Class B. Reducing the IP routing table size allows for faster delivery of IP packets and lower memory requirements. For example.255. classless routing better utilizes address space.CCNP Practical Studies: Routing NOTE EIGRP is considered an advanced distance vector protocol because EIGRP sends out only incremental updates. Classful routing protocols apply the same rules.255. 1.0. NOTE The following three blocks of IP address space for private networks have been reserved according to RFC 1597: • • • 10. This method of routing does not scale well.0–191. 1.0. A Class B network uses the mask 255.0 is applied and so forth. Examples of classless routing protocols are OSPF.0.255 Table 2-4 summarizes the addressing ranges in Class A.168.0. If a router is configured with a Class A address 10.16.000 IP routing table entries on the Internet.255. .31.255.543 254 N/A N/A Examples of classful routing protocols are RIPv1 and IGRP. 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 1.214 65. Table 2-4.255 Maximum Hosts 16.0.0 224. 1.0.1.0 128.0.21 - . and Class E is reserved for future use.1.0–223.255. With classless routing. C.0.255. there are over 80.0. and apply a Class C mask (255.0.1.777. the ability to apply summarization techniques enables you to reduce the size of a routing table. and link-state protocols are more complex.) Class A.0.0. IS-IS.0.0. or /24.

You also configure a number of loopback interfaces to populate the IP routing table. There is not always one right way to accomplish the tasks presented here. NOTE To determine which router requires a clock to enable communication at Layer 2 of the OSI model. it never goes down. . use the show controller command to determine which end of the network is the data circuit-terminating equipment (DCE). Routing IP with Directly Connected Networks Routing IP with Cisco Routers First. clocking is required to enable the two routers to communicate. and you can use it as a tool to populate routing tables. A loopback interface is a software interface that can be numbered from 0-2147483647. R1 is directly connected to R2 with back-to-back serial cables. Refer to Figure 2-2 for IP address assignments.108. you configure two Cisco routers for IP routing using a Class B (/16) network address. 131. Example 2-3 displays the hardware information on R1. Ethernet.0. and the serial interface. or /24). 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. and using good practice and defining your end goal are important in any real-life design or solution. Most importantly.255. configure router R1 for IP routing. Scenario 2-1: Routing IP on Cisco Routers In this scenario. with a Class C subnet mask (255. this is a modem.0. R1 and R2.22 - . Figure 2-2 shows the network for this scenario.0. Typically.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.255. Figure 2-2. As with any wide-area network (WAN) connection. You need to start by configuring the loopbacks. NOTE A loopback interface is a software interface. You can ping it and communicate with it. 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.

35.35 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).23 - . V. 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 Loopback2. To configure the loopbacks with an IP address.0 R1(config-if)#interface loopback 2 2w1d: %LINK-3-UPDOWN: Interface Loopback2. Revision 15 Channel mode is synchronous serial idb 0x61209474.255.0 . type the commands on R1 as displayed in Example 2-5. changed state to up R1(config-if)#ip address 131. changed state to up R1(config-if)#ip address 131.255. In this case.255. supplies the clock.1 255. so R2 requires a clocking source. the DCE. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1.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.1 255.35. Router R2 has the data terminal equipment (DTE).108. Example 2-4 displays the hardware information on R2. Example 2-4 show controllers s0/1 on R2 R2#show controllers s1/0 CD2430 Slot 1. Channel 0.4. simply use the following command syntax: interface loopback number The value for number is a number within the range of 0-2147483647. buffer size 1524.255. no clock .108.0 R1(config-if)#interface loopback 1 2w1d: %LINK-3-UPDOWN: Interface Loopback1..108. Controller 0.255. Example 2-5 IP Address Configuration on R1 R1(config)#interface loopback 0 R1(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Loopback0. changed state to up R1(config-if)#ip address 131. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0. Port 0. and the cable types used on the routers are V.output omitted Notice that R1 has the DCE connection so you need to configure a clock rate with the clock rate speed command.1 255.255. R1.6.5.. To configure the three loopbacks for this scenario.

CCNP Practical Studies: Routing In Example 2-5 when the first interface Loopback 0 is created.0 R2(config-if)#no shutdown R2(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Ethernet0/0. You need to enable the interfaces. no users can attach to your network. Example 2-8 Enabling E0/0 and S1/1 on R2 R2(config)#interface e0/0 R2(config-if)#ip address 131.108. but you still have no active connection on R1 serial link because R1 S0/1 connects to R2.3. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0. notice both the Ethernet and serial connections are immediately active because R2 is connected to an Ethernet switch. and you have yet to enable R2 serial interface to R1. you can enable the Ethernet interface with the command keepalive 0.1 255.255.2 255.255.3. Example 2-8 displays IP address configuration and the enabling of the hardware interfaces on R2. changed state to up On this occasion. Example 2-6 IP Address Configuration on R1 R1(config)#interface ethernet 0/0 R1(config-if)#ip address 131.108.1. You now simply configure the IP addresses for the Ethernet and serial link to R2.255. Similarly. 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. changed state to up R1(config-if)#int s 0/1 R1(config-if)#no shutdown The Ethernet interfaces is running. NOTE If you do not have access to any form of switch or hub.108.2. The Cisco IOS considers the interface active and includes the network in the IP routing table. in which case hardware is unnecessary.0 R1(config-if)#clock rate 128000 This time you did not get any messages to indicate the link is active. You have now configured two routers with IP addressing.1 255. this happens for loopbacks 1 and 2. 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.255.1 255.24 - .255. but for training purposes it is a great command to use. you get a message that indicates Loopback 0 is active. changed state to up R2(config-if)#int s 1/1 R2(config-if)#ip address 131. Example 2-7 displays the Ethernet interface and serial interface on R1 being enabled.255.108. Of course. as demonstrated in Example 2-6.255.255. 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 can assume that the Ethernet on R1 is connected to a Catalyst switch.0 R2(config-if)#no shut R2(config-if)# 2w1d: %LINK-3-UPDOWN: Interface Serial1/1. changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0. . changed state to up 2w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/1.

IA .0.OSPF NSSA external type 1.5.3. O . Now. E2 .108. The following entry describes the fact that R1 has the Class B network 131.108.0/24 is directly connected. That the gateway of last resort is not set in this case means that if the router receives an IP packet.IS-IS level-1. B .static.OSPF NSSA external type 2 E1 . namely the three loopbacks. Example 2-9 displays R1's routing table. R . M .EIGRP. which is typically represented by a next hop address.4.108. Loopback2 directly connected.108.0 is is is is is is subnetted.per-user static route.OSPF. which are denoted by the C on the left side of each routing table.connected. E . L2 . I . L1 .EIGRP.EGP i . by default if the router doesn't know the destination.mobile.ODR Gateway of last resort is not set 131.108. look at the shaded portions in Example 2-9. 3 masks C 131. Serial0/1 directly connected.7. Loopback0 directly connected.OSPF external type 1.0 131.108. B . Serial1/1 C 131. it drops the IP packet. Loopback2 C 131. S . Ethernet0/0 Example 2-10 displays R2's IP routing table.RIP.108. and the serial link to R2: 131.0.OSPF external type 1.RIP. In particular. o .25 - .108.EIGRP external. The first half of the display summarizes the abbreviations the Cisco IOS uses to denote how it learns or discovers routing entries.108.BGP D .108.OSPF NSSA external type 1.per-user static route. For example.static.108.2. EX .6.OSPF external type 2. If the router knows the gateway of last resort.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. the router forwards the IP packets to that destination or next hop address. EX .108.OSPF NSSA external type 2 E1 . Example 2-10 show ip route on R2 R2#show ip route Codes: C . E2 .108.EIGRP external.IS-IS level-2.IGRP.IS-IS level-1.0/24 is subnetted. Ethernet0/0 R2# Both of these cases show routing entries for only directly connected interfaces. 9 subnets.0.9.candidate default U .OSPF external type 2. I .0. entries denoted by D are discovered by EIGRP. N2 .0 131.0/24 131.0 131.OSPF. 5 subnets .3.0/16 is variably subnetted. you take the R1 routing table and look at it in depth. N2 .108.connected. the Ethernet. L1 .OSPF inter area N1 . 5 subnets directly connected. S .IGRP.0/24 is directly connected.BGP D .0 131.IS-IS level-2. R . O .0/24 is directly connected.0/30 is directly connected. * . E . L2 .ODR Gateway of last resort is not set C C C C C R1# 131.0 subnetted with five individual networks.8. and so forth.candidate default U .IS-IS. IA .0/25 is directly connected. M . entries that display C are directly connected networks. Loopback1 C 131.mobile.IS-IS. Example 2-9 show ip route Command on R1 R1#show ip route Codes: C . Loopback0 C 131.1.EGP i . * .OSPF inter area N1 . Loopback1 directly connected. o .

5.0.255 via Ethernet0/0 (131.0.108. Specify the networks on which RIP will run.0.0.3.1) 2w1d: subnet 131.108.0.4. to enable IP RIP.0.108.108. metric 1 2w1d: subnet 131. At this stage.108.5. Step 2.4.1.255. 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 255.108. you need to specify only the major network because RIP is a classful protocol.255 via Loopback1 (131.0.26 - . metric 1 2w1d: subnet 131.CCNP Practical Studies: Routing To make the routing table a little more interesting. metric 1 2w1d: subnet 131.108.108. Example 2-13 displays the debug commands enabled on R1.1) 2w1d: subnet 131.255.0 Now enable debugging on R1 to view the routing updates on R1.255.108. In this example.0.108.108. metric 2 2w1d: RIP: Update contains 5 routes 2w1d: RIP: Update queued 2w1d: RIP: sending v1 update to 255. Example 2-11 and Example 2-12 display the configurations required on R1 and R2. To start.0.6.4. configure RIP on both R1 and R2.1) 2w1d: subnet 131.108.255.0 in 1 hops 2w1d: RIP: Update contains 1 routes 2w1d: RIP: sending v1 update to 255.0.0. metric 1 2w1d: subnet 131.0. metric 1 2w1d: subnet 131. the Class B network is 131.5. metric 2 2w1d: subnet 131.108. metric 1 .2.255.3. configure R1/R2 with RIP and then OSPF.108.0.6.3.2.108. To enable IP RIP. metric 1 2w1d: subnet 131.0.0.1) 2w1d: subnet 131.3. metric 1 2w1d: subnet 131.1.108. metric 1 2w1d: subnet 131.108.2 on Serial0/1 2w1d: 131. metric 1 2w1d: subnet 131.5.255. R1 is not aware of any IP networks on R2 and vice versa. Enable the routing protocol with the command router rip.255.108.108.6. Example 2-11 Enable IP RIP on R1 R1(config)#router rip R1(config-router)#network 131.0.255 via Serial0/1 (131.0 Example 2-12 Enable IP RIP on R2 R2(config)#router rip R2(config-router)#network 131.108. metric 1 2w1d: subnet 131. IP RIP is one of the easiest routing protocols to configure.0.0.4. metric 1 2w1d: subnet 131. 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 131.255.108.108.0.1. respectively.6.108.108. With RIP.2.255 via Loopback0 (131.0. you need to perform the following steps: Step 1.108. 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.

108.108. is directly connected.1.2. metric 2 subnet 131. 00:00:08. Loopback0 is directly connected.108.0/24 is subnetted.0. 131.3. 00:00:20.27 - . Another important field described in the IP routing table is the administrative distance and the metric.108.108.2.7.255. and 131. Serial0/1 Serial0/1 Serial0/1 Serial0/1 As you can see in Example 2-15.108. Example 2-16 displays the IP address change on R1 and R2 using the new subnet mask of 255. metric 1 subnet 131.8. Serial0/1 [120/1] via 131.108.0. and most importantly to R2 through the serial link S0/1.108.0. is directly connected. 00:00:08.0.108.252.108.9. 00:00:08. . you must use the subnet mask 255.8.0/24. R 131. 9 subnets [120/1] via 131.2.255. Example 2-15 R1's RIP Entries Only R1#show ip route rip 131.0/24 131. that is. Now change the IP address on the serial link to the most commonly used subnet.2.1.108.3. R2 is advertising the Class B subnetted networks 131.108.255. R1# 00:00:20. you typically use a subnet that allows only two hosts.6.5.255.0 131.108. metric 1 Update sent via Loopback0 Update contains 5 routes Update queued sending v1 update to 255.108. metric 2 subnet 131.108.5.4.0 131. metric 1 subnet 131.3.108.2. R1 sends information about the local interfaces so that R2 can dynamically insert these entries into its own routing table.108. [120/1] via 131.3. 00:00:20.2.0 131.252.108. 1.108. The hop count to all the remote networks in Example 2-15 is 1.0 [120/1] via 131. 131.3.0. Loopback2 is directly connected.3.0 131. the administrative distance is 120 and the metric is hop count.2.108.9.255 via Loopback2 (131. RIP works in this environment because all the networks are Class C. and 2.3. 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.108.255.2. 00:00:20.0 is subnetted.3.0.108.CCNP Practical Studies: Routing 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: 2w1d: subnet 131.0/24.6.108.108.0 131.0 131. To ensure the efficient use of IP address space when designing networks.108.3.108.2. Example 2-14 displays the IP routing table on R1. R 131.0 131. To allow two hosts. it sends updates to R1.3.108.2.7. 00:00:08.0/24. Example 2-14 R1's Ip Routing Table R1#show ip route R R R C C C C R C R1# 131.1) subnet 131.108.2. The outgoing interface is serial 0/1. [120/1] via 131.108.0 [120/1] via 131.1.9.0 131. metric 1 subnet 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 R1.0 [120/1] via 131.0 [120/1] via 131.108. Ethernet 0/0.108.108. R 131.255.2.108.0.7.0.8.3.0.2.108.2.108.4. metric 1 subnet 131.0/24 through the next hop address 131.108. Then R1 sends updates to loopbacks 0.3. R2 performs the same routing function.108. Loopback1 is directly connected.108.0. In the case of IP RIP. 9 subnets R 131.

2 masks is directly connected.108.3.108.108.9.255.0 ! ! hostname R1 .2 255. Serial0/1 [120/1] via 131.3. Serial0/1 is directly connected.108.3.1 255.108.108. 00:00:00. to a directly attached interface. Enable version 2 of IP RIP.108. a /24 network was used on all interfaces.0/24 131.28 - .108. Serial0/1 [120/1] via 131.0/24 131.0/24 131.3.108.255. you type the command version 2.0/24 C 131.0/30 131.7.252 1/1 address 131.4.2.255.5. Before you learn how to configure OSPF. Example 2-20 R1 Full Configuration version 12.108.2.108. Loopback1 is directly connected. Serial0/1 [120/1] via 131. You can also use static routes to accomplish connectivity.2.3. 5 subnets.108. whereas all the other directly connected interfaces are /24.6. Loopback2 is directly connected. Another routing protocol that understands VLSM is OSPF.0/24 131.108.108. Loopback0 is directly connected. or whatever mask is applied.0/24 131.108.5.108.3.0/24 C 131. Serial0/1 is directly connected. 00:00:00. Example 2-18 displays the enabling of RIP version 2. Remember that RIP is classful so it applies the default subnet mask.1.3.0/24 R1# variably subnetted.108.0/24 C 131. Loopback1 is directly connected.108. 2 masks [120/1] via 131.8. 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. Loopback0 is directly connected.108.1. Example 2-19 displays the new IP routing table on R1. IP RIP version 1 does not.4. Example 2-17 now displays the new IP routing table on R1.108.6. 00:00:00.3.108.0.2.0. Example 2-17 show ip route on R1 R1#show ip route 131. Because you use a variable-length subnet mask (VLSM) across this network means you need a routing protocol that understands VLSM.0/24 131.0/30 C 131.0/24 variably subnetted. Also notice that the serial link to R2 through Serial 0/1 is a /30 subnet.255.0/16 is C 131. 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. 00:00:00.0/16 is 131. To enable version 2. Loopback2 is directly connected. Ethernet0/0 Notice what happens to the IP RIP routes.252 Look at the IP routing table on R1. Ethernet0/0 The remote networks are now back in the routing table because RIPv2 understands VLSM.2.108. Example 2-20 and Example 2-21 display the full configurations for R1 and R2 using VLSM and RIPv2.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. In the first RIP example. Serial0/1 is directly connected.0/24 131. 9 subnets.

0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.255.1.0 no ip directed-broadcast ! interface Loopback2 ip address 131.0 no ip directed-broadcast ! interface Loopback2 ip address 131.0 ! hostname R2 ! enable password cisco no ip domain-lookup ! interface Loopback0 ip address 131.CCNP Practical Studies: Routing ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.1 255.108.4.255.255.0.9.255.252 no ip directed-broadcast clockrate 128000 ! router rip version 2 network 131.8.0 no ip directed-broadcast ! interface Loopback1 ip address 131.255.255.1 255.1 255.0 ! line con 0 transport input none line aux 0 line vty 0 4 end Example 2-21 R2 Full Configuration version 12.7.108.255.255.3.1 255.1 255.108.108.255.1 255.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 131.5.108.0 no ip directed-broadcast ! interface Ethernet0/0 .108.6.108.255.255.255.29 - .108.255.255.108.255.1 255.0 no ip directed-broadcast ! interface Loopback1 ip address 131.1 255.255.

252 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router rip version 2 network 131. You change the IP addresses as well to learn about VLSM. Figure 2-3. On R2.255. Figure 2-3 shows the network and areas you use for this scenario. Scenario 2-2: Basic OSPF In this scenario.30 - .0 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131. Use a /30 mask on the serial link and host addressing or a /32 mask on all the loopbacks to conserve address space.108. This IOS command is a handy command to disable when you are studying on Cisco IOS routers. which is time consuming and annoying.255. the extra serial interfaces are not configured and are in a shutdown state or are not enabled by default. the command no ip domain-lookup is configured.2 255.108.1 255. Basic OSPF .CCNP Practical Studies: Routing ip address 131.255.0 ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 ! end NOTE In both cases. you learn how to change the routing protocol to OSPF on both Routers R1 and R2. the router automatically queries the DNS server. Leave the Ethernet segments with a Class C network to enable 254 hosts to attach to the router.0.255.3.108. Every time you type an unknown command on a router in exec or priv mode.2.

areas 1 and 2 cover the Ethernets on R1 and R2 and their respective loopbacks. Before you configure OSPF.0.108. Enable the routing protocol with the command router ospf process number.4.4.255.2.10 0.108.0 area 1 131.0 area 2 0.4.0.0. Example 2-22 displays IP address changes and the removal of IP RIP.255.4.0.0.4.3 255.108.2 255.255.0 0. 1.3 0.108.108. Step 2.108. you need to perform the following steps: Step 1.0. The process number is significant to only the local router. Specify the networks on which OSPF will run and the area assignments. renumber all interfaces and remove IP RIP with the command no router rip.0 area 2 0.108.4 131.255 area 2 0.255 R1(config-if)#int lo1 R1(config-if)#ip address 131. a backbone OSPF area 0 is configured.255 R1(config-if)#int lo2 R1(config-if)#ip address 131.108.255.108.5 131.1 0.6 255.108.255 R2(config-if)#int lo2 R2(config-if)#ip address 131.255.4.255 area 1 131.0.0.4. and 2.0 area 1 131.255.0.0.255 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 R2.255.4.0.4.108.0. you configure three areas: 0.255 R2(config-if)#int lo1 R2(config-if)#ip address 131.255 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. Example 2-22 IP Address Changes and Disabling IP RIP on R1 R1(config)#int lo0 R1(config-if)#ip address 131.0.31 - . To enable OSPF. Area 0 (or area 0.2 0.3. As on all good OSPF networks.2 0.108. configure R1 for OSPF by using the process number 1 and for R2 using process number 2.0.1. You can run more than one process.4.0.255.4 255.0.255.3.1 255. the area ID defines the OSPF area assignment.0 area 0 .108.0 area 2 0.108.255.108.0. Example 2-24 and Example 2-25 display the new OSPF configurations on R1 and R2. The IOS command to enable OSPF per interface is network address wildcard-mask area area-id The wildcard mask defines what networks are assigned.0.0.6 131.0 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 131.1 131.CCNP Practical Studies: Routing In this basic scenario. 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 131.108.0.4.0) is the backbone.5 255.0.0.255.255.0 area 1 131. Example 2-23 IP Address Change and Disabling IP RIP on R2 R2(config)#int lo0 R2(config-if)#ip address 131.4.

255.2.4.0.108. Example 2-28 28 R1 Full Configuration version 12.255 means 131.108. Example 2-27 uses the command show ip route ospf on Router R2 to display only the OSPF routes.1.108. Loopback0 is directly connected.1 255.255.1. 00:43:09.0/24 131. you can configure any IP address in the range 131.1. Serial1/1 Example 2-28 and Example 2-29 display the complete configurations for R1 and R2 for your reference.108.108.1 to 131.4. Loopback2 is directly connected.3.1.1.1. 9 subnets.108. Serial0/1 is directly connected.0/30 131. Example 2-26 IP Routing Table on R1 C C C C O O O C O IA IA IA IA 131.3.255 no ip directed-broadcast ! interface Loopback1 ip address 131.255 means the first three octets must match and the last octet does not matter. there are also the directly attached links. Serial0/1 [110/65] via 131. 00:01:29. 00:43:09.255 no ip directed-broadcast .1. Serial0/1 [110/74] via 131. In addition. Serial1/1 [110/782] via 131. Serial0/1 You can see from Example 2-26 that R1 discovers four remote networks (R2's Ethernet and three loopback interfaces) through OSPF.4.108.6/32 131.108.0.0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.3.108. in this case area 2.255 no ip directed-broadcast ! interface Loopback2 ip address 131.CCNP Practical Studies: Routing The wildcard mask 0. Example 2-26 displays the IP routing table on R1.4.0 indicates an exact match.108. Loopback1 is directly connected. Serial1/1 [110/782] via 131. 00:43:09. the administrative distance is 110 (more trusted than RIP at 120) and the metric used by OSPF is cost. 00:01:29.2 and the outbound interface Serial 0/1. The wildcard mask 0.0/16 is 131.108.3.2.108. Notice once again the administrative distance and metric pairing.3.1.0.255. 00:01:29.254 to be in area 1 on R1 E0/0.2.1.1/32 O IA 131.108.3 255.108.108.0.108.3. The left side indicates the routing type as O for OSPF.1.4. 9 subnets.2.0. For example. Serial1/1 [110/791] via 131.0/16 is O IA 131.108.108.4. Serial0/1 [110/65] via 131. 00:41:54.2/32 131.0.3/32 131. R1 dynamically learns the remote networks on R2 through the next hop address of 131.108. 00:01:29.0 0.108.108.3.4.108.108.108.1. In this case.1/32 131.32 - .4.5/32 131. 3 masks [110/782] via 131.255.108. The IA (inter-area) indicates the remote network is part of another area.4.3/32 O IA 131.108.255.108.2/32 O IA 131.4/32 variably subnetted. the command network 131.4.0/24 131.3.4.108.255. 3 masks is directly connected.4.0.108. In the case of OSPF.108.3. Ethernet0/0 [110/65] via 131.254 all match.2 255.108.108.2.3.1 to 131.0. Example 2-27 R2 OSPF Routing Table R2#show ip route ospf 131.0/24 R2# variably subnetted.

1 255.2 ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown 255.255.6 ! interface Ethernet0/0 ip address 131.255 area 1 network 131.108.3 0.0 0.252 .108.108.108.2 0.0 area 1 ! router rip version 2 network 131.4.1.0 area 1 network 131.108.255.255 255.0.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 131.0.1 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.108.0.33 - .0.0 area 1 network 131.0.1 0.255.0.255 255.108.0.255 255.255.108.255.108.4.0.255.255.0.255.1 255.4.0.4.255.5 ! interface Loopback2 ip address 131.1 0.255.0 255.255.255.3.108.4.108.108.1.0.252 clockrate 128000 ! router ospf 1 network 131.3.0 ! 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 131.4.255.3.2.4 ! interface Loopback1 ip address 131.255.108.0 area 0 network 131.CCNP Practical Studies: Routing ! interface Ethernet0/0 ip address 131.

To enable IGRP.4.0 area 2 network 131. You then specify the networks on which IGRP runs.4.4.34 - . The administrative domain must be the same for routers that are under a common administrative control or the same network.CCNP Practical Studies: Routing ! router ospf 2 network 131. you need to configure the same administrative domain. Figure 2-4 displays the network topology and IP addressing scheme.5 0.2. Use the command router igrp administrative domain to enable the routing protocol.6 0.108.108.0.0.4 0.0 ! 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 131.0 area 0 network 131.0.2 0.0.0 0. Figure 2-4. IGRP is a classful routing protocol. Once more. As with IP RIP. To share information between routers in IGRP.0.108. revisit the two-router scenario. In this scenario.0.108.0.0. you use a different class address as well.0 area 2 network 131. Step 2.255 area 2 network 131. In this basic scenario.0. so you have to change the IP addressing back to a nonVLSM network.108. Basic IGRP/EIGRP Network This scenario starts with IGRP and then changes the routing protocol to EIGRP.108.0.0. you need to specify only the major class network. you configure the two routers R1 and R2 for IGRP using the same administrative domain.3. you need to perform the following steps: Step 1. .

255.1 255.255.0 Example 2-31 displays the IP address changes made to router R2.4.255.0 199.100.2.0 199.1 255.100.8.3.3.100. you must specify each network in IGRP.7.0 199.9.100.1 255.3.0 199.3.100.255. Example 2-30 displays the IP address changes made to Router R1.6.0 199.100. 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. NOTE When using a class C network with the default class C mask.1.0 199.100.0 199.255.1 255.100.5.100.1 255.255.0/24 through to 199. 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. 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 199.1.0 199.255.255.9.255.0 199.2 255.100.100. 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. .255.8.9.1 255.4.255.0 199.0 199.100.100.255.6.100.100.255.0 Example 2-34 now displays the IP routing table on R1.0 199.0 199.255.100.255.255.0 199.0 199.35 - .CCNP Practical Studies: Routing Use the Class C network 199.1 255.100.100.100.255.7.2.0 Example 2-32 displays the IOS commands required to enable IGRP in AS 1.100.255.0/24.100.5.255.1 255.1 255.100.1.255.0 199.0 Example 2-33 similarly displays the IGRP commands configured on R2.

100. C 199.255. 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.2.100.100. Notice the administrative distance and metric pairing.3.0/24 is directly connected.5. you can see four remote IGRP networks learned through the next hop address 199.0/24 is directly connected. C 199. Example 2-35 Full Configuration for R1 hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 199. Typically.6. Values K1 through K5 can be configured with nondefaults with the IOS command metric weights tos k1 k2 k3 k4 k5.100.2.0 no ip directed-broadcast ! interface Loopback1 ip address 199.100.8.3.108.3.255.36 - .100.255. K1 = K3 = 1 and K2 = K4 = K5 = 0.0/24 is directly connected.1 255.0/24 [100/8976] via 199. NOTE The calculation for a composite metric is as follows: Composite metric = K1 x bandwidth + (K2 x bandwidth) / (256 .100.0/24 [100/8976] via 199.load) + K3 x delay The values K1 through K5 are constants. Loopback0 Serial0/1 Serial0/1 Serial0/1 Serial0/1 On R1.9.255.2.CCNP Practical Studies: Routing Example 2-34 R1 IP Routing Table R1#show ip route Gateway of last resort is not set I 199.100.100. 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 R2.100. the formula with K2 = K4 = K5 = 0. If the defaults are used.2. 00:00:47.2.100. In the case of IGRP.0/24 [100/8576] via 199. If K5 is not zero. 00:00:46. 00:00:46. 00:00:46.100. Serial0/1 I 199. Loopback1 C 199. The left side indicates the routing type as I for IGRP. respectively.1 255. Loopback2 C 199.100. the formula is as follows: IGRPmetric = Metric x [K5 / (reliability + K4)]. C 199.2 (R1's link to R2) and through the outbound interface Serial 0/1. where type of service must be zero.3.1.3. I 199.4.2 and the outbound interface Serial 0/1.4.100.0 . Ethernet0/0 I 199.3.0/24 [100/8976] via 199.5.3.7.0/24 is directly connected.100.0/24 is directly connected.100. R1 dynamically learns the remote networks on R2 through the next hop address of 131.

255.0 no ip directed-broadcast ! interface Loopback2 ip address 199.1 255.1 255.1 255.0 network 199.100.1.1.0 network 199.5.100.255.7.255.1 255.255.4.100.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 199.255.100.100.255.255.0 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 199.100.8.255.37 - .100.255.0 .6.0 network 199.255.CCNP Practical Studies: Routing no ip directed-broadcast ! interface Loopback2 ip address 199.255.100.0 clockrate 128000 ! router igrp 1 network 199.1 255.9.255.100.0 network 199.3.100.0 ! 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 199.3.1 255.100.0 no ip directed-broadcast ! interface Loopback1 ip address 199.0 ! 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 12.6.

You can use the command no auto-summary to disable automatic summarization.100.255.100.38 - . the default mask is assumed.100.7.0 network 199.0 network 199.9.3. you simply enable the routing protocol and define the networks. EIGRP also supports VLSM. That is.1 255.0 network 199.255.0 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. but it is multiplied by 256.2 255. the metric EIGRP uses is the same as the metric IGRP uses.2.100.8.255. Also.100.CCNP Practical Studies: Routing no ip directed-broadcast ! interface Ethernet0/0 ip address 199.0 ! 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.255. EIGRP enables network summarization by default.0 network 199.100. .3.2.100. or a classful network is assumed. Figure 2-5 shows the sample network for this EIGRP example.0 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router igrp 1 network 199. To configure EIGRP.

0 R2(config-router)#network 199.0 R2(config-router)#network 199.108.3.0/25 and 131.9.129 255.100.100. Example 2-37 displays the removal of IGRP and the enabling of EIGRP in AS 1 on Router R1.0 R2(config-router)#network 131. as displayed in Example 2-39. EIGRP Configuration Modify the Ethernet segments on R1 and R2 to use a different class address of 131.7.CCNP Practical Studies: Routing Figure 2-5.0 R1(config-router)#int e 0/0 ! change IP address on R1 e0/0 R1(config-if)#ip address 131. 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 131.0 R2(config-router)#network 199.0 R2(config-router)#network 131.1.100.0 Notice IGRP is removed first and the AS number is the same in R1 and R2 so that both routers can share information.108.6. respectively. You have not disabled automatic summarization yet.100.255. .39 - .0 R1(config-router)#network 199.4.1.128 R2(config-if)#router eigrp 1 R2(config-router)#network 199.108.1.9.0 R1(config-router)#network 199.1.3.108.128/25.1.0 !define network in eigrp R1(config-router)#network 199.100.108.255.255.128 Example 2-38 displays the removal of IGRP and the enabling of EIGRP in AS 1 on Router R2.1 255.108.255.108.1.8.5. Now view R1's EIGRP routing table.0 R1(config-router)#network 199. 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 131.1.100.9.

100.CCNP Practical Studies: Routing Example 2-39 R1's IP Routing Table R1#show ip route eigrp D 199.1. you need to disable automatic summarization.129.100. or discarded.2. 2 subnets D 131. OSPF at 110. in this case. Notice the administrative distance and metric pairing.. and IGRP at 100).100. 00:00:01.108.0/25 is subnetted. Serial0/1 D 199. Example 2-40 displays a sample ping from Router R1.108.0.100.128/25 has no entry because R1 has a locally connected subnet 131.3.100. 00:00:01.130.0/25.3. which means redistributed into an EIGRP domain. Now. Sending 5.. 00:00:55. One of these routes is to null0. Serial0/1 131.1.0/24 [90/2297856] via 199. the administrative distance is 90 (more trusted than RIP at 120.3.0/16 is variably subnetted. 00:00:55.1. 100-byte ICMP Echos to 131.40 - . you can see four remote EIGRP networks learned through the next hop address 199. Serial0/1 D 199.1.108.0/24 [90/2297856] via 199.0/24 [90/2297856] via 199.108.2.100.108.1.0/24 [90/2297856] via 199.129/25 from R1. ping the remote network 131.108.7. and the metric EIGRP uses is 256 times that of IGRP.108.9.0/16 are sent to null0. Null0 D 199.8.2. 00:00:01.1.2.0. Sending 5. 00:00:01. To solve the problem of packets being discarded.) or. R1 dynamically learns the remote networks on R2 through the next hop address of 199.108.0/16 is a summary.2 and the outbound interface Serial 0/1.100. The remote network 131. the packets are sent to null0. In the case of EIGRP. The left side indicates the routing type as D for EIGRP.108.1.9.128 [90/2195456] via 199. 00:00:55. Serial0/1 R1#ping 131.108.100.8.2.0/24 [90/2297856] via 199.108. Configure R1 and R2 to disable automatic summarization as in Example 2-41. Serial0/1 R1# On R1. 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 131.100. timeout is 2 seconds: . 2 masks D 131. You can also see that all routes for 131. Serial0/1 131.1.0. 100-byte ICMP Echos to 131.3.129.3.3.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24 [90/2297856] via 199. round-trip min/avg/max = 16/16/16 ms R1# . Example 2-42 show ip route eigrp on R1 R1#show ip route eigrp D 199.108. Success rate is 0 percent (0/5) R1# The response from the router in Example 2-40 is no reply (….3. Example 2-40 Ping Request from R1 R1#ping 131.100. 00:00:55.7.3. Packets sent to null0 are discarded.2 (R1's link to R2) and through the outbound interface Serial 0/1.0. Serial0/1 D 199.2.3.100...129 Type escape sequence to abort.129 Type escape sequence to abort.100. You'll also see D EX.108.2.100. short for the bit bucket.100.100. 2 subnets.

CCNP Practical Studies: Routing Notice that the 131.255.255.1 255.0 network 199.0 network 199.255.5.1 255.6.0 no auto-summary ! ip classless ! line con 0 transport input none line aux 0 line vty 0 4 no login ! end .108.255.108.0.4.3.255.128 no ip directed-broadcast ! interface Serial0/0 shutdown ! interface Serial0/1 ip address 199.255.100.6.41 - .0 network 199.0 network 199.100. such as classful and classless. using EIGRP. fixed-length variable subnet masks (FLSMs) and VLSM.255.255. Example 2-43 R1 Full Configuration version 12.100.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.3.1.128/25 is inserted and there is a successful ping from R1 to R2 Ethernet interface.100.255.1 255.1 255. Example 2-43 and Example 2-44 display the full configurations for R1 and R2.100. It is vital you understand these simple topics.0 no ip directed-broadcast ! interface Loopback1 ip address 199.0 ! service timestamps log uptime no service password-encryption ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 199.108.100. respectively.100.4.1 255.255.0 no ip directed-broadcast clockrate 128000 ! router eigrp 1 network 131.5.1.100.0 no ip directed-broadcast ! interface Loopback2 ip address 199.

8.100.0 no ip directed-broadcast ! interface Loopback1 ip address 199.1 255.0 no auto-summary ! no ip classless ! line con 0 line aux 0 line vty 0 4 ! end .0 network 199.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.255.100.CCNP Practical Studies: Routing Example 2-44 R2 Full Configuration version 12.255.100.1 255.255.255.255.100.128 no ip directed-broadcast no cdp enable ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 199.2 255.1 255.100.255.7.0 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router eigrp 1 network 131.7.0 network 199.100.255.3.255.100.9.255.0 ! service timestamps log uptime no service password-encryption ! hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 199.9.108.100.0 network 199.0 network 199.8.255.0 no ip directed-broadcast ! interface Loopback2 ip address 199.3.42 - .1.129 255.0.108.

8. Figure 2-6 displays the OSPF/IGRP topology and the IP addressing scheme in place between R1 and R2.7.43 - .255.3. you need to perform redistribution from one routing protocol to another.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 131.0 131. IGRP/OSPF Topology Example 2-45 and Example 2-46 display the IP addressing changes to R1 and R2.1 255.1 255.255.0 On R1.224 131.255.255 131.255. 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 131.8. Here.2 255.108.255.108.CCNP Practical Studies: Routing Scenario 2-4: Basic EIGRP This scenario covers another simple example of routing between classless and classful networks.3.108.255.1.0.108.6. . hence redistribution is required.0.108.128 131.0 131.1 255.255.108. R2 runs both IGRP and OSPF.255.108.255. Figure 2-6.108.108. so you need to enable IGRP only in AS 1. This simple two-router example uses the same class network and IGRP and OSPF.255.9.255.1 255.129 255.5. Example 2-47 enables IGRP in AS 1 on R1.0 131. again IGRP is classful.4.0 131.255.255.108.255.128 131.108.255.255.1 255. It is easier to understand this scenario if you use the same Class B address 131.255.1 255.255.1 255.1 255. respectively.255. configure IGRP.255.

Example 2-50 displays R1's IP routing table. configure IGRP to redistribute the OSPF interfaces into IGRP.0 area 0 You also need to configure redistribution on R2 so that R1 discovers the OSPF interfaces through IGRP. Loopback2 directly connected.108.1 0. you must use the metric that the routing protocol you are redistributing into uses.0. Loopback0 directly connected.0 C 131.0.0.1 0.0 C 131.0 is is is is is is subnetted.108. 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.0 C 131.0 C 131. loading (1 out of 255.0.0 area 0 R2(config-router)#network 131.0.108.CCNP Practical Studies: Routing Example 2-47 Enabling IGRP on R1 R1(config)#router igrp 1 R1(config-router)#network 131. Example 2-48 Enabling IGRP on R1 R2(config)#router igrp 1 R2(config-router)#network 131.108. Example 2-48 enables IGRP in AS 1 and OSPF with a process ID of 1.255 area 0 R2(config-router)#network 131.0 area 0 R2(config-router)#no network 131.255 area 0 R2(config-router)#network 131.4. Loopback1 directly connected. (R1 is running only IGRP.9.1. Example 2-49 displays the redistribution and also displays the various options the Cisco IOS Software requires. Therefore. Serial0/1 directly connected.8.108.8.0.8. Ethernet0/0 Example 2-51 displays R2's IP routing table.108.108.6.0.108. delay (20000 ms).8.108. As with any form of redistribution.0. as in Example 2-49.0 On R2. IGRP does not use OSPF cost but uses a composite metric.108. Follow the prompts.0.108.108.44 - . 255 being 100 percent loaded).0.0/24 C 131.3.1 0.) On R2.108.0 0. configure IGRP and OSPF.7.0.0 area 0 R2(config-router)#network 131. 255 is 100 percent loaded).0.129 0.0 0.0.0. .0 R2(config)#router ospf 1 R2(config-router)#network 131. you need to define values so that IGRP has a valid metric.0. using the ? character to discover which metric IGRP requires. reliability (1 is low. and finally the MTU (1500 bytes). Example 2-50 IP Routing Table on R1 R1#show ip route 131.108. 5 subnets directly connected. You need to advise R1 of the bandwidth (128 kbps).5. 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.

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.

- 45 -

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

- 46 -

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

- 47 -

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

- 48 -

CCNP Practical Studies: Routing
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#

- 49 -

CCNP Practical Studies: Routing
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

- 50 -

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

- 51 -

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

- 52 -

net (203.Perth.inet.30) 288 msec 14 Pos1-0.qwest.50.4.126.net (205.6.50.qwest.6) 332 msec 328 msec 18 iah-core-03.net (203.Perth.171.net (205.5. The solution can be found at the end.wel-gw1.com (203.wel-core3.net.194) 64 msec Pos5-0.171. From Example 2-68. Practical Exercise: RIP Version 2 NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter.net.18) 60 msec Pos1-0.31.Perth. the time taken.paix1.qwest. and whether multiple hops exist.reach.com (203.net.net (205.telstra.qwest.way-core4.Perth.inet. you can determine the next hop.22.net (203.net (205.6.171.wel-core3.21.telstra.31.qwest.171.146) 360 msec * 364 msec 20 atl-edge-05.50.net (205.22) 364 msec 364 msec 21 208. Ensure that both Routers R1 and R2 have full connectivity to each other.net (203.47.telstra.50.50.inet.105) 296 msec 292 msec 15 sjo-brdr-02.146) 364 msec 360 msec 19 atl-core-01.145) 344 msec 344 msec 17 iah-core-01.wel-gw1.qwest.PaloAlto.reach.145) 344 msec iah-core-03. . Use the ping command to ensure all networks are reachable.171.130 ccie-term# The trace command displays the route taken from the source to destination.telstra.paix1.inet.105) 292 msec sjo-core-02.inet.net (205.171.113.net (205.124.inet.Perth.126.net (205.inet.com (203.qwest.171.PaloAlto.69) 308 msec 304 msec 16 sjo-core-02.171.net (205. Now the source of the first hop is known.194) 60 msec GigabitEthernet4-0.telstra.53 - . NOTE The trace command works by first sending three packets with a TTL of 1.qwest.qwest.30) 288 msec sjo-brdr-02.6.telstra.6.171.PaloAlto.CCNP Practical Studies: Routing Pos4-0.194) 60 msec 13 Pos1-0.113. The next three packets are sent with a TTL of 2 and this process is repeated until the final destination is reached.8.22.net (203. The first router sees these packets and returns an error message.50.telstra.wel-core3.paix1. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own.net (203.126.4.50.wel-core3. You must use IP RIP as your dynamic routing protocol.50.Adelaide.reach.Perth.telstra.Melbourne.30) 288 msec GigabitEthernet4-0.6) 332 msec atl-core-01.net (205.qwest.net (203. Configure the network in Figure 2-7 for IP routing using the IP addressing scheme provided.171.net (203.50.8.194) 60 msec 12 Pos6-0.inet.6.171.inet.net (205.18) 64 msec Pos6-0.exi-core1.50.50.inet.inet.5.18) 16 msec 11 Pos6-0.162) 32 msec Pos6-0.6.69) 312 msec iah-core-01.qwest.

1 255.0 no ip directed-broadcast ! interface Loopback2 ip address 131. Example 2-69 R1's Full Configuration version 12. Configure loopbacks with VLSM and experiment with debug commands to discover why IP entries are added or not advertised. experiment with RIPv1 and static routes.255.1 255. which means if you use any dynamic routing protocols. Because you have /24 and /30. IGRP.252.4.108. or EIGRP and apply the skills you learned in this chapter to test connectivity.108. 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. even though you may have a dynamic routing protocol such as RIPv2 advertising the network's reachability and next hop details dynamically. static information is more trusted.108.108.1 255.255. the only way RIP can understand variable-length subnet mask is with RIPv2 or with the use of static routes.255. but you must be aware that static routes have an AD of 1.0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131. 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. The configurations in Example 2-69 and Example 2-70 answer these issues using RIPv2.255. Static routes are fine to configure.255.0 ! interface Serial0/0 shutdown ! . The serial link contains a mask that is 255.1 255. or /30.0 no ip directed-broadcast ! interface Loopback1 ip address 131.6.54 - . Examples 2-69 and 2-70 display the full working configuration on R1 and R2. If you do have access to two routers. you should change the protocols to RIPv2.255.255. static routes can be cumbersome to document and administrate. In that case. OSPF. In a changing network.5.CCNP Practical Studies: Routing Figure 2-7.255.255.1.255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.

252 clockrate 128000 ! router rip version 2 network 131.108.255.108.2 255.1 255.1 255.108.1 255.3.108.0 ! ip classless .55 - .CCNP Practical Studies: Routing interface Serial0/1 ip address 131.255.108.255.255.0 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.0.0.0 ! 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 131.255.9.255.0 no ip directed-broadcast ! interface Loopback2 ip address 131.255.0 ! interface Serial1/0 shutdown ! interface Serial1/1 ip address 131.255.108.255.7.252 ip directed-broadcast ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router rip version 2 network 131.108.0 no ip directed-broadcast ! interface Loopback1 ip address 131.8.1 255.255.108.255.2.255.3.1 255.

9.2." Example 2-71 show ip route on R1 R1#show ip route Gateway of last resort 131.108. Serial0/1 . Serial0/1 is directly connected.0/24 R1#ping 131. Sending 5.0/24 C 131. Sending 5. Serial0/1 [120/1] via 131.108. this output includes the IP routing table and sample pings to the router R2.3. Ethernet0/0 Type escape sequence to abort.0/24 C 131.8.0/24 C 131.0/24 C 131.9.3.108.0/30 R 131. "Answers to Review Questions.108.3. 00:00:05.108.0/24 R 131.8.0.108.108. 9 subnets.108.1 Type escape sequence to abort.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. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24 R 131.108.2. 00:00:15.2.108.2.0.3. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7.108.56 - .6.108.108. 100-byte ICMP Echos to 131. Serial0/1 is directly connected.108.5.1 Type escape sequence to abort.7.3. Loopback0 is directly connected.108.0/24 C 131.0/24 variably subnetted.8.3.108.108. 2 masks [120/1] via 131.7.0/24 R 131.0/24 R 131. 00:00:15.108. Loopback2 is directly connected. Serial0/1 [120/1] via 131. Serial0/1 [120/1] via 131. 2 masks [120/1] via 131. Loopback1 is directly connected.108. Use the router displays taken from R1 from the preceding Practical Exercise to answer the following questions.4.7.108.9.1. round-trip min/avg/max = 16/16/16 ms R1#ping 131.108.1. View Example 2-71 for sample output taken from R1.108.108.108. Serial0/1 [120/1] via 131. 9 subnets.2.3.8. 00:00:05.0/16 is R 131.2.3.9.2.108.108.1.2. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 is not set variably subnetted. round-trip min/avg/max = 12/15/16 ms R1#show ip route rip 131.0/24 R 131.1.3.108. Serial0/1 [120/1] via 131.2. Serial0/1 [120/1] via 131. 100-byte ICMP Echos to 131.0/16 is R 131. 00:00:15. 00:00:05.108. 100-byte ICMP Echos to 131. round-trip min/avg/max = 16/16/16 ms R1#ping 131.108.2. You can find the answers to these questions in Appendix C. 00:00:05. 00:00:15.

Enables or disables an interface. Stops the router sending routing updates on an interface. Enables RIP routing protocol. Troubleshooting command used to display messages received and sent by a Cisco router. 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. enables you to modify serial interface parameters. Enables network advertisements from a particular interface and also the routing of the same interface through a dynamic routing protocol. Escape sequence to escape from the current session and return to terminal server.57 - . 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. The process ID is local to the router. Table 2-7. Displays all routing protocols in use on a Cisco router. Enables automatic DNS lookup. Enables EIGRP routing in a particular autonomous system.108. Enables you to find the path taken from source to destination. You should have a strong knowledge base of routing principles to apply to the remainder of this book. You can have more than one OSPF process running. enables you to modify Ethernet parameters. In configuration mode. All hardware interfaces are shut down by default. 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. What does the 120 represent and what does the 1 represent? Besides a ping test. Table 2-7 summarizes the commands used in this chapter. Enables OSPF routing. Configures a name on a router. Enables you to send ICMP packets to local and remote destinations to test network connectivity. Creates a loopback interface. Displays hardware information about a particular interface. Enables IGRP routing in a particular autonomous system. The IOS command no ip domain-lookup disables automatic DNS lookups.0.0/16? From R1.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. In configuration mode. a ping test is sent to three remote networks. Enables you to use subnet zero on a Cisco router. . 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].

.

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

External Links use the LSA type 5.0. 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.0. In a tie. 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.255. Use the network command to enable the interfaces.CCNP Practical Studies: Routing Table 3-1. Summary links use LSA types 3 and 4. Network links use LSA type 2. The network command network 0.255. You can configure OSPF in one area. the following tasks are required: Step 1.0. this chapter covers how OSPF is configured in single and multiple OSPF areas. Example 3-1 displays OSPF with a process ID of 1 and places all interfaces configured with an IP address in area 0.255) what the IP address is. Autonomous system ABR located between an OSPF autonomous system and a non-OSPF network. To enable OSPF on a Cisco router and advertise interfaces. OSPF must be configured with areas.0. place it in area 0.0. Originated by area border routers (ABRs) and describe networks in the AS. A packet that contains all relevant information regarding a router's links and the state of those links. but if an IP address is enabled on any interface. Identify area assignments. Router links use LSA type 1.255.255 area 0 dictates that you do not care (255. Before covering various OSPF scenarios. OSPF has some basic rules when it comes to area assignment. Use the command router ospf process ID to start OSPF. Step 2.60 - . Configuring OSPF in a Single Area When configuring any OSPF router.0. (Optional) Assign the router ID.0 255. you can choose any area. The DR is selected based on the router priority. you must establish which area assignment to enable the interface for.OSPF) devices for use with redistribution. The backbone area 0.255 area 0 . must be configured if you use more than one area assignment. Example 3-1 Configuring OSPF in a Single Area router ospf 1 network 0. non. This ensures all routers do not need to maintain full adjacencies with each other. A backup router designed to perform the same functions in case the DR fails. Area border router Router located on the border of one or more OSPF areas that connects those areas to the backbone (ABR) network. the router with the highest router ID is selected. although good OSPF design dictates that you configure area 0. Network links Originated by DRs.0.0 255. External links Originated by autonomous system boundary routers (ASBRs) and describe external or default routes to the outside (that is.255. Describe the state and cost of the router's interfaces to the area. Step 4. Common OSPF Terms Term (DR) Description Ethernet). Step 3.255.255. or 0.

Cisco IOS enables you to configure five main network types as displayed in Table 3-2. OSPF has authentication available. OSPF uses multicasts (not broadcasts) to send updates. and troubleshoot it. OSPF allows for load balancing with up to six equal-cost paths. or /24 mask). The main challenge is that NBMA environments do not carry broadcast traffic but have the added characteristics that multiple destinations may be present. Scenario 3-1: Configuring OSPF in a Single Area In this scenario.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. monitoring. . (RIP has 15 hops only. 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. To overcome these problems. Used for multiple destinations.0. you configure two Cisco routers for OSPF routing using a Class B (/16) network (131. OSPF does have some disadvantages. Scenario 3-4 illustrates the behavior of OSPF in an NBMA environment. and in particular Cisco IOS.0. but RIPv1 does not. Table 3-2. allows you to define the networks types and also allows static OSPF neighbor configurations. and troubleshooting have a far greater IOS tool base than RIP. The other two factors are the memory and Central Processing Unit (CPU) requirements that can affect even high-end router performance.61 - . 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. OSPF converges much faster than RIP. and using good practice and defining your end goal are important in any real-life design or solution. this is not a challenge because a packet can be sent to a broadcast or multicast address and be received by all recipients.108. In a normal broadcast environment. Figure 3-1 displays two routers named R1 and R2 connected through Ethernet.255. These five possible solutions available with Cisco IOS are listed for your reference.) OSPF allows for tagging of external routes injected by other autonomous systems. You build a small network and an OSPF routing table. including the level of difficulty and understanding required to configure. OSPF and Nonbroadcast Multiaccess Environments A nonbroadcast multiaccess (NBMA) environment presents the OSPF designer a number of challenges. There is not always one right way to accomplish the tasks presented.255. This is the default mode for subinterfaces. Configure the routers of OSPF area 1 and place the loopbacks in area 1 also. but you must be mindful that the SPF calculations associated with multiple OSPF processes can consume a considerable amount of CPU and memory. monitor. because OSPF propagates changes immediately. Used in Ethernet and broadcast environments in which the election of DR/BDR takes place. NBMA mode. OSPF configuration. (RIPv2 does also.0) with a Class C subnet mask (255. OSPF. You can configure more than one OSPF process. You must also configure a number of loopback interfaces to populate the IP routing table.

NOTE Routers R1 and R2 reside in one area.255.0.0 0.0. or an exact match. To discover why loopbacks appear as /32 host routers.0.6.0.1. which displays the IP routing table on R1.0.0. Use the network command and match the IP subnet exactly.1.0 0.255.128 0.127 area 1 network 131.108.31 area 1 network 131.0 through 131.108.0 0.1.5.108.4. Basic OSPF Figure 3-1 displays the IP addressing and area assignments for Routers R1 and R2.0.0.0. The process ID can be any number between 1–65535.108. because R2 has host (or /32 subnets) masks on loopbacks 2 and 3. Example 3-2 R1 OSPF Configuration router ospf 1 network 131.108.0 area 1 network 131. Example 3-2 displays the OSPF configuration performed on R1. .0. Also.0.108.6.0. in fact. The next hop address is 131.0.108. The process ID is locally significant only and doesn't need to match between routers.0.255 with the command network 131.0.0.127 area 1 network 131.5. You might ask yourself why some of the remote networks are displayed as a /32 route when you used a /27 mask. Assign all interfaces with the area assignment 1.CCNP Practical Studies: Routing Figure 3-1. Example 3-3 R2 OSPF Configuration router ospf 2 network 131.108.0.0.0. Example 3-4 displays the three remote networks reachable through OSPF with a cost metric of 11 for all three. the inverse mask is 0.1 0.2 through Ethernet 0/0. you could apply the one IOS command to enable all interfaces configured with an IP address in the range 131.0.0 area 1 NOTE R1 has a process ID of 1 and R2 has a process ID of 2.108. examine Example 3-4.255 area 1 network 131.108. Also note that this scenario uses VLSM.108.0. Configure R1 for OSPF first.255 area 1 network 131.32 0.0. so.0 0.4.255 area 1.0 0.2 0.62 - .31 area 1 Example 3-3 displays the OSPF configuration performed on R2.108.

2.6.108.108. Example 3-7 show ip ospf interface ethernet 0/0 on R1 R1#show ip ospf interface ethernet 0/0 Ethernet0/0 is up. Hello 10. 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 3-7.108.108.108. The associated cost of the remote network 131. Example 3-6 displays R1's routing table after these changes. Ethernet0/0 O 131. 00:01:19.5. or as /32 routes.2. one per line. Example 3-5 Advertising Loopbacks as /27 on R2 and Changing the Default Cost to 1000 R2#conf t Enter configuration commands.1.108.32 displayed is 27 bits. 00:02:22. 7 subnets. The path taken to the remote network 131.108.32/27 is 1010. Loopback2 O 131. Interface address 131.2/32 [110/11] via 131.108.0/24 is directly connected.108.108.5. Ethernet0/0 R1# In Example 3-6. remember that OSPF calculates the total cost from source to destination.1.0.1. so you need to modify them also. Retransmit 5 Hello due in 00:00:06 Neighbor Count is 1.4.0/27 is directly connected.5.108.1.4. Wait 40.128/25 is directly connected.1.5.1.0/16 is variably subnetted.1.63 - . Loopback1 O 131.5. Change this default configuration and make the routes appear as /27 with the configuration on R2. Dead 40.0/27 is directly connected.128/25 is directly connected.1.1. 00:01:19. Ethernet0/0 C 131. To figure out why.108. Router ID 131.1.CCNP Practical Studies: Routing Example 3-4 R1's IP Routing Table R1#show ip route 131.32/27 [110/1010] via 131.5.108.108.108.2.108.5.108.108. The remaining loopbacks are still /32.108.1/32 [110/11] via 131.5.32 is through Ethernet 0/0.0/25 is directly connected.5. 00:02:22.1. 4 masks C 131.1. Ethernet0/0 C 131.2 (Backup Designated Router) Suppress hello for 0 neighbor(s) .0/16 is variably subnetted. as displayed in Example 3-5.108.108.0/24 is directly connected. Network Type BROADCAST. modify the cost as well to 1000. 7 subnets.108.2.108. it makes a calculation on total cost. When R1 receives the update. The 1000 is the cost R2 assigns and advertises to R1. Ethernet0/0 O 131. 4 masks C 131.4. 00:02:22.4.1.2.2.108.108. Cost: 10 Transmit Delay is 1 sec. by default. State DR.0.1/32 [110/11] via 131. The command ip ospf network point-to-point changes the route advertisement to /27.1. line protocol is up Internet Address 131. Example 3-6 R1 Routing Table R1#show ip route 131.2 Timer intervals configured. End with CNTL/Z.108. Area 1 Process ID 1.108. Loopback2 O 131.1 Backup Designated router (ID) 131. Loopback1 O 131. OSPF advertises loopbacks as host addresses.108.1.108. 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 1000.6. Interface address 131.6. the subnet 131. Priority 1 Designated Router (ID) 131. Adjacent neighbor count is 1 Adjacent with neighbor 131.2.0/25 is directly connected. To make things a little more interesting. Ethernet0/0 C 131.1/24.33/32 [110/11] via 131. Ethernet0/0 C 131. Loopback0 C 131. Loopback0 C 131.2/32 [110/11] via 131. 00:01:19.6.108.108.108. Ethernet0/0 R1# The remote network is displayed as a /32 route when a /27 mask is used because.

0 ! hostname R1 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.128 ! interface Loopback2 ip address 131.224 ! interface Ethernet0/0 ip address 131.33 255.1 255. cost = 108 / Bandwidth = 108 / 107 = 10.255.0.0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown router ospf 1 network 131.255.4.255.255.1.108.255.1.108. Another method you can use to determine the cost with an Ethernet segment is to use the cost calculation.31 area 1 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-9 displays the full routing configuration on R2.108.255.4.5.108.64 - .0.1 255.5.255.128 ! interface Loopback1 ip address 131. Example 3-8 R1 Full Configuration version 12. Example 3-9 R2 Full Configuration version 12.108.0.0.128 0.129 255.255 area 1 network 131.255.0 ! hostname R2 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.4.255.255.5. the total cost is 1000 (as advertised by R2) plus 10.CCNP Practical Studies: Routing R1# The cost associated with the path on the Ethernet segment is 10.108. Therefore.0 0.108.127 area 1 network 131. which equals 1010.0.1 255.0.4.127 area 1 network 131.0 0.108.0. Example 3-8 displays the full routing configuration on R1.224 ip ospf network point-to-point ip ospf cost 1000 .0.108.0 0.

255 ! interface Loopback2 ip address 131. .CCNP Practical Studies: Routing ! interface Loopback1 ip address 131.255 area 1 network 131.0.6. Figure 3-2 displays the routers in this scenario.0. This scenario uses four routers: R1 and R2 from scenario 3-1 and two new routers named R6 and R3.0.255 ! interface Ethernet0/0 ip address 131.108.255.255.255.0.31 area 1 network 131.108.0.1 255.0 area 1 ! line con 0 line aux 0 line vty 0 4 end Now.1 0.32 0.2 0.108.6.255.0.108.5.0 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 2 network 131.6.1.108.108. more complex network in Scenario 3-2.2 255. apply the OSPF principles to a larger. 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.0 0.108.0.0 area 1 network 131.65 - .255.255.0.1.2 255.6.

you add two new routers.0. so you need to set IP addressing and clocking as you did in the Chapter 2.CCNP Practical Studies: Routing Figure 3-2.0 and 141. Table 3-3. also know as area 0. Area 2 covering the link between R6 and R2. R6 is a backbone router and ABR.0 with different subnets. Area border router (ABR) ABRs are responsible for connecting two or more areas. and create an additional two new areas: Area 0 and Area 2. In Figure 3-2. ABRs contain the full topological database of each area they are connected to and send this information to other areas. Internal router functions include maintaining the OSPF database and forwarding data to other networks. Example 3-10 displays the modifications required on R2. and Area 1 covering the Ethernets between R1 and R2." Example 3-5 uses Cisco serial back-to-back V. OSPF Router Types Description This router is within a specific area only. Notice the IP addressing in Figure 3-2 has a mixture of the Class B networks 131. Remember that you have a link to R6.108.0. border router (ASBR) Backbone router Backbone routers are connected to area 0. All interfaces on internal routers are in the same area. R3 and R6. "Routing Principles. That makes a total of three areas: the backbone Area 0 between R3 and R6.35 cables. . enable OSPF on R3 and R6. Example 3-10 Configuration of R2 as ABR Router type Internal router R2(config)#router ospf 2 R2(config-router)#network 141.0.0. Table 3-3 displays all the possible routers types. but you need to modify R2 and enable OSPF on R3 and R6. R2 is an ABR. OSPF includes a number of different router types.10.0. and R3 is a backbone router.108.0 0.0. Router R1 requires no configuration change.108. Backbone routers can be internal routers and ASBRs.0. R1 is an internal router. Autonomous system ASBRs connect to the outside world or perform some form of redistribution into OSPF.3 area 2 Now. OSPF Topology and IP Addressing In this scenario. this scenario uses VLSM extensively to illustrate the capability of OSPF to handle VLSM. Hence. Routers R2 and R6 in this case are referred to area border routers (ABRs) because more than one area is configured on each router.66 - .

10.108.128/25 [110/65] via 141.0. Loopback0 C 141.0.128 0. 00:23:42.108.0. 00:00:32.108.1.33.0/25 is directly connected. Ethernet0 Once more.10.0.108.10.6. Loopback1 O 141. Serial1 C 141. Example 3-13 displays the IP routing table on R6.9.108.12.0. Serial1 C 141. 1 subnets C 131. Example 3-12 displays the OSPF configuration required on R3. 00:00:32.0.4 0.108.128 0.0/16 is variably subnetted.31 area 0 131.1.0.108.2.CCNP Practical Studies: Routing To enable OSPF on R6. 00:23:42. 3 masks O 141.10.33.0.12. the Ethernet network 131.108.1.0 0.108. Example 3-13 IP Routing Table on R6 r6#show ip route 141. Loopback0 C 141.108.108.10.128/25 is directly connected.0. For example.108.108.5.6. Example 3-14 R3's IP Routing Table R3>show ip route 141.0.0.0/24 is subnetted. 7 subnets.6.108.0.10.1.0/25 [110/65] via 141.9. but not the networks from R1 or R2.0 is directly connected.9.1.108.108.108.108. Example 3-15 displays R2's IP routing table.108.0. Serial0 C 141.255 area 0 Similarly.0.108.67 - . examine the routing table on the backbone network to ensure that all networks are routable.0 is directly connected.0/16 is variably subnetted.9.5.0/24 [110/65] via 141.9.108.0.127 area 0 141. 8 subnets.127 area 0 141.0/24 is directly connected.0/25 is directly connected.108.0. 4 masks C 141.108. Serial1 O IA 141.10. 00:00:32.12. Serial1 C 141.10.4 0.108.4/30 is directly connected.1.255 area 0 141.1.10.0.108. Serial1 O 141.255 area 0 Now that OSPF is configured on all four routers.0/30 [110/128] via 141.0 0.0/30 is directly connected.9. 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. 00:23:42.6.0.108.128/25 [110/65] via 141.0 [110/74] via 141.108.12. Loopback2 O 141. Example 3-14 displays R3's IP routing table. 00:23:42.0. Loopback2 C 141.108.26.108.10. .108.0 0.108.0.108.0.3 area 0 141. Serial0 C 131. 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 141.3 area 0 141. start the OSPF process with the process ID 6 and enable the interfaces to advertise the networks as displayed by Example 3-11. Serial1 131.108. Serial0 131.0.0 0.108.108. Ethernet0 r6# Example 3-13 displays the remote networks on Router R3.0.0 0.108.128/25 is directly connected.0 0.10. Example 3-14 doesn't display the networks in area 1 on Routers R1 and R2.127 area 0 141.0.10.0/25 [110/65] via 141.0.127 area 0 141.5.108.108.33.26 0. Loopback1 O 141.0/24 is subnetted.0.108.2.10. Serial0 C 141.3 area 2 141. 2 subnets O 131.10.0/24 in area 1 is not routable from R6.0/27 is directly connected.108. Examine R3's routing table.4/30 is directly connected.

32/27 is directly connected. Area 1 is not directly connected to the backbone.1.10.108.6. Loopback0 O IA 131.128/25 [110/782] via 141. Loopback1 O 131. Serial1/0 131.6.68 - .108.108.0. Area 2 is not partitioned from the backbone.9.0/24 [110/782] via 141.108.1/32 is directly connected.1.1. 00:08:05. however.4/30 [110/845] via 141. Serial1/0 O IA 141.CCNP Practical Studies: Routing Example 3-15 R2's IP Routing Table R2>show ip route 141.108. 00:46:09. If an area cannot be assigned to the backbone or is partitioned from the backbone.108.10. 00:26:20.0/24 [110/855] via 141.108. Router R1 is missing IP networks.2.2. Serial1/0 C 131.108. Serial1/0 O IA 141.1. 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.1.0/30 is directly connected. 3 masks O 131.2.108. 00:26:20.10.1/32 [110/11] via 131.2. Serial1/0 O IA 141.108. Ethernet0/0 O 131.108. Scenario 3-2 includes three areas. because Router R2 is connected to area 2.108.1.10.0/24 is directly connected. but not vice versa.10. 00:26:20.2. Serial1/0 O IA 141.0/25 [110/782] via 141.108. a virtual link is required. as in the example shown in Figure 3-2.10.9. Ethernet0/0 C 131. 7 subnets. 8 subnets. Figure 3-3. 00:46:09.5. Figure 3-3 displays the areas and the requirement for a virtual link.108.4.128/25 [110/846] via 141. area 2 is directly connected to the backbone through Router R6. that R2 has access to the remote networks in area 0 or on the backbone. The golden rule in any OSPF network is that all areas must be contiguous or all areas must be connected to the backbone.108. 00:09:06.0.0/25 [110/846] via 141.4.1/32 [110/11] via 131.2.0/16 is variably subnetted.10.108. Serial1/0 C 141.10. When designing a network. 3 masks O IA 141.2. Serial1/0 O IA 141.108. Therefore.108.108.108.1. Area Assignments and the Virtual Link Requirement . Ethernet0/0 C 131.108.108.108.1.5. 00:08:15. In fact.33. 00:46:09. Ethernet0/0 R2> Notice.2/32 is directly connected.12.108. 00:26:20.108.129/32 [110/11] via 131.0/16 is variably subnetted.108.108.1. Loopback2 C 131.10.

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. Cost of using 781 Transmit Delay is 1 sec.12.1 Example 3-18 Configuring a Virtual Link on R6 R6(config)#router ospf 6 r6(config-router)#area 2 virtual-link 131. Timer intervals configured. The following is a simplification: area area-id virtual-link router-id The area-id is the transit network between the two partitioned areas. as demonstrated in Example 3-20.1.108. Examples 3-17 and 3-18 display the configuration performed on Routers R2 and R6.1 is up Run as demand circuit DoNotAge LSA allowed.108. You can find the router-id by using the show ip ospf database command.1) (Process ID 6) You now have the information required to configure a virtual link between R3 and R6. Example 3-16 show ip ospf database Command on R2 and R6 R2>show ip ospf database OSPF Router with ID (131. view the routing tables on R3 to determine whether the area 1 networks have been inserted into the IP routing table.108. Example 3-19 show ip ospf virtual-links R2#show ip ospf virtual-links Virtual Link OSPF_VL0 to router 141.108. Hello 10. configure a virtual link between R2 and R6.CCNP Practical Studies: Routing The virtual link in this scenario is required from R2 to R6.108. To create a virtual link. Dead 40. Transit area 2.6. In this scenario. in this case area 2.2 Use the show ip ospf virtual-links command on R2. 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.69 - . State POINT_TO_POINT. Now.6.108. Wait 40. The virtual link allows information about area 1 to be sent to the backbone.12. Example 3-17 Configuring a Virtual Link on R2 R2(config)#router ospf 2 R2(config-router)#area 2 virtual-link 141. . demonstrated in Example 3-19.2) (Process ID 2) r6>show ip ospf database OSPF Router with ID (141. which displays the complete OSPF database. 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. to ensure that the virtual link is active.12. via interface Serial1/0. Note that the extensive amount of information typically supplied by the show ip ospf database command is not all displayed in Example 3-16. Example 3-16 shows you how to discover the router IDs on R2 and R6.12. this command has many options.

10.10.1.6.10.26.108. 00:01:43.224 ip ospf network point-to-point ip ospf cost 1000 ! interface Loopback1 ip address 131. Loopback0 C 141. 3 masks O IA 131.0.6.6.1/32 [110/139] via 141. Loopback2 O 141.108.32/27 [110/1128] via 141.10.108.6.10.6.108. Examples 3-21.4/30 is directly connected. R1's configuration is unchanged from scenario 3-1. Serial1 O IA 131. Serial1 131. Serial1 O 141.6.0 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 131.9.1/32 [110/129] via 141.6.108. 00:01:43.6.5.108. 00:01:43.0/24 [110/65] via 141.108.108.108. 9 subnets.108.108.255.255.0.108. Loopback1 O 141.128/25 [110/65] via 141.0/24 is directly connected.CCNP Practical Studies: Routing Example 3-20 show ip route on R3 R3#show ip route 141.10.108.10. R3.1 255.1.1/32 [110/139] via 141. 00:01:43.2 255.0/30 [110/128] via 141.108.9.6. 00:01:43.255. Serial1 O IA 131.6. 00:01:43.6.108.255. and R6.255. Serial1 O IA 141. Example 3-21 Full Configuration on R2 Current configuration: ! version 12.108.0/16 is variably subnetted.108.4.108. 00:01:43.255 ! interface Ethernet0/0 ip address 131.108.108.12.108.108.10. Serial1 O IA 131.6. 00:01:43. Serial1 O IA 131.2. Ethernet0 O IA 131.108.255.6.1.108.5.33 255.108.108. 4 masks C 141. 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 3-20.33. 00:01:44.0/27 is directly connected. Serial1 O 131.128/25 is directly connected. 00:01:43. Serial1 C 141.70 - . 00:01:43.0/16 is variably subnetted.10.255. Serial1 C 131.6.10.129/32 [110/139] via 141.0 ! interface TokenRing0/0 shutdown .6. and 3-23 show the three configurations of routers R2.10.108.10.108.0/24 [110/138] via 141. 00:01:43.108.10.108.0/25 [110/65] via 141.10.0/25 is directly connected. Serial1 O IA 131.5.2/32 [110/129] via 141. respectively.108. 8 subnets.0/24 [110/74] via 141.108.108.108.255.4. Serial1 C 141.108.255 ! interface Loopback2 ip address 131.6.2 255.1.3-22.

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

- 71 -

CCNP Practical Studies: Routing
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

- 72 -

CCNP Practical Studies: Routing
! 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.

- 73 -

CCNP Practical Studies: Routing
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

- 74 -

CCNP Practical Studies: Routing
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)

- 75 -

CCNP Practical Studies: Routing
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.

- 76 -

CCNP Practical Studies: Routing
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).

- 77 -

CCNP Practical Studies: Routing
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.

- 78 -

Included in Figure 3-4 are the IP addressing scheme.108.10. Serial1/0 O 141. and OSPF area assignments.108.1.2.108.4. 3d03h. Serial1/0 Example 3-34 displays the cost to the remote networks on R1 as 100. Serial1/0 O 141.1. 3d03h. Serial1/0 O 141.108.10.79 - .108. 00:00:35.108.2.108. Ethernet0/0 O 131.1.108.9.0/16 is variably subnetted. Figure 3-4.1/32 [110/100] via 131. Serial1/0 O 141.0/24 [110/782] via 141.129/32 [110/100] via 131.108.128/25 [110/782] via 141. Serial1/0 O 141. This scenario helps you discover some of the advanced features of OSPF.10. 9 subnets. 00:00:35.2. 00:00:35.12. Ethernet0/0 O 131.1.5.1.9. Serial1/0 O 131.10.108. 3d03h.108.10.0. such as DR election in an NBMA environment.26.128/25 [110/846] via 141. The next scenario shows you how to configure an advanced OSPF network using a three-router network over Frame Relay.0/24 [110/855] via 141.1.108.2.108. 7 subnets. 3d03h. OSPF over Frame Relay .108.108. 3d03h.108.CCNP Practical Studies: Routing Example 3-34 R2's OSPF Routing Table After the Cost Change R2#show ip route ospf 141. 3d03h.4/30 [110/845] via 141.0.0/25 [110/846] via 141. 3d03h.0/24 [110/791] via 141. Frame Relay DLCI numbering.1.2.10. 3 masks O 141.33.2. Ethernet0/0 O 131.108.108. 3d03h.108.4.108.10.2.1/32 [110/100] via 131.108.108.108.0/16 is variably subnetted.0/25 [110/782] via 141.2. Figure 3-4 displays the three-router network over Frame Relay used in this scenario. 3 masks O 131.108.10. Scenario 3-4: OSPF over Frame Relay in an NBMA Environment This scenario covers configuring OSPF over Frame Relay in an NBMA environment.1.10. Serial1/0 131.

255.248 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. which is the path to R4.108.3. Frame Relay. you can start the OSPF configuration. Start by configuring the Frame Relay parameters.108.1.1.108. Example 3-39 displays the OSPF configuration on R4 along with the IP address assignment to E0.255. as displayed in Figure 3-4.2 255.7 area 0 You must also enable OSPF on Routers R4 and R5. Example 3-35 R3's Frame Relay Configuration R3(config)#interface serial 0 R3(config-if)#ip address 141.3.0. Example 3-38 OSPF and IP Address Configuration on R3 R3(config)#interface ethernet 0 R3(config-if)#ip address 141. .108.0. needs to map Layer 2 of the Open System Interconnection (OSI) model to Layer 3. The specific DLCIs are 103. like any protocol.80 - .255.3 255.255. but this is not the case on R3 in Example 3-35. R4 and R5 map IP over Frame Relay.1 255. R3 also requires the DLCI information. and 108. Example 3-35 displays R3's Frame Relay configuration.1.108.0 R3(config-if)#router ospf 3 R3(config-router)#network 141.255 area 3 R3(config-router)#network 141.0 0.0. Now that you have enabled Frame Relay. which is the path to R5.1. because Frame Relay dynamically discovers the maps because R3 is a hub router using Frame Relay inverse Address resolution Protocol (ARP) protocol.108.255. Frame Relay inverse ARP automatically discovers the DLCI and next hop IP address.255.CCNP Practical Studies: Routing This scenario involves three routers running OSPF over Frame Relay.0.255. Example 3-36 The Frame Relay Configuration on R4 interface Serial0 ip address 141.1 107 broadcast Example 3-37 The Frame Relay Configuration on R5 interface Serial0 ip address 141.1 255. You do not use subinterfaces in this scenario to demonstrate an NBMA environment.108. Figure 3-4 displays the Frame Relay DLCIs and Local Management Interface (LMI) types.1.1 106 broadcast NOTE In Examples 3-36 and 3-37.0 0.108. Example 3-38 displays the OSPF configuration on R3 along with the IP address assignment to E0. R3 is not configured for static mapping. Example 3-36 and Example 3-37 show the configurations of R4 and R5.1.248 encapsulation frame-relay frame-relay interface-dlci 106 frame-relay map ip 141.255. respectively.248 encapsulation frame-relay frame-relay interface-dlci 107 frame-relay map ip 141.

108. 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.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. Interface address 141.10. State DR.108.108.4. of course) are not sent over a nonbroadcast OSPF network type. Example 3-42 displays the OSPF network type on R3 link to R4 and R5.1. but rather you statically configure a neighbor relationship from R3 to R4 and R5. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.0 R4(config)#router ospf 4 R4(config-router)#network 141.1 255.108.255 area R4(config-router)#network 141. The IOS on R3 in Example 3-41 tells you there are no OSPF relationships to R4 and R5.10.0.0 R5(config-if)#interface ethernet 1 R5(config-if)#ip address 141.0.1.255. enter the following command: neighbor ip address of neighbor Example 3-43 displays the configuration on R3 to remote routers R4 and R5.108.1 255.255.1 No backup designated router on this network Timer intervals configured.0 0.108.1/29.0. To enable a static OSPF neighbor relationship.108.255. Router ID 141.7 area 0 Example 3-40 displays the OSPF configuration on R5 along with the IP address assignment to E0.108.81 - .108. you do not modify the network type. . broadcasts or multicasts do not propagate over the Frame Relay.1 255. 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 3-41.6. Ensure that OSPF adjacencies are up and in a FULL state on R3.255.255. Priority 1 Designated Router (ID) 141.5.0 R5(config-if)#router ospf 5 R5(config-router)#network 141. To demonstrate OSPF over NBMA in this scenario.5. Cost: 64 Transmit Delay is 1 sec.1. Router R3 has no adjacencies. Figure 3-4 shows a classic example of OSPF over NBMA. OSPF can be configured a variety of ways to accomplish this. That lack of relationships is because OSPF Hello packets (using multicast address.1.7 area 0 NOTE Example 3-40 places the two Ethernet networks with the one OSPF statement.0 0. Network Type NON_BROADCAST.0. Example 3-42 show ip ospf interface serial 0 Command on R3 R3>show ip ospf int s 0 Serial0 is up. Hello 30.4. line protocol is up Internet Address 141. Example 3-41 displays the OSPF neighbor state on router R3.108. Example 3-40 OSPF and IP Address Configuration on R5 R5(config-if)#ip address 141.5.255.108.0. Area 0 Process ID 3. Wait 120.0.0 0.0.255 area 5 R5(config-router)#network 141. Dead 120. In an NBMA environment.0 0.5.3.

255. must become the DR.3 141. Example 3-46 R3's Full Configuration version 12.7 area 0 .255.255.0. R3.248 encapsulation frame-relay frame-relay interface-dlci 103 frame-relay interface-dlci 108 ! interface Serial1 ip address 141. The command neighbor 141.10. Example 3-46 displays the full working configuration of R3.1.3 The command neighbor 141. which indicates that the neighbor was not chosen as the DR or BDR and cannot be because the priority has been set to zero.1.1. Example 3-43 overcomes the need to change the network environment from nonbroadcast and allows a static configuration of remote OSPF routers.1. through R3.108. One more important task is required. The hub router.2 0 State FULL/DROTHER FULL/DROTHER Dead Time 00:01:54 00:01:44 Address 141.108.CCNP Practical Studies: Routing Example 3-43 Static Neighbor Configuration on R3 R3(config)#router ospf 3 R3(config-router)#neighbor 141.2 R3(config-router)#neighbor 141. or edge. for example. 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 R5.108.3 configures the neighbor to R5.108.1.108.108. Example 3-45 show ip ospf neighbor Command on R3 R3#show ip ospf nei Neighbor ID Pri 141.0.0 ! hostname R3 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.255. routers.3.0 0. Example 3-44 demonstrates how to set the priority to 0.1.5 255. 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 R3.108.108.5.108. because R3 has links to both R4 and R5 and information will be sent from R4 to R5.0 ! interface Ethernet1 no ip address shutdown ! interface Serial0 ip address 141.108.1.1 255.2 Interface Serial0 Serial0 The state shown in Example 3-45 displays a FULL adjacency and a state known as DROTHER.1 255.255.1.1 0 141.2 configures the neighbor to R4.255.108.252 ! router ospf 3 network 141.1. Router R4 and R5 are spoke.108.82 - . in effect disabling any chance for R4 or R5 to become the DR.

1.255 area 4 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-48 displays the full working configuration of R5.108.83 - .0 interface Serial0 ip address 141.108.1 107 broadcast frame-relay interface-dlci 107 frame-relay lmi-type cisco ! interface Serial1 shutdown ! router ospf 4 network 141.255.0.3 neighbor 141.0.108.4.2 ! line con 0 line aux 0 line vty 0 4 end Example 3-47 displays the full working configuration of R4.108.255.5.108.1 255.0 0.7 area 0 network 141.255.0 .3.4.1.108.6.255.0.1 255. Example 3-47 R4's Full Configuration version 12.255.0.108.1.1.255 area 3 neighbor 141.248 encapsulation frame-relay ip ospf priority 0 frame-relay map ip 141.0 ! hostname R4 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.0.0.255. Example 3-48 R5's Full Configuration version 12.0 0.0 ! hostname R5 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 141.108.255.1 255.0 0.0 ! interface Ethernet1 ip address 141.108.CCNP Practical Studies: Routing network 141.1.255.2 255.108.

0. The backbone can be configured on Cisco routers as 0 or 0.0 0.1.0.255.0.1 106 broadcast frame-relay interface-dlci 106 ! interface Serial1 shutdown ! router ospf 5 network 141.108.1.0. Scenario 3-5: Verifying OSPF Routing This scenario covers common techniques used in OSPF networks to verify correct configuration in a single OSPF area.1.CCNP Practical Studies: Routing ! interface Serial0 ip address 141. 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. Also.3.0.0. To change the name of a router. 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 R1.255. Figure 3-5 displays a simple two-router topology.0. Figure 3-5.108.3 255. Figure 3-5 displays the correct IP address assignment and OSPF area assignment. Example 3-49 displays SanFran's IP routing table.248 encapsulation frame-relay ip ospf priority 0 frame-relay map ip 141.0 0.0. notice that the backbone segment is displayed as 0. NOTE Figure 3-5 displays two routers with the names SanFran and Chicago.108.84 - . you use the hostname name command.7 area 0 network 141.108. the configurations supplied are not the full working solutions to demonstrate the power of OSPF. The two routers are named SanFran and Chicago.0.4.

State POINT_TO_POINT.1. or the backbone. the network type over the Ethernet interface is broadcast.5.4. and the router SanFran is the elected DR. Router ID 131. Cost: 1 Transmit Delay is 1 sec.1/24.7. Router ID 131. 3 subnets directly connected. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up.108.0. such as the Ethernet interface on R1 resides in area 0.5.0.1. Router ID 131. Interface address 131. like loopbacks.0 is C 131.0.1.108. line protocol is up Internet Address 131. Ethernet0/0 Example 3-49 displays no remote entries on R1.108. Cost: 90 Loopback interface is treated as a stub Host Loopback1 is up. Area 0. Area 0.0 Process ID 1.0 Process ID 1.108. Cost: 10 Transmit Delay is 1 sec.1/24.108. line protocol is up Internet Address 131. State DR.7.4.1. Area 0.7.0.0.0. Example 3-50 displays a sample output taken from the router SanFran.108.108.0 Process ID 2. Cost: 1 Loopback interface is treated as a stub Host Example 3-51 displays the loopbacks in OSPF process 2. Network Type LOOPBACK. line protocol is up Internet Address 131.108.0 Process ID 1. Router ID 131. Wait 40. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.5. Network Type POINT_TO_POINT. Cost: 90 Loopback interface is treated as a stub Host Example 3-50 displays a number of important details.85 - .108. Priority 1 Designated Router (ID) 131. Timer intervals configured.1. Router ID 131. Hello 30. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Example 3-51 displays a sample output from the show ip ospf interface command.5.0.1.0.0. Network Type LOOPBACK. Hello 10.1/24.1. Area 0. Start by ensuring that OSPF is correctly configured on R1 by using the show ip ospf interface command.0/24 is C 131.CCNP Practical Studies: Routing Example 3-49 SanFran's IP Routing Table SanFran#show ip route 131.1.108.6. Example 3-51 show ip ospf interface Command on Chicago Chicago#show ip ospf interface Loopback0 is up.5. Take the same steps on Chicago.0 is C 131. Area 0.108. line protocol is up Internet Address 131. Loopback0 directly connected.108.108.0. so OSPF looks like it is correctly configured on R1.0 Process ID 2. but the Ethernet interface is not enabled.5. are active as long as they are not administratively shutdown).108.1 No backup designated router on this network Timer intervals configured.0. line protocol is up Internet Address 131. Example 3-50 show ip ospf interface Command on SanFran SanFran#show ip ospf interface Ethernet0/0 is up. The loopbacks on Chicago and SanFran are active (software interfaces. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback1 is up. .0 is R1# subnetted. Example 3-52 displays the OSPF configuration on Chicago.1/24. Network Type BROADCAST. Loopback1 directly connected.1. Network Type LOOPBACK.108.0. Dead 120.0.0.108. Wait 120.1/24. Dead 40.

0. Dead 40. Hello 10. State WAITING. Cost: 1 Loopback interface is treated as a stub Host Example 3-54 displays that the Ethernet interface is now.108.1. Example 3-54 show ip ospf interface Command on Chicago Ethernet0/0 is up.0.0 Make sure that OSPF is enabled on Chicago's Ethernet interface.0.0. Area 0.108.0. Example 3-55 displays the OSPF characteristic of the Router SanFran. Timer intervals configured. Example 3-53 displays the removal of the incorrect command and insertion of the correct network statement.0 network 131. Move back to the router named SanFran. line protocol is up Internet Address 131.1.0 0.108.0.86 - . hence OSPF cannot run.0.0 0.7.0.0. Area 0.0 network 131.0 Process ID 2.1.255 area 0.1.0/24.0.108. Cost: 10 Transmit Delay is 1 sec.0 area 0.7. Example 3-54 displays a sample output with the show ip ospf interface command.255 area 0.0 Process ID 2.0.0.7. Hello 10. line protocol is up Internet Address 131. Network Type POINT_TO_POINT.0. Router ID 131.0.1/24.0.108.1. Router ID 131.0 Process ID 2. and check for OSPF adjacency.0.0. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.1. Wait 120.0. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback1 is up. Retransmit 5 Hello due in 00:00:16 Wait time before Designated router selection 00:01:46 Neighbor Count is 0. The fact that no adjacent neighbor is present still represents a problem.2 0. in fact.108. Cost: 1 Transmit Delay is 1 sec.108.0 0. Remove this command and install the correct network and mask command.0 area 0. Wait 40. Router ID 131.0.0. The command network 131.2/24. Dead 40.1.0.108.0.6. State POINT_TO_POINT.7.0.1.0.108. Network Type LOOPBACK.1.108. Example 3-53 Modifying the OSPF Configuration on Chicago Chicago(config)#router ospf 2 Chicago (config-router)#no network 131.0 0.0. .0 area 0.108.7.108.0.0 causes the router to enable OSPF for the interface configured with the IP address 131.0.0 0. line protocol is up Internet Address 131. This address is a reserved address for the subnet 131.CCNP Practical Studies: Routing Example 3-52 OSPF Configuration on Chicago router ospf 2 network 131. Priority 1 No designated router on this network No backup designated router on this network Timer intervals configured.0. enabled in OSPF area 0.108.0.108.1. Network Type BROADCAST.1/24.0.0 Chicago (config-router)#network 131.6. Area 0.0.0 Example 3-52 displays the fault with the router Chicago.0. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up.

255.7. 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. whereas the configured hello interval on SanFran is 30 seconds. whereas the configured interval on SanFran is 120 seconds.108. Wait 120. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) No neighbor exists on this segment.0 Process ID 1.0. Example 3-57 displays the configuration change on SanFran to ensure hello and dead intervals are configured the same way.108. the hello interval Chicago receives is set to 10 seconds. Retransmit 5 Hello due in 00:00:11 Neighbor Count is 0.1 No backup designated router on this network Timer intervals configured.1/24.5.2 2w5d: OSPF: Mismatched hello parameters from 131. Example 3-56 advises you that the Chicago dead interval is 40 seconds.7.108.108.1.87 - . such as the hello interval or dead interval. Hello R 10 C 30 Mask R 255. . The sample debug output.1. Hello 30. The hello interval is set to 10 seconds.1. by default. is four times the hello interval.0 C 255.108.2. whereas the configured hello interval on SanFran is 30. OSPF routers never become adjacent (in other words.1.1. 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. Network Type BROADCAST.1 area 0. Hence. Dead 120. 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. as displayed in Example 3-56.1.0 The error message displayed by the IOS in Example 3-56 clearly states you have a mismatch in the hello interval. Router SanFran is configured with a hello interval of 10 seconds. advises you that the hello and dead interval should be correctly set on both routers: SanFran and Chicago.108. Area 0. Remember that hello and dead intervals must match before neighboring routers can become fully adjacent. through the IP address 131. Similarly.255. line protocol is up Internet Address 131.255. Interface address 131. Cost: 10 Transmit Delay is 1 sec.1.108.0 from Ethernet0/0 131. are the same. there is a mismatch error. Router ID 131. which automatically configures the dead interval to 40 seconds thereby matching the hello and dead intervals set on the router named Chicago. 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. whereas the configured (displayed as C from the debug output) dead interval (Dead C 120) on SanFran is 120 seconds.1.108.108. Therefore.5.255. never exchange OSPF databases) unless all OSPF parameters. State DR. Example 3-56 displays Dead R 40 C 120. another mismatch. Hello R 10 C 30. Example 3-56 displays the command being enabled and a sample output taken from the router SanFran. In other words.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. These two clearly do not match. Priority 1 Designated Router (ID) 131. NOTE The dead interval.0.0. Example 3-56 advises you that Chicago's hello interval is 10 seconds.0.2 2w5d: Dead R 40 C 120.

7.108. router ID 131.1.0.1 on Ethernet0/0 seq 0x1237 opt 0x2 flag 0x1l en 32 mtu 1500 state EXCHANGE 2w5d: OSPF: Exchange Done with 131.108.1 area 0.108.108.108.108.108.5. Loopback1 is directly connected.2 2w5d: OSPF: End of hello processing 2w5d: OSPF: Rcv DBD from 131.7.108.108.0/24 variably subnetted.1 2w5d: OSPF: Elect BDR 131.1 (id) 2w5d: OSPF: NBR Negotiation Done.1 on Ethernet0/0 seq 0x1236 opt 0x2 flag 0x3 len 92 mtu 1500 state EXCHANGE 2w5d: OSPF: Send DBD to 131.7.1 on Ethernet0/0.108. 2 masks [110/11] via 131.1. Example 3-58 SanFran IP Routing Table SanFran#show ip route 131.1 (Id) BDR: 131.108.108.1.1 2w5d: DR: 131.7.108.108.7.1 on Ethernet0/0 seq 0x1236 opt 0x2 flag 0x0 l en 32 2w5d: OSPF: Database request to 131.1.0.1.108.0 from Ethernet0/0 131.108.7.88 - .1 2w5d: OSPF: Elect DR 131.7. In other words.0. We are the SLAVE 2w5d: OSPF: Send DBD to 131.1 (Id) 2w5d: OSPF: Send DBD to 131.1 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. Ethernet0/0 [110/11] via 131.1 on Ethernet0/0 seq 0x11C4 opt 0x2 flag 0x7 l en 32 2w5d: OSPF: Set Ethernet0/0 flush timer 2w5d: OSPF: Remember old DR 131.7.0.0.2.108.7. 5 subnets.7.108.1 on Ethernet0/0. you see the hello process completed.7.4.0/16 is O 131. Example 3-57 highlights the OSPF neighbor state from the initial INIT state to the FULL state.0/24 C 131.1/32 C 131.5.2.5.1/32 and 131.5. 00:01:25.108.7.108. Routers Chicago and SanFran are now OSPF neighbors. state 2WAY 2w5d: OSPF: Neighbor change Event on interface Ethernet0/0 2w5d: OSPF: DR/BDR election on Ethernet0/02w5d: OSPF: Elect BDR 0. Ethernet0/0 The Router SanFran now discovers the remote networks 131.5.1.0.108.2.0/32 through OSPF. .108.108. Example 3-58 now displays SanFran's IP routing table.6.1 2w5d: OSPF: sent LS REQ packet to 131.0/24 C 131.0.1 on Ethernet0/0 seq 0x1235 opt 0x2 flag 0x7 len 32 mtu 1500 state INIT 2w5d: OSPF: 2 Way Communication to 131.1/32 O 131.108.0.1 area 0. state FULL 2w5d: OSPF: Include link to old DR on Ethernet0/0 2w5d: OSPF: Build router LSA for area 0.108.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 131.108.108. Ethernet0/0 is directly connected.108.2 2w5d: OSPF: End of hello processing As soon as you correct the problem.7.7. and an OSPF database exchange occurs.0 from Ethernet0/0 131.7.108.0 2w5d: OSPF: Elect DR 131.7.108.7.108. length 24 2w5d: OSPF: Rcv DBD from 131. seq 0x8000 0004 2w5d: OSPF: Rcv hello from 131.1 on Ethernet0/0 seq 0x1235 opt 0x2 flag 0x2 l en 72 2w5d: OSPF: Rcv DBD from 131. 00:01:25.7.0.108.1.1 on Ethernet0/0 2w5d: OSPF: Send DBD to 131. Loopback0 is directly connected.108.0.6.

255.1.108.108.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.89 - .10.0 ! interface Ethernet0/0 ip address 131.0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown . Example 3-59 takes advantage of this tool to display commands available to the network administrator. Example 3-59 displays the debug and show commands possible on a Cisco router running IOS release 12.4. Example 3-60 displays the full working configuration on SanFran.0 hostname SanFran ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.255.1 255.255.108.255.255.255. Example 3-60 The Full Working Configuration on SanFran version 12.1 255. Cisco IOS is updated almost daily.1 255.0 ! interface Loopback1 ip address 131.5.0. so you need to reference the IOS documentation for new and ever-expanding commands. 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.

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 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! router ospf 2 network 131.0.0.0 area 0. .6.108. Ensure that both routers R1 and R2 have full connectivity to Routers R3 and R6 in the backbone.0.0.2 0.255.0 network 131.0 network 131.6. Example 3-61 The Full Working Configuration on Chicago version 12.7.1 255. Configure the network in Figure 3-6 for OSPF routing using the IP addressing scheme provided.2 255.108.CCNP Practical Studies: Routing ! router ospf 1 network 0.108.255 area 0.0.255.1 255. Use the ping command to ensure all networks are reachable.1.0.255 area 0.108.0.0 0.0.7.0 255.255 area 0.108.1.0.0 ! interface Loopback1 ip address 131.0.90 - . 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 ! hostname Chicago ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.0.255.0. You must use OSPF as your only dynamic routing protocol.0.0. The solution can be found at the end.255.108.0 0.255.0.0.0 interface Ethernet0/0 ip address 131.255.255.0 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.255.

10. you actually do need two virtual links to ensure full connectivity in any network failure situation.1 255.255.255.CCNP Practical Studies: Routing Figure 3-6.252.255.108.255.4.108.0. Configure the loopbacks with VLSM and experiment with debug commands to discover why IP entries are added or not advertised. or /30.91 - .129 255. This means that you need to configure two virtual links: one from router R2 to R6 and another between R1 and R3. 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. This second virtual link is required in case of link failure or hardware failure from the Routers R1 and R2. Remove the second virtual link from R1 to R3.128 ip ospf cost 90 ! interface Loopback2 .0 ! hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131. and see how OSPF behaves when the link between R2 and R6 fails. The following example configurations provide a solution using OSPF. The serial link contains a mask that is 255.255. This practical example is similar to Scenario 2-2 with the extra link between area 1 and area 0. You will find that because the areas are partitioned. Example 3-62 displays R1's full working configuration.128 ip ospf cost 90 ! interface Loopback1 ip address 131.255. Example 3-62 R1's Full Configuration version 12.108.4.

255.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-63 displays R2's full working configuration.0.255.255 ! interface Ethernet0/0 ip address 131.1 255.255.255.108.10.108.33 255.108.108.0.0.1.92 - .0.CCNP Practical Studies: Routing ip address 131.1.6.108.5.10.6.255.128 0.127 area 1 network 131.255 ! interface Loopback2 ip address 131.0.108.2 255.0 0.5.255.0.255.255.0 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 131.255.1 255.108.1 255.108.0 0.0.255.8 0.4.224 ip ospf network point-to-point ip ospf cost 1000 ! interface Loopback1 ip address 131.127 area 1 network 131.108. Example 3-63 R2's Full Configuration version 12.255.0 ! interface Serial0/0 ip address 141.9 255.0.5.0.255 area 1 network 131.1 network 131.0 0.0 ip ospf priority 255 interface Serial1/0 .255.255.1.252 clockrate 125000 ! interface Serial0/1 no ip address shutdown clockrate 128000 ! router ospf 1 area 2 virtual-link 141.255.108.224 ip ospf cost 90 ! interface Ethernet0/0 ip address 131.4.108.2 255.2.31 area 1 network 141.108.108.0.

1.108.255.2 0.10 255.252 ! router ospf 3 .1 255. Example 3-64 R3's Full Configuration version 12.32 0.255.0.6.1.128 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.108.255.0 0.12.1.252 ! interface Serial1 ip address 141.33.108.108.108.255.10.CCNP Practical Studies: Routing ip address 141.0 area 1 network 131.108.255.255.255.108.1 0.10.0.255.255.0.129 255.1 network 131.0.108.6.0 0.0.5 255.0 hostname R3 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.108.10.255.108.255.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Example 3-64 displays R3's working configuration.93 - .108.1 255.0 ! interface Serial0 ip address 141.0.255.252 ! 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 131.31 area 1 network 131.0.0.1 255.108.224 ip ospf network point-to-point ! interface Ethernet0 ip address 131.0 area 1 network 141.10.1 255.0.128 ip ospf network point-to-point ! interface Loopback2 ip address 141.5.255.255.0.2.

10.0.255.0.0.0.0 0.129 255. Example 3-65 R6's Full Configuration version 12.4 0.0 0.0 0.2 255.2 network 131.0.1 255.127 area 0 network 141.0.255.255.252 clockrate 125000 ! interface Serial2 shutdown ! interface Serial3 shutdown ! router ospf 6 area 2 virtual-link 131.12.255.255.0.0 hostname r6 ! enable password cisco ip subnet-zero ! interface Loopback0 ip address 141.0.0.108.128 ip ospf network point-to-point interface Loopback2 ip address 141.108.0.108.1 255.127 area 0 network 141.0 media-type 10BaseT ! interface Serial0 ip address 141.6.255.108.108.94 - .108.0.9.108.0 ip ospf network point-to-point interface Ethernet0 ip address 131.128 ip ospf network point-to-point interface Loopback1 ip address 141.10.0.0.108.255.0.3 area 2 network 141.108.9.108.10.108.12.1 255.255.0 0.127 area 0 network 141. Example 3-65 displays R6's working configuration.108.3 area 0 network 141.108.6 255.108.0.255 area 0 ! .0.255.108.128 0.1 network 131.0.26.8 0.255 area 0 network 141.10.255.0 0.0.26.10.33.0.108.9.3 area 2 ! line con 0 line aux 0 line vty 0 4 ! end Finally.255 area 0 network 141.0.0.252 clockrate 125000 ! interface Serial1 ip address 141.0 0.255.108.255.0.108.128 0.127 area 0 network 141.2.3 area 0 network 141.108.1.4 0.108.5.31 area 0 network 141.CCNP Practical Studies: Routing area 2 virtual-link 131.10.0 0.0.1.9.0.

10.10.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.108. Ethernet0/0 O 131.8/30 is directly connected.129 Type escape sequence to abort.108. Sending 5. Serial0/0 O 131. 00:15:29.4.10.4.95 - .10.128/25 is directly connected.5.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.6. 100-byte ICMP Echos to 131.108.10.108.129.0/25 is directly connected.10.5.108.10.1 Type escape sequence to abort. round-trip min/avg/max = 1/2/4 ms R1#ping 131. 8 subnets.108. round-trip min/avg/max = 1/1/4 ms R1#ping 131. Ethernet0/0 O 131. 00:15:28. Serial0/0 O IA 141.10.2.9. 100-byte ICMP Echos to 131.6. Serial0/0 C 141. Sending 5. 00:16:06. 00:15:28. 9 subnets.32/27 [110/1010] via 131. Serial0/0 O 141.108.108.1/32 [110/11] via 131.108.108. Loopback2 O 131.5. 00:15:31.108.0/24 is directly connected.4.108.0/24 [110/74] via 141. Serial0/0 O 141.2 Type escape sequence to abort.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).4. Sending 5. Serial0/0 131. 100-byte ICMP Echos to 131.108.108.1.5. Serial0/0 O 141.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10.0/16 is variably subnetted.1. 00:15:29.4. 3 masks O 141.1 Type escape sequence to abort.108.108. Serial0/0 O 141.10. 100-byte ICMP Echos to 131.10.5.108. 00:15:28.108.33.6.1.10.108. 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 141.12.5.26.108. Serial0/0 R1#ping 131.2.2.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1. Sending 5.108.6. Ethernet0/0 C 131.0/27 is directly connected. Example 3-66 shows this sample output taken from R1 and includes the IP routing table and sample pings to area 1.108.0/24 [110/129] via 141.0/24 [110/138] via 141. 00:16:04.9.10.10.4.108. 100-byte ICMP Echos to 131.108. 4 masks C 131.108.0/25 [110/65] via 141. Loopback0 C 131.10.108.108.10. .0/16 is variably subnetted.1.128/25 [110/129] via 141.1 Type escape sequence to abort.4/30 [110/128] via 141.10. Ethernet0/0 C 131.10. 00:15:28.108. Loopback1 O 131.1. round-trip min/avg/max = 1/2/4 ms R1#ping 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.33.108.108.108. 00:16:04. round-trip min/avg/max = 1/2/4 ms R1#ping 131.108.1. 00:15:28.108.2/32 [110/11] via 131.1.10.0. round-trip min/avg/max = 1/1/4 ms R1#ping 131.0/30 [110/192] via 141.108.10.108.10. 00:15:28. Serial0/0 O 141.0.1.0/25 [110/129] via 141. Sending 5.6.108.128/25 [110/65] via 141.33 Type escape sequence to abort.

33. round-trip min/avg/max = 1/2/4 ms R1# View Example 3-66 to answer the following review questions.108." 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 131.6.108. 100-byte ICMP Echos to 131.0/24 [110/74]? .CCNP Practical Studies: Routing Sending 5.1/24? Why is the remote network 141.108.96 - .0/16? What path is taken to the remote network 141.0/16 and 141.0.108.100.0.0/32 displayed as learned through the denotation: O IA? What is the cost associated with the remote network 131.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).2. "Answers to Review Questions.108. The answers to these question can be found in Appendix C.6.

Enables you to use subnet zero on a Cisco router. interface S0/0. Creates a loopback interface. Enables or disables an interface.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. The process ID is local to the router. You can have more than one OSPF running. Disables automatic DNS lookup. Enables OSPF routing. such as OSPF process ID and router ID. Displays OSPF neighbors in detail. Configures a name on a router. received and sent by a Cisco router from or to neighboring OSPF routers. enables you modify an interface number. for example interface E0/0. Interface command that changes the DR/BDR election process. 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. . Troubleshooting command that displays messages. Interface command that changes the network type. For example. Table 3-7. and dead interval. Interface command that changes the cost of an OSPF interface.97 - . Displays all routing protocols in use on a Cisco router. Displays router's topological database. providing such parameters as neighbor address. Table 3-7 summarizes the commands used in this chapter. hello interval. Displays the OSPF process and details. You saw that all OSPF areas must be connected to the backbone for proper and correct operation. such as the state of the adjacency. In configuration mode. Displays information on how OSPF has been configured for a given interface. OSPF can be configured in single or multiple areas. Displays OSPF neighbors. All hardware interfaces are shut down by default. In configuration mode. 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. enables you to modify serial interface parameters by module and interface number. Enables network advertisements out of a particular interface and also the routing of the same interface through OSPF.

.

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

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

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

LSA Types and Area Restrictions Area NSSA Totally stubby Stub TIP All OSPF packets are sent using IP protocol port number 89. This solution is Cisco-proprietary and is used to further reduce a topological database.This area is used primarily for connections to an ISP. area Not-so. Table 4-4. and 5. Basically. called stubby areas. Although similar to a stub area. 4. no translation takes place. a totally stubby area blocks LSAs of type 3 stubby as well. Totally This area blocks LSA types 3. a default route injected by the ABR. a bit. Table 4-3. Also a stub (does not permit LSA types 4 and 5) area or totally stubby (does not permit LSA types 3. OSPF runs over the IP layer (also called the Network layer) of the Open System Interconnection (OSI) model. Type 4 or 5 LSAs are not permitted. no adjacency is formed.CCNP Practical Studies: Routing Table 4-3 summarizes the functions of these new areas. This advertisement will not be propagated to the rest of the network. total stubby areas. 4.102 - . in the Hello packet is set to 0. thereby. and not-so-stubby areas in more detail. All routers that form any OSPF neighbor relationship must have the E bit set to 0 as well. respectively. Additional Area Types Area Function Type Stub area This area does not accept LSA types 4 and 5. which are summary links and external link advertisements. and not-so-stubby areas. Nor is redistribution allowed. This is a design limitation by the protocol itself. The only way to achieve a route to unknown destinations is. Table 4-4 summarizes the LSA types by area and indicates which LSAs are permitted or disallowed in certain areas. Take important note of the LSA type allowed or not allowed to fully appreciate the value of a stub area. Typically used to provide a default route. and 5) area does not allow external routes. NOTE A stub area cannot be a transit for a virtual link. If the P bit is set to zero. The scenarios that follow cover stub. otherwise. When a router is defined as a stub area. 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. Yes Yes Yes 1/2 LSA Type Permitted? 3/4 6 Yes No No No Yes No 7 Yes No No . totally stubby. The only way to appreciate these new areas is to configure them and view the OSPF database. called the E bit. All stubby advertised routes can be flooded through the NSSA but are blocked by the ABR. This area is designed to allow LSAs of type 7 only. Those functions must be performed by ABRs or ASBRs.

103 - . no other router can share the same router ID) Subnet mask Attached router Metric Because the subnet mask is carried along with the update. Without a mechanism that sends the subnet mask. Summarization occurs using the LSA type 4 packet or by the ASBR.1.109. Routing Information Protocol (RIPv1) and Interior Gateway Routing Protocol (IGRP). you can use summarization. Example 4-1 displays R1's routing table.CCNP Practical Studies: Routing VLSM and Summarization with OSPF OSPF supports a number of features.15. . When an LSA packet or routing update is received or sent. the packet includes the following information: • • • • • LSA type Router ID (unique IP address.109. Figure 4-2 displays this two-router topology with the routers named R1 and R2. OSPF can support VLSM. The two main features that interest most network designers are that it supports VLSM and provides the ability to summarize networks. there can be no support for VLSM.0. Instead of populating R1's routing table with 15 IP route entries. Sample Network for OSPF Summarization Example R2 is sending R1 15 OSPF routes ranging from 131. for example.0 to 131. 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. Figure 4-2. do not carry the subnet mask when they send out updates.

2.108.109.9. you can also externally summarize IP routes by using the summary ip-address mask command. Ethernet0/0 O IA 131.2.0 [110/11] via 131.0.2. When calculating the cost to a remote network. Ethernet0/0 O IA 131. indicated by Cisco IOS as O E1. Example 4-2 displays the summary applied to R2 under the OSPF router process ID of 1.4.108.2.109.2.2.0/24 is subnetted. Example 4-2 Summary of R2 R2(config)#router ospf 1 R2(config-router)#area 1 range 131.109.0 [110/11] via 131.108.109. Ethernet0/0 O IA 131.0 [110/11] via 131. 00:00:48.109.0 [110/11] via 131. indicated by Cisco IOS as O E2.15.108.2.2.2.2. you can summarize a simple network with 15 IP networks by using 1 IP routing entry.12.5.108.109.14.2.2. Ethernet0/0 O IA 131.7. 00:00:58.0 Example 4-3 displays R1's routing table now.2.108.109.108.255.6.109. NOTE Two more types of OSPF routes exist: external type 1 routes.109. Ethernet0/0 O IA 131. Ethernet0/0 O IA 131.108.13. Ethernet0/0 R1# By using OSPF summarization techniques.2.104 - .0 [110/11] via 131.0 [110/11] via 131. .109. 00:00:58.2.0/20 is subnetted.2.109.108. 00:00:58. such as BGP or IGRP. External OSPF routes are routing entries in OSPF route tables injected by an external routing protocol. E1 routes add the total cost to destination. 00:00:48.109.11.3.109.2.2. Ethernet0/0 O IA 131. 14 subnets O IA 131.0.108.108. 00:00:48.0 [110/11] via 131.0 255.2.109.0 [110/11] via 131.2. 00:00:58.0 [110/11] via 131. Because the networks 1 to 15 are contiguous.0. 1 subnets O IA 131. hence. 00:00:58.109. In OSPF.2. OSPF summarization examples are included among the five scenarios in this chapter.109. Ethernet0/0 The remote networks are indicated by O IA. Ethernet0/0 O IA 131.1.2.0 [110/11] via 131. Example 4-3 OSPF Route Table on R1 After Summarization R1#sh ip route ospf 131.108. Ethernet0/0 O IA 131. Ethernet0/0 O IA 131.0 [110/11] via 131.108.2. Intra-area routes are indicated by O. R2 can perform interarea summarization.109.2. and external type 2 routes. 00:00:00.10.108. 00:02:33.0. Ethernet0/0 O IA 131.2. 00:02:54.109.2. 00:01:08. 00:00:48. you can configure R2 to mask the networks by masking the first 15 networks with the IOS area area ID range address mask command.0 [110/11] via 131.108.2. Ethernet0/0 O IA 131. Remember that previously there were 15 IP routing entries.2. 00:00:58. 00:00:58.0 [110/11] via 131. whereas E2 routes include only the cost to the external network. Ethernet0/0 O IA 131. Ethernet0/0 O IA 131. 00:00:58.8.2. Example 4-1 displays an IP routing table telling you that R2 is in area 0 and another area (ABR).0 [110/11] via 131.CCNP Practical Studies: Routing Example 4-1 R1's OSPF Routing Table R1>show ip route ospf 131.2.2.2. which indicates interarea routes.109.0 [110/11] via 131.2.0 [110/11] via 131.108.240.

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

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

Assume all IP traffic is between the edge.129.0–15/32 131. large computer hosts.0/24 131. the hosts (devices.108. you configure several loopback address assignments on R1 and R2.0–31/32 131.0/24 131. Figure 4-4.108. routers and the backbone network in area 0. To simulate a large network environment. Typically in an environment like this. use the same process ID of 1 on all routers. or access.131.0/24 131.108.255.34–35/32 131. or printers) reside in the backbone and the end users are connected to the remote sites. In this scenario.108.107 - . 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 131.0/24 131.2.0 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.108. you configure an eight-router. . Figure 4-4 displays the OSPF topology and area assignment.128.16.0 131. Table 4-5.CCNP Practical Studies: Routing Scenario 4-1: Configuring OSPF with Multiple Areas In this scenario. 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.36. such as mainframes.108.32–33/32 131. use the network command. To send and receive LSAs per interface.108. three-area network with OSPF.108. and remember that the process ID is locally significant only.108. Table 4-5 displays the IP address assignment used in Figure 4-4.108.130.

OSPF.108. resides in area 11.2.14.108.108.18.6.108. Loopback8 C 131.108 - . but the network on R8 is not. you must know the router ID on R4 and R8.130. Ethernet0/0 O 131. Loopback0 C 131. 00:17:10.108.108. 2 masks O IA 131. Loopbacks are .108.0/24 is directly connected. Serial0/0 O IA 131. 39 subnets. 00:12:47.0/24 is directly connected. Configure a virtual link between R4 and R8.2.36.108. 00:12:47.2.7. Loopback13 C 131.108.2. Ethernet0/0 O 131.4/30 [110/791] via 131. N2 . Ethernet0/0 C 131.To R5 O IA 131.0/24 [110/11] via 131. the remote network on Router R8. Ethernet0/0 Example 4-4 displays the remote routers learned through Ethernet interface and the next hop address of 131.4.2. Because the cost is lower through the Ethernet LAN segment.108. Ethernet0/0 O IA 131.2.OSPF NSSA external type 2 E1 . with the IP subnet 131.108.108. 00:00:18. 00:12:47.connected. Loopback12 C 131.108. 00:07:02. The three remote networks on the access Routers R5.0/24 is directly connected.108. 00:05:29.To R7 C 131.10.0/24 [110/138] via 131. 00:12:44. Loopback3 C 131. 00:09:16.0/24 [110/11] via 131. 00:12:47.30. of course.0/24 [110/865] via 131. 00:17:10. Serial0/0 .108. Loopback11 C 131.108.108.255.128.8/30 [110/128] via 131. 00:08:21.2.0/24 is directly connected. Ethernet0/0 O 131. O .1.0/24 is directly connected.0/24 [110/11] via 131.1. 131. Ethernet0/0 O 131.2.28.2.108.108. Loopback1 C 131.108. 00:12:47. 00:12:47. 00:12:47.0/24 is directly connected.0/24 [110/11] via 131.2.2. E2 .0/24 [110/11] via 131.0/24 is directly connected. Ethernet0/0 O 131.108.0/24 is directly connected. 00:12:47.108.0/24 is directly connected.CCNP Practical Studies: Routing From Figure 4-4. Serial0/0 .0/24 [110/11] via 131.255. Loopback5 C 131.108.108.1. 00:12:47.108.255. 00:12:47.13. Loopback6 C 131. Ethernet0/0 O 131.12.108.0/24 [110/11] via 131.26.1.108.1.108.1.27.5.108. Loopback9 C 131.108.108.108.9.108.255.OSPF inter area N1 .108.1.3.108.108.1.2.108.1. and R7 are listed in Example 4-4.0/24 is directly connected.2.0/24 [110/11] via 131.108.0/16 is variably subnetted.0/30 is directly connected.20.19. Before you can configure a virtual link. Ethernet0/0 . Ethernet0/0 O 131.2.1.0/24 is directly connected.2.108. 00:12:47.1. 00:12:47.2.0/24.1.1.0/24 is directly connected.108.25.0/24 [110/11] via 131.2.2.1.12/30 [110/128] via 131.0/24 [110/11] via 131. Ethernet0/0 O 131.1.15.1.1.0/24 [110/11] via 131. Example 4-4 R1 Routing Table R1#show ip route Codes: C .255.8. Ethernet0/0 O 131.108.0/24 [110/11] via 131. 00:10:15. IA . 00:12:47.129. Loopback2 C 131.22.0/24 [110/11] via 131.2.108.108. Ethernet0/0 O 131. Serial0/0 O 131.108.0/24 [110/11] via 131.1.29.108.1.0/24 [110/11] via 131. Loopback4 C 131. Loopback10 C 131.108.108.108. Example 4-4 displays the IP routing table on R1 after OSPF has been configured on all the routers in this network. Ethernet0/0 O 131. Ethernet0/0 O 131.1.0/24.0.1. 00:17:10.108.31.108.OSPF NSSA external type 1. which is typically a loopback address or the highest IP address assignment.108.0/24 is directly connected.2. The show ip ospf database command displays the local router ID.0/24 [110/11] via 131.108.To R6 O IA 131.0/24 is directly connected.11.255.108. Ethernet0/0 O 131.20/30 [110/855] via 131. which is R2.108.108. Ethernet0/0 O 131.255. There is. 00:07:51.0/24 is directly connected.131. R1 chooses the path to R2 as the preferred path.16/30 [110/855] via 131.255.108. 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 131.23.2.2. Ethernet0/0 O IA 131.108.108.2.24.108.108.108. Serial0/0 O IA 131.1.108.108.108.108.2.255. R6.OSPF external type 2.108. Ethernet0/0 O 131.0/24 [110/138] via 131.255.16. 00:17:10. Ethernet0/0 O 131. Ethernet0/0 O 131.108.108.108.2.1.OSPF external type 1.131.17.108.0/24 [110/11] via 131.2.2. Loopback7 C 131. another path on R1 through the serial link to R2.21.

D ID (IP addr) associated with virtual link neighbor R8(config-router)#area 10 virtual-link 131.29.0/24 [110/11] via 131.4/30 [110/791] via 131.0/24 [110/11] via 131.0/24 [110/11] via 131.2.108. Ethernet0/0 O IA 131.108.255.108.1.108.6 Example 4-8 displays the IP routing table on the core router. Ethernet0/0 O IA 131.27.2.0/16 is variably subnetted.1.108.2. Ethernet0/0 O 131.108.108. 00:00:48.22 Example 4-7 displays the virtual link configuration on R8 along with the IOS ? command to display the available options.108.108.25.0/24 [110/11] via 131.108. and the router ID is the IP address of the remote router.0/24 [110/865] via 131.2. 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.28. The transit area in this example is area 10.1. 00:00:48.0 because of the virtual link configuration. Ethernet0/0 O 131.2. Ethernet0/0 .108. Ethernet0/0 O 131.12/30 [110/128] via 131.108. Ethernet0/0 O 131.30. 00:00:47.2.1.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 131.20/30 [110/855] via 131.255.108.1.108.0/24 [110/11] via 131.108. Serial0/0 O 131.2.0/24 [110/865] via 131.108.108.108.108.21.2. Serial0/0 O IA 131. along with the remote network 131.1. R1.108.255.2. Ethernet0/0 O 131. Ethernet0/0 O 131. 00:00:47. Ethernet0/0 O 131.108.108.0/24 [110/11] via 131. Ethernet0/0 O IA 131.108.23. 00:00:48. Serial0/0 O IA 131.255.108. 2 masks O IA 131.108.0.1. Ethernet0/0 O 131. 00:00:48.108.108.108.255.1.108. 00:00:47. To configure a virtual link.1.131.0/24 [110/11] via 131.108.108.1.255. Example 4-8 show ip router ospf Command on R1 R1#show ip route ospf 131.255.1. Serial0/0 O IA 131.2.108. Example 4-5 displays the router ID on Routers R4 and R8. 00:00:48.255.128. 00:00:48.108.108. Ethernet0/0 O IA 131.31. 41 subnets.0/24 [110/11] via 131.131.255.22) (Process ID 1) Example 4-6 displays the virtual link configuration on R4.2.2. 00:00:47. Example 4-6 Virtual Link Configuration on R4 R4(config-router)#router ospf 1 R4(config-router)#area 10 virtual-link 131.2.1. 00:00:48. 00:00:48.255.22.108.255. 00:00:48.108.2. Ethernet0/0 O 131.0/24 [110/11] via 131.130. 00:00:48.1.2.255. 00:00:47. 00:00:48. Ethernet0/0 O 131.109 - .108.2. A router ID that is a physical interface is prone to network failure and OSPF recalculations.108. Example 4-5 Router ID on R4 and R8 R4#show ip ospf database OSPF Router with ID (131.0/24 [110/138] via 131. 00:00:48.108.26.0/24 [110/11] via 131.1.108.108.2. use the IOS command area transit area router-id.B.C.108.2.0/24 [110/11] via 131.108.1.255.1. 00:00:48.108.8/30 [110/128] via 131.2.24.16/30 [110/855] via 131.108.2.129. which lead to network downtimes. 00:00:48.0/24 [110/138] via 131.6) (Process ID 1) R8#show ip ospf database OSPF Router with ID (131.108. 00:00:47.

108.108.108.255.255. 00:00:50. R1 is a backbone router.108. maximum is 1 Last retransmission scan time is 0 msec. 00:17:10.20. number of retransmission 1 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 1.108. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 To view the status of the virtual link. Timer intervals configured.1 255.19.2.2.255. 00:00:49.108.1.2.255.1 255.108.5.108. Wait 40. retransmission queue length 0. Example 4-9 displays sample output from this command used on R4.108.2.0/24 131. Example 4-9 show ip ospf virtual-links on R4 R4#sh ip ospf virtual-links Virtual Link OSPF_VL0 to router 131. 131.108.1.108.110 - . Pay particular attention to the shaded sections and the router functions within the OSPF network. look at the full working configurations on all routers. State POINT_TO_POINT.1 255. 00:00:50. 00:00:49.36.2. 131.255. maximum is 0 msec You have successfully configured a complex network with eight Cisco routers in multiple areas.0/24 131.2. even with only eight routers.0/24 [110/11] [110/11] [110/11] [110/11] [110/11] [110/11] via via via via via via 131.1.255.0 ip ospf network point-to-point ! interface Loopback2 ip address 131. Transit area 10. Before using summarization on this network to reduce the IP routing table size. Retransmit 5 Hello due in 00:00:09 Adjacency State FULL (Hello suppressed) Index 2/4. Dead 40.1.22 is up Run as demand circuit DoNotAge LSA allowed.255. Hello 10. Example 4-10 displays R1's full working configuration.1 255.0/24 131.18.255.0 ip ospf network point-to-point ! interface Loopback1 ip address 131.3. 00:00:50. 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 131.2.0/24 131.0/24 131.255. Cost of using 64 Transmit Delay is 1 sec.0 ip ospf network point-to-point ! interface Loopback4 .108. 131.108.1. 131.4.1. Also note how the clockrate command is used to enable back-to-back serial high-level data link control (HDLC) connections among Cisco routers.108.108.CCNP Practical Studies: Routing O O O O O O 131. 131.16. via interface Serial2. The routing table.108.0 ip ospf network point-to-point ! interface Loopback3 ip address 131. has over 20 IP route entries. use the show ip ospf virtual-links command.17.108.

0 ip ospf network point-to-point ! interface Loopback12 ip address 131.0 ip ospf network point-to-point ! interface Loopback13 ip address 131.108.108.255.255.0 ip ospf network point-to-point ! interface Loopback7 ip address 131.8.255.15.108.1 255.255.255.255.255.255.108.1.255.9.108.108.255.CCNP Practical Studies: Routing ip address 131.255 area 0 ! line con 0 line aux 0 line vty 0 4 end Example 4-11 displays R2's full working configuration.252 clockrate 125000 ! interface Serial0/1 shutdown ! router ospf 1 network 131.0 ip ospf network point-to-point ! interface Loopback11 ip address 131.0 ip ospf network point-to-point ! interface Loopback5 ip address 131.255.255.108.255.255.108.12.1 255.14.255.10.108.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 131.255.1 255.1 255.255.108.1 255.255.255.255.1 255.255.255.1 255.7.111 - .108.1 255.6.1 255.0.255.1 255.11.0 ! interface Serial0/0 ip address 131.108.255. .0 ip ospf network point-to-point ! interface Loopback10 ip address 131.1 255.1 255.255.0.0 ip ospf network point-to-point ! interface Loopback9 ip address 131.0 ip ospf network point-to-point ! interface Loopback8 ip address 131.0 0.108.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 131.13.

255.255.16.255.255.1 255.255.0 ip ospf network point-to-point ! interface Loopback6 ip address 131.255.255.18.108.255.21.26.1 255.108.108.255.0 ip ospf network point-to-point ! interface Loopback2 ip address 131.1 255.255.255.1 255.1 255.255.108.255.108.112 - .0 ip ospf network point-to-point ! interface Loopback7 ip address 131.25.22.108.108.255.108.1 255.28.255.0 ip ospf network point-to-point ! interface Loopback10 ip address 131.0 ip ospf network point-to-point ! interface Loopback5 ip address 131.17.108.255.0 ip ospf network point-to-point ! interface Loopback1 ip address 131.0 ip ospf network point-to-point ! interface Loopback4 ip address 131.0 ip ospf network point-to-point ! interface Loopback8 ip address 131.1 255.0 ip ospf network point-to-point ! interface Loopback3 ip address 131.0 ip ospf network point-to-point ! .0 ip ospf network point-to-point ! interface Loopback11 ip address 131.27.1 255.1 255.0 ip ospf network point-to-point ! interface Loopback9 ip address 131.0 ip ospf network point-to-point ! interface Loopback13 ip address 131.23.255.255.1 255.108.255.255.108.1 255.1 255.255.108.255.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 131.19.1 255.24.108.255.255.20.255.255.

255.0 ! interface Serial0 ip address 131.255.108.108.30. R3 is an ABR.255.108.252 clockrate 128000 ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown ! interface Serial1/3 shutdown ! router ospf 1 network 131.1.31.1 255.CCNP Practical Studies: Routing interface Loopback14 ip address 131.252 clockrate 128000 ! interface Serial2 .108.255 area 0 ! ip classless ! line con 0 line aux 0 line vty 0 4 ! end Example 4-12 displays R3's full working configuration.255. Example 4-12 R3's Full Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.108.0.255.255.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 131.36.108.255.5 255.0 ip ospf network point-to-point ! interface Loopback15 ip address 131.255.0 0.0 ! interface Serial1/0 ip address 131.108.255.255.1 255.255.255.0 ip ospf network point-to-point ! interface Loopback16 ip address 131.108.2 255.255.1 255.255.255.255.2 255.0.113 - .255.29.9 255.3 255.108.255.255.255.252 ! interface Serial1 ip address 131.

255.22 network 131.6 255.108.36.4 0.255.255 area 10 network 131.108.13 255. .0.36.255.255.255.255 area 10 network 131.108.0.255.0.0.0.108.255.255.255.255.255.252 clockrate 128000 ! interface Serial2 ip address 131.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-14 displays R5's full working configuration.255.108.255.114 - .252 ! interface Serial1 ip address 131.0.0.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-13 displays R4's full working configuration.3 area 0 network 131.255.0. Example 4-13 R4's Full Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet 0 ip address 131.36.108.255.108.4 255.0.0.255. R4 is an ABR.16 0.3 area 10 network 131.0.108.0.0 0.252 clockrate 128000 ! interface Serial3 shutdown ! router ospf 1 network 131.17 255.0.3 area 0 network 131.255.8 0.252 clockrate 128000 ! interface Serial3 shutdown ! router ospf 1 area 10 virtual-link 131.12 0.21 255.108.0 ! interface Serial0 ip address 131.255.20 0.108.0 0.0.0 0.108.255.255.CCNP Practical Studies: Routing ip address 131.0. R5 is an internal OSPF area.3 area 10 network 131.255.108.0.108.108.

1 255.3 area 10 ! line con 0 line aux 0 line vty 0 4 end Example 4-15 displays R6's full working configuration.1 255.0.0 0.252 ! interface Serial1 shutdown ! router ospf 1 network 131.0. Example 4-15 R6's Full Configuration hostname R6 ! enable password cisco ! ip subnet-zero ! interface Ethernet0 ip address 131.255.255.108. Example 4-16 R7's Full Configuration hostname R7 ! enable password cisco ! ip subnet-zero no ip domain-lookup . R7 is an internal OSPF area.108.128.129.0.8 0.0.0.255.255.255. R6 is an internal OSPF router.0 0.255.CCNP Practical Studies: Routing Example 4-14 R5's Full Configuration hostname R5 ! enable password cisco ! interface Ethernet0 ip address 131.255.0.128.0 ! interface Serial0 ip address 131.255.16 0.255.255.10 255.108.0.129.255 area 10 network 131.115 - .0 ! interface Serial0 ip address 131.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-16 displays R7's full working configuration.255 area 10 network 131.108.255.18 255.255.108.108.0.108.252 interface Serial1 shutdown ! router ospf 1 network 131.108.

116 - .108. 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. you need to have a more detailed view of the network. OSPF.255.108.130.255. as you have seen. The access-level routers.0.255 area 11 network 131.6 network 131. R8 is an internal OSPF area.0 interface Serial0 ip address 131. R6. which pass on routing information to other core or remote routers.108.255.0. and R4. R2. and R8. Example 4-17 R8's Full Configuration hostname R8 enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.255.131.0 0.255.108.0 ! interface Serial0 ip address 131. R5.1.1 255.108.255.12 0. requiring a virtual link because area 11 is not connected to area 0.1 255.0.255. namely R1.255. R7.255.108.255.255. The aim of any network designer is to use summarization wherever possible.31. For the core routers in area 0.130. Therefore.108.0.255 area 10 network 131.3 area 10 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-17 displays R8's full working configuration.0 to 131.0.3 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. has some advanced features to allow summarization.252 interface Serial1 shutdown ! router ospf 1 area 10 virtual-link 131.255.20 0.0. The first method you can apply is intra-area summarization on the backbone Routers R1 and R2.108.108.0 0.255. the backbone. R3.CCNP Practical Studies: Routing interface Ethernet0 ip address 131.252 ! interface Serial1 shutdown ! router ospf 1 network 131.0.131. A total of 30 networks (contiguous) exist from 131.255. 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 0.108.14 255.0.108. these routers are perfect examples of how you can use .22 255.

108.0/24 [110/129] via 131. O .255.16.0/24 [110/139] via 131. 04:14:51.108.0/24 [110/129] via 131.255.255. 04:14:50. First.255.7.0/24 [110/129] via 131. 04:14:51.0/24 [110/139] via 131.30. 03:51:04.9. Serial0 O IA 131. IA .CCNP Practical Studies: Routing summarization to reduce the size of routing tables. Serial0 O IA 131. 04:14:51. Serial0 O IA 131.108.108.255.108.EGP 131.108.108.255.31.108.9.0/24 [110/129] via 131.255.9. 04:14:53.108. 41 subnets.16/30 [110/983] via 131.9. Serial0 O 131.9.0/24 [110/139] via 131.108.0/24 [110/129] via 131. Serial0 O IA 131. Serial0 O IA 131.108. Serial0 C 131. 04:14:53.108.255. Serial0 O IA 131.108.108. Serial0 O 131.255. 04:14:50.108.9. Example 4-18 R5's Current IP Routing Table R5#show ip route Codes: C .9. 04:14:53.108. 04:14:53. Serial0 Use OSPF summarization for the core IP networks ranging from 131.5. 04:14:53.0/24 [110/129] via 131.255. Serial0 O IA 131. Serial0 O IA 131. 04:14:52.255.255.9.19.117 - . Serial0 O IA 131.108.0/24 [110/993] via 131.9.OSPF external type 2.108.0/24 [110/139] via 131.27.108.9.9.28.17. Serial0 O IA 131. 04:14:52. Serial0 O IA 131.0/16 is variably subnetted. Serial0 O IA 131.255. 03:51:25.108. Serial0 O IA 131.OSPF NSSA external type 1.0/24 [110/993] via 131.255. 03:51:14.108.1.9.108.108.108. 03:51:35.108.0/24 [110/129] via 131.108.20/30 [110/983] via 131.0/24 [110/11] via 131. Serial0 O IA 131.9. .255.9.108. 04:14:51. N2 .9.108. Example 4-18 displays R5's IP routing table.10.0/24 [110/139] via 131.0/24 [110/129] via 131.108. 04:14:53.0/24 [110/139] via 131.255.OSPF inter area N1 . 04:14:53.9.108.9.108.14. 03:51:14. 04:14:52. Ethernet0 O IA 131. 04:14:52.108.255. 03:51:25.108.108.108.2. Serial0 O IA 131.255.255.36.0/24 [110/139] via 131. Serial0 O IA 131.108. Serial0 O IA 131.108. 03:51:04.108.0.108.108.108.128.9.9.0/24 [110/129] via 131.108.9.108. Serial0 O IA 131.255.9.9.3.108.108.108.9.255.9.9.255.255 on Routers R3 and R4. Serial0 O IA 131.108. 03:51:25. Example 4-19 displays the use of the IOS area area ID range mask command on R3.255.108.0/24 is directly connected.8.108.108. 03:51:14.255.255.25.9.0 to 131.108.0/24 [110/139] via 131. Serial0 O IA 131.255. 04:14:53.0/24 [110/139] via 131.255.108.0/24 [110/139] via 131. 03:51:25.255.9. Serial0 O IA 131.OSPF.130.18. 04:14:52.255.108.108. 2 masks O IA 131.129. Serial0 O IA 131.255.26.255.108.9.6.108.13.0/24 [110/139] via 131.0/24 [110/138] via 131.22.108.0/24 [110/139] via 131.108.0/24 [110/139] via 131. Serial0 O IA 131.9.1. Serial0 O IA 131. 04:14:52.11.108.255.0/24 [110/138] via 131.255. Serial0 O IA 131. Serial0 O IA 131. Serial0 O IA 131. 04:05:58. Serial0 O IA 131.255.9.255.255.0/24 [110/139] via 131.255.108.108.255.15.108. Serial0 O IA 131.9.108.108.108.255.108. Serial0 O 131.OSPF NSSA external type 2 E1 .0/24 [110/129] via 131.131. E2 .OSPF external type 1.9. 04:14:51. use some summary commands.255.0/24 [110/139] via 131. 04:14:53. 04:14:52.24.108.0/24 [110/129] via 131.108.108.9. Serial0 O IA 131. 03:51:14. Only a single exit point to the core of the network exists.108. Serial0 O IA 131.connected.0/30 [110/128] via 131.108.108. Serial0 O IA 131. 03:51:25.23.255.20.9.8/30 is directly connected. Serial0 C 131. 03:51:25.108.9. 04:14:53.9.108.0/24 [110/129] via 131. Serial0 O IA 131. E .108.4.108.9. Serial0 O IA 131.255.21.12/30 [110/128] via 131.9.9.108.12.108. 03:51:15.29.0/24 [110/129] via 131.9.108.108.255.255.108. 04:14:53.108.255.255.0/24 [110/139] via 131.31.4/30 [110/919] via 131.108.108.9.0/24 [110/129] via 131. so you can configure stubby networks. Serial0 O IA 131.108.

round-trip min/avg/max R5#ping 131.9.0 255. timeout is !!!!! (R1 Ethernet e0/0 address) Success rate is 100 percent (5/5).12/30 [110/128] via 131.131.108.108. hence.108. 05:00:08.255. Serial0 O IA 131.108.1. 100-byte ICMP Echos to 131. you can perform network summarization on R3 and R4.OSPF inter area N1 .108.255. timeout is !!!!! Success rate is 100 percent (5/5).0/24 [110/993] via 131.0.9.36. 100-byte ICMP Echos to 131. 11 subnets.0. E2 .108.255. 05:09:00.0 to 131. 00:46:25. round-trip min/avg/max R5#ping 131.OSPF.224.108.9. 05:09:00.108.108.108.108.108.9. Example 4-20 Summary on R4 R4(config)#router ospf 1 R4(config-router)#area 0 range 131.108. Serial0 O 131.255.108.255.1. Also displayed in Example 4-21 are a few ping requests to IP networks covered in the summary range 131.108.OSPF NSSA external type 2 E1 .1. Serial0 C 131.0/19.2.2.0 255.9.130. 05:09:00.8/30 is directly connected.108. IA .108.D IP mask for address R3(config-router)#area 0 range 131.108.255.OSPF NSSA external type 1.0 View the IP routing table on R5.1.108.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. Example 4-21 Summary on R5 R5#show ip route Codes: C .108.108.3.31.108. Serial0 O 131.108.108. Example 4-21 displays R5's routing table after network summarization is configured on R3 and R4. 05:09:00. Sending 5.0/30 [110/128] via 131.16/30 [110/983] via 131. which are networks covering the range 131.224. Routers R3 and R4 are ABRs.255.OSPF external type 2 131.0/19 [110/129] via 131. Example 4-20 displays the OSPF summary on R4.255.255.OSPF external type 1.1.1.255.1 Type escape sequence to abort. 05:14:53.108.129.0 The IOS tells you only ABRs can perform OSPF summarization.0/24 [110/138] via 131.9. Serial0 O IA 131.20/30 [110/983] via 131.108.0/16 is variably subnetted.255.255.0 ? A.118 - . timeout is 2 seconds: = 32/32/32 ms 2 seconds: = 28/31/32 ms 2 seconds: . Sending 5. N2 .108.255.108.108. Serial0 O 131. 05:09:00.3.9. Ethernet0 O IA 131. Serial0 O IA 131. Serial0 C 131. Serial0 O IA 131.0/24 [110/993] via 131.1 Type escape sequence to abort.255.0. 05:09:00.0. Serial0 R5#ping 131.0. 05:09:01.4/30 [110/919] via 131. Sending 5.255.1 Type escape sequence to abort.255.108.0/24 [110/11] via 131.108. O .9.0/24 is directly connected.C.B. Serial0 O IA 131.1.connected.255.255.108. 100-byte ICMP Echos to 131.128.9. 3 masks O IA 131.9.108.108.108.255.

To create a stub network. configure the following commands on R8: .1. The same occurs on Routers R6.31. you have significantly reduced the IP routing table size on R5 to nine remote OSPF entries. Cisco's IOS displays the message in Example 4-23.108. 100-byte ICMP Echos to 131.31. use the area area id stub command.CCNP Practical Studies: Routing !!!!! Success rate is 100 percent (5/5). So. R7. 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. 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. Example 4-22 displays the stub configuration on R3. and R8. Create a stub network between Routers R3 (the ABR) and R5. round-trip min/avg/max = 32/32/32 ms R5#ping 131. round-trip min/avg/max = 32/32/36 ms By using a simple command on the ABRs. Also because R5 and R7 have single exit points to the core. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).119 - . Figure 4-5 displays the change of area assignments to remove the necessity of a virtual link between R8 and R4.1 Type escape sequence to abort. To change the area assignment on R8 from 11 to 10. Sending 5. you can configure a stub network. You cannot configure a stub network on R8 because you have a virtual link.

9 Interface Serial0 The OSPF relationship between R3 and R5 is down because if one router is configured as a stub.108.0 0.255.13 Pri 1 State DOWN/ Dead Time Address 131.108. Example 4-25 displays the configuration of a stub network on R5 and the OSPF relationship change to full adjacency.108. Example 4-24 displays R5's OSPF neighbor state after you configure the ABR R3 as a stub network in area 10. you must ensure that OSPF is still active on R5.0.108.255. . Example 4-24 show ip ospf neighbor Command on R5 R5#show ip ospf neighbor Neighbor ID 131.108.0.255 area 11 network 131.255.131.108.13 Pri 1 State FULL/ Dead Time 00:00:38 Address 131. and in this case. the neighboring router must also be configured as a stub. OSPF Sample Network After R8 Area Change no network 131.0 0.CCNP Practical Studies: Routing Figure 4-5.255 area 10 Because a change has been made to OSPF area assignment.0. Example 4-26 displays the new IP routing table after the stub configuration is completed on both Routers R3 and R5.0.120 - .9 Interface Serial0 Now.255. view the IP routing table on R5.131. R5 has not yet been configured as a stub. 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.

255. 00:01:22.0. 3 masks O IA 131.9.108. Serial0 O*IA 0.108.9.255.9.9. Serial0 C 131.108. Example 4-28 displays the no-summary option configured on R5.0.255.9.255. 00:01:22.255.108.108. R3.255. 00:01:23.0/24 [110/993] via 131. Serial0 C 131.0/30 [110/128] via 131. Serial0 You now have on R5 a default route labeled 0. which effectively means any packets to unknown destinations are sent to the next hop address 131. so there is no reason for R5 or R6 to have network entries for every individual IP route in the core.255. and R8. All IP traffic is destined for the core anyway.9 (R3). Serial0 O IA 131.0/24 is directly connected. you can assume that all IP traffic from the edge routers is destined for the core network.108. Serial0 O 131. 00:01:22.108.108.128.255. 00:01:22.CCNP Practical Studies: Routing Example 4-26 R5's Routing Table R5#sh ip route Gateway of last resort is 131.255.108. Configuring a stub network performs exactly this function.0.255. 00:01:23.108.0.0. .108.121 - .108.9.255.108. Serial0 O IA 131.108.9. To further reduce the IP routing table. To ensure OSPF full adjacency is achieved between R3. with the no-summary option. 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. 00:01:22.9 (R3).0.255.0/16 is variably subnetted.36.0/24 [110/11] via 131.108. Serial0 O IA 131. you must configure both the core and edge routers. 00:01:22.9 to network 0.108. Serial0 O IA 131. R5.108. View the IP routing table on R5 in Example 4-29 and compare it to Example 4-26.255.4/30 [110/919] via 131.0.108. area 10 in this case. 00:01:22. R6. Example 4-29 displays R5 IP routing table. R4.9. R7.8/30 is directly connected. Serial0 O 131.0/24 [110/128] via 131.108.255. 10 subnets. This option prevents the ABR from sending summary link advertisements from other areas except the area that connects R5.0/19 [110/129] via 131.131.108.108.255.129.0 131. 00:01:22.12/30 [110/128] via 131.131.108.108.0/0 [110/65] via 131. Now. You have a gateway of last resort.255.108. Serial0 O IA 131.16/30 [110/983] via 131.255.255.108.0/24 [110/993] via 131.9. 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.20/30 [110/983] via 131.0. Ethernet0 O IA 131.108. Example 4-27 displays the configuration of the core router.255.9.9.108.0 through the next hop address 131. Serial0 O 131. it provides a default route.255. 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. 00:01:22.

108.255.3 area 10 network 131.0.0. which is area 10.0/24 [110/148] via 131.9.255. Serial0 O 131.0.255.108.0.108.108.9 to network 0.3 area 0 network 131.0. The shaded portion highlights the configuration required for the stub network.20 0.255.108.8/30 is directly connected.0.0.0 area 10 stub no-summary Example 4-31 displays R4's full OSPF working configuration.0.255. You now have only 8 remote entries instead of over 30. 00:01:04.108.0 255.255.0.108. 00:01:04.108.9.9.20/30 [110/138] via 131.0.3 area 10 ! .108. The shaded portion highlights the configuration required for the stub network. Example 4-30 R3's OSPF Working Configuration router ospf 1 network 131.128.130. 2 masks O 131.0. 00:01:04. 00:01:04.255.3 area 10 network 131.16/30 [110/138] via 131.108. Serial0 O 131.108.0.255.0 255.255. as shown in Example 4-18. Serial0 O*IA 0.0/24 [110/138] via 131.224.0/24 [110/148] via 131. Ethernet0 O 131.0.16 0.255.0.255.9. Example 4-31 R4's OSPF Working Configuration router ospf 1 area 0 range 131.108.12 0.255.108.36.255 area 10 network 131.0 area 10 stub no-summary network 131. the OSPF routing process changes because the remaining configuration is identical to that in Examples 4-10 to 4-17.108. Serial0 C 131.108.108.0 0. NOTE The configuration in Example 4-30 contains only the message in Example 4-23.0.0.8 0.108. 00:01:04.108.131. 00:01:04. Serial0 The only networks displayed now are the default network and networks residing in the same area as Router R5.36. List the full OSPF working configurations of the ABR Routers R3 and R4 and the edge routers that are configured as stubby networks.9. Example 4-32 R5's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.0/16 is variably subnetted.3 area 0 network 131.255.9.224.108.0 131. The use of the stub configuration is effective in this type of network topology.0.255.108. 00:01:04.0.255.108.0.108.128.0.255.0.0/0 [110/65] via 131.108.9.0/24 is directly connected.108. Serial0 O 131.0.255.255.255.108.129. 9 subnets.3 area 10 network 131.0. Serial0 O 131.122 - .CCNP Practical Studies: Routing Example 4-29 R5's IP Routing Table R5#show ip route Gateway of last resort is 131.4 0.108.0. Serial0 C 131.108.3 area 10 Example 4-32 displays R5's OSPF working configuration. 00:01:04.255.0/24 [110/74] via 131.108.0.36.108.0. Serial0 O 131.255 area 10 area 0 range 131.12/30 [110/128] via 131.9. Example 4-30 displays R3's OSPF configuration.108.0 0.255.255.255 area 10 network 131.0.0 0.0 0.108.4 0. The shaded portion highlights the configuration required for the stub network.

0.0. Example 4-34 R7's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131. R8.0. The shaded portion highlights the configuration required for the stub network.0.123 - .108.255 area 10 network 131.130.8 0. .0.108.255 area 10 network 131.0 0.3 area 10 Example 4-35 displays R8's OSPF working configuration.108. Scenario 4-3: Configuring Integrated IS-IS This scenario shows you how to configure another link-state protocol.129.108.255 area 10 network 131. in a three-router topology.CCNP Practical Studies: Routing Example 4-33 displays R6's OSPF working configuration.3 area 10 Example 4-34 displays R7's OSPF working configuration.0.0 0.108. with the routers named R4. Example 4-35 R8's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131.255.0.255.255.0 0.20 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. The shaded portion highlights the configuration required for the stub network.0.0.0.12 0. IS-IS.108.3 area 10 TIP To best appreciate OSPF and the features covered here.131. Example 4-33 R6's OSPF Working Configuration router ospf 1 area 10 stub no-summary network 131. The shaded portion highlights the configuration required for the stub network.0. The topology for this scenario is displayed in Figure 4-6.

IS-IS supports VLSM. The IP addressing scheme is displayed in Figure 4-6. which describes the area and system ID. IS-IS with VLSM Where this scenario covers redistribution. and you configure the three routers to be in domain 1 using the network entity known as the simple format. NOTE Three methods (referred to as network entities) can define the area: simple format. 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 . OSI format.CCNP Practical Studies: Routing Figure 4-6.124 - . Note that VLSM is in use. you use these routers to connect to an OSPF router.

d7bd. configure the first router.64fc. The areas are encoded as 00. 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.0001. and the system IDs are the MAC addresses from the local Ethernet interface.00e0.28ca.00 Now.0001.0050.0050.5460.64fc.125 - . You must also enter the global command clns routing. All routers reside in one area.5460.00 R8— 00b0. Example 4-37 Configuration on R8 R8(config)#router isis R8(config-router)#net 00.00b0. Figure 4-6 shows a small three-router network. net ID is 00.b055. The tag groups routers in one domain.d7bd. Example 4-36 displays the configuration required to enable IS-IS on Router R4.98e8.98e8.0001. The MAC addresses of the respective routers are as follows: • • • R4— 0050.00 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.0001.0001.b055. net ID is 00.00 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 .98e8.00b0. net ID is 00.28ca.64fc. Configure the network interfaces with the command net network-entity-title. Enable IS-IS per interface with the command ip router isis.00 R9— 00e0.d7bd. Example 4-36 Configuration on R4 R4(config)#router isis R4(config-router)#net 00.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. for IS-IS.0001.5460. Example 4-37 displays the configuration of IS-IS on R8. R4.

28ca. Serial2 [115/20] via 141.108.IS-IS.5. Notice the path to the remote network 141.4.IS-IS level-2.108.255. all of which are labeled L1 (level 1 route) because all three routers reside in area 1 as configured by the net command.108. Example 4-39 R4's IP Routing Table R4#sh ip route Codes i .0/16 is variably subnetted. Serial3 141.3.255. The IS-IS metric is between 0 and 63. The default metric is set to 10.00 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.CCNP Practical Studies: Routing Example 4-38 displays the configuration completed on R9.108. Serial2 141. as does OSPF.IS-IS inter area C C C i L1 i L1 i L1 141. Example 4-39 displays R4's IP routing table. . which is displayed in Example 4-41.8/30 is calculated with two paths: one path through Serial 2 and the other through Serial 3.255.0/24 [115/20] via 141.255. use the command show isis database. Example 4-38 Configuration on R9 R9(config)#router isis R9(config-router)#net 00.255.108. Ethernet0 141.IS-IS level-1.b055.255.0001.2. 2 masks 141.8/30 [115/20] via 141.0.126 - . Serial2 141. examine the IP routing tables for IP connectivity.108. 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. As with OSPF.255.0/24 [115/20] via 141. Serial3 R4's routing table has four remote entries. the command set for monitoring IS-IS is large.2.108. and the total metric is calculated from source to destination. ia . 6 subnets. Example 4-40 displays the IS-IS neighbor states with the show clns isis-neighbor command. Now look at a few examples of the most commonly used show commands. In other words.4/30 is directly connected. L1 .00e0.108. namely Routers R8 and R9.108. IS-IS supports equal cost path load balancing. L2 . The administrative distance for IS-IS is 115 and is followed by the metric.2. This means all routers share the same IS-IS link-state database.0/24 is directly connected.108.255. Serial3 141.108.5.0/30 is directly connected. To view the linkstate database on an IS-IS router.108.

28CA. OL Overload bit.00-00 * 0x00000009 R8. Checksum LSP Holdtime Amount of time the LSP remains valid.6 255.252 clockrate 128000 ! interface Serial2 ip address 141. Before you look at redistributing IS-IS with OSPF. IS-IS.108.B055. is an advanced link-state routing protocol that you can use in large environments to route IP.0 ip router isis ! interface Serial0 shutdown ! interface Serial1 ip address 131. LSP Checksum of the entire LSP packet. in seconds.127 - .255. Detects whether the area is partition-repair capable.255.00-00 0x00000007 00E0. Example 4-42 displays R4's full working configuration.2. ATT Attach bit.255.B055. 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. Field Descriptions of show isis database Command Field Description LSPID The link-state protocol data unit (PDU) ID. 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. P P bit.00-00 0x00000007 00E0. as OSPF.255.00-00 0x0000000B Table 4-6 summarizes the output in Example 4-41.28CA. here are the full working configurations of the three routers in this IS-IS topology.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 R4.1 255.108.28CA.B055.255.01-00 0x00000002 IS-IS Level-2 Link State Database: LSPID LSP Seq Num R4. This indicates that the router is also a Level 2 router and it can reach other areas.00-00 * 0x00000007 R8.17 255.252 ip router isis clockrate 128000! interface Serial3 .108.00-00 0x0000000A 00E0. 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.255.255.255.

d7bd.4.CCNP Practical Studies: Routing ip address 141.255.1 255.2 255.255. 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 141.5 255.128 - .00 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-43 displays R8's full working configuration.64fc.108.255.108.252 ip router isis clockrate 128000 ! router isis net 00.0 ip router isis ! interface Serial0 ip address 141.255.108.1 255.255.255.00 line con 0 line 1 8 line aux 0 line vty 0 4 ! end Example 4-44 displays R9's full working configuration.255.255.3.0050.255.5460.252 ip router isis ! interface Serial1 ip address 141. Example 4-44 R9's Full Configuration hostname R9 ! clns routing ! interface Ethernet0 ip address 141.255.108.108.0001.255.1 255.255.255.00b0.98e8.252 ip router isis ! router isis net 00.10 255.108.255.255.252 ip router isis .255.0001.0 ip router isis ! interface Serial0 ip address 141.

255. 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 . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. Sending 5. Example 4-45 Sample Ping Requests from R4 R4#ping 141.108. Table 4-7 summarizes the most common IS-IS configuration and show commands.b055. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.129 - . round-trip min/avg/max = 28/46/104 ms R4# The IS-IS IOS command set is comprehensive.255. Sending 5.255.4. Sending 5.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 141.1. Table 4-7.3.108.00e0.1 Type escape sequence to abort.108.9 Type escape sequence to abort.4.108.28ca.9.0001. round-trip min/avg/max = 28/36/60 ms R4#ping 141.108. Sending 5.255.108.CCNP Practical Studies: Routing ! interface Serial1 ip address 141. round-trip min/avg/max = 16/17/20 ms R4#ping 141. round-trip min/avg/max = 16/16/20 ms R4#ping 141.10.3. 100-byte ICMP Echos to 141. 100-byte ICMP Echos to 141.255.255.1. 100-byte ICMP Echos to 141.108.10 Type escape sequence to abort.9 255.00 ! 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. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.252 ip router isis clockrate 128000 ! router isis net 00.

For OSPF.108. Figure 4-7.15. 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 .0 to 131. Figure 4-7 displays the OSPF network and IS-IS.108. you must configure a metric that is used within the IP dynamic routing protocol.255.CCNP Practical Studies: Routing Scenario 4-4: OSPF and Integrated IS-IS Redistribution In this scenario. you must define a cost metric. OSPF and Integrated IS-IS Network Topology Because R4 is within both the OSPF and IS-IS domain.2. for example. you integrate the IS-IS network you configured in Scenario 4-3 with an OSPF network. The ? tool is used to bring up the available options. To configure redistribution between any IP routing protocols. you can configure redistribution between OSPF and IS-IS.130 - . 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. Router R1 has loopbacks ranging from 131.

Ethernet0 i L1 141. you must define the IS-IS router type. (The router type along with IS-IS metric is between 0–63. Serial1 C 141. Serial1 131.108. Serial0 i L1 141. L1 . Serial1 i L2 131.0/30 [115/20] via 141.0/24 [115/30] via 141.connected. you configure L2 routes.3.255.IS-IS level-2.0.2.108. 2 masks C 141.0/24 is subnetted.108. L2.255.108. and L1/2.0/24 is directly connected.9.4/30 is directly connected.108.255.0 [115/30] via 141.255. Any value between 0 and 63 is a valid metric. L2 .255. ia .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.0/24 [115/20] via 141.IS-IS inter area 141. 6 subnets. 15 subnets i L2 131. you need to define the OSPF process ID from which the OSPF routes will be injected. Serial1 i L2 131.131 - .108. the chosen value of 10 is used.9.108.0 [115/30] via 141.14.108.9.9.) Three options are available when you are redistributing from OSPF to IS-IS: L1.9.108.108.108.IS-IS level-1. View the IP routing table inside in IS-IS network.8/30 is directly connected.108.108.15. In this scenario.4. Finally. Example 4-47 R8's IP Routing Table R8#show ip route Codes: C . Serial1 i L1 141.255. i .255. Example 4-47 displays the IP routing table on R8.255.108.0.0/16 is variably subnetted. Serial1 .108. Serial1 C 141. you need to define an IS-IS metric.9.255.108. Because OSPF uses cost as the metric for making routing decisions and IS-IS uses L1 or L2. The OSPF process ID is 1.0 [115/30] via 141.IS-IS.108.254.

1.2.255.255.255.108.8.2.108.108.108.255.11.0 [115/20] via 141.0 [115/20] via 141.9 (R9) and R9 sends the request to R4.108.108. Ethernet0 131. Serial0 i L2 131.108.0 [115/20] via 141. Serial1 131. Serial0 C 141.0/24 [115/20] via 141.2. Serial0 i L2 131.255.108.3. which comes from the addition of the 10 used in redistribution and the two hop counts between R4 to R9 and R9 to R8.255.12.108.108. Serial0 i L2 131. Serial1 i L1 141.108.255.4/30 [115/50] via 141.IS-IS.108.108.11.0 [115/30] via 141.0 [115/20] via 141.9.2. and a metric of 30. Serial0 i L2 131.9.108.0 [115/20] via 141.255.1.255.108.108.5.108.255.1. Serial0 i L2 131.0 [115/20] via 141.4.108.108.255. Serial1 Example 4-47 displays the remote OSPF routes redistributed from the OSPF backbone on R1 into IS-IS as L2 routes.108. Serial1 131.3.0 [115/20] via 141.1.108.1.10. Serial0 i L2 131. Serial1 131.108.255.108.15.108.108.108.255.IS-IS level-2. Serial0 i L1 141.108.255.14.9. Serial1 C 141. L2 . Serial0 i L2 131.108. Serial0 [115/50] via 141.108.1.IS-IS level-1.8/30 is directly connected.0.108.108.0 [115/30] via 141. i .108.108.108.4.255.108.7.255.0/30 is directly connected.1.2. Serial1 131.0 [115/30] via 141.255.255.13. Serial0 i L2 131.0 [115/20] via 141.9.255.10. Try to ping the remote address. Serial1 131.108. Serial0 i L2 131.0 [115/30] via 141.9.0 [115/20] via 141.108.7. 2 masks C 141. Example 4-48 displays a sample ping request from R8 to the L2 IS-IS route 131.0 [115/20] via 141.108.255.108.0 [115/30] via 141.108.108. Sending 5.1.1 (R2's loopback address). Serial1 131.255.0 [115/30] via 141. Serial1 131.0 [115/30] via 141. Serial1 i L1 141.108.12.255.1. timeout is 2 seconds: .108.8.1.108.108.13.108. Serial0 i L2 131.9. Serial0 i L2 131. Serial0 i L2 131.10.108.9.132 - .4.255.0/24 is subnetted.108.108.0 [115/20] via 141.255.108. L1 . Example 4-48 Sample Ping Request to 131.1. * candidate default 141.108.connected.108.108.6.1.108. R8 has a routing entry for this network.255..108.255. 15 subnets i L2 131..0 [115/20] via 141.9.255.0/24 is directly connected.255.1.108.9.0/24 [115/20] via 141.0 [115/30] via 141.2. Serial1 131. Serial1 131.108.255.. Serial0 i L2 131.108.10.108.108. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.3.108.2.108.0 [115/20] via 141. The reason the ping request receives no replies is because R8 sends the request to the next hop address of 141.255..9.0 [115/20] via 141.0 [115/30] via 141. Serial1 131.108.1.1.108.0 [115/30] via 141.1.9. 6 subnets.108.9. Success rate is 0 percent (0/5) R8# The ping request receives no replies.255.1 from R8 R8#ping 131.1.9. Serial1 131.108.108.108.255.108.6.108.255.0.0/16 is variably subnetted.1.254.0 [115/30] via 141.108. Serial0 .5.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. Serial0 i L2 131.255.255.0 [115/30] via 141. Example 4-49 displays R9's IP routing table confirming the next hop address.9. Example 4-49 IP Routing Table on R9 R9#sh ip route Codes: C .0 [115/20] via 141.

100-byte ICMP Echos to 131. Sending 5.1 R4>ping 131. ping requests are replied to when R4 pings the address 131. round-trip min/avg/max = 1/2/4 ms R4> The last hop you need to look at is R1.CCNP Practical Studies: Routing Example 4-49 displays the next hop address of 141. . Now. R4 can ping the remote address as confirmed by Example 4-50.1 Type escape sequence to abort. Example 4-51 displays R1's OSPF routing table. Example 4-50 Sample Ping from R4 to 131.2.255.1 (R4).2.2.1. Remember that R1 is configured for OSPF only. 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 R1.108. and because R1 and R4 are maintaining a full OSPF adjacency and the next hop address is a directly connected LAN.108.133 - .108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.1.108.2.

254.108.8/30 [110/100] via 131. Once more. Ethernet0/0 .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.108.0.0.108. So far you have only configured one-way redistribution.0/16 is variably subnetted.255.108. 3 subnets. but this time. you must also advise the OSPF domain of the IS-IS routes. 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. Example 4-53 R1's OSPF Routing Table R1>sh ip route ospf 141.0/24 [110/100] via 131. Now. configure redistribution on R4.2. 00:00:00. which is required whenever redistribution is configured to a classless domain and a 30-bit mask on serial connections. 00:00:00.0 is subnetted using a Class C address. 2 masks O E2 141. Example 4-53 displays R1's OSPF routing table.2.254.108.0/24 [110/100] via 131.108. Ethernet0/0 O E2 141. 00:00:00. Example 4-52 displays the configuration options when redistributing from IS-IS to OSPF.134 - .108.2.3.254.108. Ethernet0/0 O E2 141. configure IS-IS to OSPF redistribution.4. view R1's IP routing table.

1. round-trip min/avg/max R8#ping 131. 2 masks O E2 141.108.4. round-trip min/avg/max R8#ping 131. round-trip min/avg/max R8#ping 131. 100-byte ICMP Echos to 131.8. Sending 5. 00:07:29.108. timeout is !!!!! Success rate is 100 percent (5/5).4. Sending 5.255.5.CCNP Practical Studies: Routing Three remote networks are present. you can redistribute routes with the appropriate metric and route type (1 or 2 in OSPF or L1/L2 in IS-IS). 100-byte ICMP Echos to 131.108. 00:07:39. 100-byte ICMP Echos to 131. timeout is !!!!! Success rate is 100 percent (5/5). Example 4-55 show ip route ospf Command on R1 R1>sh ip route ospf 141. round-trip min/avg/max R8#ping 131. but none of the directly connected links on R4 are present. round-trip min/avg/max R8#ping 131.1.7. Example 4-56 Sample Pings from R8 to R1 R8#ping 131.108. Ethernet0/0 O E1 141.1.108. 100-byte ICMP Echos to 131.2. 00:07:29.3. 00:07:29.1/24 through 131.2.108.0/24 [110/100] via 131. Example 4-54 displays the configuration of locally connected routes to be injected into IS-IS on R4.108.108. You can now provide connectivity between the two different routing domains.8/30 [110/100] via 131.108.10.108.108. Configure this and use type 1 OSPF routes this time.254.4.5. Ethernet0/0 You have seen the power of the command redistribute. Sending 5.2. Ethernet0/0 O E1 141.108.2. Sending 5. You also need to redistribute any locally connected routers on R4.108.2. Confirm connectivity by pinging from R8 to R1 loopback addresses 131.108.7.1/24.3.254.0/16 is variably subnetted.0/30 [110/110] via 131.1 Type escape sequence to abort. 00:07:39.108. Ethernet0/0 O E2 141.255.254.0/24 [110/100] via 131. timeout is !!!!! Success rate is 100 percent (5/5). timeout is !!!!! Success rate is 100 percent (5/5).108. Sending 5. 00:07:39.108.0.254.108.8.2.1 Type escape sequence to abort.2.255.1 Type escape sequence to abort.1. Sending 5. Ethernet0/0 O E2 141. timeout is !!!!! Success rate is 100 percent (5/5).2.3. timeout is !!!!! Success rate is 100 percent (5/5).135 - .108.254.1. as displayed in Example 4-56.1 Type escape sequence to abort.108.108.108.2.1 Type escape sequence to abort. 100-byte ICMP Echos to 131. 100-byte ICMP Echos to 131. By simply using keywords.1 Type escape sequence to abort.6.254.1. 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.1. 6 subnets.108. round-trip min/avg/max R8#ping 131. 100-byte ICMP Echos to 131.108.108.108. Ethernet0/0 O E1 141.0/24 [110/110] via 131.108.108.108. Sending 5.6. 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: .1 Type escape sequence to abort.2.4/30 [110/110] via 131.

8.0 [115/158] via 141.108.108.10. round-trip min/avg/max = 16/18/20 ms R8#ping 131.1 from R9 R9#trace 131.108.0 [115/158] via 141. Sending 5.2.108. Serial1 i L2 131. 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 131.10.136 - . Example 4-59 show ip route isis Command on R9 R9#sh ip route isis 141.108.108.9.108.108.10.1 1 141.108.108.255.0 [115/158] via 141. Serial1 i L2 131.108.255.108.10.108.4/30 [115/20] via 141.1/24.108.108.10.255. so the only path to the OSPF backbone is through R8.254.108.108.0 [115/158] via 141.0 [115/158] via 141.0/16 is variably subnetted.1 Type escape sequence to abort. Example 4-58 displays a sample trace when the primary path fails.2.0 [115/158] via 141.0 [115/158] via 141. Serial1 i L2 131.255. 2 masks i L1 141.108.4.2.13.255.10.10. 100-byte ICMP Echos to 131.108.10.10.15.108. 15 subnets i L2 131.255.12.10.0/24 [115/20] via 141.1. round-trip min/avg/max = 16/17/20 ms R8#ping 131.108. Serial1 i L2 131.255.108.255.0 [115/158] via 141.10.6 20 msec 16 msec 16 msec 3 131.108.1 Type escape sequence to abort. as displayed in Example 4-57.108.108.10.2.0/24 [115/30] via 141.1 Type escape sequence to abort. 100-byte ICMP Echos to 131.0.108. Tracing the route to 131.108.255.108.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).1 8 msec 8 msec 12 msec 2 131.3.255.2.2.1 1 141.0 [115/158] via 141.10.11.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Serial1 i L2 131.108. Serial1 i L2 131. 5 subnets. Serial1 i L2 131.255.10. Serial1 i L2 131.9. Example 4-57 Trace Route to 131.108. Sending 5.7.1 12 msec 8 msec * Assume the link between R9 and R4 fails.255. Example 4-59 displays R9's IS-IS routing table when the link failure to R4 occurs.108.10.10. Serial1 i L1 141.10. Serial1 i L2 131.9.5.108.0 [115/158] via 141.255.255.108.0 [115/158] via 141.2.254.1.254.108.0 [115/158] via 141.10 8 msec 8 msec 12 msec 2 141.1 Type escape sequence to abort.255.6. Serial1 i L2 131.108.108.255. Serial1 i L1 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.10.10. Serial1 131.0 [115/158] via 141.255.108.1 16 msec 16 msec * The new IP routing table on R9 contains a path to all OSPF routes through the Serial connection to R8.108.108. Serial1 .0.255.108.108.0/24 is subnetted.108.108.108.108.108. Serial1 i L2 131.108. Tracing the route to 131.108. Serial1 i L2 131.14. Example 4-58 Trace on R9 Through R8 R9# trace 131.255.

you should try to accomplish five basic goals with dynamic routing protocols: • • • • • Functionality— The network works. Keeping these calculations to a minimum means the CPU/memory requirements are also kept low. Any large network should be able to foresee new challenges before the network grinds to a halt. the maximum is 1000. the maximum is 350.0 [115/158] via 141. the network must always be functioning. The number of calculations any given router must perform given m LSAs is mlogm. When architecting a network.CCNP Practical Studies: Routing i L2 i L2 131. Manageability— This point refers to proactive management. Determine the number of routers in each area. The following are some general guidelines when designing a large OSPF network.3.255. 100 routers require 100log 100 or 100 x 2 = 200.10. the maximum is 60. Practical Exercise: OSPF and RIP Redistribution NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter. 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. cost drives most network designers. and Simon. By no means are these rules standard. Cost effectiveness— In reality. Serial1 Scenario 4-5: Recommendations for Designing OSPF Networks This scenario presents some of the design recommendations found in common literature. Adaptability— With ever-increasing new technologies.108.10. You must use only RIPv1 and OSPF as your IP routing . your network should cope with and embrace new features. 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.108. Implementing a hierarchical IP addressing scheme and performing summarization wherever possible are two key points in any large OSPF network. The number of areas per domain is 1. no matter what failure or scenario. Configure the edge router named Sydney for RIP and ensure IP connectivity among all four routers. OSPF is such a large topic that many books have been written about it.108. The minimum routers per single area is 20. 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. Configure the network in Figure 4-8 for OSPF between the three routers named SanFran. such as new acquisitions.2. Anything between 40–50 is an acceptable number. such as Voice over IP.0 [115/158] via 141. For example. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own. For a concise guide to OSPF and a more detailed guide. Mel. your initial topology or design must be able to cope with growth and new challenges. The IETF standards committee provides the following sample design guidelines: • • • TIP The minimum number of routers per domain is 20.255. You can manage and configure OSPF so that the preceding five criteria are fully supported.137 - . the better able you are to provide users the ability to work around network failures. The solution can be found at the end. Scalability— As the network grows in size. that is. The bigger your budget. Serial1 131.

(RIPv2 does). Sydney is running RIP only.255.0 no ip directed-broadcast . The following are the full working configurations of all four routers with the shaded portions highlighting critical configuration commands.1. Also.CCNP Practical Studies: Routing protocols. Example 4-60 displays the full working configuration of Router Sydney.108. 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.255. you must also provide summary addresses for all networks.1 255. 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.138 - . because you are using RIPv1. 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. Configure summarization wherever possible to minimize IP routing tables. 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. Ensure that a default route appears on all routers so users can connect to the Internet.

108.0 ! interface Serial0 shutdown ! interface Serial1 shutdown ! interface Serial2 ip address 141.1.252 clockrate 128000 ! .108.108.255. Simon is running OSPF and RIP.2.4 255.108.0 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..255..108.255.0) are assumed to be Class C.0. Because RIPv1 is classless and the subnet 141.255.255.0/24 is configured locally.1 255.255. Current configuration: ! version 12.255.255. You must always be careful when redistributing information from one routing domain into another.5 255.0.255.139 - . Simon advertises the non /24 subnets as Class C networks so the RIP domain (Sydney router) can inject them into the routing table.108. 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.1 255.108.CCNP Practical Studies: Routing ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown ! router rip network 141. Example 4-61 Full Working Configuration of Router Simon Building configuration.255.252 clockrate 128000 ! interface Serial3 ip address 141.1.128 ! interface Ethernet1 ip address 141.

255.108.108.108.6 255.108.255.0 255.108.108.3.255 area 0 ! line con 0 line 1 8 line aux 0 line vty 0 4 ! end .248 ! interface Serial0 ip address 141.255.0 summary-address 141.255.0 Null0 ip route 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 141.255.4. 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 0.0 redistribute connected subnets redistribute rip metric 10 subnets network 141.2.255.255.0.0 255.108.127 area 0 network 141.0 255.255.0.CCNP Practical Studies: Routing router ospf 1 summary-address 141.255.0 255.140 - .255.255.255.255.4.0 Null0 ! line con 0 line aux 0 line vty 0 4 ! end Example 4-62 displays the full working configuration of Router Mel.0.0.255.0 255.1 255.0.108.108.0 0.255.108.3.0 summary-address 141.252 ! interface Serial1 shutdown ! router ospf 1 network 141.0 summary-address 141.2.0 ! = ip route 141.255.255. Mel is running OSPF only.108.108.0 0.255.255.255.0.0.3.

108.4.108.2 255.0 [120/1] via 141.0/24 is subnetted. Example 4-64 Sydney IP Routing Table Sydney#show ip route Gateway of last resort is 141.4.108.1.1 255. Ethernet0/0 The answers to these question can be found in Appendix C. this default route is injected by using the default-information originate always command. answer the following questions relating to the preceding Practical Exercise on OSPF/RIP routing.255.3.0.0 R C R R R R* 141.0/0 [120/2] via 141.108.255.108.2.0.2.240 ! interface Serial0 ip address 141.0 Serial1 ! line con 0 line aux 0 line vty 0 4 ! end Review Questions Based on the following IP routing table.255.4.0.4.0 0.0 0. 00:00:05.CCNP Practical Studies: Routing Example 4-63 displays the full working configuration of Router SanFran. Ethernet0/0 141.108. Example 4-63 Full Working Configuration of Router SanFran hostname SanFran ! no ip domain-lookup ! interface Ethernet0 ip address 141.252 ! interface Serial1 shutdown ! router ospf 1 network 141. which is the Internet connection.108.0.255 area 0 default-information originate always ! ip route 0. 5 subnets 141.1.0. "Answers to Review Questions. Ethernet0/0 141.4. Ethernet0/0 141.0 [120/2] via 141.108.1.0/24 take? .255.141 - .0. Example 4-64 displays the IP routing table of Router Sydney. Ethernet0/0 141.255.255.0.0 is directly connected.0 [120/1] via 141.0/24? What path does the packet sent to the IP subnet 171.0. Under the routing OSPF process.108.108. 00:00:05." 1: 2: 3: What does the routing entry shaded in Example 4-64 display? In Example 4-64.0. 00:00:05.1. 00:00:05.0.0.108.1. Ethernet0/0 0.108.1.4. 00:00:05.108.4 to network 0.4.108.0 [120/2] via 141.108.1. what is the hop count or metric to the remote network 141.255.255. SanFran has a default static route pointing to Serial 1.108.108.

interface loopback Creates a loopback interface. The capabilities of link-state routing protocols are demonstrated in this chapter along with some challenging scenarios. ip subnet-zero Enables you to use subnet zero on a Cisco router. Table 4-8. interface S0/0. 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. Mel. Summary of IOS Commands Used in This Chapter Command show ip route router ospf process id network mask Purpose Displays IP routing tables. summary network mask Enables summarization of external routes in OSPF. Enables OSPF routing.142 - . Displays OSPF virtual links. interface Ethernet0/0. 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. 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. Displays the OSPF process and details. You can have more than one OSPF running. Displays OSPF neighbors. Displays a router's topological database.Enables a more specific route on loopback interfaces. All hardware interfaces are shut down by default. . to-point interface ethernet In configuration mode. no ip domain-lookup Disables automatic DNS lookup. redistribute Redistributes from one IP routing protocol to another. hostname name Configures a name on a router. for example. mod/num interface serial mod/num In configuration mode. Table 4-8 summarizes the OSPF commands used in this chapter. Although only one solution per scenario is presented. The process ID is local to the router. enables you modify the Ethernet. number ip ospf network point. Enables network advertisements from a particular interface and also the routing of the same interface through OSPF.CCNP Practical Studies: Routing 4: 5: 6: 7: 8: What type of OSPF routers are the Routers Simon. for example. area area id range mask Enables interarea summarization in OSPF. ip ospf name-lookup Enables OSPF DNS lookup. [no] shutdown Enables or disables an interface. and SanFran. such as OSPF process ID and router ID. enables you to modify serial interface parameters by module and interface number. 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. if any.

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

108. Example 5-1 R1 EIGRP Configuration R1(config)#router eigrp 1 R1(config-router)#network 131. by default.144 - . the AS needs to be the same. Example 5-1 displays the configuration of EIGRP on R1. view the configuration after you enter the network 131. 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.108. Figure 5-1 displays a simple two-router EIGRP network in Autonomous System 1.1.0 command. a Class B network. Term Discovering and Maintaining Routes in EIGRP EIGRP uses hello packets to discover new neighboring routes.108. 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. "Routing Principles. 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. you must first enable EIGRP with the command router eigrp autonomous system while in global configuration mode. and after it finds a neighbor. Two-Router EIGRP Network To start EIGRP on a Cisco router. the Cisco routers advertise all IP network entries.0 Notice that 131.1. Figure 5-1. This section shows you how to enable EIGRP on both routers in Figure 5-1." This chapter covers EIGRP in greater detail using a simple two-router topology.0 is. . Next.1.CCNP Practical Studies: Routing Table 5-1. For routers sharing the same IP domain.

0. use the show ip eigrp neighbors command.0 to 131. A topology table is created from updates received from all EIGRP neighbors. the network 131. 131. which are covered in this chapter.com/univercd/home/home.1. you use hello packets to ensure that both routers are active and running.2. Example 5-4 EIGRP Neighbors on R1 R1#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 0 131.108. The holdtime indicates the length of time. .. Any updates or changes are sent immediately and both routers maintain topology tables.1 0.108. Q Cnt indicates the number of update.145 - . For example.0..0. To view EIGRP neighbor relations between two Cisco routers.108.4(T) supports the use of the wildcard mask.1.2. you can configure the Class B network.0 . R1 discovered a remote EIGRP neighbor through the Ethernet interface (displayed as Et0/0). query.108. The EIGRP topology table is used to maintain IP routing entries in the IP routing table.0. in seconds.0/24.108.0. 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. Example 5-5 displays the EIGRP topology table on R1 using the IOS show ip eigrp topology command.0.CCNP Practical Studies: Routing Example 5-2 displays the running configuration of R1.. router eigrp 1 network 131. This URL can be accessed for free and contains every command available on Cisco routers and switches.1. To maintain EIGRP between R1 and R2.0.15.108. Example 5-2 R1 EIGRP Configuration . or reply packet that was received from this neighbor. Example 5-3 displays the same EIGRP configuration on R2. which works as the OSPF wildcard mask does. Example 5-4 displays the EIGRP neighbors on R1.. For example. query. Consult the latest command reference on the Cisco Web site at www.0. EIGRP needs only the major network boundary when using the network command. Sequence number (SEQ NUM) is the last sequenced number used in an update. that the Cisco IOS Software waits to hear from the peer before declaring it down. truncated for clarity.0 R2 has a number of loopbacks to populate the IP routing tables ranging from 131.108.cisco.1. Retransmission timeout (RTO) indicates the amount of time the IOS software waits before resending a packet from the local retransmission queue.0 command places the Ethernet interface of R1 in EIGRP 1. EIGRP supports summarization and VLSM. NOTE IOS version 12.2 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 131.108.108. Example 5-3 R2 EIGRP Configuration R2(config)#router eigrp 1 R2(config-router)#network 131. or reply packets that the IOS software is waiting to send to the neighbor. The AS is set to 1 on both routers to enable both routers to share IP routing information.htm for more information. and the outbound interface the EIGRP neighbor (in this case R2) was discovered. instead of entering the address 131.

108.2 (409600/128256).108.0/24. .108. Ethernet0/0 P 131. Ethernet0/0 P 131. Ethernet0/0 P 131.0/24.1.2 (409600/128256).108. Also. DUAL is an algorithm developed by Cisco that performs the calculations on the topology table. Entries in this topology table can be updated by changes in the network or interface failures.108. DUAL is based on detecting a network change within a finite amount of time.108. 1 successors.108. if a network failure does occur.0/24.108.2 (409600/128256).11. FD is 409600 via 131.108. which increases convergence time. Because the algorithm is calculated almost instantaneously. 1 successors.15.108. FD is 409600 via 131.108.108.2 (409600/128256).108.0/24.Passive.0/24.108.1.Update. Any changes sent among neighboring routers are sent reliably (using sequence packets and ensuring packet delivery).108. Ethernet0/0 P 131. 1 successors. 1 successors.0/24. 1 successors.108.1.108. FD is 409600 via 131.1.1.5.108.7.2 (409600/128256). 1 successors. Table 5-2 summarizes the contents of the topology table in Example 5-5.0/24. 1 successors. FD is 409600 via 131.8.2 (409600/128256).2 (409600/128256). Ethernet0/0 P 131. Ethernet0/0 Example 5-5 displays a wealth of information about all the remote entries EIGRP discovers. FD is 409600 via 131.2 (409600/128256).6.1.108.146 - .1.0/24.1. FD is 409600 via 131.14.108. Ethernet0/0 P 131. 1 successors. Ethernet0/0 P 131. 1 successors.1.0/24. notice the number of different IOS show commands possible. and with a finite time. Ethernet0/0 P 131. Ethernet0/0 P 131. FD is 409600 via 131.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 .2 (409600/128256). Ethernet0/0 P 131. FD is 409600 via 131.108. Q . FD is 409600 via 131.0/24. updates are sent and received quickly.Reply status P 131.108. Ethernet0/0 P 131.Query. 1 successors. 1 successors.2 (409600/128256). Ethernet0/0 P 131. For example. R .0/24.108. 1 successors.0/24.1.1.9.108.3.1. Ethernet0/0 P 131. U . the topology table receives an update to recalculate the path to the remote entry using the algorithm called Diffusing Update Algorithm (DUAL).108. in order.4. A . r .108.108.2 (409600/128256).1. 1 successors.2 (409600/128256).13.1.1. FD is 409600 via 131.0/24. FD is 409600 via 131. FD is 409600 via 131. FD is 281600 via Connected. FD is 409600 via 131.12.0/24.2.108.108.10. 1 successors. 1 successors.0/24.2 (409600/128256).2 (409600/128256).Reply. Ethernet0/0 P 131.Active. FD is 409600 via 131.

(Active means the remote entry is being recalculated.8.0 [90/409600] via 131.108. hence only one successor.108. Feasible distance. 00:31:02. No Enhanced IGRP computations are being performed for this destination. 00:31:02. Replies State Via (409600/128256) Ethernet0/0 Now that R1 has established a relationship with R2. Ethernet0/0 D 131.108.0/24 and so on successors FD Definition State of this topology table entry. Enhanced IGRP computations are being performed for this destination.EIGRP external 131.5. 00:31:02.0 [90/409600] via 131.0 [90/409600] via 131. Ethernet0/0 D 131.108. Interface from which this information was learned. Ethernet0/0 D 131.108.108.108. This information appears only when the destination is active.108.2. Exact enhanced IGRP state that this destination is in.108.2. The first N of these entries. Reply status.108. 00:31:02. 00:31:02.2.0 [90/409600] via 131.0 [90/409600] via 131.12.255.0 [90/409600] via 131.4.108. Indicates that a reply packet was sent to this destination. This value is used in the feasibility condition check.108.1. This information appears only when the destination is in active state.108.7.6.108.108. Indicates that a query packet was sent to this destination.108.CCNP Practical Studies: Routing Table 5-2. 00:31:02.2.2. Example 5-7 displays R1's new topology table. 00:31:02.1.1.108.0 [90/409600] via 131.1.2. you can expect to see remote IP routing entries.0/24 is subnetted.108. Ethernet0/0 If you simulate a network failure by shutting down the network 131. Active. EX .1. Ethernet0/0 D 131.2.1. Query. 00:31:02. It can be the number 0.108. 00:31:04. 00:31:02.15.2. by maintaining a topology table.147 - . Passive.0 [90/409600] via 131. Ethernet0/0 C 131.1.1. Number of successors.0 on R2. Ethernet0/0 D 131. These indicate the destination IP network number and mask.108. it does not have to send a query for that destination. where N is the number of successors.0 [90/409600] via 131.1.2.108.) Example 5-6 displays R1's IP routing table.9. Ethernet0/0 D 131. .2.0 [90/409600] via 131.108.108. R1 has only one path. R1's next hop address is 131.108.0 is directly connected. Ethernet0/0 D 131. The first number is the Enhanced IGRP metric that represents the cost to the destination.108. EIGRP Topology Table Definitions Term Codes P A U Q R r 131. Number of replies that are still outstanding (have not been received) with respect to this destination.108.0 [90/409600] via 131.0 [90/409600] via 131. the feasibility condition is met. Indicates that an update packet was sent to this destination. 00:31:02.11.1.2. Flag that is set after the software has sent a query and is waiting for a reply.13.108. 2. Update. The second number is the Enhanced IGRP metric that this peer advertises.1. Ethernet0/0 D 131. 00:31:02.108.10.1. or 3. 00:31:02. 1.108. are the current successors. with all entries in a passive state. Reply. and that path is a feasible successor.2. 15 subnets D 131. Ethernet0/0 D 131.0. Ethernet0/0 D 131.2.108.1.0.108. Example 5-6 R1's IP Routing Table R1#show ip route Codes: D .1. This number corresponds to the number of next hops in the IP routing table.1.1.0 [90/409600] via 131.EIGRP.14.2. IP address of the peer that tells the software about this destination. Ethernet0/0 D 131.0 [90/409600] via 131.15. The remaining entries on the list are feasible successors. 00:31:02.2. Ethernet0/0 D 131.3.255.108. If the neighbor's reported distance (the metric after the slash) is less than the feasible distance.2.108. Ethernet0/0 D 131. in this case 255.15. After the software determines it has a feasible successor.

0/24. Ethernet0/0 P 131.108.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. Ethernet0/0 P 131. 1 successors. 1 successors.108. 1 successors. 1 successors.1. FD is 409600 via 131. 1 successors.1. FD is 409600 via 131.108. For remote entries with multiple routes. FD is 409600 via 131.108. FD is 409600 via 131. FD is 409600 via 131.108. 1 successors. you can discover the number of paths available and why EIGRP chooses a certain path. To demonstrate this.4. Ethernet0/0 P 131.0/24.0/24.1.0/24. EIGRP maintains IP routes by using DUAL and maintaining an EIGRP topology table.2 (409600/128256).6.108. Ethernet0/0 P 131. FD is 281600 via Connected. so by simply viewing the topology table.108.0/24.108.2 (409600/128256).2.2 (409600/128256).1. Ethernet0/0 P 131. FD is 409600 via 131. all updates contain an entry for the subnet mask.108. Example 5-8 displays R1's topology table after the networks on R2 have been changed.2 (409600/128256).1. 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).148 - . .108. and. 1 successors.12.11.2 (409600/128256).108.108.2 (409600/128256).108.0/24.0/24. 1 successors.3.1. 1 successors. Ethernet0/0 Example 5-7 does not display the remote entry 131.0/24.1.0/24.2 (409600/128256).2 (409600/128256). it is not present in the IP routing table.108.108.0/24. Ethernet0/0 P 131.108. 1 successors.108.10.2 (409600/128256).108.2 (409600/128256).5.1.8. FD is 409600 via 131. FD is 409600 via 131. The EIGRP routing algorithm always chooses the path to a remote destination with the lowest metric.108.1.108.108. Ethernet0/0 P 131. 1 successors. Ethernet0/0 P 131.1. EIGRP uses the feasible condition (FC) to determine the best path. FD is 409600 via 131.108. FD is 409600 via 131.1. FD is 409600 via 131.0/24.0/24.14.1. 1 successors.1.108. 1 successors.15. Ethernet0/0 P 131. FD is 409600 via 131.0/24.108. Ethernet0/0 P 131.2 (409600/128256). modify the IP networks on R2. 1 successors.2 (409600/128256).13. The topology table maintains all paths to remote networks. EIGRP supports the use of VLSM.108. FD is 409600 via 131.108. Ethernet0/0 P 131.0/24. Ethernet0/0 P 131. therefore.1.7.108.0/24.2 (409600/128256).9. Ethernet0/0 P 131.108.

2.2 (409600/128256). 1 successors.1.108. Ethernet0/0 D 131.108.108.0/26 [90/409600] via 131.108. 00:58:15.0.108.0/28 [90/409600] via 131.108. Example 5-9 R1's EIGRP Routing Table R1#show ip route eigrp 131. Ethernet0/0 P 131. 15 subnets. FD is 409600 via 131.2.108. FD is 409600 via 131.108.3.9.12.108. 00:02:22. Ethernet0/0 P 131.108. Ethernet0/0 P 131.1. Ethernet0/0 P 131. 00:02:32. Ethernet0/0 P 131.108.2 (409600/128256).1.2 (409600/128256).13.14.2. Ethernet0/0 Example 5-8 displays a range of non-Class C networks.2.0/26.1.0/30.108. Ethernet0/0 P 131.108.108.2 (409600/128256).6.1.108. 1 successors. Ethernet0/0 D 131. 1 successors. 00:02:35.1.0/27 [90/409600] via 131.108.108.2 (409600/128256).2 (409600/128256).108.5.0/28.0/25 [90/409600] via 131.0/30.8.108.7.8.1. 1 successors.108. 00:02:20.0/24.9. 00:20:15.0/29.1.5.11. FD is 409600 via 131.10. Ethernet0/0 P 131. 1 successors.1. FD is 409600 via 131.1.108. Ethernet0/0 D 131.2.11.1. FD is 409600 via 131. FD is 409600 via 131.108.108.108. Ethernet0/0 D 131.2.0/25.108.108.0/24. 7 masks D 131. Ethernet0/0 D 131.108.1. Ethernet0/0 D 131. FD is 281600 via Connected. 00:02:30.1.108.1.108. Ethernet0/0 D 131.1.108.108.108.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. 1 successors. 1 successors.0/29.2.108.0/30 [90/409600] via 131.14.0/27.0/27 [90/409600] via 131. Example 5-9 displays the new IP routing table for completeness.0/30 [90/409600] via 131.10.2.1.2. FD is 409600 via 131. 1 successors. FD is 409600 via 131. 1 successors.1. FD is 409600 via 131.12. Ethernet0/0 P 131.2.0/25 [90/409600] via 131. FD is 409600 via 131.1.2 (409600/128256). FD is 409600 via 131.4.108.108.108.108. Ethernet0/0 D 131. FD is 409600 via 131.0/25.2 (409600/128256).108. 1 successors.2.0/30.0/27.2.1. 00:02:37.108.108. 00:02:34.108. 1 successors. 1 successors. 00:02:27.108.2 (409600/128256). 1 successors. FD is 409600 via 131.108.2.2 (409600/128256).108. FD is 409600 via 131.0/24 [90/409600] via 131.1. 00:02:25. Ethernet0/0 P 131.108.2.1. 00:02:29.1.1.108.1. 00:02:39. 00:02:24. Ethernet0/0 D 131.108. demonstrating the powerful use of VLSM with EIGRP. Ethernet0/0 P 131.0/27.1.108.2 (409600/128256).2 (409600/128256). 1 successors.2.108.0/24.2 (409600/128256).0/16 is variably subnetted. Ethernet0/0 D 131.108.108.3. Ethernet0/0 P 131.108.1.7.4.0/30 [90/409600] via 131.0/27 [90/409600] via 131.108. Ethernet0/0 D 131. 1 successors.108.149 - . Ethernet0/0 D 131. Ethernet0/0 P 131.0/29 [90/409600] via 131.13. Ethernet0/0 P 131.6.1.1.2.2 (409600/128256).108.108. Ethernet0/0 .0/24 [90/409600] via 131.15.15. Ethernet0/0 D 131.1. Ethernet0/0 P 131.108.108.0/29 [90/409600] via 131.

15. The bandwidth command does not always have to reflect the actual bandwidth of the interface.255. Example 5-11 Summary on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip summary-address eigrp 1 131. First.15. EIGRP automatically summarizes at the major network boundaries.0 to 131.0–131.0 255.8. you must disable automatic summarization on R2. for example.108.108. even though the path might be over a slower wide-area network (WAN) link. Setting a variance value lets the Cisco IOS Software determine the feasibility of a potential route. Summarization in EIGRP can be configured on any router in the same AS.255–131.108. this is also configurable using the ip bandwidth-percent eigrp AS percent command. To manually summarize networks. Example 5-10 displays the disabling of automatic summarization on R2.15.108.255.150 - . To perform static summarization.108.248. you can apply the mask 255. The allocated bandwidth for EIGRP must be the same on each virtual circuit between two remote routers. so you must ensure that EIGRP packets or updates are sent over a nonbroadcast network.) EIGRP does not have any way of statically defined neighboring.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).8.248. you must disable this feature with the no auto-summary IOS command.108. . up to 50 percent of any link can be consumed by EIGRP.255–131. Example 5-11 displays the summary command completed on R2's link to R1. EIGRP aggregated traffic over all virtual circuits should not exceed the access line speed. on an interface level with the ip summary address eigrp autonomous system mask command.255. you must advertise the supernet. By default.8.8. The use of the bandwidth command should reflect the true speed of any interface.255 as displayed in Example 5-12. Example 5-10 Disabling Automatic Summarization on R2 R2(config)#router eigrp 1 R2(config-router)#no auto-summary Because the networks 131. under the routing process.108.8. Re-examine Figure 5-1 and summarize the networks 131. In fact. 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.15.108. 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. The multiplier times the local best metric for the destination must be greater than or equal to the metric through the next router. The IOS variance command provides another method for achieving unequal load balancing.0 are contiguous. EIGRP Route Summarization and Large IP Network Support EIGRP supports the use of summarization to conserve IP routing table size. The bandwidth command is used in EIGRP metric calculation and defines the amount of bandwidth. (By default.0 to incorporate the range of networks from 131.0 R1 should now have only one remote routing entry for the networks 131.255.

[90/409600] via 131.2.1.0/24 D 131. 00:01:13.0 or /24). the used-by date of EIGRP is fast approaching.0/21 D 131.108.5. .108.108.0/24 D 131.1. The serial links will use a two-host subnet to demonstrate the use of VLSM with EIGRP.1.1. 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.108. you can use several Cisco IOS enhancements.1. and the abilities to use good practice and define your end goal are important in any real-life design or solution.2.0/16 is D 131.3. 00:01:13. Scenario 5-1: Configuring EIGRP In this scenario.1.6.108.108. In the following five scenarios. There is no one right way to accomplish many of the tasks presented. such as the amount of routing information exchanged between routers. to fine-tune EIGRP.0.0/24 variably subnetted.108. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 To support large IP networks. [90/409600] via 131. 8 subnets. 00:01:14. and the number of alternative paths between routers. [90/409600] via 131.255.2.255. such as network summarization. Intermediate System-to-Intermediate System (IS-IS). you configure eight Cisco routers for IP routing using a Class B (/16) network 131. EIGRP can scale in a well-designed IP network. As with any legacy protocol.0/24 D 131.108. Open Shortest Path First (OSPF).108.108. especially in today's large IP-based network.7.8. Figure 5-2 displays a network with seven routers in AS1 and one remote router in AS2.0/24 D 131. the number of routers in your network. load balancing.0. the network diameter of your network (hop count in EIGRP is still 255).108. and reducing the load on WAN links with the bandwidth command.2. [90/409600] via 131. [90/409600] via 131. 00:01:13. and with proper configuration.CCNP Practical Studies: Routing Example 5-12 R1's EIGRP Routing Table R1#show ip route eigrp 131. it can be well-maintained.0/24 D 131. 2 masks [90/409600] via 131.108.108.1.2. 00:01:13.108.2.108. [90/409600] via 131. 00:01:13.4.0 with a Class C subnet mask (255. you configure and monitor some sample EIGRP networks and apply the knowledge you have gained. Assume the core backbone network resides on the Ethernet between R1 and R2.2. and Border Gateway Protocol (BGP) are far more common routing protocols. 00:01:13.2.151 - .108. Several factors can contribute to a poorly designed network.

108. issue the show ip eigrp interfaces command.0/24 131.128. Note the use of VLSM across the WAN Links. Example 5-13 displays enabling EIGRP on R1.1-35.0.255.0/24 131.0/24 IP Address Range Start by enabling EIGRP on all the routers in AS 1.108.108.108. To display the interface running EIGRP.108.CCNP Practical Studies: Routing Figure 5-2. 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 131.0.255.36.108.0/30 131.1/24 131.1/24 131.131.129.108. . The same configuration commands are applied to all routers in AS 1 because the same Class B network.1/24 131.0/24 131.0.108.255.2.108.1-33.0–131.1-31. Table 5-3. 131./24 131.0 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 131.108.130.152 - . EIGRP in AS 1 and AS 2 The IP address assignment for the WAN links is described in Table 5-3.108. IP Address Assignments Router R1 R2 R3 R4 R5 R6 R7 R8 WAN links LAN link 131.1-15.32.1.16.108. is in use.0.0/24 168.34.1.108.

153 - . R1 has established a neighbor relationship to R2 through Ethernet 0/0 and R3 through S0/0. In other words. display the neighbors on R1 by using the show ip eigrp neighbors command on R1.108.2) and R3 (131. Example 5-16 displays R1's EIGRP IP routing table. 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 13.108. namely R2 (131. Next.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.CCNP Practical Studies: Routing Example 5-14 displays the interfaces running EIGRP on 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. Example 5-15 displays the sample output taken from R1. .2). note that you have EIGRP neighbors through E0/0 and S0/0.1.108.108. Also.1.255.2 131.

Ethernet0/0 D 131.0/24 [90/409600] via 131.24.2.20.25. Serial0/0 D 131.0/24 [90/409600] via 131.108.0/24 [90/409600] via 131. 00:04:16.0/24 [90/409600] via 131.1.108.2. 00:04:15.108. Serial0/0 D 131.1.108.2.21.2. 00:04:15.108.131.0/24 [90/409600] via 131.2.0). Ethernet0/0 D 131.2.23.0/24 [90/409600] via 131. Example 5-18 EIGRP in AS 2 on R8 R8(config)#router eigrp 2 R8(config-router)#network 168.CCNP Practical Studies: Routing Example 5-16 show ip route eigrp on R1 R1#show ip route eigrp 131.36.108. Ethernet0/0 D 131.108. Serial0/0 D 131. Ethernet0/0 D 131.108.31. 00:04:15.255.0/24 [90/409600] via 131.108.255.108.0. 00:04:16. Ethernet0/0 D 131.255.255. 00:00:10.108.108.0.1.108.1.108.20/30 [90/21529600] via 131. Example 5-17 EIGRP in AS 2 on R4 R4(config)#router eigrp 2 R4(config-router)#network 168.255. Ethernet0/0 D 131.108.1.108.2.108.29.1.108.108. 00:04:15. 00:04:15.2.131.1.108.0. Serial0/0 [90/21555200] via 131.0).108.2.2. Serial0/0 D 131.108. 00:04:14.108.1.1.2.0 You should expect to see a neighbor between R4 and R8.2. Ethernet0/0 D 131.2.255.16/30 [90/21529600] via 131.2.108. 00:04:16.0/16 is variably subnetted.108.108.1.0/24 [90/21529600] via 131.1.22. Serial0/0 D 131. 00:00:10.4/30 [90/20537600] via 131. R4 resides in two autonomous systems: 1 and 2.108.255.108. 00:04:15. 00:04:15.108.0/30.1.131.108.2. 00:04:15.255.2.2. 00:04:16. Ethernet0/0 D 131.108. Ethernet0/0 D 131.0/24 [90/21529600] via 131.2.2. 00:04:14.108. Ethernet0/0 D 131. .108.108.0 Example 5-18 displays the EIGRP configuration on R8 in AS 2 (network 168.108. 00:00:15.108.1.130. 00:04:15.1.16.108.108.1. 00:04:14.0.108.2.131.108. configure EIGRP on R4 and R8 in AS 2.108.17.0/24 [90/409600] via 131.26.18. The serial link between R4 and R8 contains the network 168. Serial0/0 [90/21529600] via 131.255.0/24 [90/409600] via 131.108. 00:04:15.28.19. 41 subnets.108.0/24 [90/21555200] via 131.255.12/30 [90/21504000] via 131.0/24 [90/409600] via 131.129.255.108.8/30 [90/21504000] via 131. 2 masks D 131.2.0/24 [90/409600] via 131. Ethernet0/0 D 131.128.2.2. Example 5-19 displays the EIGRP neighbors on R4. Example 5-17 displays the EIGRP configuration on R4 in AS 2 (network 168.0/24 [90/409600] via 131.2. Ethernet0/0 D 131.1.1.2.0/24 [90/409600] via 131.2.255. 00:04:14.108. 00:04:16.108. Serial0/0 D 131. 00:04:16.0/24 [90/409600] via 131.0/24 [90/409600] via 131. Ethernet0/0 D 131. R1 has no path to the remote network on R8 in EIGRP AS 2.108.27.1. Ethernet0/0 D 131. 00:04:15.108.1. Ethernet0/0 D 131.0/24 [90/409600] via 131.2.0. 00:04:15.1. 00:00:15.2.154 - . Next. Ethernet0/0 D 131. 00:04:15.255.108.108.2.108. Ethernet0/0 [90/21529600] via 131.0/24 [90/20537600] via 131.30. Ethernet0/0 R1 has a dual path to three remote networks because the composite metric is the same. 00:04:15.108. Ethernet0/0 D 131. Ethernet0/0 D 131.108.108.131.

3 Et0 IP-EIGRP neighbors for process 2 H Address Interface 0 168.131.2 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 2.2.131. 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.0/24 is directly connected.131. Serial0 C 168. 2 subnets. Example 5-20 displays the IP routing table on R8. R4 must provide two-way redistribution.36. R4 must be configured for redistribution because EIGRP does not automatically redistribute among different autonomous systems.2. Ethernet0 R8 has no remote EIGRP entries because R4 is not redistributing IP networks from EIGRP AS 1 into 2.131.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. and ensure connectivity to the rest of the network. 2 masks C 168. 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.) If the routers in AS 1 want to send data to AS 2.1.108. The ? tool is used here to highlight the parameters the Cisco IOS requires. 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 . R4 has established EIGRP neighbors with routers in AS 1 and AS 2. Example 5-20 show ip route neighbors on R8 R8#show ip route 168.5 Se0 1 131. Route maps or distributed lists should always be applied to ensure routing loops do not occur. Example 5-21 displays the configuration of two-way redistribution between AS 1 and 2.108.155 - .0/16 is variably subnetted.255.18 Se1 0 131.0. (EIGRP and IGRP automatic redistribution occurs only if the AS is the same. Display the IP routing table on R8.108.255. Hence.0/30 is directly connected.

Serial0 D EX 131.108.131.30.0/24 [170/26112000] via 168.0/30 is directly connected.2.2.27. Serial0 D EX 131.108.108.2. Serial0 D EX 131.108.1. 00:03:00.20.1. 00:03:00.108.131.1.131.131.7. 00:02:59.6.1.108.2.131.2.2.10.108.2.108. 00:02:59.0.13.18. 00:02:59.1.1.1.0. 00:02:59.16.1. Serial0 D EX 131.108.108. Serial0 D EX 131.2.0/24 [170/26112000] via 168.131.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. Ethernet0 131. 00:02:58.1.2.3.255.255.108.0/24 [170/26112000] via 168.255.0/16 is variably subnetted.131. Example 5-22 show ip route Command on R8 R8#show ip route Codes: C .1.131. Serial0 D EX 131.29.2. 00:02:58. 00:02:58.131.1.36.108.131.9.2.2.21.0/24 [170/26112000] via 168.108.131.131.0/24 [170/26112000] via 168. 00:03:00.1.131. Serial0 D EX 131.2. 00:02:59.131.4. Serial0 D EX 131.2.131.2.23.2.156 - .2. 2 masks C 168.131.2.5.108.2.EIGRP external 168.1.2.0/24 [170/26112000] via 168. Serial0 D EX 131. Serial0 D EX 131.131.1.131.0/24 [170/26112000] via 168.131.16/30 [170/26112000] via 168.131. 00:02:59.131. Serial0 D EX 131. 00:02:57. 00:02:58.0/24 [170/26112000] via 168. 00:02:57.131.131.131.108.31. 00:03:00.1. Serial0 D EX 131. Serial0 D EX 131.1.1.1.2.131. 00:02:58.1.connected.108. 00:02:59.108. 00:02:58.131.24.1. 00:02:57.0/24 [170/26112000] via 168.2.131. 00:02:58.0/24 [170/26112000] via 168. Serial0 D EX 131.1. 00:02:59. EX .131. Serial0 D EX 131.108.0/24 [170/26112000] via 168.108.0/24 [170/26112000] via 168. 00:02:58. 00:02:59.0/24 [170/26112000] via 168. Serial0 D EX 131. 00:02:58. Serial0 .0/24 is directly connected.108.108.1. 00:02:59. 00:02:58. 00:02:59.EIGRP.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168.255.2. Serial0 D EX 131.131.28.2.0/24 [170/26112000] via 168.1.0/24 [170/26112000] via 168.0/24 [170/26112000] via 168. Serial0 C 168.25.1.0/24 [170/26112000] via 168.0/16 [170/26112000] via 168. Example 5-22 displays R8's IP routing table. 00:02:59.0/24 [170/26112000] via 168.1. you can expect to see R8 with IP routing information from AS 1. 00:03:00.1. Serial0 D EX 131.12.131.2.108. Serial0 D EX 131.108.8.2.1.2.108.1.0/24 [170/26112000] via 168.2.108.131.4/30 [170/26112000] via 168.131.108. D . 00:02:58. Serial0 D EX 131.2.0/24 [170/26112000] via 168.15.1.0/24 [170/26112000] via 168.108.0/24 [170/26112000] via 168. Serial0 D EX 131.2. Serial0 D EX 131.1. 00:03:00.1.11. 2 subnets.1.1.0/24 [170/26112000] via 168.2.131.131.17.1. 00:02:58.131.108. Serial0 D EX 131. 00:02:58.0/24 [170/26112000] via 168.129.108.108.130. Serial0 D EX 131.1.19.1.2.2. Serial0 D EX 131.0/24 [170/26112000] via 168. 00:02:58.1. Serial0 D EX 131. Serial0 D EX 131.108.1.0/16 is variably subnetted.108.22. Serial0 D EX 131. Serial0 D EX 131.131.12/30 [170/26112000] via 168. 41 subnets.26.108.2.1. 00:03:00.1.1.0/24 [170/26112000] via 168.128. Serial0 D EX 131. Serial0 D EX 131.2.108.131.1.0/24 [170/26112000] via 168.108.131.2.108. 00:03:00.108.0/24 [170/26112000] via 168. Serial0 D EX 131.131. 00:02:59.108. 00:02:58.108.255. Serial0 D EX 131.131. Serial0 D EX 131.131. 00:02:59.14.2.2.131. Serial0 D EX 131.131.108.108. Serial0 D EX 131.0/24 [170/26112000] via 168. 3 masks D EX 131.2. 00:02:59.0/24 [170/26112000] via 168.108.2.0/30 [170/26112000] via 168.0/24 [170/26112000] via 168.131. Serial0 D EX 131. Serial0 D EX 131.2.0/24 [170/26112000] via 168.0. Serial0 D EX 131. Serial0 D EX 131.2.0/24 [170/26112000] via 168.8/30 [170/26112000] via 168.2.1.

255.0 ! interface Loopback7 ip address 131.108.255.0 ! interface Loopback9 ip address 131.255.255.0 ! interface Loopback12 ip address 131.108.1 255.255.108.3. 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. Example 5-23 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.255.108.108. such as the bandwidth statement used to match the wire speed between routers.0 ! interface Loopback3 ip address 131.255.255.157 - .255.CCNP Practical Studies: Routing R8 has an expanded IP routing table.12. Take particular note of the shaded sections.255.255.108.1 255.255. By default.255.108.255.1 255.108.255.0 ! interface Loopback10 ip address 131.108.255. Notice that all the networks from AS 1 are tagged as D EX.108.1 255.9.1 255.108.255.13.255.0 ! interface Loopback4 ip address 131. Before you configure EIGRP to summarize wherever possible in Figure 5-2.0 ! interface Loopback2 ip address 131.108.1 255.4.1 255.255. and the AD distance is 170 (or less trusted than Internal EIGRP set at 90).0 ! interface Loopback8 ip address 131.5.255.14.1 255.255.0 ! interface Loopback5 ip address 131.108.11.0 ! interface Loopback11 ip address 131.0 ! interface Ethernet0/0 .255. or external EIGRP.1 255.0 ! interface Loopback13 ip address 131.8.255.7.255.10.1 255.255.255.1 255.6.0 ! interface Loopback6 ip address 131.0 ! interface Loopback1 ip address 131.1 255. here are the full working configurations of all eight Cisco routers running EIGRP. Cisco IOS routers set the bandwidth to 1544 kbps. Example 5-23 displays R1's full working configuration.15.108.255.255.2.1 255.1 255.

0 255.0 ! line con 0 line aux 0 line vty 0 4 ! end Example 5-24 displays R2's full working configuration.1 ! interface Loopback2 ip address 131.255.255.255.22.108.1 ! interface Loopback6 ip address 131.255.255.21.16.0 255.1 ! interface Loopback1 ip address 131.1 ! interface Loopback3 ip address 131.108.108.255.255.255.255.108.252 clockrate 128000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131.255.255.108.255.108.255.0 255.18.0 255.255.20.23.0 ! interface Serial0/0 bandwidth 128 ip address 131.108.108.0 255.0 255.255.255.1 ! interface Loopback7 ip address 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 131.108.255.1 255.17.0 255.255.1 ! interface Loopback5 ip address 131.19.108.0 255.255.1 ! interface Loopback8 ip address 131.0.255.108.108.255.255.24.1 255.1.158 - .0 .25.1 ! interface Loopback9 ip address 131.1 ! 255.255.255.1 ! interface Loopback4 ip address 131.108.0 255.CCNP Practical Studies: Routing ip address 131.255.

26.0 ! ip classless ! line con 0 line aux 0 line vty 0 4 end Example 5-25 displays R3's full working configuration.255.255.255.30.0 media-type 10BaseT ! interface Serial0 ip address 131.255.255.108.5 255.255.108.29.108.255.255.108.1 ! interface Loopback15 ip address 131.2 255.0 ! interface Serial1/0 bandwidth 128 ip address 131.108.159 - .108.0 ! interface Ethernet0/0 ip address 131.CCNP Practical Studies: Routing interface Loopback10 ip address 131.255.108.0 255.108.255.252 clockrate 128000 ! interface Serial1/1 shutdown router eigrp 1 network 131.255. Example 5-25 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.255.1.255.0.0 255.255.255.255.255.255.255.108.31.255.2 255.0 255.1 255.28.0 255.1 ! interface Loopback11 ip address 131.3 255.1 ! interface Loopback13 ip address 131.255.108.108.252 bandwidth 125 ! .1 ! interface Loopback16 ip address 131.36.1 ! interface Loopback14 ip address 131.0 255.27.255.

108.0 ! .36.108.252 bandwidth 125 clockrate 125000 ! interface Serial2 ip address 131.255.0 ! router eigrp 2 redistribute eigrp 1 metric 125 20000 255 1 1500 network 168.131.108.0.255.0. Example 5-26 R4's Full Working Configuration hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.255.4 255.255.131.17 255.252 clockrate 125000 ! router eigrp 1 redistribute eigrp 2 metric 125 20000 255 1 1500 network 131.13 255.0.255.255.255.0 ! interface Serial0 bandwidth 125 ip address 131.255.255.255.255.108.CCNP Practical Studies: Routing interface Serial1 ip address 131.255.252 ! interface Serial1 bandwidth 125 ip address 131.108.9 255.255.255. 1 and 2.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-26 displays R4's full working configuration.108.255.255.108.255. R4 is redistributing between the two EIGRP autonomous systems.252 bandwidth 125 clockrate 125000 ! interface Serial3 no ip address shutdown ! router eigrp 1 network 131.255.108.252 clockrate 125000 ! interface Serial2 bandwidth 125 ip address 168.6 255.255.160 - .1 255.1 255.252 clockrate 125000 ! interface Serial3 ip address 141.2.

252 ! interface Serial1 shutdown ! router eigrp 1 network 131.161 - .255.18 255.108.255.252 ! interface Serial1 shutdown ! router eigrp 1 network 131.108.1 255.255.255.10 255.0. . Example 5-27 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 131.108.255.CCNP Practical Studies: Routing line con 0 line aux 0 line vty 0 4 end Example 5-27 displays R5's full working configuration.255.255.108.0 ! line con 0 line aux 0 line vty 0 4! end Example 5-29 displays R7's full working configuration.128.0.108.0 ! interface Serial0 bandwidth 125 ip address 131. Example 5-28 R6's Full Working Configuration hostname R6 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 131.108.255.0 ! 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.255.129.1 255.255.

252 ! interface Serial1 shutdown ! router eigrp 1 network 131.2.252 ! interface Serial1 shutdown ! router eigrp 2 network 168.255.131.131.255.14 255. R8 is running EIGRP in AS 2 only.0 ! line con 0 line aux 0 line vty 0 4 ! end .0 ! interface Serial0 bandwidth 125 ip address 168. Example 5-30 R8's Full Working Configuration hostname R8 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 168.1 255.2 255.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 131.255.108.255.108.1.255.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-30 displays R8's full working configuration.162 - .108.0.131.255.130.0 ! interface Serial0 bandwidth 125 ip address 131.255.1 255.255.255.0.

128.130. Ethernet0 131.16/30 [90/21017600] via 131. Serial1 C 131.255.0/16 [170/25625600] via 131.4. Ethernet0 C 131.4/30 [90/21017600] via 131. Ethernet0 D EX 168.0.0 to 131.0/30 [170/25625600] via 131.108.108.108.0.255.0/16 is variably subnetted.1.0/16 is variably subnetted.129.4. 3 subnets.108.36.108. 40 subnets.36.14.255.0/24 [170/25625600] via 131. Serial2 D 131.8/30 is directly connected.108.131.108. Ethernet0 D EX 168. 11:17:46.108.255. Ethernet0 D 131.108.0/24 [90/21017600] via 131.108.4. 11:13:47. Serial0 D 131.108.31.163 - . R1 and R2 Connected Networks The networks ranging from 131. 10:54:34.CCNP Practical Studies: Routing Scenario 5-2: Summarization with EIGRP In this scenario. Figure 5-3 displays the connected routes being advertised by R1 and R2. 10:54:34.255.0/24 [90/21043200] via 131.108.108. Ethernet0 C 131. Serial1 . in other words. Example 5-31 displays the IP routing table on R3.108.0/30 is directly connected.0.36.4.108.1.131. 10:54:34.10.255. 3 masks D EX 168.4. 2 masks D 131.255.0/24 [90/21017600] via 131. 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. 31 subnets or IP routing entries populate the routing tables in AS 1 and AS 2.108. 11:17:46.12/30 is directly connected.2.108. Example 5-31 R3's IP Routing Table R3#show ip route 168. 11:13:41.108.4.255 reside on two routers. Figure 5-3.131.36.108. Serial2 D 131.131.36.36. 11:17:45.

11:17:47. Serial0 131.108.255.8.0/24 [90/21145600] via 131. Ethernet0 [90/21145600] via 131.108.108. Ethernet0 [90/21145600] via 131.108.26.1.22.108.4.108.29.0/24 [90/21120000] via 131. Serial0 131. 11:17:48. 11:17:47. Serial0 131.108.1.108.0/24 [90/21145600] via 131. 11:17:49.108.108.0–131.0/24 [90/21120000] via 131.15.108.108.11.1. 11:17:51.108. Serial0 131.108.255. 11:17:49. 11:17:50.1.108.31.30.108.108. Serial0 131. Serial0 131.0/24 [90/21145600] via 131. 11:17:48.0/24 is directly connected.255. Serial0 131.4.31.1.108. Ethernet0 [90/21145600] via 131.4. To summarize the EIGRP network. Ethernet0 [90/21145600] via 131.1.5.10. Serial0 131.108.4. Serial0 131.108.0/24 [90/21145600] via 131. Serial0 131. 11:17:48.7.108. Ethernet0 [90/21145600] via 131.0. 11:17:50.255.108.108. Serial0 131.0/24 [90/21120000] via 131. Serial0 R3 has 31 separate network entries for the ranges 131. 11:17:48.0/24 [90/21120000] via 131.4.4.255. Serial0 131.108. Serial0 131.4. 11:17:50. 11:17:48.108.108.255. 11:17:51. 11:17:51. Serial0 131.0/24 [90/21145600] via 131. 11:17:50.18.255.108.0/24 [90/21017600] via 131.0/24 [90/21145600] via 131.0/24 [90/21145600] via 131. 11:17:47.0/24 [90/21145600] via 131.1.108.108.23.0/24 [90/21120000] via 131.108.0/24 [90/21120000] via 131.1. 11:17:49.0/24 [90/21120000] via 131.0/24 [90/21120000] via 131.1.108.108.255. Serial0 131. 11:17:50.1.1.36.16.108. 11:17:49.108. Example 5-32 Summary Configuration on R1 with ? Tool R1(config)#interface serial 0/0 .255.36.14. Ethernet0 [90/21145600] via 131.1. Ethernet0 [90/21145600] via 131.0/24 [90/21120000] via 131.13. Serial0 131.255.0/24 [90/21120000] via 131.4.0/24 [90/21145600] via 131. Serial0 131.255. 11:17:48. Serial0 131.108. 11:17:49.255.108. 11:17:47. Ethernet0 [90/21145600] via 131.20.108.255. 11:17:49.108. Ethernet0 [90/21145600] via 131.108.4.0/24 [90/21145600] via 131.0/24 [90/21145600] via 131.1. 11:17:48.255. Serial0 131. The subnet mask covering this range is 255.255.255. 11:17:50. 11:17:47.0/24 [90/21120000] via 131.36.9. Ethernet0 [90/21145600] via 131.24. 11:17:49.108.1. 11:17:50.108.1.0/24 [90/21145600] via 131.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 131.28.1. 11:17:50. Serial0 131.4.4. Apply summarization on R1 for its directly connected links.108.36.108.27.108. 11:17:47.36.108.108. 11:17:48.108. Serial0 131. Ethernet0 [90/21145600] via 131. 11:17:51. 11:17:50. Serial0 131.255.36.108.4.108.108.108. 11:17:47. you apply the ip summary-address eigrp AS IP address mask command.1.1. Ethernet0 [90/21145600] via 131.108.255.4.12.108.108.108.0–131. 11:17:48.108.108. Serial0 131. 11:17:47.108.255.108.1. Serial0 131. Serial0 131.1.108. Serial0 131.1.36.255.0/24 [90/21145600] via 131.108. 11:17:47.108. 11:17:48.255.108. Ethernet0 [90/21145600] via 131.36.1.36.36.1.240.0/24 [90/21145600] via 131.164 - .1.255.255.108. Ethernet0 [90/21145600] via 131.15.1.108.36.255. 11:17:47.255.108.108.255.0/24 [90/21120000] via 131.36. Serial0 131.108.108.19.0/24 [90/21120000] via 131. Ethernet0 131. Serial0 131.1.255.108.0/24 [90/21145600] via 131.255.255.36. You can clearly summarize the networks on R1 and R2 to reduce the IP routing table.108.1.1.0/24 [90/21145600] via 131.0/24 [90/21120000] via 131.108.4.1. 11:17:50. 11:17:49.4. Example 5-32 displays the interface configuration required for summarizing the networks ranging 131.108. 11:17:50.21.3.108.108. Serial0 131.255.1. 11:17:50.17.4.1.108. 11:17:50.25.1.4.108.2.36. Ethernet0 [90/21145600] via 131.255.36.108.36.6.1.108.36.108.108. 11:17:49. Ethernet0 [90/21145600] via 131.255. Serial0 131.108.1.255.108. 11:17:49.255.

0/24 [90/21171200] via 131.1. Example 5-33 R3's IP Routing Table R3#show ip route eigrp 168.0/24 [90/21017600] via 131.108. 00:02:51.36. 00:02:49.108. 00:02:46.108.131.4.36.108.108.255.36. 00:02:48. Ethernet0 D 131.108. 00:02:53.36.108. Ethernet0 D 131.27.3.36.108.36.108.4.24.4. 00:02:51.0/24 [90/21043200] via 131. Ethernet0 D 131. Serial0 D 131.0/24 [90/21145600] via 131.0/24 [90/21171200] via 131.0/24 [90/21171200] via 131.0/24 [90/21171200] via 131.36.36. Ethernet0 . 00:02:49. 00:02:51.36. Serial0 D 131.108. 00:02:48.30.0/24 [90/21145600] via 131. Serial0 D 131. 00:02:50.108.108.108. Serial0 D 131.36.1.108.108.108. Ethernet0 [90/21145600] via 131. Serial0 D 131.4.108.22.4. 00:02:48.36.108.0/24 [170/25625600] via 131.0/24 [90/21145600] via 131. 00:02:45. Ethernet0 D 131.10.108. 00:02:46. 00:02:53.108. Ethernet0 D 131.11.0/24 [90/21171200] via 131.108.108.108.0/24 [90/21145600] via 131.255.4.108. Ethernet0 D 131. 00:02:49.108.36.108.D IP address R1(config-if)#ip summary-address eigrp 1 131. Serial1 D 131.108.108. 00:02:49.255. Ethernet0 [90/21145600] via 131.36.108. Ethernet0 D 131.108. 00:02:45.108.108.0/20 [90/21120000] via 131. Ethernet0 D 131.0/24 [90/21171200] via 131. Ethernet0 D 131. Ethernet0 [90/21145600] via 131.29. Ethernet0 131.36.255.1. 00:02:48.4.0/16 is variably subnetted. Serial0 D 131. Ethernet0 [90/21145600] via 131.10.36.108. 00:02:49.0/24 [90/21171200] via 131.255.4.36.0/16 [170/25625600] via 131. Ethernet0 [90/21145600] via 131.B.0/24 [90/21017600] via 131.255. Serial0 D 131.108. Ethernet0 [90/21145600] via 131.108. Ethernet0 [90/21145600] via 131.108.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.108. 00:02:45.2.108. 3 masks D 131.255.108.4.36.4.255.0/24 [90/21171200] via 131.108.5.108.C.4.108.4. Serial0 D 131.128.0/24 [90/21171200] via 131. 00:02:51.0/24 [90/21145600] via 131. Ethernet0 D 131.255.0 255.108.1.108. 00:02:51.108. 00:02:51. 00:02:51.0.4.1.4. 00:02:49.25. 3 subnets.14.36.1.108.4.36.0/24 [90/21145600] via 131. Ethernet0 [90/21145600] via 131.1.108.14.4.1. display the IP routing table on R3.240. 00:02:49.108.36.31.36.4.108.1.255. 00:02:51.0.108. 00:02:50.108.0/24 [90/21171200] via 131.0/24 [90/21171200] via 131.4. Serial2 D 131. Ethernet0 D 131.108.1.36. Ethernet0 D 131.0/24 [90/21171200] via 131.0/24 [90/21145600] via 131.1.0/24 [90/21145600] via 131.108.2.36.108.108.21.0/24 [90/21171200] via 131.108. 00:02:48.0.131.15. 00:02:46.255. 00:02:52.108.4.108. Ethernet0 D 131.255. 00:02:49.108.108.108.108. Serial0 D 131.1.129.131.108.4/30 [90/21017600] via 131.108.4.13. Ethernet0 [90/21145600] via 131.1. Ethernet0 D 131.108.36. 00:02:49.36.131. Example 5-33 displays the IP routing table on R3 after summarization is configured on R1.23.4.108.12. Ethernet0 D 131.4. 00:02:51.108.108. 00:02:49.4. 00:02:45. Ethernet0 D EX 168.108.0/24 [90/21043200] via 131.108.108.36.4.28.8.36. Serial0 D 131.4. 3 masks D EX 168.4. Ethernet0 D 131.0/16 is variably subnetted.108.255. 00:02:52.0 Next. 00:02:50. Serial0 D 131. 00:02:52.36.26.108.1.255.36. Ethernet0 [90/21145600] via 131.0/24 [90/21145600] via 131.6.16/30 [90/21017600] via 131. 00:02:49. 00:02:50. 00:02:45. 00:02:51.4.108.108.36.0/24 [90/21171200] via 131.255.108.4.4.165 - .108.4.9.0.4. 41 subnets.0/24 [90/21145600] via 131.36.108.108.36.4. Ethernet0 D 131.0/30 [170/25625600] via 131. 00:02:49.255.0/24 [90/21145600] via 131.7.4. 00:02:49. Ethernet0 D EX 168.130. Ethernet0 D 131.

16. Serial0 [90/21145600] via 131.1. Ethernet0 131.36.255.108.18.108. Ethernet0 D 131. 3 masks D EX 168.1.16.108.108. Serial0 131.108.240.108.108.36. 00:02:17.131. you must perform the same summary configuration on R2 because R2 has 15 directly contiguous networks ranging from 131.0/30 [170/25625600] via 131.108.108.4/30 [90/21017600] via 131.0/16 is variably subnetted.130.255.36.108.0 in R3's routing table. Example 5-36 show ip route eigrp on R3 R3#show ip route eigrp 168.108.4. Ethernet0 131. 00:02:51. Serial0 R3 still has the 15 network entries advertised through the next hop address 131.4.36.240.255. Two summary commands are required: one to R1 through Ethernet 0/0 and another to R4 through Serial 1/0. you configured only R1 to summarize to R3.108.108. Ethernet0 D 131. 00:02:14.108.1.4.108.0 R2(config-if)#interface serial1/0 R2(config-if)#ip summary-address eigrp 1 131. (This encompasses the range 131.0. Serial0 131.4.131.0. is where you need to apply the same summary command used in Example 5-32. Example 5-34 Summary on R1 Pointing to R2 R1(config)#interface ethernet 0/0 R1(config-if)#ip summary-address eigrp 1 131. Serial0 131.108.4. 00:02:17.16/30 [90/21017600] via 131.4.19. Ethernet0 131.1.108. as well as the summary address 131.255.16. 00:02:51. Ethernet0 D EX 168. Example 5-35 displays the summary configuration on R2.255.255. 00:02:50. 00:02:14.1.255.0 255.108.255.4. When you performed summarization.0/24 [170/25625600] via 131.36.4. 00:02:51.108.0/20 [90/21145600] via 131. 00:02:50.0 Before you look at R3's IP routing table.1.0/20 [90/21120000] via 131.108.129.108.0/24 [90/21043200] via 131.166 - .131.108. Example 5-34 configures summarization on R1 pointing to R2. 00:12:20. Ethernet0 D EX 168. 00:02:17. 3 subnets.CCNP Practical Studies: Routing D D D D D [90/21145600] 131.0 Example 5-36 displays the IP routing table on R3.1. Ethernet0 131.36.1.0.) R3 has two paths to the remote router R1.131.108.128.0/24 [90/21145600] [90/21145600] 131.0/24 [90/21017600] via 131. Prior to summarization.108.108.0–131.255.20.255.0/24 [90/21145600] [90/21145600] via via via via via via via via via via via 131.4.0.31.108.255.108.0 to 131.255. Serial2 D 131.240.255. Example 5-35 Summary on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip summary-address eigrp 1 131. 12 subnets.108.108. namely Ethernet 0/0.15.108.36. Serial0 131.36.4.4.108. Ethernet0 131.108.1.1. 00:02:22.36. Ethernet0 D 131.0/24 [90/21043200] via 131.0.16. Serial1 D 131.0 255.108.255.108. 00:02:17. 00:02:14.108. 00:02:50.36. or R4. 00:02:14. you must also provide the same summary address to R2. 00:02:50.108.2.108. Serial0 131.36. 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.255.108.4. 00:02:50.4.17.0.0/24 [90/21145600] [90/21145600] 131. 3 masks D 131.255. 00:02:51.108. now only 12 subnets are present in the Class B network 131.0/20.16.36. . there were 41 subnets. 00:02:17. Cisco EIGRPenabled routers always accept an incoming route with a more specific destination. 00:02:51.36.0/24 [90/21145600] [90/21145600] 131.108. 00:02:50.0/24 [90/21017600] via 131.108.14.108. Ethernet0 D 131.255.108.108.1.108.0/24 [90/21145600] [90/21145600] 131.1.4.108.0/16 [170/25625600] via 131.0/16 is variably subnetted.108.36. The interface that R1 and R2 are adjacent to. Serial0 D 131.10. Ethernet0 131.0 255. 00:12:20.

2.0 255.255.128.0 ! interface Serial0/0 bandwidth 128 ip address 131.5.255.255.108.108. Also. 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. 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.240.0 255.3. 3 masks D 168. in turn. Serial2 D 168.108.108.0/30 [90/21017600] via 131.0 clockrate 128000 Scenario 5-3: EIGRP and VLSM This scenario demonstrates the capability of EIGRP to handle VLSM with a simple four-router topology. Null0 131.5.0/16 is a summary.108.108.0 255. 11:30:01. Example 5-39 Summary EIGRP Configuration on R2 interface Ethernet0/0 ip address 131.255.255.131.0/20 [90/21120000] via 131.255.3.0 ip summary-address eigrp 1 131. 11:30:01.18. 11:30:01.255. 3 subnets.108.255.255.1.255. Example 5-38 Summary EIGRP Configuration on R1 interface Ethernet0/0 ip address 131.131.255.108.0/24 [90/21043200] via 131.255.108.108.108.108.0/24 [90/21043200] via 131.108.255. Ethernet0 D 131.0/20 [90/21145600] via 131.0.108.CCNP Practical Studies: Routing Also.2.0 ! interface Serial1/0 bandwidth 128 ip address 131.108. Serial0 D 131.108.0. 11:30:01.108. 00:06:28.252 ip summary-address eigrp 1 131.108.0 ip summary-address eigrp 1 131.255.36.0.255. Ethernet0 D 131. there is only one path (lower metric) taken to R2's directly connected interfaces.5.108.0 255. Serial0 Because R4 is directly connected to R2.108.108.255. 00:06:28. while load balancing is taking place for R1's directly connected networks.36.3.0.0/24 [90/21017600] via 168. Example 5-38 displays the summary EIGRP configuration on R1.240. Example 5-37 show ip route eigrp Command on R4 R4>sh ip route eigrp 168.16.108. Serial0 D 131.255. Example 5-37 displays R4's IP routing table to demonstrate similar benefits.3. .16.240.255.130.108. 00:06:28.8/30 [90/21017600] via 131.3.5 255.36.36.1.255. 4 masks D 131.108.36.240.255.2 255.255. Ethernet0 [90/21145600] via 131.131.12/30 [90/21017600] via 131. 00:06:27. Ethernet0 D 131.108.1.108. Ethernet0 D 131.0/24 [90/21017600] via 131.0.0.16.36. Ethernet0 D 131.252 ip summary-address eigrp 1 131. Serial1 D 131.1 255.0/24 [90/21017600] via 131.108. Figure 5-4 displays the four-router topology along with the IP addressing scheme.131. 00:06:29.1.0/16 is variably subnetted.3.0/16 is variably subnetted. 11:29:38.167 - . 11:30:01.129.1 255. 13 subnets.0 clockrate 125000 Example 5-39 displays the summary EIGRP configuration on R2. summarization reduces the EIGRP topology table.108. 11:29:40.

CCNP Practical Studies: Routing Figure 5-4.108. is reserved for private use and not routable in the Internet. 10.1. as displayed by Example 5-41.0. VLSM and EIGRP Topology Four routers in Figure 5-4 reside in the same AS.0/16 is variably subnetted.0 View the IP routing table on R1 to ensure that all subnets are routable through R1.108. R3 is . Serial0/0 R1's IP routing tables display a total of two dynamically learned EIGRP routers: one route to the network 131.0. 00:06:19. Example 5-41 EIGRP Configuration on R3 and R4 router eigrp 1 network 131. Serial0/0 131.1.108.0/8 [90/20537600] via 131.108.0 network 10.1.18.108. so the EIGRP configuration is the same on R1 and R2.168 - .108.108. Example 5-40 displays the EIGRP configuration on routers R1 and R2.20/30 [90/20537600] via 131.1.0. respectively.1. 3 masks C 131.0.1. Ethernet0/0 D 131.0/25 and 10.16/30 is directly connected.0.0.0.0.0.2.0 R3 and R4 require both 131. 4 subnets.128/25.0 through R3.1. Example 5-42 R1's IP Routing Table R1#show ip route D 10. Both routers reside in AS 1 and are connected to only the network 131. VLSM is used on all four routers. 00:08:55.0.20/30 (the serial link between R2 and R4) and one to network remote network 10. Also. The Class A address.0 network statements. Ethernet0/0 C 131.1.0.108. so you do not need to configure any redistribution.108.0.0/28 is directly connected. are configured on the Ethernet interfaces on R3 and R4. 10. Enable EIGRP in AS 1 on all four routers. Example 5-42 displays R1's routing table.0.108. the Class A addresses. Example 5-40 EIGRP Configuration on R1 and R2 router eigrp 1 network 131.1.0/8.108.1.1.0. Take a closer look at the remote IP network on R3.0 and 10.0.

20/30 (the serial link between R1 and R3) and the entire Class A network 10.0.1.0. Serial1/0 131. Example 5-46 displays the summary on R3.1.1.108.0.1.255.2.20/30 is directly connected.0 network.0.1. .169 - .1. Summarize 10.108. Ethernet0/0 R1 still assumes the entire Class A network is through R3 because even after you disable automatic summarization.108. automatically summarizes at the network boundary for any IP networks not locally configured. 00:02:16.108.1.20/30 [90/20537600] via 131.0.0. Routers R1 and R2 do not contain more specific routing entries for the 10. both routers assume the default Class A mask of 255.128/25 on R4.16/30 [90/20537600] via 131.128 R3 and R4 send an update to R1 and R2.108.0/16 is variably subnetted. Because R1 and R2 do not have any interfaces configured in the Class A address 10.0/28 is directly connected. 3 subnets. Ethernet0/0 C 131.0 255. Example 543 displays R2's IP routing table.255.128 Example 5-47 displays the summary on R4. or R3.0.0/8 [90/20537600] via 131.0 through R4. 3 subnets.0/25 on R3 and 10.18.1. You can turn this feature off with the no auto-summary command under the EIGRP routing process. Example 5-48 displays R1's IP routing table. 2 masks C 131.108. 00:00:24.0.1.1.22. Therefore.0.108.CCNP Practical Studies: Routing configured with the network 10. 2 masks D 131.0/8 [90/20537600] via 131.0.1.0.0. Example 5-46 Summary Configuration on R3 R3(config)#interface serial 0 R3(config-if)#ip summary-address eigrp 1 10. Serial0/0 131.1.1. Example 5-43 R2's IP Routing Table R2#show ip route D 10.1. you must still summarize on the edge routers: R3 and R4.0/25. yet R1 assumes that the entire Class A network is available through Serial 0/0.0.128 255. Example 5-45 R1's EIGRP IP Routing Table R1#show ip route eigrp D 10.108.1. Example 5-44 displays the disabling of automatic summarization on R1 and R2.108.0/16 is variably subnetted.108.108.255.0.1. 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. by default.1.1. 00:02:15.0. Ethernet0/0 R2 also has two remote EIGRP routes: one pointing to the remote network 131. 00:00:24.1. Disable automatic summarization on R1 and R2.1.0. EIGRP. Serial1/0 D 131. Example 5-47 Summary Configuration on R4 R4(config)#interface serial 0 R4(config-if)#ip summary-address eigrp 1 10.255.

1.17 255.CCNP Practical Studies: Routing Example 5-48 R1's IP Routing Table R1#show ip route 10. and sends the subnet mask along with the network information.0/16 is variably subnetted.108.0.1. Serial1/0 D 131.108.1. Example 5-50 displays R1's full working configuration. Example 5-49 R2's IP Routing Table R2#show ip route 10.255. Ethernet0/0 D 131. displays R2's IP routing table.255.0/8 is variably subnetted.0. 2 masks C 131.1. Ethernet0/0 C 131.255. Ethernet0/0 EIGRP supports VLSM. 2 subnets.0/0 [90/20537600] via 131.108.0/0 [90/20537600] via 131.108. EIGRP supports VLSM as all IP routing updates do.1.1.0/8 is variably subnetted.1. 3 subnets.1 255.1.2.108. 2 masks D 10. Ethernet0/0 D 10.1.108.108.128/25 [90/20537600] via 131. 00:02:00.0.0.1.1.108.20/30 is directly connected. 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 131.1.1. Serial1/0 131. Ethernet0/0 131.22.252 clockrate 125000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131.18.1.240 ! interface Serial0/0 bandwidth 128 ip address 131. 00:02:07.108. 00:03:17.20/30 [90/20537600] via 131.108.2. 00:04:46. Serial0/0 Example 5-49.255.0.108.170 - . 00:01:29.1.108. . 3 subnets. Ethernet0/0 C 131.16/30 is directly connected.108.1. 00:06:06.0/28 is directly connected.108.1. for completeness.1.1.1. 2 masks D 10. 2 masks C 131.128/25 [90/20563200] via 131. 2 subnets. Serial0/0 D 10.0/28 is directly connected.0.0 no auto-summary ! line con 0 line aux 0 line vty 0 4 end Example 5-51 displays R2's full working configuration.108.1.108.0.108. when configured appropriately.16/30 [90/20537600] via 131.1. and you have just seen how careful you must be when using EIGRP as your IP routing protocol.1.1.0/16 is variably subnetted.

1.1.1.0 .18 255.255.2 255.1 255.255.255.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 131.255.21 255.252 clockrate 128000 ! interface Serial1/1 shutdown ! interface Serial1/2 shutdown! interface Serial1/3 shutdown ! router eigrp 1 network 131.108.0.252 ip summary-address eigrp 1 10.128 bandwidth 125 ! interface Serial1 shutdown interface Serial2 shutdown interface Serial3 shutdown ! router eigrp 1 network 131.255.255.255.255.1.171 - . Example 5-52 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 10.108.0 no auto-summary line con 0 line aux 0 line vty 0 4 ! end Example 5-52 displays R3's full working configuration.108.0.108.0 255.255.108.1.255.128 ! interface Serial0 ip address 131.1.1.240 ! interface Serial1/0 bandwidth 128 ip address 131.

255.1.1.1.255.22 255.1.CCNP Practical Studies: Routing network ! line con line aux line vty ! end 10.0.0. Example 5-53 R4's Full Working Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 10.252 ip summary-address eigrp 1 10.0.108.0 network 131.128 ! interface Serial1 shutdown interface Serial2 shutdown interface Serial3 shutdown ! router eigrp 1 network 10.0 0 0 0 4 Example 5-53 displays R4's full working configuration.1.0.128 255.255.255.0.0 ! line con 0 line aux 0 line vty 0 4 end .172 - .255.255.129 255.128 interface Serial0 bandwidth 125 ip address 131.108.

131.108. you configure a network composed of six Cisco routers running a combination of IP routing protocols. The Class B network. IP Routing Topology Using EIGRP.108. for example.173 - . IGRP. The Class A network resides in OSPF area 0.0. and OSPF NOTE The IGRP domain is configured with a Class C mask everywhere because IGRP does not support VLSM.CCNP Practical Studies: Routing Scenario 5-4: Configuring Advanced EIGRP and Redistribution In this scenario. Finally. Router R3 needs to run EIGRP in AS 1 and IGRP 10. 141. Example 5-54 displays the EIGRP and IGRP configuration on R3.0. R3 must ensure that EIGRP updates are sent to interfaces E0 and Serial 0 only. to R7 and waste CPU and WAN bandwidth because R7 is configured for IGRP only. . is present on all routers. you must make the interfaces not in IGRP AS 10 passive. is located in IGRP AS 10. the Class B address. The same condition applies to the IGRP process. The classful behavior of IGRP and EIGRP means you must be careful when using the same class network among different routing domains. namely EIGRP in AS 1.0. and because you are using the same Class B address. Start by configuring R3.0. There is no reason to send EIGRP updates. and OSPF. you should also make interfaces not in IGRP 10 passive. R3 and R4 need to have redistribution configured among the different routing domains. Figure 5-5. as displayed in Figure 5-5. IGRP in AS 10.

you must still advise EIGRP of the metric values because the AS numbers are different. . Example 5-55 displays how to configure redistribution from IGRP to EIGRP. examine R7's IP routing table to see whether the EIGRP networks are installed. Configure redistribution between EIGRP and IGRP (both ways) on R3.0.0 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 5-56 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. 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. 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.CCNP Practical Studies: Routing Example 5-54 EIGRP and IGRP Configuration on R3 R3(config)#router eigrp 1 R3(config-router)#network 131.108. Example 5-57 displays R7's IP routing table.174 - . 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. 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.

Sending 5.108. .255.0/24 is subnetted.108.0/30 is directly connected.0.254.0 is directly connected.108.0/30 networks.108.108.0 [100/84100] via 131.0/24 is subnetted. Serial0 I 131. 2 subnets C 131.0/16 is variably subnetted.128/25. 100-byte ICMP Echos to 131.") Example 5-58 displays the static IP routing configuration on R7 pointing to the remote networks 131.0/24 is directly connected.255. static routes are covered in Chapters 6.9. Serial0 I 131.9 Type escape sequence to abort. 131. Ethernet0 131.255.255. 1 subnets C 141. You can use static routes to overcome this limitation because static router have a more trusted administrative distance of 1.0 is directly connected. Serial0 C 131.255.0 131.0.128. Serial0 S 131.255.0.0/24 [100/84100] via 131.108.254. round-trip min/avg/max = 28/32/36 ms R7#ping 131. The variably subnetted network.108.128/25 is directly connected. such as the Serial link between R1 and R2 (/30) or the Ethernet segment between R3 and R4 (/25).108. "Basic Border Gateway Protocol.108.252 255.175 - . 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.108.255.128/25 and 131.108.255.4/30 is directly connected. round-trip min/avg/max = 16/16/20 ms R7#ping 131.108.255.2.252 Serial0 Serial0 Serial0 Serial0 Example 5-59 displays R7's routing table along with some successful pings to the non-Class C networks.2. are not present in R7's routing table.108.5 Type escape sequence to abort.255.255.255. Those networks in the EIGRP domain that are not Class C networks.5.128. 100-byte ICMP Echos to 131.2.8 255. Sending 5.108.108.2.108.108.108.255. Example 5-59 R7's IP Routing Table and Ping Requests R7#show ip route 141. Ethernet0 131. Serial0 S 131. 1 subnets C 141.255.1. 00:00:05.0 is directly connected.108.0.108.108.255.128 255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).8/30 is directly connected. 3 masks S 131.252 255.6.128 131.108.255.0/24 is subnetted.1.108. (You have yet to learn how to configure static routes.4 131.255.108. 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. Example 5-60 displays the redistribution from OSPF into EIGRP 1. you need to make any interfaces not required in the EIGRP domain passive. Once more. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255. You can use static routes on R7 to correctly identify the networks in the EIGRP domain.255. Serial0 S 131.1.108.108. 100-byte ICMP Echos to 131.254.108.1.254. 00:00:57.255. is not present on R7's IP (IGRP) routing table because IGRP does not support VLSM.108. Serial0 R7#ping 131. Sending 5.6 Type escape sequence to abort.255.108.CCNP Practical Studies: Routing Example 5-57 show ip route on R7 R7#show ip route 141. 6 subnets. timeout is 2 seconds: !!!!! Configure R4 for redistribution because R4 is attached to the EIGRP 1 domain and OSPF.

0/16 is variably subnetted.108.108. EIGRP domains have subnetted networks.2.254.108.128/25 [90/20537600] via 131.108. Serial0/0 R1 has an IP routing entry for all EIGRP networks in AS 1.2.108. 00:08:30.1.2. Serial0/0 D 131. 00:19:06.4/30 [90/20537600] via 131. 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.108.108.2.0. Serial0/0 C 131.255. 6 subnets.0/24 [90/21504000] via 131.255. Serial0/0 [90/25657600] via 131.108. 00:19:06.0. 00:19:06.1.0/30 is directly connected.EIGRP.EIGRP external. .connected D . Example 5-62 displays R1's IP routing table.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. 00:19:05. as well as the external EIGRP network routing from OSPF and IGRP.108. 00:08:30. Serial0/0 D 131.8/30 [90/21529600] via 131. 00:19:06.1.1.108. EX .2.0/16 [170/21529600] via 131.108.0.255. 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. Ethernet0/0 C 131. Serial0/0 D 10.0.255. Remember. 00:19:06.176 - .108.255.2.108. Ethernet0/0 D 131. Example 5-62 R1's IP Routing Table R1>sh ip route Codes: C . 3 masks D 131.108.2.255. D EX 141.2.108. so you must apply the keyword subnets when redistributing from EIGRP to OSPF.255.2.0/8 [90/25657600] via 131. Ethernet0/0 131.0/24 is directly connected.255.108. Ethernet0/0 [90/21529600] via 131.

108.252 clockrate 125000 ! interface Serial0/1 shutdown ! router eigrp 1 network 131.177 - . round-trip min/avg/max = 32/33/36 ms R1>ping 131.255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 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 131.128.CCNP Practical Studies: Routing To confirm network connectivity.1.108. round-trip min/avg/max = 28/30/32 ms R1>ping 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.1 255.255. Sending 5.1 255.1 Type escape sequence to abort. Sending 5.108. 100-byte ICMP Echos to 131. ping from R1 to all the remote networks. Sending 5.129.1.255.2. 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. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.255.2.129 Type escape sequence to abort.255. 100-byte ICMP Echos to 10.255.108.1 Type escape sequence to abort. Example 5-63 displays a ping request and reply from R1 to all the remote networks in Figure 5-5.9.108.1.128. 100-byte ICMP Echos to 131. Sending 5.108. Example 5-64 provides the full working configuration of R1.0 ! interface Serial0/0 bandwidth 125 ip address 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 28/31/32 ms R1>ping 10.1.108.108. 100-byte ICMP Echos to 141.0 line con 0 .9 Type escape sequence to abort.0.1. Sending 5.108.108.108.1. Example 5-63 Sample Ping Request from R1 R1>ping 141. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.1.1. round-trip min/avg/max = 16/16/16 ms R1>ping 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.

255.255.108.255.1.108.0 ! interface Serial1/0 bandwidth 128 ip address 131.0 bandwidth 125 clockrate 125000 ! interface Serial3 shutdown ! .252 clockrate 128000 ! interface Serial1/1 shutdown ! router eigrp 1 network 131.108.252 bandwidth 125 ! interface Serial1 shutdown ! interface Serial2 ip address 131.178 - .CCNP Practical Studies: Routing line aux 0 line vty 0 4 ! end Example 5-65 provides the full working configuration of R2.255.108.255.108.255.108.255.129 255. 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 131.254.255.2 255.0 line con 0 line aux 0 line vty 0 4 end Example 5-66 provides the full working configuration of R3. Example 5-66 show running-config on R3 hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.2.1 255.128 ! interface Serial0 ip address 131.5 255.255.0.255.255.255.2 255.

255.255.108.CCNP Practical Studies: Routing router eigrp 1 redistribute igrp 10 metric 128 20000 255 1 255 passive-interface Serial2 network 131.128 interface Serial0 shutdown ! interface Serial1 shutdown ! interface Serial2 bandwidth 125 ip address 131.108.3 area 0 line con 0 line aux 0 line vty 0 4 end Example 5-68 provides the full working configuration of R7.108.108.0.0.2.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-67 provides the full working configuration of R4.130 255.9 255.179 - .108.0 ! router ospf 1 redistribute eigrp 1 metric 100 subnets network 131. .255.0. Example 5-67 show running-config on R4 hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.255.8 0.255.108.0.0.252 clockrate 125000 ! interface Serial3 shutdown ! router eigrp 1 redistribute ospf 1 metric 128 20000 255 1 1500 passive-interface Serial2 network 131.0 ! router igrp 10 redistribute eigrp 1 metric 128 20000 255 1 1500 passive-interface Ethernet0 passive-interface Serial0 network 131.255.

8 0.252 Serial0 ! line con 0 line aux 0 line vty 0 4 end Example 5-69 provides the full working configuration of R8.255.8 255.108.108.4 255.0 255.255. Example 5-69 show running-config on R8 hostname R8 enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Ethernet0 ip address 10.0.252 Serial0 ip route 131.255.252 Serial0 ip route 131.108.255.108.255.254.0.0 ! interface Serial1 shutdown ! router igrp 10 network 131.2.0 0.255.128 255.255 area 0 network 131.128.0.255.1 255.180 - .255.1.252 interface Serial1 shutdown ! router ospf 1 network 10.255.108.255.108.10 255.255.255.1.255.255.0.255.0 ! ip route 131.1.108.3 area 0 ! line con 0 line aux 0 line vty 0 4 ! end .2 255.0.0 ! interface Serial0 bandwidth 125 ip address 131.255.255.0 ! interface Serial0 bandwidth 125 ip address 131.0 network 141.255.0.255.255.1 255.108.1.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 141.128 Serial0 ip route 131.108.255.108.

255.2 131.2 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. . 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.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. 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. Properly using show and debug commands can be valuable. NOTE This scenario uses the network in Figure 5-5 (the one you configured in Scenario 5-4) to demonstrate these commands.108. Example 5-71 displays the topology table with the show ip eigrp topology command. The EIGRP process is also identified as 1.1.108.181 - . This scenario uses the network in Figure 5-5 to demonstrate some common show commands that verify that EIGRP is operating correctly. 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.

2 (21504000/20992000).255. FD is 21504000 via 131. Serial0/0 via 131. Example 5-72 displays sample output from R1 with the show ip eigrp interfaces command. You must be in privilege mode to view the debug command set. The P on the left side indicates that remote networks are passive and routable.255.108.108. Serial0/0 via 131. FD is 20537600 via 131. Q . and acknowledges R1 uses to ensure that EIGRP is running correctly and with adjacent EIGRP routers.2.8/30. Any active entry (displayed as A) should concern you if any entries remain active or stuck in active (SIA). Ethernet0/0 P 131.Active. 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. With every version of IOS. 1 successors.0/16. Serial0/0 P 141.128/25. FD is 25657600 via 131.2 (20537600/281600). Ethernet0/0 The table in Example 5-71 contains a wealth of information.2 (21529600/21017600).255. Ethernet0/0 P 131.4/30.0.2 (25657600/25145600). r . 1 successors. 2 successors.254. FD is 21529600 via 131. Example 5-74 displays the debug commands possible with EIGRP on Cisco IOS running version 12-0.255.2 (25657600/25632000).108.1.2 (21529600/21504000).1. Example 5-73 displays the output from the show ip eigrp traffic command. A .108. Ethernet0/0 P 131. 1 successors.108.2 (21529600/21017600).255. R .255. there are always new commands and changes in IOS displays.10-enterprise code.0. U .Reply. Serial0/0 P 131.0.108.Update.108. Serial0/0 P 131. 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. . replies.0/8.108.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 . FD is 21529600 via 131.0/24. 1 successors. namely to R2 through Ethernet 0/0 and R3 through Serial 0/0.255. FD is 20537600 via 131.Query. Serial0/0 P 131.108.182 - . 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.108.0/30. The output in Example 5-72 displays two interfaces running EIGRP in AS 1 and one peer per interface.1. the EIGRP topology table installs the remote network in an active state.108. FD is 20512000 via Connected.2 (20537600/20512000).108. Because a reply has not been received.255.Reply status P 10. queries. 2 successors.108. FD is 281600 via Connected. 1 successors. Use the ? tool to view all your options.108.Passive.108.0/24.1. Traffic commands show how many updates. 1 successors.

You use route maps to ensure that networks are not advertised incorrectly.htm. The RIP network attached to Brussels shares the identical subnet in the EIGRP 1 domain. Configure the network in Figure 5-6 for EIGRP in autonomous system 1. visit the Cisco web site for free information at www. you must also use passive interfaces on Router Sydney.0/24. Summarize wherever possible to reduce the IP routing table on the Router SanFran.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. You can also use distribute lists. Figure 5-6. Likewise for RIP.108. EIGRP Network Practical Exercise Solution All routers in this practical exercise use the same Class B network. any redistribution you configure on the Router Sydney has to ensure that these networks are not propagated.0.183 - . Therefore. The solution can be found at the end.cisco. to avoid a routing loop. namely 131. Ensure that SanFran has all the remote entries being advertised by Router Sydney and the router in the RIP domain.com/univercd/home/home. . you should make sure passive interfaces are not running RIP. To stop EIGRP updates from being sent to the RIP domain. 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: EIGRP NOTE Practical Exercises are designed to test your knowledge of the topics covered in this chapter.

you can provide a summary in EIGRP AS 1 covering the networks 171. "Advanced BGP.109.1.255." Example 5-76 Sydney's Full Working Configuration hostname Sydney ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 171.1 255.1 255.255.108.0 with the following command: ip summary-address eigrp 1 171.109.0 no auto-summary ! line con 0 line aux 0 line vty 0 4 end Example 5-76 displays the configuration required on Router Sydney.252.0 interface Ethernet0/0 ip address 131.255.252.0 ! interface Serial1/0 bandwidth 128 ip address 131.108.255.255.0 Example 5-75 displays the configuration required on Router SanFran.0 ! interface Loopback2 ip address 171.255.1 255.255.0 255.255.109.109. To make the configuration a little more interesting.3.1 255.255. Route maps are covered in more detail in Chapters 6 and 7.0 255. Example 5-75 SanFran's Full Working Configuration hostname SanFran ! ip subnet-zero no ip domain-lookup ! interface Ethernet0/0 ip address 131.1 255.255.0 no ip directed-broadcast ip summary-address eigrp 1 171.108.1.109.108.255.CCNP Practical Studies: Routing For summarization.1.0.184 - .2.0.255. route maps have been applied to redistribution on Router Sydney.255.109.2 255.0 ! interface Serial0/0 shutdown ! interface Serial0/1 shutdown router eigrp 1 network 131.108.0–171.1.255.0 ! interface Loopback1 ip address 171.3.0 clockrate 128000 ! router eigrp 1 .0.255.

0/22 is subnetted.1.255 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.255. 00:05:41.255.0 [90/409600] via 131.0 is directly connected. Ethernet0/0 131.108.0.0.0.2 255.109.108.1.108.0 network 171.2.0.1.255.109. Ethernet0/0 . Example 5-77 Brussels' Full Working Configuration hostname Brussels ! enable password cisco ip subnet-zero no ip domain-lookup interface Ethernet0 ip address 131.0.0/24 is subnetted.0.108.0.108.2.185 - . Example 5-78 show ip route Command on SanFran SanFran#show ip route D D C 171. 1 subnets 171.CCNP Practical Studies: Routing redistribute rip metric 128 20000 255 1 1500 route-map riptoeigrp passive-interface Serial1/0 network 131.0.255.108. which shows the remote RIP link and the summary address advertised by Router Sydney. Ethernet0/0 131.108.108.0 ! line con 0 line aux 0 line vty 0 4 end Example 5-78 displays SanFran's IP routing table. 2 subnets 131.0 no auto-summary ! router rip redistribute eigrp 1 metric 2 route-map eigrptorip passive-interface Ethernet0/0 network 131.108.0 router rip network 131.1.108.109.0 0.0 [90/20537600] via 131.108.0 ! interface Serial0 bandwidth 125 ip address 131.0. 00:05:41.1.255.0 ! access-list 1 deny 131.255.1 255.

1.1. 00:13:26 ago. 00:13:32 ago.0. Refer to the examples to answer the first question. Sending 5. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171.0.3. Hops 1 SanFran#ping 171. traffic share count is 1 Total delay is 6000 microseconds.3.1. via Ethernet0/0 Route metric is 409600. minimum bandwidth is 10000 Kbit Reliability 255/255.2.0 and 171.108. Sending 5. distance 90.109.186 - . 171.109.2. type internal Redistributing via eigrp 1 Last update from 131.2.2. 00:13:38 ago Routing Descriptor Blocks: * 131.2 on Ethernet0/0.108.108. distance 90. Hops 1 SanFran#ping 171. distance 90.108. traffic share count is 1 Total delay is 6000 microseconds. type internal Redistributing via eigrp 1 Last update from 131.3. as seen by Router SanFran along with a successful ping to the remote networks.1.109. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).CCNP Practical Studies: Routing Review Questions The following questions are based on material covered in this chapter. via Ethernet0/0 Route metric is 409600. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171. 00:13:38 ago.0. minimum bandwidth is 10000 Kbit Reliability 255/255.1. The answers to these questions can be found in Appendix C. 100-byte ICMP Echos to 171. metric 409600.1.109. minimum bandwidth is 10000 Kbit Reliability 255/255. type internal Redistributing via eigrp 1 Last update from 131. metric 409600.1.0 Routing entry for 171. timeout is 2 seconds: !!!!! .109.1.1.109.109. minimum MTU 1500 bytes Loading 1/255.0 Routing entry for 171. 171.1 Type escape sequence to abort.108.0.0/24.109.2. from 131. 00:13:32 ago Routing Descriptor Blocks: * 131.1.2 on Ethernet0/0." Example 5-79 displays the detailed paths to the three remote networks.1 Type escape sequence to abort.0/22 Known via "eigrp 1".2. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). minimum MTU 1500 bytes Loading 1/255.108. 100-byte ICMP Echos to 171. Hops 1 SanFran#ping 171. Sending 5. from 131. minimum MTU 1500 bytes Loading 1/255.108.109. metric 409600. "Answers to Review Questions.2.1. via Ethernet0/0 Route metric is 409600.108.0 Routing entry for 171.109.1 Type escape sequence to abort.109.1.2. Example 5-79 show ip route and ping on SanFran SanFran#show ip route 171.3.109.1.109. 100-byte ICMP Echos to 171.2.108. from 131.0/22 Known via "eigrp 1".1. Examples 5-79 and 5-80 are from the previous Practical Exercise.109.2. traffic share count is 1 Total delay is 6000 microseconds.1. 00:13:26 ago Routing Descriptor Blocks: * 131.1.2 on Ethernet0/0.109.0/22 Known via "eigrp 1".

and 3.108.0/24 on SanFran. Example 5-80 show ip route 171. you see the output displayed in Example 5-80. round-trip min/avg/max = 1/3/4 ms If you perform a show ip route to the network 171. 1: 2: 3: Example 5-79 displays the IP routing table of the Router SanFran.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: 131.0.0 on SanFran SanFran#show ip route 171.109.2 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? .4.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).1. Which networks does the entry 171. 2.4.0 % 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 1.109.109.4.109.187 - .

CCNP Practical Studies: Routing Summary Although EIGRP is not an industry standard across routing vendors. it is a potentially useful protocol for routing IP. along with some detailed configurations. 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 . 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. EIGRP terminology and the fundamental operation of EIGRP is covered in this chapter.188 - . showing how EIGRP interacts with other classful and classless routing algorithms. Table 5-4 summarizes the most useful commands from this chapter.

only BGP updates are sent between peers. such as the Internet. This information is stored so that routing loops can be avoided. BGP sessions are maintained by keepalive messages. called attributes. Routers configured for BGP are typically called BGP speakers. Chapter 7. and 4 on a Cisco IOS router. An AS is a set of routers under the same administrative control. 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. No other routing protocol in use today relies on TCP. Basic Border Gateway Protocol (BGP4) Defined The different versions of BGP range from 1–4. 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. You can. which include the next hop address and origin. BGP peers exchange full BGP routing tables initially. however. Any network entry must reside in the BGP table first. such as a loss of network availability. BGP has its own BGP table. Keepalives— These messages are sent periodically to ensure that connections are still active or established. This allows TCP to ensure that updates are sent reliably. "Advanced BGP. Full routing tables are exchanged only during the initial BGP session. 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. BGP enables you to create an IP network free of routing loops among different autonomous systems. . BGP has a complex array of metrics. BGP supports variable-length subnet masking (VLSM) and summarization (sometimes called classless interdomain routing [CIDR]). 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. The Internet consists of over 80. After that. BGP uses TCP as the transport layer protocol. However. 3. BGP4 is covered only slightly in the CCNP routing examination. Basic Border Gateway Protocol This chapter focuses on Border Gateway Protocol Version 4 (BGP4). Updates are sent over TCP port 179. and there is no doubt that only BGP can handle such a complex routing table. Any network changes result in update messages.CCNP Practical Studies: Routing Chapter 6. This chapter covers the basics of Border Gateway Protocol (BGP). Update messages— Any change that occurs. configure BGP Versions 2. leaving the routing protocol to concentrate on gathering information about remote networks and ensuring a loop-free topology. unless a change occurs.189 - . the following section describes the BGP attributes. BGP uses Transmission Control Protocol (TCP) as its Layer 4 protocol (TCP port number 179)." covers more advanced BGP topics and scenarios. Before you look at some simple examples. and any two BGP routers that form a BGP TCP sessions are called BGP peers or BGP neighbors. The key characteristics of BGP include the following: • • • • • • • • • BGP is termed a path vector protocol. 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. the industry standard is Version 4.000 BGP network entries. Notification— These messages are used only to notify BGP peers of receiving errors. ensuring that only useful data is sent. BGP4 is defined in industry standard RFC 1771.

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

If the MED is the same. therefore. Step 8. prefer the route with the lowest MED. Prefer the route with the shortest AS path. the routers must be synchronized. Step 10. Step 3. In other words. 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. before sending the route information. Step 9. which reduces any unnecessary traffic. consider it. such as Open Shortest Path First (OSPF). prefer the path with lowest BGP router ID. If the weight is the same. If the local preference is the same. The process a Cisco router running BGP4 takes is as follows: Step 1. Step 7. Prefer the route with the highest weight (Cisco IOS routers only). and. Prefer the closest path. prefer the route with the origin set to originated (through BGP). Step 5. . if all paths are equal.191 - . prefer the route this local router originated. Step 4. If the origin codes are the same. If this is equal. which is covered later in this chapter. Finally. prefer EBGP over IBGP.CCNP Practical Studies: Routing Figure 6-1. prefer the largest local preference attribute. Step 6. You can disable this feature with the no synchronization command. The benefit of this additional rule in IBGP TCP sessions is that information is not sent unless the remote path is reachable. If the next hop address is reachable. saves bandwidth. Step 2. IGP is preferred to EGP followed by incomplete. The BGP routing decision is quite complex and takes into account the attributes listed in Table 6-1.

3.108. you use the network command to advertise networks that originate from the router and need to be advertised through BGP.0 R1(config-if)#interface loopback 1 R1(config-if)#ip address 131. you see how to configure IBGP and EBGP among the three routers in Figure 6-1.1.2.255.2 remote-as 2 Finally. .108. To identify peer routers.0.0 to 131.1 remote-as 1 At this stage.4.1 255. 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. apply the following command: neighbor ip-address | peer-group name remote-as autonomous system number Next.255. ranging from 131.CCNP Practical Studies: Routing Configuring BGP To start BGP on a Cisco router.108. Use some loopback interfaces on R1 and advertise them through BGP to R2 and R3.108.0 R1(config-if)#interface loopback 2 R1(config-if)#ip address 131. the following command is required: router bgp autonomous system number To define networks to be advertised.192 - . Example 6-4 Loopback Configuration on R1 R1(config)#interface loopback 0 R1(config-if)#ip address 131. no BGP entries are on any routers.255. Because these networks are local to R1 and present in R1's IP routing table as connected routes.1 remote-as 1 R2(config-router)#neighbor 131.1.108.255. With BGP.2.255. because no network statements have been applied.108. you can apply the network command as displayed in Example 6-5.255.255.108.2 remote 1 Example 6-2 displays the IBGP configuration to R1 and EBGP configuration to R3.1 255.4. 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. Example 6-3 EBGP on R3 R3(config)#router bgp ? <1-65535> Autonomous system number R3(config)#router bgp 2 R3(config-router)#neighbor 131.255.0 You must next advertise these loopbacks with the network command. Example 6-4 displays the three new loopback addresses on R1.1 255.108. Example 6-1 displays the IBGP configuration on R1 to R2. Example 6-3 displays the EBGP connection from R3 to R2.108. Example 6-2 IBGP/EBGP on R2 R2(config)#router bgp 1 R2(config-router)#neighbor 131.

0/24 *> 131.1. therefore.2. d damped. Example 6-7 show ip bgp on R2 R2#show ip bgp BGP table version is 7.108.incomplete Network * i131. Disable synchronization on R1 and R2. Because R1 and R2 are running only IBGP and no other interior gateway protocol.108.0.0 R1(config-router)#network 131. R3 does not have any entries at all.2. or advertised through BGP.3.internal Origin codes: i .0 0.1 Status codes: s suppressed.108.0.1. * valid. either in the BGP table or IP routing table.193 - .255.0/24 *> 131.0 is directly connected. Example 6-6 also displays the path as i.255. ? . ? .1 131. e .108. d damped.1. in turn.0 mask 255.2.0 Example 6-6 displays the BGP table on R1. . i .108.108.3.0 is directly connected.255.0/24 * i131.1. and it learns the remote loopbacks on R1 through the next hop address 131.4. local router ID is 171.EGP. local router ID is 131. * valid.1 Metric LocPrf Weight Path 0 100 0 i 0 100 0 i 0 100 0 i R2's local router is 131.255.108. > best.0/24 Next Hop 0. Example 6-8 confirms this with only the locally connected routes visible on R2. the origin attribute is set to i or IGP.CCNP Practical Studies: Routing Example 6-5 network Command on R1 R1(config)#router bgp 1 R1(config-router)#network 131.IGP.0 or local interfaces). Example 6-7 displays the BGP table on R2.0. using the command show ip bgp.1. Serial1/0 C 131. R2's IP routing table does not have the BGP entries inserted because of synchronization. h history. or R1's Ethernet interface.1. Ethernet0/0 To enable BGP to insert the routes.108. Example 6-9 displays the no synchronization command on R1 and R2.EGP.108.108.109.3.0 mask 255.108.108. > best.1.0.1.0 R1(config-router)#network 131.1.0/24 Next Hop 131.0. The local router ID is 131.4.2. Example 6-6 show ip bgp on R1 R1#show ip bgp BGP table version is 4.108.108.IGP.0.255. R2.0.1.1 131.108. does not propagate the loopbacks to R3.255.255.0/24 * i131.108.0 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.internal Origin codes: i . 2 subnets C 131.108.4. e .0/24 is subnetted.0.0 mask 255.0. Example 6-8 show ip route on R2 R2#show ip route 131.0 0.108. i .incomplete Network *> 131. you must disable synchronization or configure an IGP routing protocol.1 Status codes: s suppressed. Notice that R2 has set the local preference to 100 (default value).3. h history.

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 [200/0] via 131.255.0.108.108.1. > best.108. .255. Scenario 6-1: EBGP and IBGP Configure the four-router topology in Figure 6-2 for IBGP and EBGP. Again.0) are reachable from R3 and R4.108.4. e .3.2. Ethernet0/0 The three remote networks are inserted into the IP routing tables as BGP-learned networks.108.108.0 is directly connected. and to ensure a loop-free topology.7.108.255. and use back-to-back serial connections among Cisco routers. h history.0 [20/0] via 131. 131.incomplete Network Next Hop Metric LocPrf Weight Path *> 131.0/24. and the abilities to use good practice and define your end goal are important in any real-life design or solution.108.0 is directly connected. 5 subnets C 131. do not disable synchronization on any router. There is no one right way to accomplish many of the tasks presented.5.0/24 is subnetted. Example 6-11 displays R3's BGP and IP routing table.1 0 1 i *> 131.0–131.0/24 is subnetted.108. Serial1/0 B 131.2.4.0 [200/0] via 131.0 [200/0] via 131. local router ID is 131.108. ? . transverse autonomous system number 1.108.4.108.0. Example 6-11 R3's BGP and IP Tables R3>show ip bgp BGP table version is 10. Example 6-10 R2's Routing Table R2#sh ip route 131. 00:00:43 B 131. use loopback interfaces to help populate BGP tables.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.255.5. d damped.108.108.0–131.108.1.0 is directly connected.108.108.1 0 1 i R3>show ip route 131.0 [20/0] via 131.108.108. Ethernet0 Notice that the next hop address on R3 is R2.0 is directly connected.1.1.108.0/24 131.108.1.1.3. 00:02:09 B 131.108.255.108.1. The AS path on R3 indicates that the remote networks.IGP.4. 00:02:09 C 131.0/24) and R2 (131. 5 subnets C 131. such as route maps and the changing the BGP attributes.255.3.EGP. i .1.0/24 131. OSPF is configured between R1 and R2. Serial0 B 131.194 - .2. as displayed in the BGP table in Example 6-11. Ensure that the loopback addresses on R1 (131.1.0 to 131.2 Status codes: s suppressed.108.108.internal Origin codes: i .108.255.255.0 [20/0] via 131.108.255. 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.1 0 1 i *> 131.2.1. 00:00:43 B 131.1.108.108. * valid. 00:02:09 B 131.0/24 131.108.108.2. 00:00:43 C 131.

you configure BGP on four routers and ensure that all BGP peers have remote IP routing entries.108.0 131.1.0 0.195 - .108.1.0 131.0.108.7.108.0.0.2.0/24. 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 131.2 Interface Ethernet0/0 .0.1.0.5.0.0 131.255 0.3.1 1 FULL/BDR Dead Time 00:00:36 Address 131.0. notice that this network contains a potential routing loop.108. Example 6-12 displays the OSPF configuration on R1.0.255 0.0.255 area area area area 0 0 0 0 Example 6-14 confirms that OSPF neighbors are active to R2.6.0 131. IBGP/EBGP In this scenario.1.255 0.255 area area area area 0 0 0 0 Example 6-13 displays the OSPF configuration on R2. so you discover how BGP helps you avoid loops.0 0.108.255 0. the loopbacks are placed in area 0.CCNP Practical Studies: Routing Figure 6-2.108.108.0.108.0.0.255 0.0. 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. R1 and R2 are running OSPF across the Ethernet subnet 131.108.0.4.0. Also. Example 6-14 show ip ospf neighbor on R1 R1#show ip ospf neighbor Neighbor ID Pri State 131.0 131.108.255 0.7.0.0 131.

255.255. both on R1.108.0 R1(config-router)#network 131.0.4.255.2 Metric LocPrf Weight Path 0 100 0 ? R1's BGP table has no information about the locally connected loopbacks 131. d damped.255.0 The same network configuration is required on R2.108.255. i . e . Example 6-19 displays the BGP table on R1 after the loopbacks on R1 and R2 are advertised through BGP. You use the clear ip bgp ip–address-of-peer command to clear a specific BGP peer.255.108.4. .0 Next Hop 131.108.EGP.IGP.255. or 131.0 mask 255.108.4.5.7.255.0 R2(config-router)#network 131. you must use the clear ip bgp * command to clear the TCP sessions (* for all BGP TCP peers).0 NOTE Whenever you make BGP configuration changes on Cisco IOS routers.internal Origin codes: i . and the only network in the BGP table is the remote network 131.108. * valid.1.6 remote-as 3 Now that you have configured BGP4 (by default.108.108.108.108.108.2. 131. h history.0.0 mask 255.1.255.196 - .6. enable IBGP between R1 and R2 and EBGP connections between R1/R3 and R2/R4.0.0 mask 255. ? . Example 6-17 displays the network configuration on R1.3. Example 6-15 IBGP/EBGP Configuration on R1 R1(config-router)#router bgp 1 R1(config-router)# neighbor 131.108.1 Status codes: s suppressed.255.3.0 mask 255.0 R1(config-router)#network 131.108. Example 6-18 displays the network configuration on R2. Example 6-15 displays the IBGP configuration to R2 and the EBGP configuration to R3. BGP Version 4 is enabled on Cisco IOS routers).0 R2(config-router)#network 131.CCNP Practical Studies: Routing Next. local router ID is 131.255. > best.0. Example 6-16 displays R1's BGP table.incomplete Network *i131. Example 6-16 R1's BGP Table R1#show ip bgp BGP table version is 1.2 remote-as 1 R1(config-router)# neighbor 131.0 mask 255.108.0.255.0 through R2. Example 6-18 Inserting Local Loopback on R2 R2(config)#router bgp 1 R2(config-router)#network 131.0 mask 255. You need to use the network command to configure the local interfaces.255.2. Example 6-17 Inserting Local Loopback on R1 R1(config)#router bgp 1 R1(config-router)#network 131.108.

0.108.108.0.108.0/24 131.0.1.incomplete Network Next Hop Metric LocPrf Weight Path *>i131.0/24 * i131.4.108.108.2 0 100 0 i One of the most important commands used in BGP networks is the IOS show ip bgp neighbor command.108.EGP. By default.0 0 32768 i *> 131. local router ID is 131.1.4. Example 6-22 displays the remote BGP peers on R1.108.0. BGP automatically summarizes at the network boundary.5. ? . e . To turn off this behavior.108.108.0.108.108.0 0. h history.2 0 100 0 i * i131.1 Status codes: s suppressed.4.108.1.EGP.5. i .2 0 100 0 ? *> 131.0/24 131.0.0/24 0. Example 6-21 displays R1's BGP table. You can change any BGP attribute. and the local preference is 100 for the remote networks.1.6. notice that the default weight on R1 is set to 32768 (for local networks). d damped.4. as you discover shortly.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 131.1. you apply the no auto-summary command.0 0.2). * valid.108.IGP.108.0.108. .108.108.197 - .0/24 *> 131.CCNP Practical Studies: Routing Example 6-19 R1's BGP Table R1#show ip bgp BGP table version is 4.2 command.108.0/24 0.1.IGP.0 131. you can expect the BGP table on R1 to contain only specific network entries.0/24 131.3.1 Status codes: s suppressed. > best. h history. > best.2 131.0/24 * i131. 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. Also.108.2 131. which displays the remote BGP peers and their states. * valid.3.108.0/24 0.1.108. These settings are set by default.2.2 0.0/24 *> 131.2 0 100 0 i * i131.0 *> 131.0 0 32768 i *> 131.108.0. Example 6-21 R1's BGP Table R1#show ip bgp BGP table version is 5.0/24 131.1. i .0 reachable through R2 (131.2).0.0/24 * i131.108.1. Note that the information relates to the BGP peer to R2 and R3.108.7.0/24 Next Hop 131.1.internal Origin codes: i . The first entry in Example 6-19 displays the remote network 131.0. ? .108.0.108.6.0.incomplete Network * i131.internal Origin codes: i .1.0 0 32768 i * i131.0. e .108.108.0.2.1. Example 6-20 displays this configuration completed on R1 and R2. local router ID is 131. d damped.7.

255.0. 0 notifications. 0 notifications. up for 00:04:30 Last read 00:00:30. Offset 0. 0 in queue Prefix advertised 14. internal link Index 1. keepalive interval is 60 seconds Minimum time between advertisement runs is 5 seconds Received 1297 messages. total data bytes: 206 BGP neighbor is 131.108.108. with data: 8. Anything other than the keyword established between two BGP indicates a problem.108. The possible BGP states are as follows: . remote router ID 131.1. table version = 0 Last read 00:17:54. keepalive interval is 60 seconds Minimum time between advertisement runs is 5 seconds Received 0 messages.1. hold time is 180. 0 in queue Sent 0 messages. 0 notifications.1.198 - . 0 in queue Sent 1290 messages. withdrawn 0 Connections established 0. due to User reset 4 accepted prefixes consume 128 bytes 0 history paths consume 0 bytes Connection state is ESTAB.2. dropped 6 Last reset 00:04:39. but not to R3.6. remote AS 3. withdrawn 0 Connections established 7.CCNP Practical Studies: Routing Example 6-22 show ip bgp neighbors on R1 R1#sh ip bgp neighbors BGP neighbor is 131.108. remote AS 1. dropped 0 Last reset 00:17:55. remote router ID 0.108. unread input bytes: 0 Local host: 131. nagle Datagrams (max data segment is 1460 bytes): Rcvd: 16 (out of order: 0). 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. ACK hold: 200 ms Flags: higher precedence. external link Index 2.255. Mask 0x4 BGP version 4.1 BGP state = Established. suppressed 0. 0 notifications.1. RTV: 1263 ms. 0 in queue Prefix advertised 0. I/O status: 1. You have yet to configure BGP on R3. maxRTT: 300 ms. Foreign port: 179 Enqueued packets for retransmit: 0. table version = 5. with data: 10.0. suppressed 0. Local port: 11632 Foreign host: 131. total data bytes: 509 Sent: 13 (retransmit: 0).2. Offset 0. Mask 0x2 BGP version 4. hold time is 180.0 BGP state = Active. 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. RTTO: 3547 ms. KRTT: 0 ms minRTT: 0 ms.

note the EBGP connection between R3 (AS 3) and R4 (AS 2).108. remote router ID 131.108. Offset 0. you enable EBGP between R1 and R3. 0 in queue Prefix advertised 16. Example 6-23 displays the BGP configuration on R3.108. hold time is 180. up for 00:58:56 Last read 00:00:56. 0 notifications. hold time is 180.0 R3(config-router)#neighbor 131. OpenSent— BGP is waiting for an open message from the remote peer.0 mask 255. and an EBGP peer to R3. keepalive interval is Minimum time between advertisement runs is 5 seconds Received 1351 messages.108.. Mask 0x2 BGP version 4. BGP neighbor is 131. this is the final stage of BGP peer negotiation during which both peers exchange their BGP tables.255. Foreign port: 11001 . 0 notifications. such as clearing the BGP peers. Established— After a keepalive message is sent. which is initiated by an operator of BGP.1. Foreign port: 179 . remote router ID 141. due to User reset 4 accepted prefixes consume 128 bytes 0 history paths consume 0 bytes Connection state is ESTAB.199 - . suppressed 0. R1> R1 has two established peers: one IBGP peer to R2.255. Local port: 179 Foreign host: 131.CCNP Practical Studies: Routing • • • • • • Idle— BGP is waiting for a starting event.0/24 as originating from AS 3. table version = 8. I/O status: 1. OpenConfirm— BGP is waiting for a keepalive message. 0 in queue Sent 48 messages. remote AS 1. so that R3 advertises the network 141. Next. 0 in queue Sent 1347 messages.108. 0 in queue Prefix advertised 8.108. dropped 1 Last reset 00:38:38.255. remote AS 3.6. unread input bytes: Local host: 131. 60 seconds 0 60 seconds 0 .108. Offset 0. Connect— BGP is waiting for the TCP connection to be completed.5 remote-as 1 The BGP peers on R1 are displayed in Example 6-24 (truncated for clarity).. Active— BGP is trying to acquire a remote peer by initiating a new TCP connection.1. Also.108.1.255. table version = 8.1 BGP state = Established.255. withdrawn 0 Connections established 2. unread input bytes: Local host: 131.1.108.255.1.1.255. due to Peer closed the session 1 accepted prefixes consume 32 bytes 0 history paths consume 0 bytes Connection state is ESTAB. keepalive interval is Minimum time between advertisement runs is 30 seconds Received 46 messages.108. withdrawn 1 Connections established 7.. 0 notifications.108.2.2.1 BGP state = Established. 0 notifications.6. Example 6-23 EBGP Configuration on R3 R3(config)#router bgp 3 R3(config-router)#network 141. internal link Index 1. Mask 0x4 BGP version 4. suppressed 0. external link Index 2. up for 00:38:16 Last read 00:00:16. Example 6-24 show ip bgp neighbors on R1 (Truncated) R1>show ip bgp neighbors BGP neighbor is 131. along with the network statement. Local port: 11632 Foreign host: 131.1. dropped 6 Last reset 00:59:05.5. I/O status: 1..

Example 6-26 displays the BGP peers on R4 in a summarized format.108.255.255.1.108.0.108.108.B.108. local AS number 2 BGP table version is 9.CCNP Practical Studies: Routing Example 6-25 enables EBGP between R4 and R2.1.1.255.C.0/8 A. as displayed by the IOS show ip bgp summary command.9 remote 3 R4(config-router)#network 151. Example 6-25 Configuring BGP on R4 R4(config)#router bgp 2 R4(config-router)#neighbor 131.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. 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.C.1 4 1 32 22 13 0 0 00:01:21 7 131.. .D IP prefix <network>/<length>.255.0 The show ip bgp summary command is a useful command that summarizes all BGP peers. scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131.0.g.255.B.108. Example 6-26 show ip bgp summary on R4 R4#show ip bgp ? A.0 mask 255.1 remote-as 1 R4(config-router)#neighbor 131.200 - . 35.9 4 3 7 8 13 0 0 00:01:15 5 Table 6-2 summarizes the descriptions and field definition.255. 8/0 paths.

108.255. or the current state. Current state of the BGP session/the number of prefixes the router has received from a neighbor or peer group.3.10.0 is directly connected. 1 subnets B 151.1/24.108.0/24 [20/0] via 131. 00:56:24 151. 00:06:11 B 131. Last version of the BGP database sent to that neighbor. the router ID of R4 is 151. Serial0 C 131.1/32 [20/0] via 131. PfxRcd.10. 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. IP address of a neighbor.255.108.5. 00:56:23 B 131.108.1.255.108.4.108. Example 6-28 displays R3's BGP table.108.108.CCNP Practical Studies: Routing Table 6-2. To view more information about how the BGP entries were learned.1/32 [20/0] via 131. view the BGP table with the show ip bgp command.6. the neighbor is shut down.10.2.10. 00:06:10 B 131. in Example 6-26. Number of messages waiting to be sent to that neighbor. loopback address.0/24 [20/0] via 131.108. view some IP routing tables to ensure that you are routing IP.255. 00:06:10 B 131.108.8/30 is directly connected. if the state is not Established. 00:06:10 B 131.10.108.0/24 [20/0] via 131.108.108. 00:05:46 R3 has a full set of BGP routes for all BGP AS networks.2.108.5.4/30 is directly connected.108.255. Internal version number of BGP database. BGP version number spoken to that neighbor. Ethernet0 131.0/24 [20/0] via 131. 3 masks C 131. Number of messages from that neighbor waiting to be processed. Next. Peer autonomous system.108. 00:06:11 B 131. Example 6-27 displays R3's IP routing table.255.255. or lowest IP address. 12 subnets.255. Last version of BGP database injected into main routing table.0/24 is subnetted.1. 00:56:22 B 131.108.10.0/16 is variably subnetted.1/32 [20/0] via 131.0. as displayed in Example 6-26.108. 00:06:10 B 131. 1 subnets C 141. and the connection is idle.108. Example 6-27 R3's IP Routing Table R3#show ip route 141. The length of time that the BGP session has been in the Established state.201 - . router identifier specified by the bgp router-id command.0. When the maximum number (as set by the neighbor maximum-prefix command) is reached.0 [20/0] via 131.4.10. 00:56:23 B 131.108. Serial3 B 131.0/24 [20/0] via 131.0.5.108. BGP messages sent to that neighbor.1.108.255.5.7.0/24 [20/0] via 131.255.255. .108.108.108.5. appears in the entry.108.108. For Example. Typically you see only version 4.0/24 is subnetted.255.255. the string. No information below the state indicates an active peer.108.3.0/24 [20/0] via 131.1. BGP messages received from that neighbor.

108.10 weight 1 Example 6-30 displays the BGP table on R3 after the configuration change.108.255.255.108.0.3. i .0/24 131.4.108.0/24 131.108.1 Status codes: s suppressed.) Example 6-29 Changing the Weight on R3 R3(config)#router bgp 3 R3(config-router)#neighbor 131.108. ? .108.5.108. ? .1/32 131. (Static routes can be used to change this behavior.108.1.0/24 0. change the weight on R3 to prefer the path through R4.internal Origin codes: i .108.255.108.108.255. not originated by local router).10 0 2 1 ? *> 131. Example 6-30 show ip bgp on R3 R3#show ip bgp BGP table version is 16.108.108.6. * valid.108.incomplete Network Next Hop Metric LocPrf Weight Path * 131.5 0 0 1 i *> 131.2. local router ID is 141.255.10 0 2 1 ? *> 131. e .10 0 2 1 i *> 131.108.255. Start by analyzing why the remote network 131.5 0 0 1 i *> 131.10 0 2 1 ? *> 131.255.108.0/24 131.255.5 0 0 1 i *> 131.10 0 2 1 ? *> 131.108.3.255.108.202 - .108.0/24 131.108.10 0 2 1 ? *> 131.108.108.5 0 1 ? *> 131.108.255. d damped.6. local preference the same.255.5 0 0 1 i *> 131.10 0 2 1 i *> 141.108.7.0/24 131.0/24 131.108.10 0 2 1 i *> 141.1/32 131.5.1.0/24 131.0/24 131.1/32 131.108.255.255.1. BGP does not load balance and always chooses one path.108.255.1/32 131.2.0/24 131. The next decision is based on the path with the shortest AS path.255.0/24 131.108.1.108.0/24 131.5.108. is preferred as the path through R4.108.1 Status codes: s suppressed.2.10 0 0 2 i A lot of information is stored here.108.CCNP Practical Studies: Routing Example 6-28 R3's BGP Table R3#show ip bgp BGP table version is 16.108.255.108.255.0/24 131. i .10 0 2 1 i *> 131.255.5 0 0 1 i *> 131.0/24 only. h history.3.0/24 0.EGP.internal Origin codes: i .IGP.1.108.4.) 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.0 0 32768 i *> 151.108. h history.108.255.108. Clear the BGP TCP peer session on R3 to R4 with the clear ip bgp 131.255.1/32 131.108.108.108.2.108.5 0 0 1 i *> 131.0/24 131. > best.1.1.1.108.255. local router ID is 141.0/24 131.IGP. weight equal.0.5 1 0 1 ? *> 131.0/24 131. The path to R1 is through one AS path only as opposed by two AS paths to R4.108.255. 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. d damped.0.10 0 2 1 ? *> 131.108.7.10 0 2 1 i *> 131.0 0 32768 i *> 151. > best.255. Example 6-31 displays the BGP table on R3 after the BGP TCP peer is established again.10 command.108.255.1/32 131.108. Because weight has a higher preference than AS path.255.108. e .108.0 has a dual path and why the next hop address 13.108.EGP.4.108.108.incomplete Network Next Hop Metric LocPrf Weight Path * 131.1.108.4.255. (There are many ways to accomplish this task.3.10 0 0 2 i The change is not implemented because you must first clear the BGP peer session.108. or the link to R1.10 0 2 1 ? *> 131.0/24 131. * valid. .255.10 0 2 1 ? *> 131.10 0 2 1 i *> 131.1.0.

255. 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. local router ID is 141.IGP.1 255.10 1 2 1 i *> 131.108. Provided here for your reference are the four configurations on the Routers R1 through R4.10 1 2 1 ? *> 131.1 255.108.255.0 0.255.255.108.1 Status codes: s suppressed.108.CCNP Practical Studies: Routing Example 6-31 show ip bgp on R3 R3#show ip bgp BGP table version is 32. * valid.2.1/32 131.0 0 32768 i *> 151.1.EGP.IGP.108.5 100 0 1 i *> 131.252 clockrate 125000 ! router ospf 1 network 131.0/24 131.10 1 2 1 ? *> 131.108.10. d damped.255. You have successfully configured a four-router topology with BGP4. h history.10 1 2 1 i *> 141.108.108.108.10 0 1 2 i Even though the path to the remote network 131. the path to 131.6. Example 6-32 display R1's full working configuration.EGP.255. d damped.7.3.255.1.5 100 0 1 i *> 131.3. > best.108.0.10 1 2 1 ? *> 131.0 ! interface Ethernet0/0 ip address 131.5 100 0 1 i *> 131.255. All entries advertised through the next hop address 131.255.0/24 131.108. or R4.108. i .5 100 0 1 ? *> 131.255. > best.2.0/24 131.108.108.108.1.1/32 131.255.4.0/24 131.108.1.255.0/24 131.0/24 131. e .3.108.255.incomplete Network Next Hop Metric LocPrf Weight Path *> 131.1.0/24 is now preferred through R4 (weight is 1) as opposed to the link through R1.108.0/24 131.incomplete Network Next Hop Metric LocPrf Weight Path R3#show ip bgp BGP table version is 16.255.108.5 255.1. * valid. have the weight value set to 1.0/24 0. e .108.4.255.0. ? .4.255.255.0 ! interface Serial0/0 ip address 131.0. ? .108.255.108.5.0.internal Origin codes: i .108.255.108.108.2.108.108. local router ID is 141.255. i .1 255.255.108.255.108.1 255.10 1 2 1 ? * 131.1/32 131.108.108.255.108.255 area 0 .108.0 ! interface Loopback1 ip address 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.internal Origin codes: i .0 ! interface Loopback2 ip address 131.108.108.1.255.0/24 131.1. h history.203 - .10 1 2 1 i *> 131.1 Status codes: s suppressed.1.

0 mask 255.0 mask 255.2 remote-as 2 no auto-summary ! line con 0 line aux 0 line vty 0 4 end .4.1 255.255.255.6.108.0.108.0.108.1 255.1 255.0 network 131.CCNP Practical Studies: Routing network 131.108.255.0 0.108.204 - .1.255.108.2 remote-as 1 neighbor 131.2.255 area 0 network 131.1.255.3.0 mask 255.3.0 redistribute ospf 1 metric 100 neighbor 131.255.255 area 0 network 131.255.255 area 0 network 131.0 interface Loopback1 ip address 131.0.255.1 255.0 0.0.7.0 0.0 mask 255. Example 6-33 R2's Full Working Configuration hostname R2 ! enable password cisco ! no ip domain-lookup interface Loopback0 ip address 131.108.255.5.108.0 0.0.6 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.108.108.1 remote-as 1 neighbor 131.0.255.5.255.0 ! interface Loopback2 ip address 131.0 network 131.255.1.0 neighbor 131.7.108.0 mask 255.108.255.0 mask 255.255 area 0 network 131.0 0.255.2 255.108.108.0 clockrate 128000 ! router ospf 1 network 131.0 ! interface Serial1/0 ip address 131.0.255.108.4.0.0.255.108.0.255.7.108.0 ! interface Ethernet0/0 ip address 131.0.255 area 0 network 131.255.0.108.255.108.255.108.255.0.6.255.0 0.255.108.108.0 0.255 area 0 ! router bgp 1 network 131.0 network 131.6.255 area 0 ! router bgp 1 network 131.255.2.0 network 131.5.0.255.1.

255.1.108.108.108.0 neighbor 131.9 remote-as 3 ! line con 0 .255.108.252 bandwidth 125 ! interface Serial1 shutdown ! interface Serial2 shutdown ! interface Serial3 ip address 131.205 - .10 remote-as 2 neighbor 131.255.108.255.108.5 remote-as 1 neighbor 131.255.255.1.CCNP Practical Studies: Routing Example 6-34 display R3's full working configuration.1 255.108.6 255.10 weight 1 ! line con 0 line aux 0 line vty 0 4 ! end Example 6-35 display R4's full working configuration.9 255.255.255.1.255.2 255.108.108.0 interface Serial0 ip address 131.108.255.0 neighbor 131.255.255.255. Example 6-34 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 141.255.1.255.0 mask 255.108. Example 6-35 R4's Full Working Configuration hostname R4 ! enable password cisco no ip domain-lookup interface Ethernet0 ip address 151.0 media-type 10BaseT ! interface Serial0 ip address 131.252 ! router bgp 3 network 141.255.1 255.255.0 mask 255.255.255.1 remote-as 1 neighbor 131.255.108.252 ! interface Serial1 shutdown ! router bgp 2 network 151.255.255.

1.1 update-source Ethernet0/0 .1 update-source Ethernet0/0 Example 6-37 displays the EBGP configuration on R2.255.1/24. With BGP.1.255.0 mask 255.0/24.108.108.108. 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. you can use static routes to the remote peer address.1 (Ethernet 0/0). Also.0/24 (Ethernet 0/0). BGP needs to advertise the update source IP address to EBGP. it is 131. Example 6-37 EBGP Configuration on R2 R2(config)#router bgp 2 R2(config-router)#network 161.1.1.1.1. Example 6-36 displays the EBGP configuration (with multihop) on R1.108.0 R1(config-router)#neighbor 161. BGP Topology Enable BGP on R1 and configure the network command to advertise the Ethernet IP network 131.1/24.108. you use static routes to load balance BGP over a dual-path connection between two routers.108.0 mask 255.108. Figure 6-3 displays a simple two-router BGP topology.255.108.108. Example 6-36 EBGP Configuration on R1 R1(config)#router bgp 1 R1(config-router)#network 131. it is 161.1. and in the case of R2. you need to peer the BGP neighbors using the Ethernet IP addresses. if the next hop address in EBGP is not used.1.255. to achieve load balancing.1.1.108. synchronization is not an issue in this network.108. BGP chooses only one path to a remote network. Because you are running EBGP.1. In the case of R1.1 ebgp-multihop R2(config-router)#neighbor 131. Also. In the case of R1. and in the case of R2. To achieve any form of load balancing of two or more network paths.1 remote-as 2 R1(config-router)#neighbor 161. because the next hop address is not a directly connected address.1.1 ebgp-multihop R1(config-router)#neighbor 161. Figure 6-3. the next hop peer address is 161.206 - .0 R2(config-router)#neighbor 131. The IOS command to enable EBGP multihop is neighbor peer address ebgpmultihop. such as in this scenario in which you want to achieve load balancing.108.108.1. you must enable EBGP multihop so that the EBGP peer is established.1 remote-as 1 R2(config-router)#neighbor 131.

1. display the IP routing table on R1. Example 6-40 Static Route Configuration on R1 R1(config)#ip route 161.1.0/24 is directly connected.108. 2 subnets.0.0 255.0 serial 0/1 To ensure that R2 can route to the remote network 131. remote AS 2. Example 6-39 displays R1's IP routing table.108.0/30 is directly connected. Example 6-42 shows a truncated display of the peer with R2.255.108.1. To discover why.1. hold time is 180.0.0.255.0 BGP state = Active.108. Configure two static routes on R1 pointing to the remote network through Serial 0/0 and Serial 0/1.108. 2 masks C 131.1.1.255. external link Index 1.108.255. Example 6-40 displays the IP static route configuration on R1. Example 6-41 displays the IP static route configuration on R2. 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. remote router ID 0. keepalive interval is 60 seconds Minimum time between advertisement runs is 30 seconds Received 0 messages.1.0/16 is variably subnetted. 0 in queue Sent 0 messages. withdrawn 0 Connections established 0. Example 6-38 show ip bgp neighbors on R1 R1#show ip bgp neighbors BGP neighbor is 161.255. Offset 0. Example 6-41 Static Route Configuration on R2 R2(config)#ip route 131. 0 notifications.0 serial 1/0 R2(config)#ip route 131.207 - . Mask 0x2 BGP version 4.255. Example 6-39 show ip route on R1 R1#show ip route 131.108.0.108.0 serial 1/1 The BGP peers on R1 display the established peer to R1.108. 0 in queue Prefix advertised 0. .255.1.0 255. Serial0/0 C 131.108. No active TCP connection R1 has no peer relationship to R2. ensure that BGP peer sessions are up with the show ip bgp neighbor command. install two static routes pointing to R1 over Serial 1/0 and Serial 1/1.0 255.4/30 is directly connected.0 serial 0/0 R1(config)#ip route 161. Ethernet0/0 R1 does not have any entries for the remote network 161.0/24 and thereby cannot establish a TCP session to R2.CCNP Practical Studies: Routing Now that R1 and R2 are configured with EBGP.0 255.255.255. table version = 0 Last read 00:03:37. Serial0/1 C 131.108. Example 6-38 displays the peers on R1. suppressed 0. 0 notifications.1.255.

1. sending 00:09:27: IP: s=161. Offset 0. rcvd 3 00:09:27: IP: s=131. so you can see on which outbound interface the ping request is sent..1.208 - . 100-byte ICMP Echos to 161. This command enables you to view where IP packets are sent to and received from.108. 0 notifications.255. Sending 5.1 (Serial0/0).1.255.1. 0 in queue Sent 7 messages.1.108.255.108.5 (Serial0/1). 0 notifications. d=161.1 (Serial0/1).[truncated display] Ensure that load balancing is taking place by pinging the remote network 161.1 (Serial0/1). Example 6-43 shows the ping request after the debug ip packet command is enabled. which contain the critical commands used to achieve load balancing between R1 and R2. withdrawn 0 Connections established 1.108.1 (Serial0/0). 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 100.108.1.1 (Serial0/0).255. sending 00:09:27: IP: s=161. It is important to note that BGP still only sends packets through one path. d=131. 0 in queue Prefix advertised 1.108.1.108.108.1 (Serial0/1). load balancing is occurring.5 (Serial0/1). rcvd 3 00:09:27: IP: s=131.108. therefore.1. sending 00:09:27: IP: s=161.108.108.1/24 from R1. Turn on debug ip packet. sending 00:09:27: IP: s=161.1 (Serial0/0).1 (Serial0/0). d=131.108. len 100. dropped 0 Last reset 00:04:21.255.1 (Serial0/1). Example 6-44 displays the full working configuration of R1.1. len 100.108. len 100. The second ping request is sent through Serial 0/1.108.108.108.108. remote router ID 161. in effect you are load balancing BGP by using static routes. . d=161.1.1.108. rcvd 3 00:09:27: IP: s=131. d=161.1 (Serial0/0). table version = 3. d=131. len 100. up for 00:03:51 Last read 00:00:51.1.1.5 (local).255. and the reply is received through Serial 0/1. len 100. round-trip min/avg/max = 16/17/20 ms 00:09:27: IP: s=131. Take note of the shaded sections. rcvd 3 00:09:27: IP: s=131.108. external link Index 1. d=131.1 Type escape sequence to abort. remote AS 2.1. but because IP at Layer 3 is load balancing. Mask 0x2 BGP version 4. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).5 (local).108.108. len 100. suppressed 0.1. d=161. hold time is 180. len 100.CCNP Practical Studies: Routing Example 6-42 show ip bgp neighbors on R1 R1#show ip bgp neighbors BGP neighbor is 161. keepalive interval is 60 seconds Minimum time between advertisement runs is 30 seconds Received 7 messages.255.1 (Serial0/0). len 100. Example 6-43 Debug Output on R1 R1#debug ip packet IP packet debugging is on R1#ping 161.255.108.1 (Serial0/0).108. len 100.1 BGP state = Established. sending 00:09:27: IP: s=161.1 (Serial0/0).1 (local).1.1 (local). 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. d=131.255. d=161.255.108.1.108.1 (local). .

1 ebgp-multihop 255 neighbor 161.255.108.1.1 255.255.255.1.252 clockrate 125000 ! router bgp 1 network 131.108.0 no ip directed-broadcast ! interface Serial0/0 ip address 131.255.255.0 Serial0/0 ip route 161.0 Serial0/1 ! line con 0 line aux 0 line vty 0 4 end Example 6-45 displays R2's full working configuration.1.255.108.252 clockrate 125000 ! interface Serial0/1 ip address 131.1 remote-as 2 neighbor 161.1 update-source Ethernet0/0 ! ip route 161.0 255.255.255.1.255.255.1.108.108.0 neighbor 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 131.255.1.1.108.108.0 mask 255.108. .5 255.1 255.108.255.255.255.0 255.209 - .

108.1 255.255.255.1.1. .0 mask 255.0 255.1.255.1 remote-as 1 neighbor 131.255.1.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 161.0 neighbor 131.0 ! interface Serial1/0 ip address 131.255.108.1.6 255.255.108.252 ! router bgp 2 network 161. based on data traffic.108.255. you configure EBGP using the next hop addresses and use policy-based routing to allow certain network design policies to affect IP routing decisions.0 Serial1/0 ip route 131.255.0 255.255.255.108. 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. Figure 6-4 displays the same two-router network used in Scenario 6-3.2 255.108.1.0 Serial1/1 ! line con 0 line aux 0 line vty 0 4 end Scenario 6-3: BGP with Policy-Based Routing In this scenario.210 - .108.255.255.255.1 ebgp-multihop 255 neighbor 131.252 interface Serial1/1 ip address 131.1. for expensive links.1 update-source Ethernet0/0 ! ip route 131. except this time you configure two EBGP sessions between R1 and R2 and use BGP to route dynamically without static routing.108.108.255.

108.0 131.255.255.6 remote-as 2 Example 6-47 displays the two EBGP sessions configured on R2.108.1.0/24 because BGP does not load balance as you discovered in Scenario 6-2. Two-EBGP Session Topology Configure two EBGP TCP sessions between R1 and R2. Example 6-46 displays the EBGP configuration on R1.108.211 - .255.5 remote-as 1 Example 6-48 displays the IP BGP table on R1 after the two BGP sessions are established.0 R2(config-router)#neighbor 131.1. h history.255.108. local router ID is 131.1.108.255. you don't need EBGP multihop because you are using a directly connected peer. d damped.2 because of its lower IP addresses.255.internal Origin codes: i .255. * valid.108.1.EGP.2 remote-as 2 R1(config-router)#neighbor 131.0 mask 255.108. e . Assume that all traffic from the Ethernet segment on R1 .) Example 6-46 EBGP on R1 R1(config)#router bgp 1 R1(config-router)#network 131.IGP. i .108. ? .0 R1(config-router)#neighbor 131.255. The path is chosen through 131.0 mask 255.255.255. (Notice.6 131.0/24 * 161.108. > best.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. Example 6-47 EBGP on R2 R2(config)#router bgp 2 R2(config-router)#network 161. all other parameters that BGP bases decisions on are equal in this case.108.255. Example 6-48 BGP Table on R1 R1#show ip bgp BGP table version is 3.2.CCNP Practical Studies: Routing Figure 6-4.0.incomplete Network *> 131.0.5 Status codes: s suppressed. to reach the remote network 161.108. 131.255.108.108.1.255.0/24 *> Next Hop 0.1 remote-as 1 R2(config-router)#neighbor 131.

1 default-originate R2(config-router)#neighbor 131. > best. First. you learn to configure policy-based routing to illustrate how you can use route maps to achieve this. local router ID is 131. 1 subnets B 161. configure R1 to choose a different next hop address for IP ICMP packets destined for the remote network 161.108. 3 subnets.EGP.108. ? .1.108.6 131.0/0 [20/0] via 131.108.108. Example 6-50 show ip bgp Command on R1 R1>show ip bgp BGP table version is 4.108.6 and all other traffic is sent through 131.255.108.5 Status codes: s suppressed.108. Next.108.108.1.5 default-originate Example 6-50 displays the BGP default route in R1's BGP table.108.0/30 is directly connected.IGP.internal Origin codes: i .108.1. Example 6-49 Default Route Configuration on R2 R2(config)#router bgp 2 R2(config-router)#neighbor 131. Example 6-51 show ip route Command on R1 R1>show ip route Gateway of last resort is 131.2.108. Serial1/1 C 131.1 (Serial 1/0 to R2). * valid. you apply the policy statement on the outbound interface and reference a route map. suppose you want to send internal traffic through one path and all Internet traffic through the second link. To configure policy routing. Two default statements are configured for redundancy purposes. 00:13:58 Policy routing needs to be configured on R1 to ensure that IP ICMP packets destined for the remote network 161. But. Policy routing is based on incoming packets only.0.108.0.2 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 131.108.0/24 * 161. h history.108. configure R2 to advertise a default route to R1. 2 masks C 131.0/24 *> Next Hop 131.108. Internet-based traffic).1.0 (Serial 1/1) than for all other destinations (for example.2. .255.0.0 *> *> 131.1. so you need to apply the policy command on the Ethernet interface on R1. Ethernet0/0 161.2.212 - .108. Example 6-49 displays the configuration on R2 so that it sends a default BGP route to R1.6.108.4/30 is directly connected.0 131.CCNP Practical Studies: Routing bound for 161.0.255.255.0/16 is variably subnetted. e .0/24 is subnetted.incomplete Network * 0. 00:23:11 B* 0. Serial1/0 C 131. To illustrate policy-based routing.255.0 must be sent through the next hop address 131.108.1.108.255.1. Example 6-51 confirms this when you view the IP routing table on R1.0.255.0/24 is directly connected.0 131.0.0.255.108. You can force BGP to complete this task by using policy-based routing or changing BGP attributes. and all traffic destined for the Internet is sent through Serial 1/0.6 131.2 0.255.0 [20/0] via 131.0.108. or Serial 1/1. i .0.255. The IOS command is ip policy route-map route-map-name.255.2 to network 0.108.0.255.255.1.255.108. which will be through the second link (Serial 1/0).255.0/24 are sent through the next hop address 131. d damped.

6.6) and all default traffic through Serial 1/0 (next hop address 131.108.0. An extended ping request along with a debug ip policy on R1 displays any policy routing.108.108. you cannot verify policy routing with the IP routing table.108.255.108.108. Unfortunately.108.108.1.2.108. 00:22:52 B* 0.108.2.108.255.1–131.4/30 is directly connected.1.1 Repeat count [5]: Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: y Source address or interface: 131. or Serial 1/0.108. This example assigns a route map called nondefault. Example 6-55 displays an extended ping using the source address 131.255.108.0 0.0 [20/0] via 131. 1 subnets B 161.CCNP Practical Studies: Routing Example 6-52 displays the policy routing interface configuration on R1.1.255.0/24 through Serial 1/1 (next hop address 131.2. is sending all traffic through Serial 1/0 on R1.1.108. Serial1/0 C 131. 00:22:52 Example 6-54 stills displays that all remote networks are routed through 131.1 (R1's Ethernet interface) to the remote network 161.255.6 access-list 100 permit icmp 131.1.0.0/0 [20/0] via 131.1. Example 6-54 displays R1's IP routing table.0.1. you must set the conditions on R1 so that policy routing can occur. Example 6-53 Route Map Configuration on R1 route-map default permit 10 match ip address 100 set ip next-hop 131.0/16 is variably subnetted.0.1).108.0/4.1.108.0/24 is directly connected.108. Example 6-55 Extended Ping on R1 R1#debug ip policy Policy routing debugging is on R1#ping Protocol [ip]: Target IP address: 161.0/24 is subnetted.108.255 The route map on R1 policy routes any IP ICMP packets with a source address in the range 131. 2 masks C 131.255 through the next hop address 131. 3 subnets. 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.0.0 0.108.1.0.255 161. Example 6-52 uses the ? tool to illustrate the options available to you. Example 6-53 sets all IP ICMP traffic from the Ethernet segment on R1 destined for 161.108. Ethernet0/0 161.1. Serial1/1 C 131. Example 6-54 show ip route on R1 R1#show ip route 131.0/30 is directly connected.213 - .0.1 Type of service [0]: Set DF bit in IP header? [no]: Validate reply data? [no]: .1.108. as displayed in Example 6-50.0.255. Remember that BGP. The route map name is an arbitrary name you can assign.255.255.108.255.

1 (local). d=161.1. len 100. permit 00:26:57: IP: s=131. len 59.1.255.1.108. 100-byte ICMP Echos to 141. d=161.108.1.CCNP Practical Studies: Routing Data pattern [0xABCD]: Loose. permit 00:26:57: IP: s=131. policy routed 00:26:57: IP: local to Serial1/1 131.1.2.108.1. policy routed 00:26:57: IP: local to Serial1/1 131.108. permit 00:26:57: IP: s=131. len 100.1. d=141.1.108.108.1.1.108.108.108. round-trip min/avg/max = 16/18/20 ms 00:26:57: IP: s=131.1. len 100. policy rejected -.1 (Serial1/1).1.108.1.1 (local).255.1. permit 00:26:57: IP: s=131.6. len 100.1.6 00:26:57: IP: s=131.1 (local).1 (local).1.normal forwarding 00:30:37: IP: s=131.1. len 100. len 100.108. Example 6-56 ping 141.1. Example 6-56 displays a ping request to the unknown network 141.6 00:26:57: IP: s=131.1 (Serial1/1).108. policy match 00:26:57: IP: route map default. d=141.108.108.108.214 - .normal forwarding 00:30:35: IP: s=131.normal forwarding 00:30:35: IP: s=131.255.1.6. policy rejected .6 00:26:57: IP: s=131.1 (local).255. Timestamp.1.1. d=161. d=161. Sending 5.1. len 100. permit 00:26:57: IP: s=131. d=161.108.1 (local).108.1. Sending 5. policy routed 00:26:57: IP: local to Serial1/1 131.1.1.1 (local).108.1. len 100.108.108. item 10. Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. d=131.1 (Serial1/1).108.108. len 59.108.5 (local).1.1.255.1. d=141.1.255. len 100.108. item 10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 (local).1 (local).108. policy match 00:26:57: IP: route map default.1 on R1 R1#ping 141. policy rejected . Record. item 10.1 (local).108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). policy rejected .255.1 (local).108.normal forwarding 00:30:35: IP: s=131.1.108.1. policy match 00:26:57: IP: route map default.108. policy routed 00:26:57: IP: local to Serial1/1 131.1 (Serial1/1).108.108. item 10. d=161.108. d=141.1 (local).1 (local). policy rejected .6 00:26:57: IP: s=131.1.1. d=161. len 100. policy match 00:26:57: IP: route map default. policy match 00:26:57: IP: route map default.1.108.1 (local).255. len 100.1. policy rejected -. d=161.255. len 100. d=161. item 10.1. Strict.108.1 (local). len 100.1.1 (Serial1/1).108.1.108.1.normal forwarding .6 Example 6-55 displays the five ping requests successfully policy routed through Serial 1/1.108. round-trip min/avg/max = 16/16/20 ms 00:30:35: IP: s=131.1.1. policy routed 00:26:57: IP: local to Serial1/1 131.108.108.108.108.255.255. d=141.108.normal forwarding 00:30:35: IP: s=131.255.255.108.255. 100-byte ICMP Echos to 161.normal forwarding 00:30:39: IP: s=131.1 Type escape sequence to abort. or the next hop address 131. len 100.1 (local).1 on R1 and the subsequent policy debug output. len 100. policy rejected . d=131.255. d=161.108.108.

108.1. d=161.108. d=161. item 10.1 (local).1.108.1 (local).108. Configure R1 to send all Telnet traffic originated from the network 131.1 (local).108.1 /source-interface ethernet 0/0 Trying 161.108. policy match 01:04:00: IP: route map default.0.1.1 (local).108.1 (local).1 (local).1. policy match 01:04:00: IP: route map default.108. the IP datagram is forwarded through the normal outbound interface.0. policy routed 01:04:00: IP: local to Serial1/1 131.1 (local).1 (local).108.1.255.CCNP Practical Studies: Routing R1 sends all packets to an unknown destination through normal forwarding through Serial 1/0. d=161.1.1.108. d=161.1. Example 6-57 displays the access-list configuration to allow Telnet sessions through Serial 1/1.1 (Serial1/1).108.1 (local).108. len 43. you can also base routing on port numbers.1 (local).6 01:04:00: IP: s=131.108.6. d=161.1 .1.108. d=161.0.1.6 01:04:00: IP: s=131. d=161. permit 01:04:00: IP: s=131.1.1.108.0 0.215 - . policy match 01:04:00: IP: route map default.108. item 10.1.1.108.1.1 (local).1.1. policy routed 01:04:00: IP: local to Serial1/1 131.108. policy match 01:04:00: IP: route map default.6 01:04:00: IP: s=131. With the use of extended access lists.1. policy routed 01:04:00: IP: local to Serial1/1 131. len 52. len 40.1. len 40.255.108. you can do this if you want Telnet sessions to go through one interface or another.1 (Serial1/1).108.1 (Serial1/1). d=161. d=161. permit 01:04:00: IP: s=131. permit 01:04:00: IP: s=131. d=161. d=161.255.1.0 0. len 40.1 (local). item 10. d=161.255 eq telnet Example 6-58 Sample debug ip policy Output on R1 R1#debug ip policy Policy routing debugging is on R1#telnet 161.108.1.1.108.108.255. permit 01:04:00: IP: s=131.108. This simple scenario demonstrates the powerful use of policy-based routing on source and destination addresses.108. policy match 01:04:00: IP: route map default.1. len 52.108. len 44. permit 01:04:00: IP: s=131. policy match 01:04:00: IP: route map default.1.6 01:04:00: IP: s=131. For example. item 10. hence.1. policy match 01:04:00: IP: route map default. len 43. len 43.1. len 44.108.1 (local).108.0. policy routed 01:04:00: IP: local to Serial1/1 131.1. permit 01:04:00: IP: s=131.1 (Serial1/1). Open R2> 01:04:00: IP: s=131. len 49.108. policy routed 01:04:00: IP: local to Serial1/1 131.. item 10.108.108.1.108.108.108.1 (Serial1/1).255.6 01:04:00: IP: s=131.1.255.108. policy routed 01:04:00: IP: local to Serial1/1 131. len 49.1. len 40. d=161. d=161. permit 01:04:00: IP: s=131.1. d=161.1. item 10.1 (Serial1/1). policy routed 01:04:00: IP: local to Serial1/1 131.108.6 01:04:00: IP: s=131.108. policy match 01:04:00: IP: route map default.255.1.1.108. Example 6-57 Allowing Telnet to Be Policy Routed on R1 access-list 100 permit tcp 131. The debug output in Example 6-56 displays a nonmatching policy.1 (local). len 43.1. item 10.108.108.1.108. d=161.1.108..1.0/24 through the next hop interface 131.108.1.1. permit 01:04:00: IP: s=131.1 (local). len 43.1.1 (Serial1/1).1. policy routed .255 161.108.1 (local).6 01:04:00: IP: s=131.108. len 43.255.1 (Serial1/1). item 10.1.1.1.

255 161.108.252 clockrate 128000 ! interface Serial1/1 ip address 131. d=161. R1 sends all Telnet traffic through Serial 1/1.255.108.2 remote-as 2 neighbor 131.255 161.108. permit s=131.108. d=161.1.6 s=131. R2 has no login on vty 0 4 lines.108.1 (local).0.108.108.1.1.108.108.108.0 0.1.0 0.255.255 access-list 100 permit tcp 131.108.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 Serial1/1 131.255.252 clockrate 128000 ! router bgp 1 network 131.0 ip route-cache policy ip policy route-map default ! interface Serial1/0 ip address 131.255 eq telnet route-map default permit 10 match ip address 100 set ip next-hop 131. you are immediately placed at the R2 prompt.108.108. Example 6-59 displays R1's full working configuration.108.1 from R1 using the source address of 131.216 - .255.255. policy match route map default.1.1 255.108.108.1.6 remote-as 2 ! ip local policy route-map default access-list 100 permit icmp 131. when you telnet from R1 to R2.1.255.255.108. policy IP: local to Serial1/1 131.255.1.1.1. len 40. .0. Example 6-59 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Ethernet0/0 ip address 131.1 255.255.6 Example 6-58 displays a sample debug output when you telnet to 161. therefore.108.1.0.0 0.255.0.6 line con 0 line aux 0 line vty 0 4 no login ! end Example 6-60 displays R2's full working configuration.255.255.5 255.0. Because a policy is matched on access list 100.0.255.255.0 mask 255.108.0 neighbor 131.1.1.1 (Serial1/1). item 10.1 (local).255.0.0.1.0 0. len 40.

255.100. and R2 peers to an EBGP peer with the IP address 151.255. such as no-export (do not advertise to EBGP peers) and noadvertise (do not advertise this route to any peer). can substitute for community-number.255.108.967. including an Internet connection on R1 and R2.255. Some well-known community attributes. 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. The IOS set community community-number [additive] command is used to define a value.200.255.217 - . NOTE The community attribute is a number defined in the range 1 to 4.108.CCNP Practical Studies: Routing Example 6-60 R2's Full Working Configuration hostname R2 ! enable password cisco ! interface Loopback0 ip address 141.108.5 remote-as 1 neighbor 131.2 255. you configure a well-known BGP community and discover the advantages of peer groups. Typically.255. In this scenario.108. To apply the community attribute to a remote BGP neighbor.294.1. such as the community attribute and peer groups.255.252 interface Serial1/1 ip address 131.255.252 router bgp 2 network 161.1.0 mask 255.108. In this scenario. R1 peers to an EBGP peer with the IP address 141. A community is a group of routers sharing the same property.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.255.255.6 255.5 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.255 ! interface Ethernet0/0 ip address 161.1.108.255.108.0 neighbor 131.108. A peer group is a group of BGP neighbors sharing the same update policies.255.1 remote-as 1 neighbor 131.1 (Remote AS 1002).1 255.1.0 ! interface Serial1/0 ip address 131. .108.1 255.1 (Remote AS 1001). 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 131.199. use the neighbor command: neighbor {ip address | peer group} send-community Figure 6-5 displays a simple four-router topology.255.255.255.1.

Figure 6-5.1.199. 141.1. so the Internet routers do not use R1 as a transit path.199.CCNP Practical Studies: Routing large companies have more than one Internet connection. Example 6-62 displays the route map configuration on R1. IBGP Example 6-61 displays the community attribute setting on R1. which informs the neighboring router not to use R1 for any traffic not destined for the network 131.1 R1(config-router)#neighbor 141.1 remote-as 1001 send-community route-map setcommunity ? route-map setcommunity out R1 is configured for EBGP and IBGP.1. You have yet to apply the route map named setcommunity (arbitrary name).1.108. you set the community attribute (well-known) no-export on R1 and R2.0/16.1.199. Therefore.1 in Apply map to incoming routes out Apply map to outbound routes R1(config-router)#neighbor 141. is the Internet gateway. The EBGP connection to the remote peer address. Apply the well-known community no-export. you must send the 6community to the remote peer and apply an outbound route map.1.1 R1(config-router)#neighbor 141. 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 .199.218 - .0. so to ensure that R1 and R2 are not the transit paths for any ISP-based traffic. Example 6-61 BGP Configuration on R1 R1(config)#router bgp 1 R1(config-router)#neighbor 141.199.

including a community number and the two other well-known community values: local-AS and no-advertise.108. 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.1. and set the same policies on all four routers.100. R3.219 - .2 weight 1000 R1(config)#route-map setattributes R1(config-route-map)#set community 2000 R1(config)#access-list 1 deny 0.2 route-map setattributes in R1(config-router)#neighbor 131. you need to complete the same set of IOS commands (seven IOS commands in total) and have different route maps and access lists. You must ensure that the ISP connected to R2 does not use R2 as a transit path. configure IBGP on R1.1 send-community R2(config-router)#neighbor 151. the name is an arbitrary name. Also set the next-hop-self attribute on all IBGP peer sessions.1 se R2(config-router)#neighbor 151.108. Example 6-64 configures R1 for IBGP to R2 only.1. sets the next-hop-self attribute (no defaults routes permitted). Example 6-63 Community Configuration on R2 R2(config)#router bgp 1 R2(config-router)#neighbor 151.1.108. Clearly with a large network.108.1. First.0. . Example 6-64 R1's IBGP Configuration to R2 R1(config-router)#neighbor 131. To create a BGP peer group. such as the weight and community value. R3. Example 6-65 creates a peer group on R1 named internal. R1–R4.100. Next. Ensure that R1 sets the community to the value 2000. For a small network such as this.100.CCNP Practical Studies: Routing Notice that the ? tool displays all the community variations. beginning in router configuration mode. to the peer groups. configure the four routers. and sets the weight to 1000.100. and R4). for IBGP.2 send-community R1(config-router)#neighbor 131. Example 6-63 configures R2 to ensure that the ISP is not using the network of Routers R1–R4 as a transit path.0. again.1. or R4. this is not scalable. Example 6-66 displays all the available options you can assign to a peer group.1 remote-as 1002 R2(config-router)#neighbor 151.1.2 next-hop-self R1(config-router)#neighbor 131. to demonstrate the power of peer groups.1.100.1.1.1 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.1. and apply that policy on R1 to all three remote routers (R2. Take advantage of peer groups and configure one policy.0 To configure R1 to set the same attributes and conditions to R3 and R4.1 remote-as 1002 R2(config-router)#neighbor 151.108. the configuration on R1 can grow quite large. sends the community value of 2000. Assume the network designer has asked you to ensure that R1 does not receive any default routes from R2. use the neighbor peer-group command.2 distribute-list 1 in R1(config-router)#neighbor 131.

namely route reflectors (you might notice this network is fully meshed.108. .1.14 peer-group internal R1 has defined three remote IBGP peers with one statement that sets all the parameters defined by the peer group internal.108.255. 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. Chapter 7 describes two other main methods used in BGP networks to scale in large networks. apply these settings to all the remote peers. Example 6-67 displays the setting of a distribution list to stop a default route from being accepted on R1.108. The beauty of using peer groups is that you can add more BGP peers by using only one command. R3. You can configure BGP peers to override configuration options if required.2 peer-group internal neighbor 131. setting the remote AS number to 1 (same on all IBGP peers). every BGP routers has a peer to each other) and confederations.6 peer-group internal neighbor 131. and ensuring that community 2000 is sent to R2. Example 6-68 shows how to make R2. R3.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. and R4 members of the peer group called internal.220 - . Example 6-69 displays the full working configuration on R1. This scales much better than configuring a multitude of IOS commands on several routers.255. advertising the next-hop-self attribute. Take note of the shaded sections that configure R1 to set local-based policies to all three IBGP peers. and R4 Members of the Peer Group Internal router bgp 1 neighbor 131. R3. 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. that is. Example 6-68 Making R2. and R4.

255.2 255.199.0.1 remote-as 1001 neighbor 141.255.252 ! interface Serial1/2 ip address 131.252 neighbor internal peer-group neighbor internal remote-as 1 neighbor internal distribute-list 1 in neighbor internal route-map setattributes in neighbor 131.252 network 131.1.1 send-community neighbor 141.6 peer-group internal neighbor 131.0.1.108.255.255.0 interface Serial1/0 bandwidth 128 .255.255.199.14 peer-group internal neighbor 141. Notice R2 is not configured for peer groups.108.255.1 route-map setcommunity out access-list 1 deny 0.0 ! interface Serial1/0 ip address 131.255.108.1.0 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 R2.255.255. Example 6-70 R2's Full Working Configuration hostname R2 ! enable password cisco ! interface Ethernet0/0 ip address 131.12 mask 255.1.199.108.255.255.221 - .108.108.252 no ip directed-broadcast ! router bgp 1 no synchronization network 131.4 mask 255.255.255.199.1.255.2.108.255.1.CCNP Practical Studies: Routing Example 6-69 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Ethernet0/0 ip address 131.1 255.108.1 255.255.13 255.2 peer-group internal neighbor 131.252 clockrate 128000 ! interface Serial1/1 Description Link to Internet ip address 141.255.108.255.255.5 255.

252 clockrate 128000 ! router bgp 1 no synchronization network 131.9 255.255.5 remote-as 1 neighbor 131.10 remote-as 1 neighbor 151.255.1.255.108.255.255.108.2 remote-as 1 neighbor 131.255.108.100.255.108.252 ! router bgp 1 no synchronization network 141.100. Notice R3 is not configured for peer groups.252 no ip directed-broadcast no ip mroute-cache ! interface Serial1/1 Description Link to Internet ip address 151.8 mask 255.108.108.255.255.6 255.108.255.1.2.255.255.108.255.1.255.222 - .255.255.108.0 mask 255.8 mask 255.108.255.1 255.255.9 remote-as 1 ! no ip classless route-map setweight permit 10 match ip address 1 .252 neighbor 131.252 neighbor 131.255.255.252 network 131.CCNP Practical Studies: Routing ip address 131.1.1 remote-as 1 neighbor 131.0 mask 255.255.1 255.1 remote-as 1002 neighbor 151.255.1 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 R3.0 network 131.1 send-community neighbor 151.10 255.255.252 ! interface Serial1 ip address 131.255.255.1 255.1.108.108.108. Example 6-71 R3's Full Working Configuration hostname R3 ! enable password cisco ! interface Ethernet0 ip address 141.255.252 ! interface Serial1/2 ip address 131.108.100.255.255.1.252 network 131.255.4 mask 255.0 ! interface Serial0 ip address 131.255.255.255.255.255.100.108.

108.252 network 131.108.108.252 network 151. but also during your certification exams.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 R4.12 mask 255.108.108.0 mask 255.255.255.255.255.252 clockrate 125000 ! router bgp 1 no synchronization network 131. Example 6-72 R4's Full Working Configuration hostname R4 ! enable password cisco ! interface Ethernet0 ip address 151.108.255.255.10 255.255.1 255.1.108.255.0 mask 255.255.255.1 remote-as 1 neighbor 131.0 ! interface Serial0 ip address 131.255.252 clockrate 125000 ! interface Serial3 ip address 131.255.0 neighbor 131.2 255. Notice R4 is not configured for peer groups.255. Show and debug commands can be valuable.255.255. 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.108.14 255. not only in the real-life networks you come across.223 - .255. .252 clockrate 125000 ! interface Serial1 ip address 131.255.1.255.13 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.255.255.108.

The various networks are listed along with the next hop address.8/30 131.255.255.108.255.108.0.1 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. the BGP table version is displayed as 11 and the local router ID is 131. metric (MED).13 Status codes: s suppressed. BGP attributes. the local AS of 1.108.0. > best. Entries are then inserted into the IP routing table.IGP. local AS number 1 BGP table version is 11.108. 73/63 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ 131.108.0 0 32768 i * i 131.14 0 100 1000 i *> 131. memory can be a limiting factor. (i is for IGP. Memory is important in BGP because in a large network. and selected paths. such as the Internet. i .0/30 131.108.108.108. 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.255. Example 6-74 show ip bgp R1>show ip bgp BGP table version is 11.108.6 0 100 1000 i *>i151. d damped. As more BGP entries populate the IP routing table. 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.255.255. local router ID is 131. 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.1. part of the origin codes.108.199.255.0/24 131. h history. if no changes occur. and the path.108.0.6 0 100 1000 i *> 131. Example 6-74 displays the BGP table on R1 in Figure 6-4.255.1.255.108.108.108.108.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. using 854 bytes of memory. including the local router identifier 131.1. weight.108.108.255.224 - .13.) .1. e .2 4 1 194 195 11 0 0 131.108. Notice the show ip bgp command can be performed in executive mode.14 0 100 1000 i *>i141. * valid.13. and the BGP table version of 11.) The BGP table is one that confuses most people.12/30 0.1.4/30 0.108. such as remote and local network entries.6 0 100 1000 i *>i131. (The output indicates an idle session.108. (An increasing version number indicates a network change is occurring.2 0 100 1000 i * i 131.255.255. ? .6 4 1 84 83 11 0 0 131.14 4 1 152 152 11 0 0 141.0 0 32768 i * i 131.255. Example 6-73 show ip bgp summary on R1 R1#show ip bgp summary BGP router identifier 131.incomplete Network Next Hop Metric LocPrf Weight Path *>i131.14 0 100 1000 i Again.255. The BGP table is not an IP routing table.0/24 131. more memory is required.EGP.1.13. and the up/down time displays this connection was never established.internal Origin codes: i .255. this number remains the same.108.) It also shows six network paths on R1. 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.255. Most engineers are familiar with a standard Cisco IOS IP routing table and mistakenly apply the same principles to the BGP table. The BGP table displays information.0.2 0 100 1000 i * i 131. local preference (Locpref).

14 0 1000 1000 i *> 131.255.2. notice that the clear and debug commands are performed in privileged mode.11039 812D0054 131. You can.108.C.255.255.108. and you can expect BGP to send updates and keepalives across each TCP session.255. The most widely used tool when establishing why BGP is or is not peering is the debug ip bgp events command.0/24 131.6 0 1000 1000 i *> 131.108.225 - . resulting in no downtime. The foreign addresses list the TCP port as 179.6 0 1000 1000 i *>i131. has three TCP sessions in an established state.0. Next.1. > best. configure soft configurations with the neighbor peer address soft-reconfiguration inbound command.14 0 100 1000 i The ? tool displays a number of options. because BGP loses peering to any remote peers.108.0. The command to clear all sessions is clear ip bgp *.2 0 1000 1000 i * i 131.108. .0. You would never use this command during normal working hours.13.108.179 (state) ESTAB ESTAB ESTAB Router R1.1.internal Origin codes: i .255. Example 6-75 displays the BGP table after the change is configured and you clear all BGP peers sessions on R1.255.255.EGP.6 0 1000 1000 i *>i151. Also. 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.255.108.IGP.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 11.108.108.8/30 131.255. use the clear ip bgp peer-ip-address command.108. 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. ? . * valid.108.14.255. To clear a single peer router.11041 Foreign Address 131.0.108.1. local router ID is 131.1.255.1. e .255.13 Status codes: s suppressed. Debugging BGP is useful. which enables you to make changes and not have to clear the TCP peer.179 131.108. On Cisco IOS routers. Example 6-77 displays the sample output taken from R1 when the BGP sessions are cleared for demonstration purposes.108.0 0 32768 i * i 131. i . Example 6-76 displays the output from the show tcp brief command on R1.108.CCNP Practical Studies: Routing If a BGP configuration change is completed on Cisco IOS routers. d damped.108.255.5. instead of the default value of 100.4/30 0. h history. however. including clearing BGP sessions based on AS numbers or remote peer address.108.0/24 131.179 131. Example 6-75 clears all BGP sessions on R1 after a configuration change to set all IBGP peer localpref attributes to 1000. The TCP port numbers are also listed.1.108. the BGP peer session must be cleared.6.108. as displayed in Example 6-76.255. for example.14 0 1000 1000 i *>i141. This tells you that R1 has three TCP sessions active. and the local address is a number TCP generates.255.108. clear all BGP sessions on R1 with this debug command turned on to discover the session you activated.0/30 131.11040 812CF508 131.B. 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.12/30 0.incomplete Network Next Hop Metric LocPrf Weight Path *>i131.2 0 1000 1000 i * i 131.0 0 32768 i * i 131.108.1. Example 6-76 show tcp brief R1#show tcp brief TCB Local Address 812CC228 131.

2 computing updates. neighbor version 0. start version 1.108. throttled to 1. starting at 0.255.6 update run completed.108. start version 9.0 4d01h: BGP: 131.108.0.6 computing updates.108.2 sending KEEPALIVE 4d01h: BGP: 131.255.255. ran for 0ms.6 update run completed. Example 6-78 displays a sample output taken from R1 after the TCP peers are established.14.14.255. check point net 0. throttled to 1.0. starting at 0.108.255. neighbor version 1.0 4d01h: BGP: 131.255. You can view keepalives with the debug ip bgp keepalives command. starting at 0.226 - .108.6 computing updates.108.255.108. and 131.108.255.0.255.14 went from OpenSent to OpenConfirm 4d01h: BGP: 131.255.108. .108.108.255.255.108.255.0. ran for 0ms.0.108. starting at 0.0.2 KEEPALIVE rcvd R1 is sending and receiving keepalives to the three remote peers to ensure that the remote routers are still active. table version 1. 131.1.0 4d01h: BGP: 131.108. check point net 0. check point net 0.0 4d01h: BGP: 131.1.14 computing updates.255.108.2 went from OpenConfirm to Established 4d01h: BGP: 131.108. Assume that R1 is reloaded. start version 1.1.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: 131.108.0 4d01h: BGP: 131.6 went from OpenConfirm to Established 4d01h: BGP: 131. table version 1. throttled to 9.255. throttled to 1.108.108. ran for 0ms.6 KEEPALIVE rcvd 4d01h: BGP: 131.14 went from Idle to Active 4d01h: BGP: 131.108.14 went from Active to OpenSent 4d01h: BGP: 131.1.0.0. neighbor version 0. start version 1.255.108.1. After the sessions are active.0.0. table version 9.6 went from Active to OpenSent 4d01h: BGP: 131.2 went from Active to OpenSent 4d01h: BGP: 131.2.2 went from Idle to Active 4d01h: BGP: 131. ran for 0ms.108.108.0.1.108.0 4d01h: BGP: 131.255.108.14 went from OpenConfirm to Established 4d01h: BGP: 131.0.255.108. only changes are sent across the TCP peers.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: 131.6 went from Established to Idle 4d01h: BGP: 131. Example 6-78 debug ip bgp keepalives on R1 R1#debug ip bgp keepalives BGP keepalives debugging is on 4d01h: BGP: 131.14 KEEPALIVE rcvd 4d01h: BGP: 131.1.108.1.0.6 went from Idle to Active 4d01h: BGP: 131.0 4d01h: BGP: 131. neighbor version 0.1. neighbor version 0. neighbor version 1.14 sending KEEPALIVE 4d01h: BGP: 131.108.0.6 went from OpenSent to OpenConfirm 4d01h: BGP: 131. neighbor version 0.2 update run completed.14 went from Established to Idle 4d01h: BGP: 131. table version 1.255.108.0.2 went from OpenSent to OpenConfirm 4d01h: BGP: 131.255.6 sending KEEPALIVE 4d01h: BGP: 131.2 went from Established to Idle 4d01h: BGP: 131.108.1.255.14 update run completed. check point net 0.0.255.108. neighbor version 0.

108.11044 131. Ensure that both Routers R1 and R2 have full connectivity to each other. configure the network in Figure 6-6 for IP routing. Example 6-79 show tcp brief on R1 R1#sh tcp TCB 812CF984 812CCB20 812CC6A4 brief Local Address 131. .CCNP Practical Studies: Routing If you display the TCP sessions now.108.255.108. EBGP Topology • • • • All even routes have weight set to 100. Use the ping command to ensure that all networks are reachable.108.179 (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. All odd routes have MED set to 200.13.11043 Foreign Address 131. All even routes have MED set to 100.1. 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. Example 6-79 displays the TCP sessions on R1.227 - .2.6.11042 131.108.179 131.1.255.5. You must use BGP4 as your dynamic routing protocol.255. Ensure that all routes received by R2 are tagged as follows: Figure 6-6.108.14. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own.1. All odd routes have weight set to 200.179 131. Using the IP addressing scheme provided and BGP4 as your routing protocol. The solution can be found at the end.

252 or /30.0 255.255.0.255.108. as they contain critical IOS commands that ensure the desired solution is achieved.255.108.1 ! interface Loopback2 ip address 131.255.104.0 .102.1 ! interface Loopback1 ip address 131. The serial link contains a mask.0 255.108.1 ! interface Loopback13 255.0 255.0 255.1 ! interface Loopback11 ip address 131.1 ! interface Loopback4 ip address 131.1 ! interface Loopback5 ip address 131.0 255.1 ! interface Loopback3 ip address 131.0 255.111. Examples 6-80 and 6-81 display the full working configuration on R1 and R2.112.255.255.109.255.108.255.255.255.0 255.108.255.108. therefore.255.0 255.255.110.0 255. The 16 loopbacks on R1 are advertised to R2 using the redistribute connected command.1 ! interface Loopback10 ip address 131. 255. the route map on R2 is applied to both EBGP peers in case of link failure.106.255.255.103.107. The no-auto summary command ensures that R2 sees all 16 individual routes.108.255. respectively.108.255.1 ! interface Loopback6 ip address 131.0 255.255.108. The dual-path connections between R1 and R2 allow redundancy.CCNP Practical Studies: Routing Practical Exercise Solution You will notice that all the IP addressing schemes are /24. or all even networks match these criteria.108.255.108.255.108. The access list on R2 must be set with a mask of 0.108.1 ! interface Loopback12 ip address 131.228 - .255.0 255.1 ! interface Loopback9 ip address 131.254.255.255.101.255.255.255.0 255.1 ! interface Loopback7 ip address 131.113. BGP has no issues with VLSM.255. except for the serial link between R1 and R2.108. Example 6-80 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.255. There are two EBGP sessions between R1 and R2.255.105. Take note of the shaded sections.1 ! interface Loopback8 ip address 131.

108.108.255.255.108.255.CCNP Practical Studies: Routing ip address 131.255.255.2 255.1.252 ! router bgp 1 redistribute connected metric 100 neighbor 131.115.255.6 255.2 remote-as 2 neighbor 131.1.108.1 255.116.255.1 255.1 255.5 255.1 255.108.255. 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 161.255.0 ! interface Loopback15 ip address 131.255.255.252 ! interface Serial1/3 ip address 131.0 ! interface Ethernet0/0 ip address 131.252 clockrate 128000 ! interface Serial1/3 ip address 131.255.255.0 ! interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 ip address 131.255.108.108.255.255.114.229 - .255.255.108.0 ! interface Loopback14 ip address 131.255.0 interface Serial1/0 shutdown ! interface Serial1/1 shutdown ! interface Serial1/2 ip address 131.255.1 255.255.6 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.255.1 255.255.108.108.108.255.252 clockrate 128000 ! .

1 route-map setweight in neighbor 131.255.108.11009 613ED584 131.EGP.108.1.255.108.0.255.108.0.101.255.6.CCNP Practical Studies: Routing router bgp 2 network 161.108.108.108.255.1.5 100 200 200 1 ? *> 131.230 - .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. How many BGP sessions are in use? Example 6-82 show tcp brief R2>show tcp brief TCB Local Address 613EE508 131.1.108.255.108.1 100 200 200 1 ? * 131. The answers to these question can be found in Appendix C.1.0/24 131.108.1 remote-as 1 neighbor 131.incomplete Network Next Hop Metric LocPrf Weight Path * 131.108. Example 6-83 displays the BGP table on a Cisco BGP router.255." 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.108.255.1.108.internal Origin codes: i .255.255.108.255.IGP.0/24 131.179 131.108.255.254.0/24 in Example 6-83? Use Example 6-83 to answer questions 4-6. e .1 100 200 200 1 ? .0 neighbor 131. d damped.1. ? .0 0.255.255. "Answers to Review Questions.108.255.5 remote-as 1 neighbor 131. > best.23 4: Foreign Address 131.1. Example 6-83 show ip bgp R2>show ip bgp BGP table version is 21.108. * valid.2.11008 611654BC 161.0 mask 255.179 131.108.11051 (state) ESTAB ESTAB ESTAB Which path is chosen to the remote network 131.1.108. local router ID is 161.5 100 200 200 1 ? *> 131. i .5 route-map setweight in no auto-summary ! access-list 1 permit 131.5.108.1 Status codes: s suppressed. h history.

1.0/24? Example 6-84 displays the output from the show ip bgp summary command for a Cisco BGP-enabled router. 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.255.255.0. 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. What is the BGP autonomous system that R2 resides in? How many BGP sessions are active.108.108.231 - .0. along with techniques used to load balance BGP using static routes.0/24 5: 6: 7: 0.108.0/24 originate from? What is the metric and local preference for the remote network 131. Table 6-3.101. 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.1. Table 6-3 summarizes the BGP commands used in this chapter. 119/80 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131.101. local AS number 2 BGP table version is 21.108. higher or lower weight.1 4 1 2755 2699 21 0 0 1d20h 131.CCNP Practical Studies: Routing *> 161.108. The BGP principles presented in this chapter's Practical Exercise will benefit you in the next chapter's advanced BGP scenarios.0 0 32768 i Which autonomous system does the network 131.1.5 4 1 2755 2699 21 0 0 1d20h 8: 9: 10: On a Cisco router. You learned how to successfully configure IBGP and EBGP. 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.108.

.

you can easily calculate the number of peers by using the formula n(n-1)/2. 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. BGP only propagates updates learned from IBGP connections to other IBGP sessions that are fully meshed. 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. all routers must peer to one another. To maintain accurate and up-to-date information in IBGP networks. IP.233 - .CCNP Practical Studies: Routing Chapter 7. Having this many routers leads to a large number of TCP BGP peers. A route reflector is a BGP router configured to forward routing updates to BGP peers within the same autonomous system (AS). Route reflectors are not used in External BGP (EBGP) sessions. Fully meshed networks contain a BGP peer to every BGP speaker in the network. Figure 7-1 displays a simple four-router network running IBGP. where n is the number of BGP routers. BGP deals with large BGP networks using two methods: • • Route reflectors Confederations (advanced form of route reflectors. . and as the network grows even to just 100 routers. BGP is a routing protocol designed for use in large IP networks. confederations are beyond the scope of this chapter. NOTE To avoid routing loops. For a 100-router network." 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. there are 100(100-1)/2 = 100(99)/2 = 4950 TCP peers. "Basic Border Gateway Protocol. In fact. the scalability and administration of BGP becomes a task you must carefully consider. IBGP works well in small networks. Consider a network consisting of 100 routers. 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.) Route reflectors are used to address the scalability issues in large IBGP networks.

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

2. R1 is configured as an IBGP peer to all clients. All updates contain the originator-ID attribute.2 neighbor 131. and R4 (peer address 131.2 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. Clients receive all updates from the route reflector only.108. The usual BGP routing algorithm is applied to all BGP routes to ensure a loop-free topology.3. Hence.2 neighbor 131. TIP Cluster is a term used to describe a route reflector and the clients. and R4. Nonclients (not part of a cluster) must still be fully meshed to maintain full connectivity. the four routers in Figure 7-2 form a BGP cluster.2.2).2 ! connection to R3 neighbor 131. In any cluster. Example 7-1 Configuration on R1 for Route Reflection router bgp 1 ! Connection to R2 neighbor 131. 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. For example.235 - . to perform core routing functions.108.CCNP Practical Studies: Routing The level of complexity.3. R3. The following are the characteristics of router reflectors: • • • • • • • • Route reflector configuration is enabled only on the route reflector.2 neighbor 131.4. Updates are sent from the route reflector to all clients. as you would normally configure an IBGP network. and scalability concerns in a large BGP network can be overcome by specifying a core router(s). and R4. The concept of confederations is based on multiple subautonomous systems. .2).2 ! Connection to R4 neighbor 131. which ensures a loop-free topology. Route reflectors preserve all BGP attributes.2. apply the following IOS command to all IBGP peers: neighbor ip-address route-reflector-client Next. Example 7-1 displays the configuration on R1.108. clients are configured normally as IBGP peers. manageability. Route reflectors reduce the need to configure IBGP (full-mesh) large networks. which is configured as the route reflector. such as routing updates to all edge routers. whenever you configure route reflectors. Configuring Route Reflectors Configuring route reflectors is a relatively straightforward exercise.3. configure the four routers in Figure 7-2 for route reflectors with R1 configured as the route reflector. to R2 (peer address 131. Also.108. R3.4.108. R3 (peer address (131. there must be at least one route reflector.108. you must still configure the IBGP session indicating the IBGP peer to R2. in which the route reflector ignores any update it receives with its own originator-ID. also known as a route reflector.108.108.4.2). On the route reflector.108.

0/0 ip prefix-list ccnp permit 0. 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.0. .0.0. two or more connections provide the same BGP routing information.0. In this case. the following IOS command syntax is required: neighbor {ip address | peer-group} prefix-list prefix-list-name {in | out} To verify prefix list configuration. for redundancy.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. however. routing involves knowing only the next hop and not the full path to a remote destination.0. all networks starting with 131.0. they are connected to two different ISPs. this has little or no value because all traffic to a default route is sent through the ISP connection.0. but in practice.0. It is not uncommon to accept a full BGP routing table. most organizations have one or more connections to the Internet. you might want to accept all networks in the range 4. typically.0.255. use the show ip prefix-list command in exec mode. the BGP connection between the company and the ISP is termed a multihomed connection.0 Prefix lists are a new and a more efficient way of identifying routes for matching and filtering BGP information. This presents a problem because. for example.0/0 ge 8 le 24 Multihoming Connections to the Internet Today.255 and reject all other networks.236 - . Prefix lists are efficient because BGP routers perform lookups on only the prefix (beginning) address and can make faster routing decisions.0.0/8 ip prefix-list ccnp deny 131. in practice. Prefix List Examples Using the Prefix Name CCNP Filtering required Deny default routes Permit a default route Permit exact prefix 30. traffic transverses the Internet. and the BGP network designer must ensure that the ISPs do not use the company's network as a transit. For example. Remember. a prefix list accomplishes this task efficiently and easily. therefore.0.0.108.0. specific routing information is not received through their Internet connection.0/0 ip prefix-list ccnp permit 30. Table 7-1 displays some common prefix list examples used in today's large BGP networks.0. and only a default route is accepted. and to allow the network designer flexibility. Connections can be to the same ISP. When a company connects two or more connections to the Internet.255. as long as a next hop router exists. 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. 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 to 4.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.0/8 ge 25 ip prefix-list ccnp permit 0. Table 7-1.0.

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

h history. displays something quite different.0/30 131. d damped.108.108.108.108. are established.108.255.1.108.108. > best.1.6).2 4 333 15 13 1 0 0 131.2 route-reflector-client ! RR to R3 R1(config-router)#neighbor 131.255. 7/4 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ 131.108.108.255.108.108.108. i .108.255.255.255.0/24.incomplete Network Next Hop Metric LocPrf Weight Path *> 131.3. Example 7-3 R1 Route Reflector Configuration R1(config)#router bgp 333 ! RR to R2 R1(config-router)#neighbor 131. Example 7-5 show ip bgp Command on R1 R1#show ip bgp BGP table version is 5.2). Example 7-4 show ip bgp summary Command on R1 R1#show ip bgp summary BGP router identifier 131.108.0.2 0 100 0 i *>i131.108.108. R3.255.4/30 131.255.2 4 333 10 12 3 0 2 131.0. Example 7-6 displays the IP routing table on R1. however.2 0 100 0 i *>i131. ? .255.1.255.CCNP Practical Studies: Routing Example 7-2 R1 IBGP Configuration R1(config)#router bgp 333 ! Peer to R2 R1(config-router)#neighbor 131.internal Origin codes: i .5.3. The IP table on R1.6 route-reflector-client ! RR to R4 R1(config-router)#neighbor 131. local AS number 333 BGP table version is 3.2 0 100 0 i * i131.255.6 remote-as 333 ! Peer to R4 R1(config-router)#neighbor 131.255.108.4.1.6 0 100 0 i R1 dynamically learns the remote networks 131.2). so you must configure R1 to reflect BGP information to R2. Example 7-3 displays the configuration with R1 as a route reflector. and R4.108.2 remote-as 333 R1 is the route reflector.1. * valid. and R4 (131.0/24 131.0 0 32768 i * i 131.2 route-reflector-client Example 7-4 displays the BGP neighbors on R1 in summary format.108.255.6 0 100 0 i * i131.108.IGP.2 remote-as 333 ! Peer to R3 R1(config-router)#neighbor 131.6 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.255. local router ID is 131.5 Status codes: s suppressed.4.108. to R2 (131. 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.108.238 - . R3 (131.0/24 131.108. .1. e .255.108.0/24 and 131.108.EGP.255. Example 7-5 displays the BGP table on R1.108.0/24 0.

255. 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 7-8.0/24 0. i .255.6.108.0/24 [200/0] via 131. B .108. 3 subnets.0/24 131.2 % 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 .0.255.239 - . 2 masks C 131.108.255.108.4.0/24 (R3) and 131.255.1.0 * i 131. Serial1/0 B 131. so you must disable synchronization.4/30 131. Ethernet0/0 The R1 routing table contains no BGP entries because. with route reflectors.1.255.108. ? .6 R2#show ip route 131.2 * i131. Example 7-9 show ip route on R2 R2#show ip route C 131.0/30 131.3. In this simple case. 2 masks C 131.0/24 (R4).255. Example 7-7 displays disabling synchronization on Router R1. Ethernet0/0 R2.255.4/30 is directly connected.255.BGP 131. Serial1/1 C 131.1.CCNP Practical Studies: Routing Example 7-6 show ip route on R1 R1>show ip route 131.108.108.108. Serial1/1 C 131.0/24 [200/0] via 131.4. > best.108.EGP. 00:00:32 B 131. IBGP does not insert any network into the IP routing table due to synchronization. d damped.1. and R4.internal Origin codes: i . R2.108.108.0/24 is directly connected. even though synchronization is disabled.1 * i131.1.108.0/30 is directly connected.255.0/16 is variably subnetted.0/16 is variably subnetted.108. * valid. 5 subnets. local router ID is 131.IGP. h history. Example 7-8 show ip route on R1 R1#show ip route Codes: C .108.108.3. Ethernet0/0 R1 can now reach the two remote networks: 131.108.108.incomplete Network Next Hop *> 131.108. Serial1/0 C 131. e . Disable synchronization on R1. the same command should be completed on all four routers in Figure 7-3. Example 7-10 show ip bgp and show ip route on R2 R2#show ip bgp BGP table version is 3.6 % Subnet not in table R2#show ip route 131.connected.108.108.3.4.255.0 is directly connected.108.255. has no remote BGP entries.7.0.0/24 is directly connected.0.108.108.0/30 is directly connected. Verify that R2 can also reach these networks because R2 is a route reflector client. view the BGP table on R2.0/24 131.108. Example 7-10 displays the BGP table on R2. you have no other IGP configured.108. R3.255.4/30 is directly connected.108. Example 7-9 displays the IP routing table on R2.2 * i131.255. 00:00:32 C 131.108.2.6 * i131. To discover why.1 Status codes: s suppressed.108.0.

4.1.108.108.1.255.4. Example 7-12 displays the IP routing table on R2 and some successful ping requests to R3 E0 (131.2.255.108.0 mask 255. Example 7-11 displays the configuration on R1.255.255. configure R1 to advertise the WAN links to R2 and R3. 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 131.108.255.4.3.1/24) and R4 E0 (131.3. the route reflector.252 R1(config-router)#network 131. Take particular note of the shaded sections.255. round-trip min/avg/max = 16/16/20 ms R2#ping 131.108.108.1 Type escape sequence to abort. 5 subnets.108.1. To fix this.1. Example 7-12 show ip bgp on R2 and ping on R2 R2#show ip route 131.0/24 is directly connected.108. and a reply to the remote networks attached to R3 and R4.3.108.1/24). which contain critical commands.1. here are the full working configurations on all four routers. the BGP table on R2 displays the remote BGP entries in its IP routing table.108. 00:02:58 B 131.255.255.108. 00:03:20 C 131.0/30 [200/0] via 131. Sending 5.108.255. Example 7-11 Advertising WAN links on R1 R1(config)#router bgp 333 R1(config-router)#network 131. especially on R1. 100-byte ICMP Echos to 131.1.4 mask 255.1.4/30 [200/0] via 131.108.252 clockrate 128000 ! interface Serial1/1 .6.252 After you clear all the BGP sessions on R1 with the clear ip bgp * command.0/24 [200/0] via 131.1 Type escape sequence to abort. Example 7-13 displays R1's full working configuration.0.1. 2 masks B 131. Before you consider a more complex route reflector scenario.1 255. 00:03:25 B 131.0/16 is variably subnetted.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.108.255.255.4.255. 100-byte ICMP Echos to 131.108.108.108. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). a successful ping request.3. round-trip min/avg/max = 16/16/20 ms Example 7-12 displays the remote BGP entries on R2. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).240 - .5 255.255.108.255.0 ! interface Serial1/0 ip address 131. In other words. BGP does not insert any remote network when the next hop address is not routable.255.0/24 [200/0] via 131.108.108. 00:02:58 B 131. Ethernet0/0 R2#ping 131.

252 network 131.255.108. 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 131.252 bandwidth 125 ! interface Serial1 shutdown router bgp 333 .1 255.255.6 remote-as 333 neighbor 131.255.108.255.255.108.255.1.1 255.255.255.255.2 255.2 remote-as 333 neighbor 131.108.2 route-reflector-client neighbor 131.255.108.255.108.255.255.0 ! R2 is a RR client to R1 router bgp 333 no synchronization network 131.108.0 mask 255.108.255.255.CCNP Practical Studies: Routing ip address 131.255. Example 7-15 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.0 network 131.255.252 ! router bgp 333 no synchronization network 131.1.1.255.255.108.108.2 route-reflector-client 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.0 neighbor 131.6 255.1.108.108.108.3.255.1.255.108.108.0 ! interface Serial0 ip address 131.241 - .255.0 mask 255.0 mask 255.2 remote-as 333 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.252 neighbor 131.255.4 mask 255.1.255.

4 mask 255.108.252 neighbor 131.254.254.252 clockrate 125000 ! interface Serial1 shutdown ! router bgp 333 no synchronization network 131.4.255.255.242 - .255.1 for R1.1 255. 131.108. Figure 7-4.5 remote-as 333 ! line con 0 line aux 0 line vty 0 4 end Example 7-16 displays R4's full working configuration. and 131.255.0 ! interface Serial0 bandwidth 125 ip address 131.3.4 for R4.2 255.108.255.254.108.108.0 mask 255.253.CCNP Practical Studies: Routing no synchronization network 131.254.108.255.5 for R5.255.0 network 131.0 mask 255.4.0 network 131.255.255. 131.252 neighbor 131.255.108.3 for R3.255.255.1 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 7-1.108.255.0 mask 255.255.108.108. and each router is assigned a loopback address of the form 131.108.2 for R2.108.255. 131.108.255.255. OSPF is the interior routing protocol used on routers R1–R5. Scenario 7-2 Physical Topology . 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.

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

254. In fact.108. and R5. R3. R1 is configured to peer to R2 but not as a route reflector.CCNP Practical Studies: Routing Example 7-17 configures all IP-enabled interfaces on R1 in area 0.254.108.0 on R1 and displays the enabling of R1 to reflect BGP information to R3.2 remote-as 333 neighbor 131.108.5 remote-as 333 neighbor 131.0.255.108.108.254.1. Example 7-19 displays the configuration of R2 as a backup route reflector to R3.255. and R5 using the loopback interfaces as the source and peer addresses.3 route-reflector-client neighbor 131.255. OSPF is used as the IGP to ensure IP connectivity among all loopback interfaces.1 remote-as 333 neighbor 131.4 route-reflector-client neighbor 131.5 update-source Loopback0 neighbor 131.0 mask 255. and R5. Example 7-17 R1 OSPF Configuration R1(config)#router ospf 1 R1(config-router)# network 0.3 update-source Loopback0 neighbor 131.254.108.108.4 remote-as 333 neighbor 131.108.254.108.1.5 remote-as 333 neighbor 131. R4.108.1.108.0 mask 255.254.4 remote-as 333 neighbor 131.108.108.1.255.5 route-reflector-client neighbor 131.3 remote-as 333 neighbor 131.108.5 route-reflector-client Example 7-18 displays the local advertisement of the network 131. configure one of the edge routers. For redundancy purposes. R4.1 update-source Loopback0 neighbor 131. Next.255.254. R4.5 update-source Loopback0 neighbor 131.254.4 update-source Loopback0 neighbor 131. for IBGP. configure IBGP on R1 and use the loopback addresses as the next hop addresses because as long as you have IP connectivity. BGP is established.254.0.0 neighbor 131.108.2 update-source Loopback0 Example 7-19 displays the local advertisement of the network 131.0 on R2 and the enabling of R2 to reflect BGP information to R3.254.254. R4. R1 is configured to peer to the loopback interfaces to ensure that as long as there is IP connectivity.108.254.2 update-source Loopback0 neighbor 131. Example 7-18 configures IBGP on R1 to act as a route reflector to R3.108.254.254.108. IBGP is established.244 - .108.254.3 route-reflector-client neighbor 131.108.0 255.108.4 update-source Loopback0 neighbor 131.108.254. BGP should remain active.108.254.2 remote-as 333 neighbor 131.3 update-source Loopback0 neighbor 131.4 route-reflector-client neighbor 131. .254.254.108.3 remote-as 333 neighbor 131. R2 is configured to peer to the loopback interfaces to ensure that as long as there is IP connectivity.255.254.0 neighbor 131.255. good IBGP design always uses loopbacks so that one routing failure does not result in loss (TCP fails) of IBGP connectivity.108. and R5.254.108.108.108. Next.254.255. Example 7-18 IBGP on R1 router bgp 333 network 131.255 area 0 Configure the same two commands on R2–R5 to enable OSPF as the IGP. Example 7-19 IBGP on R2 router bgp 333 network 131.

254.245 - .CCNP Practical Studies: Routing Example 7-20 displays the IBGP configuration on R3 pointing to R1 and R2.1.5. view the IP routing table on R3.254.0. use the network command to advertise this network to R1 and R2. Because R3 is locally connected to 131. advertised by R1 and R2.254.108. you can take a look at the BGP tables.0 131.4.254.0/24 * i *>i131.108.4 131.255.108. Example 7-23 show ip bgp on R3 R3#show ip bgp Network *>i131.0 mask 255.0 mask 255.2 remote-as 333 neighbor 131.108.255.2 update-source Loopback0 All the routers in Figure 7-5 have IBGP peers configured.2 remote-as 333 neighbor 131.254.0/24.108.1 remote-as 333 neighbor 131.108. To confirm IP connectivity. Example 7-23 displays the BGP table on the client router R3.1.108.255.254.3.108.108.254. Example 7-21 IBGP on R4 router bgp 333 network 131.108.4 131. Example 7-24 displays the IP routing table on R3.1 remote-as 333 neighbor 131.254.0 mask 255.2 remote-as 333 neighbor 131.5 131.254.0 neighbor 131.255.108.108.0/24 (indicated with the next of 0.5.255.0.254.108. 131.0/24.0 neighbor 131.0.2 update-source Loopback0 Example 7-22 IBGP on R5 router bgp 333 network 131.108.108.108.108.108.2 update-source Loopback0 R3 is configured normally for IBGP to R1 and R2.0/24 *>i131.254.0.108.254.108.2 131. remember that you have OSPF configured as the IGP. After the BGP peer sessions are established on routers R4 and R5.108.108.1 update-source Loopback0 neighbor 131.5.3.108.1 update-source Loopback0 neighbor 131.1 remote-as 333 neighbor 131.254.0 neighbor 131.4.108.0.108.1 0. Example 7-20 IBGP on R3 router bgp 333 network 131. respectively.108.254.0.108.108.0/24 * i *> 131. .0). R4 advertises 131.3.0/24 * i Next Hop 131.108.255.254. and R5 advertises 131.4.3. Also present in the BGP table is the remote network.254.5 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 131.1 update-source Loopback0 neighbor 131.108.254.254. Example 7-21 and Example 7-22 display the IBGP configuration on R4 and R5.

108.108.254. .1/32 [110/801] via 131.255.5.254.108.255. Serial0 O 131. 00:29:59. 12 subnets.108.2/32 [110/811] via 131.255. Even though BGP (view the BGP table in Example 7-23) has inserted the remote networks. 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.108.4/32 [110/1582] via 131. 00:38:44.108.5.108.0/16 is variably subnetted.3/32 is directly connected. O .255.255. Example 7-26 show ip route on R3 R3#show ip route 131. Serial0 C 131.5. Serial0 O 131.2/32 [110/811] via 131.connected.5.5.255. 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.4/30 is directly connected. 01:04:33.255.4.5.5.0/24 [110/1591] via 131.108.108.108. 00:04:10.255.5.108. 00:29:59.108.1/32 [110/801] via 131.255.254. and 131. 12 subnets.5.0/24 [110/810] via 131.108.8/30 [110/1581] via 131.5.BGP.246 - . Ethernet0 O 131. Serial0 O 131.254.5/32 [110/1582] via 131. 131.4.3.5.108.1.108.108.108.255. 01:04:33. as OSPF discovered routes.0.108.108.4/32 [110/1582] via 131.255. 00:21:51.108.254.108.108.0/24.108. Change the default administrative distance on all five routers so that internal BGP is the preferred path in this five-router network.108.4.108.255.255. 131.5/32 [110/1582] via 131. Example 7-25 displays the disabling of synchronization on all five routers.108.5.3.8/30 [110/1581] via 131.255. Serial0 O 131.255.5.108.1.5.0/24 [110/1591] via 131. Serial0 O 131.3/32 is directly connected.0/30 [110/1581] via 131. 01:04:33. B .108. Serial0 O 131.108. Serial0 C 131.5.4/30 is directly connected.0/24 [110/1591] via 131. 00:29:59.108.5.108.108.108. 00:29:59. Serial0 R3's IP routing table displays the remote networks 131.5.255.0.108.255.0/30 [110/1581] via 131. Serial0 O 131.255.OSPF 131.1. 00:29:59. Serial0 O 131.0/24.254.0/16 is variably subnetted. Serial0 O 131.108.0/24 discovered by OSPF (indicated by the O on the left side of the IP routing table). 00:21:53. Serial0 C 131.108.108. compared to 200 for IBGP.108.5.0/24 [110/810] via 131. Example 7-26 displays the IP routing table on R3.255.108. 3 masks O 131.108.5.255.254. Serial0 O 131.254.108. 3 masks O 131.108.0/24.0/24 [110/1591] via 131. Serial0 C 131.5.255. 00:04:22.255. 01:04:33. Serial0 O 131.254.0/24 is directly connected.108. 00:29:59. Serial0 C 131. Serial0 The reason that OSPF is chosen for the preferred path is that OSPF has a lower administrative distance of 110.0/24 is directly connected. you can expect to see BGP routing entries in the IP routing table on R3. Serial0 O 131. Ethernet0 O 131.108.CCNP Practical Studies: Routing Example 7-24 show ip route on R3 R3#show ip route Codes: C .4. 00:04:22. 01:04:33. Serial0 C 131.5.254. Loopback0 O 131.108.255.108.108. 01:04:33.108.108.5.255.0/24 and 131. Loopback0 O 131.

Example 7-27 displays the distance configuration on R1 and is configured on all five routers.108.5.108.108. Serial0 O 131.5.5/32 [110/1582] via 131.255.255.108. 01:18:33. By default. you use the concept of a backdoor to ensure that your IGP is the preferred routing method.0/24 [109/0] via 131.1.0/24 [109/0] via 131. and the local distance is also changed to 109.254. a lower AD is always preferred.0/30 [110/1581] via 131.108.108.0/16 is variably subnetted. 01:18:33. Serial0 O 131. Example 7-28 displays the IP routing table on R3 after the TCP peers are cleared. the next hop address is the EBGP connection. Serial0 O 131.0/24 is directly connected.3.255. Changing the administrative distance is not always the most desirable method because all routers typically need modification.254. 00:01:38 B 131.5. far lower than OSPF (AD is 110). 01:18:33.1/32 [110/801] via 131.108.0/24 [109/0] via 131.108. 01:18:33. the internal distance is for IBGP routes (default is 200). as in this scenario.108.255.1.108.108. For example.108.108.4.255.3/32 is directly connected.5. therefore. R4.2. Serial0 O 131.108. Serial0 C 131. 00:01:37 C 131.255.CCNP Practical Studies: Routing NOTE The same scenario can be duplicated using EBGP.0.255.108.108. Specifying the network allows the router to choose OSPF as the preferred path rather than the EBGP discovered path.2/32 [110/811] via 131.4/30 is directly connected. You use the ? tool to display the options as you enter the values. 01:18:33. if EBGP is configured between two routers and OSPF is the interior routing protocol.4/32 [110/1582] via 131.108. 01:18:33. Ethernet0 B 131.5.8/30 [110/1581] via 131.254.108. Example 7-28 show ip route on R3 R3#sh ip route 131.254.254.108. the external distance is unchanged at 20.254. and the local distance defines the AD for locally connected routes (default is 200). Serial0 B 131.108. 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). 3 masks O 131. and R5.108.108. To change this default behavior without the changing AD values. 12 subnets.5. 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).254. . use the network <network subnet-mask> backdoor command. 00:00:50 R1 now uses BGP with an AD of 109 as the preferred path to the remote networks connected to R1/R2. in which case. Loopback0 O 131.247 - .5. EBGP administrative distance is 20.5.255.255. Serial0 C 131.255.

Example 7-31 displays R1's full working configuration.5.0/24 * i Next Hop 131.108.254.EGP.108. ? . e .108.108.108.108.254.0/24 *>i *> 131. Example 7-29 displays the current BGP table on R3.254.108.1. simulate a routing BGP failure to R1 and ensure that R2 becomes the preferred path on all route reflector clients.EGP. local router ID is 131.1.0.0 ! interface Serial1/0 .0 0 32768 i *>i131. ? .incomplete Network * i131. Example 7-30 show ip bgp on R3 after R1 Failure R3#show ip bgp BGP table version is 86.254.254.0.254. h history.4 131.254.internal Origin codes: i . local router ID is 131. d damped.internal Origin codes: i .3.108.108.5.108.108. Next.CCNP Practical Studies: Routing This scenario built a redundant IBGP network. > best.1 255.0/24 *>i131.1.255.255.255.4. * valid. h history. 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. i .108.IGP. d damped. Before you build upon this scenario and add the EBGP connections to the two different ISP routers.2 131.1 (R1's loopback address).108.0.108.254.108.3 Status codes: s suppressed. i .108.1.0/24 * i *>i131. the preferred path is through R2 (a route reflector).1 0.255.0 131.108.5 0 100 0 i The path to 131.IGP. Example 7-30 displays the BGP table on R3 after the BGP failure.0/24 131.254.incomplete Network Next Hop Metric LocPrf Weight Path *>i131. > best.0/24 0.108.108.0/24 is through R1.254.1. When the TCP peer to R1 fails on R3.108.0/24 131. view the full working configurations of R1–R5.1 255.4 0 100 0 i *>i131.0/24 is now through R2.3.248 - . e .0/24 131.3 Status codes: s suppressed.254.108.108.0.108.4 131.2 0 100 0 i *> 131.5 131.5 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. * valid.108.254.255 ! interface Ethernet0/0 ip address 131. the peer address is 131.254.4. Example 7-29 show ip bgp on R3 R3#show ip bgp BGP table version is 84.

108.255.5 update-source Loopback0 neighbor 131.255.108.255.255.4 update-source Loopback0 neighbor 131.0 mask 255.255.108.255.255.255.4 remote-as 333 neighbor 131.255.0 mask 255.1 255.255.254.255 ! interface Ethernet0/0 ip address 131.5 remote-as 333 neighbor 131.252 clockrate 128000 ! interface Serial1/3 shutdown ! router ospf 1 network 0.2 255.254.254.252 clockrate 128000 ! interface Serial1/1 ip address 131.255.108. Example 7-32 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.255.108.4 route-reflector-client neighbor 131.1.254.3 route-reflector-client neighbor 131.254.255.0.254.249 - .108.0 255.108.255.255 area 0 ! router bgp 333 no synchronization network 131.0.108.5 255.255 area 0 ! router bgp 333 no synchronization network 131.2 255.255.254.3 remote-as 333 neighbor 131.108.254.108.0.1.1 remote-as 333 .CCNP Practical Studies: Routing ip address 131.108.254.108.255.255.108.255.9 255.0 255.2 remote-as 333 neighbor 131.108.1.255.254.108.254.0 neighbor 131.2 update-source Loopback0 neighbor 131.0 ! router ospf 1 network 0.0 neighbor 131.108.252 ! interface Serial1/2 ip address 131.255.254.108.254.108.108.5 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.0.255.3 update-source Loopback0 neighbor 131.

254.255.254.108.6 255.255.254.2 remote-as 333 neighbor 131.252 bandwidth 125 ! interface Serial1 shutdown ! router ospf 1 network 0.108.108.255.4 update-source Loopback0 neighbor 131.254.108.3 255.254.254.254.5 remote-as 333 neighbor 131.255.2 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.108.254.255.3 remote-as 333 neighbor 131.108.4 route-reflector-client neighbor 131.254.254.0 neighbor 131.5 update-source Loopback0 neighbor 131.0.255.254.250 - .108.254.255.255.254.2 update-source Loopback0 distance bgp 20 109 109 ! line con 0 line aux 0 line vty 0 4 ! end .3.255 ! interface Ethernet0 ip address 131.3.108. Example 7-33 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 131.108.108.255.108.108.255.254.3 route-reflector-client neighbor 131.108.108.255.254.0.CCNP Practical Studies: Routing neighbor 131.1 remote-as 333 neighbor 131.2 remote-as 333 neighbor 131.108.108.0 ! interface Serial0 ip address 131.5 route-reflector-client neighbor 131.4 remote-as 333 neighbor 131.255.108.255 area 0 ! router bgp 333 no synchronization network 131.1 255.0 255.1 update-source Loopback0 neighbor 131.255.0 mask 255.108.108.108.3 update-source Loopback0 neighbor 131.1 update-source Loopback0 neighbor 131.

255 area 0 ! router bgp 333 no synchronization network 131.108.108.255.255.0 ! interface Serial0 ip address 131.0 ! interface Serial0 ip address 131.255.255.251 - .108.108.0 mask 255.5.1 255.255 ! interface Ethernet0 ip address 131.255. Example 7-34 R4's Full Working Configuration hostname R4 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.2 remote-as 333 neighbor 131.4.4 255.108.1 255.0 255.0.255.254.2 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.255.255.255.4.0.254.254.252 ! interface Serial1 shutdown ! .1 remote-as 333 neighbor 131.108.255.255.5 255.108.0 neighbor 131.254.255 ! interface Ethernet0 ip address 131. Example 7-35 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 131.255.255.108.254.255.108.255.108.1 update-source Loopback0 neighbor 131.252 clockrate 125000 ! interface Serial1 shutdown ! router ospf 1 network 0.255.108.255.254.2 255.10 255.255.CCNP Practical Studies: Routing Example 7-34 displays R4's full working configuration.

Figure 7-6 displays the EBGP connections on R1 and R2 and the IP addressing.254. 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.1 update-source Loopback0 neighbor 131.255 area 0 ! router bgp 333 no synchronization network 131.108.0 neighbor 131.108.5.108.2 remote-as 333 neighbor 131.108. Example 7-36 configures ISP1 for EBGP and allows a default route to be advertised to the EBGP peer to R1. you configure two routers and inject default routes along with a large IP routing table to simulate an ISP router.0 mask 255.255.255.108.254. you build upon the IBGP network in Figure 7-4 and configure EBGP on R1 and R2 and simulate a dual-homing ISP connection.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. Because most CCNP candidates do not have two ISP connections to configure in a lab environment.254.254.255.1 remote-as 333 neighbor 131.0 255.255.252 - .CCNP Practical Studies: Routing router ospf 1 network 0. .0.0. Figure 7-6.

108.0. e .1.2 remote-as 333 neighbor 160. > best.100.0/24 *>i * i131.0. because it has a direct connection to the EBGP peer to ISP1.0 131.internal Origin codes: i .108.108.108. d damped.4.108.0/24 *>i * i131.254.1.1.108.0.0 *> * i131.0/24 *>i * i131.108.254.108.EGP.254.0/24 *>i Next Hop 171.5.3.1.108.2 remote-as 333 neighbor 171.108.5 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 .1 0.100.108.1 Status codes: s suppressed.2 Status codes: s suppressed.254.4.254.CCNP Practical Studies: Routing Example 7-36 EBGP on ISP1 router bgp 50001 neighbor 171.incomplete Network * i0.108. i . * valid. * valid.3 131.254.108.5 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 R1.108. are providing default routes to R1 and R2.1.100.1 160.108.5.3 131. d damped.1. Remember that both Internet routers.IGP.1. e .1 131.108.254.2 default-originate View the BGP tables on R1 and R2 and ensure that the BGP table contains a default route.108.0.4 131.108.253 - .2 131.5 131.1.254. Example 7-38 displays R1's BGP table.0/24 *> * i131.incomplete Network *> 0.108. ? .254.0. h history.1 0.254. Example 7-38 R1's BGP table R1#show ip bgp BGP table version is 8. h history.5 131.0 * i *> 131.0/24 *>i * i131.100.3 131. Example 7-39 displays R2's BGP table.1.4 131.108. local router ID is 131.0/24 *>i Next Hop 171. ISP1 and ISP2. Example 7-37 EBGP on ISP2 router bgp 4000 neighbor 160.0.3 131.254.IGP.254.108.0 131. local router ID is 131.108.EGP.1 160.254.3. selects ISP1 for default-based traffic. i .108.108. ? .2 default-originate Example 7-37 displays the EBGP configuration on ISP2.0/24 * i * i131.108.4 131.108.internal Origin codes: i .254.254. > best.254.4 131.108.0. respectively.108. Example 7-39 R2's BGP table R2#show ip bgp BGP table version is 12.1.0.

Ideally.108.3.254. Example 7-40 MED Modification on R2 R2(config)#router bgp 333 R2(config-router)#neighbor 131. the BGP table on R2 displays the preferred default route 0. Example 7-40 displays the MED configuration on R2. so to enable BGP to compare MED in different autonomous systems.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. Example 7-41 show ip bgp on R2 R2#show ip bgp BGP table version is 9.100.108. Example 7-42 displays the configuration on R2 to allow MED to be compared between R1 and ISP2.0.108.254. you must enable the bgp always-compare-med command.0/24 131.1. the preferred path to the next hop 160. because R2 has a direct connection to the EBGP peer to ISP2.4 100 100 0 i * i131.0 0 32768 i *>i131. * valid. and MED influences only EBGP connections. as shown in Example 7-41. unless R1 loses the connection to ISP1.254.108. local router ID is 131.EGP.1.100. resulting in loss or slow user-data transfer.1 route-map setmedr1 in R2(config-router)#neighbor 160.108.1 100 100 0 50001 i * i131.254.CCNP Practical Studies: Routing Similarly.254.3 100 100 0 i *>i131. d damped. This means that traffic is sent to different ISP routers for any traffic to the Internet. i .108.2 Status codes: s suppressed.0.108.254.5 100 100 0 i *>i 131.108.254 - . you modify the MED value on R2 to ensure that all default traffic is sent through R1. To demonstrate another method.0/24 131.108. 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. R2 selects ISP2 for all default-based traffic. e .108. > best.100.254.0.1. ? .3 0 100 0 i * i 131.1. are in different autonomous systems.254. and BGP decisions are even though the two routers. The bgp always-compare-med command allows the MED values to be compared.0/0 through R1.1 200 0 4000 i * i 171. a dual-home connection is for redundancy purposes only. is through ISP2. R1 and R2.1 100 100 0 i *> 0.1.internal Origin codes: i .incomplete Network Next Hop Metric LocPrf Weight Path *> 0. h history.4 0 100 0 i * i 131. R1 (in AS 333) and ISP2 (in AS 4000) are in different autonomous systems.0.108. such as HTTP traffic. .108.0/24 131.0. even though the MED is lower. an example using AS_Path manipulation follows.IGP.0 160. This traffic pattern is undesirable because IP packets might take different paths and not reach the destination in a timely manner.5. the BGP table on R2 is displayed.0/24 131.5 0 100 0 i As displayed in Example 7-41.108. Configure R2 to send all default traffic through the connection on R1 to ISP1.0.4.1.108. The MED attribute is compared only for paths from neighbors in the same AS. To accomplish this task.254. Lower MED values are preferred.

5 100 100 0 i Example 7-43 shows that the new preferred path is through R1 because the MED is lower.255.108.4 0 100 0 i * i 131.252 clockrate 128000 ! router ospf 1 network 0.254.254.0 255.4 update-source Loopback0 neighbor 131. Before removing the configuration comparing MED on R2 and demonstrating how the AS_Path attribute can also be used to accomplish the task.108.108.0. local router ID is 131.254.254.255.0/24 131.CCNP Practical Studies: Routing Example 7-43 displays the BGP table on R2.108.1 200 0 4000 i *>i 171. Example 7-44 displays R2's full working configuration.108.100.3 update-source Loopback0 neighbor 131. > best.2 Status codes: s suppressed.3 100 100 0 i *>i131.EGP.108.108.254.IGP.1 100 100 0 50001 i * i131.0 mask 255.255 area 0 ! router bgp 333 no synchronization bgp always-compare-med network 131.254.1 route-map setmedr1 in neighbor 131.108.0. Example 7-43 show ip bgp on R2 R2#show ip bgp BGP table version is 9.108.0 ! interface Serial1/3 ip address 160.254.108.0 neighbor 131.0/24 131.255. i .0/24 131.255.254.3.255.108.1 update-source Loopback0 neighbor 131. e .0.108.108.255.255.108.108.108.108.1.254.4 remote-as 333 neighbor 131.0 160.255.254.1 remote-as 333 neighbor 131.2 255.255 - . h history.3 0 100 0 i * i 131.0 0 32768 i *>i131.108.4 100 100 0 i *>i131.5 0 100 0 i * i 131.108.254.5.1.108.0.2 255.0. d damped.108.2 255.254. 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 131.254.254.108.108. ? .255.100.internal Origin codes: i .1. * valid.1.4.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.108.254.254.1.3 route-reflector-client neighbor 131.incomplete Network Next Hop Metric LocPrf Weight Path * 0.0/24 131.255.0.254.254.1.4 route-reflector-client .3 remote-as 333 neighbor 131.1 100 100 0 i *> 0.

254.0 ! 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. configure the AS_Path to 4000 3999 3998 on R2 for all incoming routes from ISP2.CCNP Practical Studies: Routing neighbor 131.0.1 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. Next.1.256 - . Example 7-46 displays the BGP table on R2.254.1.254.100.100.5 update-source Loopback0 neighbor 131.5 remote-as 333 neighbor 131.1 remote-as 4000 neighbor 160.1. Example 7-45 AS_Path Manipulation of R2 R2(config)#router bgp 333 R2(config-router)#no neighbor 160.5 route-reflector-client neighbor 160.108.108. . 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 setmedisp2 in R2(config-router)#no neighbor 131.254. you learned the BGP routing decisions and one of the decisions are based on shortest AS_Path.1.108.100.1 route-map setmedr1 in R2(config-router)#neighbor 160.1 route-map setmedisp2 in distance bgp 20 109 109 access-list 1 permit 0.100.108.0.

IGP. In the next scenario.108. Example 7-47 displays the configuration on R1 to allow only default routes and displays setting the no-export community to ISP1. d damped. 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.108. h history.1. do not use the network between R1 and R2 as a transit path.254. 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. Example 7-48 also shows the use of a well-known community value: no-export.254.0.1.254. 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 route-map noexport ? R1(config-router)#neighbor 171.3 0 100 0 i *>i 131.1 filter R1(config-router)#neighbor 171.3 0 100 0 i * i131.EGP.254.1. You can use a filter list along with a route map to permit a default route. ISP1 and ISP2. you use prefix lists to accomplish the same task.5 0 100 0 i R2 now prefers the path through the next hop address 171.0.0/24 131.108. 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.108.2 Status codes: s suppressed.0.4.internal Origin codes: i . local router ID is 131.0/24 131.254.1.0 160.1 0 4000 3999 3998 4000 i *>i 171. Example 7-47 R1 Allowing Only Default Routes (Filter List) and Setting Community R1(config)#router bgp 333 R1(config-router)#neighbor 171.0.108.1 route-map noexport out R1(config)#route-map no-export R1(config-route-map)#set community no-export R1(config)#access-list 1 permit 0.1.108. or a lower hop count away compared to 4000 3999 3998 (three hops).5. * valid. > best.1.254.1.CCNP Practical Studies: Routing Example 7-46 show ip bgp on R2 R2#show ip bgp BGP table version is 7. ? . .108.3. e .4 0 100 0 i * i131.108.0/24 0. i .5 0 100 0 i *>i 131.108. configure R1 and R2 to accept only a default route and ensure that the service providers.108.1 filter-list 1 in R1(config-router)#neighbor 171.1 0 100 0 i * i131.1 (R1's link to ISP1) because the AS_Path is only 50001 (one hop).108.1.108.incomplete Network Next Hop Metric LocPrf Weight Path * 0.108.108.4 0 100 0 i *>i 131.1 100 0 50001 i *> 131.257 - .1.108.108.254.108.1 send-community R1(config-router)#neighbor 171.254.0 Example 7-47 displays the configuration on R2 to allow only default routes and setting the no export community to ISP1.0.108.0.1 filter-list 1 R1(config-router)#neighbor 171.108.1.0/24 131.0 0 32768 i * i 131.100.108.

258 - .1 255.2 remote-as 333 neighbor 171.255.1 route-map setcommuntiy out R2(config-router)#neighbor 160.255.100.1.100.0 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.2 default-originate line con 0 line aux 0 line vty 0 4 ! .1.1 send-community R2(config-router)#neighbor 160.108.255.100.1.108.1.255. Example 7-49 displays ISP1's full working configuration.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 160.1. Example 7-49 ISP1's Full Working Configuration hostname ISP1 ! enable password cisco ! ip subnet-zero ! interface Serial0 ip address 171.1.100.2 default-originate ! line con 0 line aux 0 line vty 0 4 ! end Example 7-50 displays ISP2's full working configuration.1 filter-list 1 in R2(config)#access 1 permit 0.1.252 ! interface Serial1 shutdown ! router bgp 4000 neighbor 160.2 remote-as 333 neighbor 160.1.252 interface Serial1 shutdown ! router bgp 50001 neighbor 171.100. view the full working configurations of the four main routers in this scenario.1 255.108.1.0. Example 7-50 ISP2's Full Working Configuration hostname ISP2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Serial0 ip address 160.0.100.

254.3 remote-as 333 neighbor 131.252 ! interface Serial1/2 ip address 131.252 clockrate 128000 ! interface Serial1/1 ip address 131.108.255.108.4 update-source Loopback0 neighbor 131.1 route-map noexport out neighbor 171.108.3 route-reflector-client neighbor 131.254.1 255.0.108.5 update-source Loopback0 neighbor 131.1.108.3 update-source Loopback0 neighbor 131.255.108.254.9 255.1 remote-as 50001 neighbor 171.108.259 - .1.1.255.108.108.2 update-source Loopback0 neighbor 131.255.0 neighbor 131.0 mask 255.255.252 clockrate 128000 ! interface Serial1/3 ip address 171.252 clockrate 128000 ! router ospf 1 network 0.108.254.254.255.255.1.254. Example 7-51 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero no ip domain-lookup ! interface Loopback0 ip address 131.108.1 filter-list 1 in distance bgp 20 109 109 ! route-map noexport permit 10 .255.255.255.5 route-reflector-client neighbor 171.0 no ip directed-broadcast ! interface Serial1/0 ip address 131.1 send-community neighbor 171.255 area 0 ! router bgp 333 no synchronization network 131.255.255.254.255.108.108.254.108.108.4 route-reflector-client neighbor 131.108.1 255.255.1.254.2 255.254.5 remote-as 333 neighbor 131.1 255.2 remote-as 333 neighbor 131.108.108.0.254.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.1.5 255.0 255.255.108.1.108.254.255.255.4 remote-as 333 neighbor 131.CCNP Practical Studies: Routing end Example 7-51 displays R1's full working configuration.255.255.108.

255.108.1 send-community neighbor 160.254.108.254.0 neighbor 131.254.1 filter-list 1 in distance bgp 20 109 109 ! access-list 1 permit 0.108.0 mask 255.108.3 route-reflector-client neighbor 131.5 remote-as 333 neighbor 131.1.3 remote-as 333 neighbor 131.0.5 route-reflector-client neighbor 160.254.254.254.255.108.0 route-map setcommunity permit 10 set community no-export ! route-map setcommuntiy permit 10 set community no-export ! .255.100.255.4 remote-as 333 neighbor 131.100.1.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.255.260 - .108.1 remote-as 4000 neighbor 160.4 route-reflector-client neighbor 131.1 route-map setcommuntiy out neighbor 160.0 255.0.255.255 no ip directed-broadcast ! interface Ethernet0/0 ip address 131.108.108.254.100.1.100.2 255.0.255.0.108.2 255.255.254.108.100.254.255 area 0 ! router bgp 333 no synchronization bgp always-compare-med network 131.5 update-source Loopback0 neighbor 131.254.108.100.1.1 update-source Loopback0 neighbor 131.4 update-source Loopback0 neighbor 131.255.1.108.1.2 255.1.1 remote-as 333 neighbor 131.255. Example 7-52 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup interface Loopback0 ip address 131.108.254.252 clockrate 128000 ! router ospf 1 network 0.108.254.1.1 route-map aspath in neighbor 160.0 ! interface Serial1/3 ip address 160.3 update-source Loopback0 neighbor 131.

261 - .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 .

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

0.0.0.0.0.255.0 255.0.0.0.0 Null0 4.0.0.100.255 access-list 1 permit 11.0 0.0.0 255.0–150.0. Example 7-54 Prepending Routes on ISP1 router bgp 50001 neighbor 171.255.0.255 access-list 1 permit 7.0.0.0.0 255.0. 101.255.255 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 0.0 Null0 142.0.0.0.0 Null0 2.0.0.255.0 Null0 100.255 access-list 1 permit 2.0.0 0.0 0.0 Null0 6.255.255.0.0.108.0.0.0 255.0 255.0 0.255.0 255.0. All other networks are prepended with the autonomous systems 400.0.0 Null0 7. and 200.0.0 Null0 146.255.0.0 Null0 148.0.0.0.255.0 null0 Example 7-53 displays the static route configuration of Class A networks ranging from 1. Null routes and loopbacks are great learning tools.0.0 255.255 access-list 1 permit 4.0.255.255. and finally the Class B networks ranging from 141.0 255.255.0 255. In a real-world BGP environment.0.0.100.255.0.255 access-list 1 permit 9.255.0.100.0.0 0.255.0.108.100.0 255.255.0.0 255.0.255.0.255.0.0 255.0.0 255.0.0.0.0.0 Null0 3.255 access-list 1 permit 5.0.100. the router ISP1 would have more specific entries to all these networks.0.0 0.0.0 Null0 101.1.0 Null0 0.0.0.0. 300.0 Null0 102.0.0 Null0 141. the Class A networks 100.0.100.255. and 102.0 255.100.0–11.0.0 255.0.0.0 0. 0.0. The origin AS is 1000.0 255.0 Null0 143.100.0.0.255.0 255.0.0 Null0 141. is a default route advertisement.0 Null0 147.0.0. with the path through 998 999. Example 7-54 configures all networks in the range 1.255.2 route-map prepend out access-list 1 permit 1.0.0.0.0.0.0 Null0 144.255.0 255. The last entry.0.0 0.255.0.0 255.255.0.100.0 Null0 150.0.0.255 access-list 1 permit 8.0.0. and a static route would be configured so that information can be sent over the EBGP peers without the need for dynamic routing advertisements.0.100.255.0.100.0/16.0.255.0/0.0.0.0 Null0 5. The route map name is set to prepend.0 0. To simulate a real environment.0.0 255.0.0. configure ISP1 to prepend some of the static routes with varying autonomous systems.0 Null0 8.0 255.255.0.0.0.0 255.0.255.0.255 access-list 1 permit 6.0.0.0.0.0.0.100.0 Null0 145.255.0.0 255.0.0.255.0.0.0 Null0 10.0 0.0.0 0.0.0 255.0–11.0.0.0 Null0 11.0.0.0.0 Null0 149.255.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 1.0.255 access-list 1 permit 3.0.255.0.255 access-list 1 permit 10.0.0.1.263 - .0.255.0.0.

0.1.0.0.0 141.0 147.108.100. and 200 or {400 300 200}.108.1 171.1.108.108.0.0 146.0.1.100.108.1.1.0.1 171.1.0.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). Example 7-55 confirms that the attributes are set correctly.100.108.0.0 6.108. Similarly.0 143. by viewing the BGP table on R1.0 145.0.internal Origin codes: i .1.1 Status codes: s suppressed.1 171.0.100.0.1 171. The networks defined in access list 2 are prepended with an AS of 400.264 - .1 171.0.0 131.1 171.0.0.1 171.0.1 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 ISP1.0 3.108.254.1. * valid.0.108.0.100.0/24 141.0.108.0.1 171.108.1.0 148. h history.IGP.0.100.0.0.1. Example 7-56 displays the IP (BGP routes only) routing table on R1.0 10.0 5.0 11.1.0.1 171.0 142.0.1.1.108.0 8.108.108.0.1.0 144.100.0 4.1 171.1.1. local router ID is 131.0.108. view the IP routing table on R1.1.0 171.0 101.0 7.0.1.108.1 171.108.108. line 20 in the route map (route-map prepend permit 20) statement configures all networks in access list 2 with an IGP origin attribute.0. e .1 171.108.1 171.0.108. 300.0.1.0.108.0.1 0.incomplete *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> *> Network 1.EGP.1 171.0 2.108.1. d damped. .108.1.1 171.1 171.1 171.0 149.1.100.108.1 171.0.0.100.1. All subnets allowed by access list 1 prepend all networks to 998 999 and set the origin to IGP.0.0.0 Next Hop 171.1 171. To demonstrate full IP connectivity.108.0. Example 7-55 show ip bgp on R1 R1#show ip bgp BGP table version is 25.108.0 102.0.1 171. > best.1. i . ? .0 100.1 171.

100.1.108.0. Next.0/8 [20/0] via 171.0.1.108.1. Cisco IOS (internal only) allows a router to generate as many routes as you could ever need to simulate the Internet.108. . 00:04:03 Example 7-56 displays all the networks advertised through ISP1.1.108.1.1.0/16 [20/0] via 171. matching the following criteria: • • • • NOTE Permit the default route 0. When you view the final configuration.0. 00:04:03 B 148.1.0. but because you have configured a null0 route.1.0/8 [20/0] via 171.0.0. 00:04:03 B 143.0.0.108.0.1.1.0/16 [20/0] via 171.0.0. so you might want specific routing information such as this. 00:04:03 B 145.1.0/16 [20/0] via 171.1.0.100.1.0.108.0. (This might be a network. such as BGP generators.0.0.0/8 [20/0] via 171. 00:04:03 B 142.0/16 [20/0] via 171.0/8 [20/0] via 171.1.1.1.1. For the purposes of this exercise. such as OSPF.108.0.0/16 [20/0] via 171. 00:04:02 B 2. You do not need to specify the sequence.0/16 [20/0] via 171. to be fully aware of all the entries advertised from ISP1 because you already have a default route. 00:04:02 B 141.108.0.0.108.0.0. Example 7-56 shows many BGP entries.0. 00:04:03 B 11.0.1.1. you configure a prefix list on R1 to stop any BGP routes.0/8 [20/0] via 171.108. you could peer to your corporate Internet gateway and receive the full BGP table.108. for example.0.0.1.1. 00:04:02 B 100.100.0.108.0. which might be in use on Router R1. As you can determine.0/16 [20/0] via 171.) Deny all other routes. Manually generating routes to null0 using static routes is a great learning tool to deploy in any practice lab.0/8 [20/0] via 171.108.0.1. 00:04:02 B 141.0.1. or an internal network running an IGP.100.0/8 [20/0] via 171. Alternatively. 00:04:03 B 7. 00:04:03 B 10.1.0.0/8 [20/0] via 171. 00:04:03 B 149.0.0.265 - . This is especially true because ISP1 is advertising the nonroutable 10.108.108.108.1.108.0/8 [20/0] via 171.0.0.1. 00:04:02 B 3.0.108.1.0. 00:04:03 B 8.1. Configure a prefix list on R1 to stop unnecessary routing traffic.0.1. 00:04:03 B 147. There is no need for R1.0.1.0/8 [20/0] via 171. 00:04:02 B 4.0.108.1.0/8 [20/0] via 171.0.1.1. Allow any routes in the range 1. the ping request reaches ISP1.108.) NOTE If you try to ping any of these networks from R1.1.1.100.0. although this is not a recommended exercise.0.108.1. Prefix lists follow sequence numbers just as route maps do.108.0/8 [20/0] via 171. where a virtual private network might be configured for extranets. but not 10.1.0/16 [20/0] via 171. 00:04:03 B 144.100.1.1.100. or the IBGP network. Allow all routes 141.0. 00:04:03 B 146.0/8 [20/0] via 171.1. There are other methods to generate BGP routes.0. 00:04:02 B 1.1.108.0.100. 00:04:02 B 5.0 network. all you need to be interested in is generating routes. the packets are dropped on ISP1.108.1.1.0/24.1.100. you will discover the IOS has inserted the sequence numbers for you.0/16 only. 00:04:02 B 6.0.1.1.1.0/16 [20/0] via 171.0. (Next hop address is 171.1.1. the initial number is 5 and is incremented by 5 each time.108. the EBGP peer address of ISP1.0.CCNP Practical Studies: Routing Example 7-56 show ip route bgp on R1 R1#show ip route bgp B 102. 00:04:02 B 101.0/16 [20/0] via 171.0–11.0.

e.1 prefix-list ccnp in R1 is configured to apply a prefix list to all inbound traffic from the router ISP1.0.0.108. .266 - .0/16 Prefix lists. configure a prefix list on inbound traffic from ISP1 on R1.0. Example 7-57 uses the ? to guide you through the various options.0/8 R1(config)#ip prefix-list ccnp permit 45.1 prefix-list ccnp ? in Filter incoming updates out Filter outgoing updates R1(config-router)#neighbor 171.B.108..0..0.D IP prefix <network>/<length>.1.0.0. As yet.0.C.0. named ccnp in Example 7-58.0/8 R1(config)#ip prefix-list ccnp permit 6.108.C.0/8 R1(config)#ip prefix-list ccnp permit 2. 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. implicitly deny all other networks. As with an access list.0.0/8 R1(config)#ip prefix-list ccnp permit 2.1.0.1.0/8 R1(config)#ip prefix-list ccnp permit 4.0. 35. Example 7-57 Initial Prefix List Configuration on R1 Pointing to ISP1 R1(config-router)#neighbor 171.0.0.0.0.0/8 R1(config)#ip prefix-list ccnp permit 9.0. you need to configure the options for the prefix list to perform any filtering.0. You do not need to deny any other networks because the Cisco IOS automatically denies all networks not specifically permitted in the prefix list. First.1 prefix-list ? WORD Name of a prefix list R1(config-router)#neighbor 171. Example 7-58 displays the prefix list configuration in global configuration mode.0/8 R1(config)#ip prefix-list ccnp permit 5.0. by default.0/8 R1(config)#ip prefix-list ccnp permit 0.0/8 R1(config)#ip prefix-list ccnp permit 141.0.0.0.0.D IP prefix <network>/<length>.0.g. you have not defined the prefix list.0.0/8 R1(config)#ip prefix-list ccnp permit 1.0.0/8 R1(config)#no ip prefix-list ccnp permit 45.0/8 R1(config)#ip prefix-list ccnp permit 8.0. e.0.B.0/8 R1(config)#ip prefix-list ccnp permit 7.0. Example 7-57 displays the filter list configuration in BGP configuration mode. Example 7-59 displays the configuration on R1 when the show running-config command is entered in privilege mode on R1 (truncated).CCNP Practical Studies: Routing Configure a prefix list on R1 to obtain the preceding objectives.0.0.g. 35.0.0/8 R1(config)#ip prefix-list ccnp permit 3.0/8 R1(config)#ip prefix-list ccnp permit 11.0/0 R1(config)#ip prefix-list ccnp permit ? A.1.

108.0.108.0 171.0/8 ip prefix-list ccnp seq 15 permit 2..1 prefix-list ccnp in ! ip prefix-list ccnp seq 5 permit 0.incomplete Network Next Hop Metric LocPrf Weight Path *> 0.1 0 0 50001 998 999 i *> 8. d damped.108.0 171.0/0 ip prefix-list ccnp seq 10 permit 1. NOTE The examples of prefix lists are practically endless.0.0. local router ID is 171.0 171.0.0.108.1.0. h history.1 0 0 50001 998 999 i *> 3.0/8 ip prefix-list ccnp seq 50 permit 9. 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.0 171.0.1 0 0 50001 998 999 i *> 5.0/8 ip prefix-list ccnp seq 30 permit 5.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfbgp.0/8 ip prefix-list ccnp seq 60 permit 141.truncated ! router bgp 333 network 131. i .1 0 0 50001 998 999 i *> 7.0.1.1 0 0 50001 998 999 i *> 6.0.0.1 remote-as 50001 neighbor 171.0.cisco.0/8 ip prefix-list ccnp seq 40 permit 7.0 171.1.1.2 Status codes: s suppressed.0 171.0.108.1 0 0 50001 998 999 i *> 2.htm#xtocid798074. Current configuration: !.0 171. For more great examples.1 0 0 50001 998 999 i *> 11. .1.0.0.108.0/16 The Cisco IOS automatically configures sequence numbering starting from 5–60..0.1.0.1. * valid.1.0.108.0.0.0.0.0.255.0.0 171.108.0/8 ip prefix-list ccnp seq 45 permit 8.108.1 0 0 50001 998 999 i *> 4.0.0.0.1.EGP.108..0/8 ip prefix-list ccnp seq 25 permit 4.CCNP Practical Studies: Routing Example 7-59 show running-config on R1 R1#show running-config Building configuration.0 171.0.0.0.1..108.1.0 171.108.0.internal Origin codes: i .0.0 0 32768 i R1 defines only the networks in the prefix list named ccnp.0.255.0.0/8 ip prefix-list ccnp seq 35 permit 6.1.1 0 50001 i *> 1.0 mask 255. > best.1.0.108.1.108. e .0.108.0.1.0/8 ip prefix-list ccnp seq 20 permit 3. Example 7-60 show ip bgp on R1 R1#show ip bgp BGP table version is 12.0.IGP.1 0 0 50001 998 999 i *> 131.0/24 0.0. Example 7-60 displays the BGP table on R1 after the BGP peer is cleared and re-established on R1.0.0 neighbor 171.267 - .0.0.1. visit www.0.0.0. ? .0/8 ip prefix-list ccnp seq 55 permit 11.0.

0/0 ip prefix-list ccnp seq 10 permit 1.0.255. Example 7-62 ISP1's Full Working Configuration hostname ISP1 ! enable password cisco ! interface Serial0 ip address 171.1 255.0.0.108.252 ! router bgp 50001 redistribute static .1.0/8 ip prefix-list ccnp seq 50 permit 9.0.0.0.1 prefix-list ccnp in ! ip prefix-list ccnp seq 5 permit 0.0/8 ip prefix-list ccnp seq 35 permit 6. use the Class A 10.2 255.0 ! interface Serial1/3 ip address 171.255.0.0/8 ip prefix-list ccnp seq 30 permit 5.0 private address for network-layer addressing on all network devices and.0/16 ! line con 0 line aux 0 line vty 0 4 end Example 7-62 displays ISP1's full working configuration. 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.108.0/8 ip prefix-list ccnp seq 55 permit 11.0.1 remote-as 50001 neighbor 171.0/8 ip prefix-list ccnp seq 25 permit 4.1. therefore.0.0 mask 255.255.0/8 ip prefix-list ccnp seq 15 permit 2.0.0.0.1 255.1.108. Some ISPs.0.0.CCNP Practical Studies: Routing Typically.0.0.0. for example.0.0.0/8 ip prefix-list ccnp seq 45 permit 8.255.0.255.108.1. block this network from all BGP sessions using prefix lists.0.0 neighbor 171.0.268 - . 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 131.252 clockrate 128000 ! router bgp 333 network 131.1.255.0/8 ip prefix-list ccnp seq 60 permit 141.0.0. 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. Example 7-61 displays R1's full working configuration.0.1.255.108.1.108.0/8 ip prefix-list ccnp seq 40 permit 7.255.0/8 ip prefix-list ccnp seq 20 permit 3.

0 0.0.0 255.0.2 route-map prepend out ! ip classless ip route 0.0.255.255.0.0.0.0.0 Null0 ip route 145.1.255.255.255 access-list 1 permit 7.0.0 Null0 ip route 5.255 access-list 1 permit 6.255.0.0.2 remote-as 333 neighbor 171.255.255 access-list 1 permit 4.0 0.255.0 Null0 ip route 146.0 255.0 0.0.255 access-list 1 permit 9.0.255.255.0 255.0 Null0 ip route 3.0.0.0 Null0 ip route 11.0.0.0.2 default-originate neighbor 171.0.100.0.0 Null0 ip route 102.0.0.0 Null0 ip route 149.0 255.0.0 255.255.255.255.0.108.0.0 255.CCNP Practical Studies: Routing neighbor 171.0.269 - .0 0.255.0 Null0 ip route 6.255.100.0.0.0.0.0.0.0 255.0 Null0 ip route 101.0 Null0 ip route 7.255.0 Null0 ip route 148.0.0 Null0 ip route 8.0.0 Null0 ip route 141.0.255.0.108.0.0 Null0 ! access-list 1 permit 1.255.0 255.0 0.255.0.1.0.108.0.0.0.0 0.0.0 255.0 255.0 Null0 ip route 143.0 Null0 ip route 10.0.255.0.255.0.0 255.0.0.0 255.255 access-list 1 permit 11.0.1.0.0.100.0 Null0 ip route 1.100.0.0.0 0.0.255.0 0.0.255 access-list 1 permit 5.0 Null0 ip route 141.255 access-list 1 permit 10.255.0.0.0 255.0.0.0.255.0 255.0 Null0 ip route 142.0.0 255.0.0 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 .0.255.255.0.0 Null0 ip route 2.0 Null0 ip route 147.0.0 0.0.0.0.0.0.0.0 255.0.0.0 255.100.100.0 255.255.108.255.255 access-list 1 permit 3.0.0.0.0.0.0.0.0.0 255.0 0.0.0.0 255.255 access-list 1 permit 8.100.0.0.0.0 255.0 Null0 ip route 100.0 255.0.0.0.0.255.255.255.0.0.0.255.0.255 access-list 1 permit 2.0 0.0 Null0 ip route 4.0.100.0.0.0.0 Null0 ip route 144.0.255.0 255.100.

1. The network 1. the origin attribute is set to IGP (meaning that BGP advertised this network through the network command). best.0.0. best #1) Not advertised to any peer 50001 998 999 171.0/8 R1#show ip bgp 1.0. version 3 Paths: (1 available.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. ref 2 Example 7-64 shows that the remote entry is reachable through the next hop address 171. 35.0/8 is through the AS paths 50001 (ISP1).0/8 is not advertised to any peer because R1 has only one EBGP peer to ISP1.1 (ISP1). valid.0.0.0. Example 7-64 displays the output of the IOS show ip bgp 1. This scenario covers some of the more advanced BGP monitoring commands.0.108. NOTE The following sample IOS displays are taken from the two-router topology in Figure 7-7. Example 7-64 show ip bgp 1..B.1 (171.0. then 998.1 from 171. localpref 100. e.0.1.0/8.1) Origin IGP.CCNP Practical Studies: Routing Scenario 7-5: Monitoring BGP and Verifying Correct Operation Chapter 6 covered common BGP show commands.B.1.g.0.htm.270 - . The full list of available show commands used in BGP is displayed in Example 7-63. Table 7-2 summarizes all the fields from Example 7-64. visit www. and finally originates from 999.108.108. Example 7-63 Full show ip bgp Command List R1#show ip bgp ? A. The path traversed to reach 1.C.0/8. external.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprrp_r/bgp_r/1rfbgp2.D A.1.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>. metric 0.0.0. For more examples of the full IOS command set.cisco. This IOS command is typically used to determine which AS path is taken to reach a remote network and the advertised peer.0/8 BGP routing table entry for 1.0.C.0.0. Suppose you want Router R1 to detail information about the remote network 1. .0/8 command.0.108.

> best. 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. IP address of a network entity.1. e—Entry originated from Exterior Gateway Protocol (EGP).0/8 Explained Field BGP table version Status codes Description Internal version number of the table. Example 7-65 show ip bgp cidr-only on R1 R1#show ip bgp cidr-only BGP table version is 12.1. * valid. It can be one of the following values: s—Entry suppressed.internal Origin codes: i .CCNP Practical Studies: Routing Table 7-2.108. Local preference value as set with the set local-preference route-map configuration command. show ip bgp 1. Origin codes Network Next Hop Metric LocPrf Weight Path To display routes with unnatural network masks (that is. use the show ip bgp cidr-only command. MED. i .108.271 - . Usually.1.incomplete Network *> 131. The origin code is placed at the end of each line in the table. Autonomous system paths to the destination network.IGP.EGP. Origin of the entry. classless interdomain routing [CIDR]).0/8.0. IP address of the next system that is used when forwarding a packet to the destination network. The status is displayed at the beginning of each line in the table.0.0 Metric LocPrf Weight Path 0 32768 i Table 7-3 displays the field descriptions for the show ip bgp cidr-only command. Status of the table entry.0. the AS path is 50001 998 999.2 Status codes: s suppressed. *—Entry is valid. ?—Origin of the path is not clear. this is a router that is redistributed into BGP from an IGP. In Example 7-66.0. You should expect the network 131. Every network change results in a new table version number incremented by 1 for every change.0. h history. local router ID is 171. The default value is 100. This number is incremented whenever the table changes. e . 1. .108.0. for example. Cisco-specific only. d damped.0/24 Next Hop 0.0 (Class B subnetted or /24 network mask). Weight of the route. >—Entry is the best entry. ? . i—Entry was learned through an internal BGP (IBGP). Example 7-65 displays the output from the show ip bgp cidr-only command on R1.

There can be one entry in this field for each autonomous system in the path. For example.108. For example. as set with the set local-preference route-map configuration command. Status of the table entry.108.0 is advertised using the network command.108.1. you would use the show ip bgp regexp ^$ command. Usually.) i—Entry originated from Interior Gateway Protocol (IGP) and was advertised with a network router configuration command. *—The table entry is valid. 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. and $ matches the end of an input string. Weight of the route. IP address of the next system to use when forwarding a packet to the destination network. >—The table entry is the best entry to use for that network. as set through autonomous system filters.1. Autonomous system paths to the destination network. show ip bgp cidr-only Descriptions Field BGP table version is 12 local router ID 171. The status is displayed at the beginning of each line in the table. if you want to discover all the paths originating locally. this is a router that is redistributed into BGP from an IGP.1) Metric LocPrf Weight Path . the ^ matches the beginning of an input string. Network (131. i—The table entry was learned through an internal BGP (IBGP) session.1. MED. ?—The origin of the path is not clear. IP address of the router.0/24) Next Hop (171. e—The route originated with EGP. Local preference value. Regular expressions are patterns that match input strings. This command is used to discover which networks match certain paths. Origin of the entry.CCNP Practical Studies: Routing Table 7-3. Hence. Internet address of the network the entry describes. e—Entry originated from Exterior Gateway Protocol (EGP). It can be one of the following values: s—The table entry is suppressed.272 - . The origin code is placed at the end of each line in the table. This number is incremented whenever the table changes. 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. character matches any single character.2 Status codes Description Internal version number for the table. Example 7-66 displays the output taken from R1 matching all networks originating locally. ?—Origin of the path is not clear.108. This IOS command is used to match networks meeting certain path descriptions.1. It can be one of the following values: Origin codes (131. I is displayed. the . 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.

108.CCNP Practical Studies: Routing Example 7-66 show ip bgp regexp ^$ R1#show ip bgp regexp ^$ BGP table version is 12. * valid.108.0.1 171.0 6.1.internal Origin codes: i . e .1 171.0 8.0.1 171.1.1. You can easily discover the power of BGP—even by using only the most basic show commands described in this book.1 171.0.0. REGEXPs are used prior to making changes to BGP neighbors to ensure that the correct networks are tagged for further processing.1.incomplete Network *> 131.108.108.0.108.1 171.108.internal Origin codes: i . h history. the output from the show ip bgp regexp ^$ command displays all locally connected originating routes. e .incomplete *> *> *> *> *> *> *> *> *> Network 1.0 11.0 Metric LocPrf Weight Path 0 32768 i Because R1 is advertising the network 131.0 4.1.0.108.1 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 998.108. ? .0.EGP.0.1.108. . i .0. you might want to implement a route map. local router ID is 171. Example 7-67 show ip bgp regexp_998_ R1#show ip bgp regexp _998_ BGP table version is 12.1 171.2 Status codes: s suppressed.1.0.1 171. i . ? .EGP.1.0 5.0 Next Hop 171.108.0.1.108.108.0 2.1.0.273 - .0 3.0.0 (connected to E0).1.108. d damped. For example.1 171. d damped.0.0.IGP. you could implement a route map that sets the MED to 100 and weight to 1000 for only those paths passing through 998. * valid. as seen on R1. > best.0. Example 7-67 displays all networks coming through AS 998. local router ID is 171.0. h history. > best.0.0/24 Next Hop 0.0.1.0.0 7.1.IGP.2 Status codes: s suppressed.

Ensure that the 15 loopbacks on R1 (131.108.0 but does accept a default route only. R1 and R2 run BGP and OSPF. or the physical layer between all routers.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 IP addressing is accurate.16. (That is.0–131. Ensure that R3 can reach all BGP-advertised networks using OSPF as the only routing protocol. All other networks must be denied on R4. redistribution is required on R1/R2).0. Practical Exercise Solution You have a lot to accomplish and you should begin by ensuring Layer 1. Five-Router Topology R1 has an EBGP peer to R5 and an IBGP peer to R2. R2 has an EBGP peer to R4 and IBGP peer to R1. For all odd networks. Ensure that R1 advertises a default route to R5 and that R2 advertises a default route to R4. Use a prefix list to accomplish this task. The Practical Exercise begins by giving you some information about a situation and then asks you to work through the solution on your own.274 - . is running. Ensure that R4 does not accept any networks in the range 131.0/24) are advertised to R5 and that R5 modifies all even networks with a local weight to 1000 and metric (MED) to 100.2. . R3 runs only OSPF. Figure 7-8. The solution can be found at the end.108. set the weight to 2000 and the metric (MED) to 200. Configure the five-router topology in Figure 7-8 for IP routing.108.

1 255.108.108.1 255.108.1 255.0 ! interface Loopback7 ip address 131. start by configuring OSPF between R1/R2 and R3.3.2.12.1 255.10.0 ! interface Loopback1 ip address 131.1 255.108.108.0 ! interface Loopback11 ip address 131.1 255. After Layer 1 is up. for example.255.0 ! interface Loopback14 ip address 131.0 ! interface Loopback2 ip address 131.255.255.5.0 ! interface Loopback13 ip address 131.0 ! interface Loopback5 ip address 131.0 ! interface Loopback9 ip address 131.255.255.108.255.108.1 255.255.CCNP Practical Studies: Routing Then.108.255.0 ! interface Loopback6 ip address 131.108.255.255.255. followed by EBGP between R1/R5 and R2/R4.1 255.0 .1 255.108. 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. Then configure IBGP between R1 and R2.8.1 255.13.255.1 255.255.0 ! interface Loopback12 ip address 131.108.255.7.0/24.11.1 255.108.275 - .6.255.108. Synchronization is disabled.255. 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). Example 7-68 displays the full working configuration on R1.15.255.255.0 ! interface Loopback3 ip address 131.255.14. 141.0 ! interface Loopback10 ip address 131.255.255.108. and the next hop self-attribute is set to R5 so that R5 is able to reach R4's Ethernet network.0 ! interface Loopback8 ip address 131.1 255.1 255.16.255.108.4.255.255.108.255.0 ! interface Loopback4 ip address 131. The shaded portions call your attention to critical commands required for full IP connectivity.255.255. perform some simple pings. from R1 to R5 and R2 to R4.255.1 255.9.255. R1 has OSPF and BGP enabled.1.255.

1.4.255.0 network 131.255.2 remote-as 100 neighbor 171.255.255.11.0.108.255.255.255.108.0 mask 255.0 0.1.0 mask 255.0 network 131.255.255.108.0 network 131.255.0 network 131.0 network 131.108.0 network 131.255.255.14.108.255.9.0 network 131.6.276 - .10. 151. .15.255.0 mask 255.0 network 131.0.255.255.0.255.255.16.108.108.0 network 131.255.1 255.0.255.0 255.1.108.0 mask 255.255.108.255.255.0 mask 255.108. The shaded portions call your attention to critical commands required for full IP connectivity.0 mask 255.2 remote-as 200 neighbor 171.108.0 mask 255.255.255.0 mask 255.0 mask 255.108.0 mask 255.12.0 network 131.108.255.255.255.255.255.0 network 131.5.255.0 mask 255.13.255 area 0 ! router bgp 100 no synchronization network 131.0 mask 255.1.3.255.0 mask 255. and the next-hop-self attribute is set to R4 so that R4 can reach R5's Ethernet network.0 mask 255.2. R2 has OSPF and BGP enabled.108.1.0.7.0 network 131.0.1.0 network 131.2 default-originate ! ip classless ip route 0.108.108.255.0/24.0 neighbor 131.255.0 network 131.8.255.0 mask 255.108.1.108.1 255.2 next-hop-self neighbor 171.108.108.108.255.255.0 network 131.108.255.0 Null0 ! line con 0 line aux 0 line vty 0 4 end Example 7-69 displays the full working configuration on R2.1.252 ! clockrate 128000 ! router ospf 1 redistribute connected metric 100 subnets redistribute bgp 100 metric 100 subnets network 0. Synchronization is disabled.0 ! interface Serial1/0 ip address 171.CCNP Practical Studies: Routing ! interface Ethernet0/0 ip address 131.0 mask 255.108.

0 ! Places all interfaces in OSPPD area 0 router ospf 1 network 0.255.255.255.108.6 next-hop-self neighbor 171.255.3 255.1.255.255.1.0 0.5 255.6 default-originate ! ip classless ip route 0.0.1.0 255.108.0.1.255.1.108.0.255 area 0 ! line con 0 line aux 0 line vty 0 4 end .108.1.255.6 remote-as 300 neighbor 171.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 131.0 Null0 line con 0 line aux 0 line vty 0 4 ! end Example 7-70 displays the full working configuration on R3.1.0 ! interface Serial1/0 ip address 171.0 redistribute ospf 1 metric 100 neighbor 131. The shaded portions call your attention to critical commands required for full IP connectivity.252 clockrate 128000 ! router ospf 1 redistribute connected metric 100 subnets redistribute bgp 100 metric 100 subnets network 0. Example 7-70 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Ethernet0 ip address 131.0.108.0.0 mask 255.277 - .1 remote-as 100 neighbor 171.255 area 0 ! router bgp 100 no synchronization network 131.108.0.255.255. R3 is running only OSPF.0.2 255.0 255.255.108.108.1.0.255.

1.1 255.255.108.255.108.1.254.255.1.255 route-map changeattributes permit 10 match ip address 1 .1.5 prefix-list default in ip prefix-list default seq 5 permit 0.0 neighbor 171.CCNP Practical Studies: Routing Example 7-71 displays the full working configuration on R4.2 255.4 255.255.108.1.6 255.255.255 no ip directed-broadcast ! interface Ethernet0 ip address 141.0/0 ! line con 0 line aux 0 line vty 0 4 end Example 7-72 displays the full working configuration on R5.0.108.255.0.1.108.255.255.1.255.0.108.254.0 ! interface Serial0 ip address 171.1 route-map changeattributes in no auto-summary ! ip classless !This ACL permits all even networks access-list 1 permit 131. 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 131.1.252 router bgp 300 network 141.0 mask 255.278 - .0 0.255.108.255.0 neighbor 171.1 255.252 ! router bgp 200 network 151. The shaded portions call your attention to critical commands required for full IP connectivity. The shaded portions call your attention to critical commands required for full IP connectivity.0 ! interface Serial0 ip address 171.255.255.1.5 remote-as 100 neighbor 171.108.108.255.108.108.108. Example 7-72 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero interface Ethernet0 ip address 151.0.1 remote-as 100 neighbor 171.1.0 mask 255.

e . * valid. which show command(s) can you use.1 Metric LocPrf Weight Path 200 2000 100 300 i 0 32768 i 200 2000 100 ? Using a route map. ? .108.0.1.1. local router ID is 171.0 9: 10: Next Hop 171.108.5 0. "Answers to Review Questions.0 171.1 0.IGP. local router ID is 131. > best.1.internal Origin codes: i . h history.0.108. which IOS command sets the weight and local preference attribute to 100.108. ? . if any? View the following BGP table. i .1.0.incomplete Network *> 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.0. What is the originating AS for the remote preferred path to the remote network 141.0/24? R5#show ip bgp BGP table version is 22.0/24 5: 6: 7: 8: Next Hop 171. i . h history.108.0/24 *> 171.2 Status codes: s suppressed.108.0/24 *> 151. Can you set the BGP attribute next-hop-self to both EBGP and IBGP peers? .EGP.108. * valid.0 *> 141.279 - .1. e . > best.254.1.0.internal Origin codes: i .incomplete Network *> 141. d damped.4 Status codes: s suppressed. d damped.1.1.108." 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. To display route reflector clients.EGP.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.0.108.108.0.IGP.

you can now understand and appreciate the level of complexity of BGP. Table 7-4 summarizes the BGP commands used in this chapter.280 - . BGP is a favorite topic on many Cisco certification examinations.CCNP Practical Studies: Routing Summary After configuring many of the advanced features deployed in today's large IP environments and the Internet community. You discovered how BGP is enabled efficiently in large IBGP networks. how BGP can be modified using BGP attributes. Displays the BGP table Displays CIDR networks (classless networks) Finds matching networks based on a regular expression . and you saw how to monitor BGP. and the resulting routing decisions that are made based on the configuration. 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. The alternative methods used to change the routing decision made by BGP were also configured. Table 7-4.

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

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). An organization might be transitioning from one protocol to another. from legacy RIP to OSPF. you must be careful when changing administrative distances. . for example. Cisco IOS routers always choose administrative distance over any metric. Table 8-1. consider the simple design rules when configuring between classless protocols and classful protocols. Table 8-1 displays the administrative distances Cisco routers use by default. to be configured on the edge of the network. Some business units within an organization might have host-based routing and require RIP. The number of reasons is countless.282 - . it is easier to configure redistribution on one router and allow immediate communication. For example. Redistributing from Classless to Classful Protocols Any form of redistribution from classless or classful IP routing protocols must be carefully configured. for example. nor do they send updates with the subnet mask. 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. Political reasons within an organization or department can impact routing algorithm decisions. TIP Classful protocols do not understand variable-length subnet masks (VLSM). RIP is fine for a LAN-based network. for example. What is definite is that you need to understand redistribution and how it is configured and controlled on Cisco IOS-based routers. hence. 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. Examples of classful protocols are IGRP and RIP. OSPF. Instead of reconfiguring potentially thousands of routers. 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. and BGP. Classless protocols understand VLSM and examples include IS-IS.CCNP Practical Studies: Routing The reasons that multiple IP routing protocols might be configured in any one network are numerous. To understand.

To solve this problem and others you encounter.283 - .255. Figure 8-1. the following rules apply: • • The router configured as a classless router has one or more interfaces attached to a major network.0. R1 Is Redistributing OSPF Routes to RIP (to R2) Figure 8-1 displays R1 configured for redistribution to R2. the local router might have the Class A network 9.2. In other words.0/24. 16 bits for Class B (255. Hence. is running RIP and has two local interfaces configured in the Class B network with Class C routers: 131. or C network.0.CCNP Practical Studies: Routing For every router configured in a classful network. The RIP process on R2 assumes all networks in the Class B network 131.0. this chapter covers the Cisco IOS command required for enabling redistribution. on the other hand.1.108.108. is reachable through R1 for networks not locally connected. and hence.0.108. Cisco IOS Command Syntax for Redistribution To configure redistribution among routing protocols.0).255. The 141. . 141. and 24 bits for Class C (255. For example.108. The router does not have any interfaces attached to the major network being advertised.0 have a 24-bit subnet mask because of the local attached interfaces.0. 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. such as a Class A.108. R2 assumes the entire Class B network.0.0. B.108.255. the subnetted routes on R1 are not passed to R2.0.0). Consider the example in Figure 8-1.0 network on R1 is advertised to R2 as a Class B network. R1 has a number of local interfaces subnetted using the Class B network 131.1. assumes the subnet mask is at the bit boundary: 8 bits for Class A (255.0).0/24 and 131.1.0.1/8 configured locally and assumes the same Class A mask on any networks received on any given interface. R2.

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

285 - . the scope of redistribution for the specified protocol. Routing redistribution is best described by examples. and how to successfully and efficiently redistribute routing protocols. . Notice that R2 has the Class 10.CCNP Practical Studies: Routing Table 8-2. you configure three routers running RIP and IGRP. Figure 8-2 displays the three-router topology with the Router R1 running RIP and IGRP. so the five practical scenarios in this chapter concentrate on how redistribution is configured on Cisco IOS routers. and you configure it for redistribution. There is no one right way to accomplish many of the tasks presented. 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. You have already encountered some redistribution in previous scenarios.0.1. Router R1 is running both RIP and IGRP. and the following five scenarios are designed to enhance your knowledge of why. Example 8-1 displays the IP address configuration on R1 and the enabling of IGRP in AS 100. RIP/IGRP Redistribution Figure 8-2 displays a simple scenario with the Class A network 9.0.0/24 network configured locally on the Ethernet interface. and the abilities to use good practice and define your end goal are important in any real-life design or solution. when.1. Start by configuring the edge devices for IGRP on R3 and RIP on R2. Figure 8-2. 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.0 subnetted with a Class C mask. Command Syntax for Redistribution Syntax value subnets Description (Optional) For redistributing routes into OSPF. Scenario 8-1: Redistributing Between RIP and IGRP In this scenario.

2 255.0 Notice.1. 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 R1.0.0 and 10. requires redistribution.1. Example 8-3 Enable IP and RIP/IGRP on R1 R1(config)#interface S1/0 R1(config-if)#ip address 9.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 R1(config-router)#exit R1(config)#router igrp 10 R1(config-router)#network 9.1 255.0.0. you need to identify only the major network boundary. No redistribution is configured at this time. Example 8-2 configures R2 for IP addressing and enables RIP.0. you must ensure that RIP updates are not sent to R3.3.0 R1(config-if)#exit R1(config)#router rip R1(config-router)#network 9.0.1 255.255. Therefore.255. Example 8-2 IP Address Configuration and Enabling RIP R2(config)#interface ethernet 0/0 R2(config-if)#ip address 10. which is running only IGRP.0 R2 is running another classful IP routing protocol: RIP.255.0. on R3.0.0. and you must ensure the metrics are converted from RIP (hop count) to IGRP (composite metric).0 R2(config)#router rip R2(config-router)#network 9.0.255.255.0.1.255.0 R3(config-if)#interface serial0 R3(config-if)#ip address 9.2 255.0.2.0.286 - .0 R2(config-if)#interface serial 1/0 R2(config-if)#ip address 9.255. which is running only IGRP.0 because IGRP is classful and automatically summarizes at the Class A network boundary. in this case 9.0.1.0. when defining networks under the RIP process. Example 8-3 displays the IP address configuration on R1 along with enabling IGRP and RIP.0 R1(config-if)#interface S1/1 R1(config-if)#ip address 9.2.1.255.1. R2 is configured for RIP and IGRP.2 255.0. and ensure IGRP updates are not sent to R2.0 R2(config-router)#network 10.255. the network command used is network 9. when enabling IGRP in AS 10.1.1.0.0. .1 255. Example 8-4 configures passive interfaces to ensure that only RIP updates are sent to R2 and IGRP updates are sent to R3.0 for both RIP and IGRP.255.0.1.0 R1 is configured locally for the Class A subnet network 9. and hence.255. Therefore.255.0 R3(config-if)#exit R3(config)#router igrp 10 R3(config-router)#network 9.0.

3.1.0.CCNP Practical Studies: Routing Example 8-5 IP Routing Table on R1 R1#show ip route 9. Example 8-7 displays the redistribution command on R1.0.1.0 is directly connected.0 is directly connected. 1 subnets C 10. Ethernet0/0 The routing table on R2 in Example 8-6 displays no network connectivity to the LAN segment 9.0.0 is directly connected.1.0/8 is reachable through R2 because R1 does not have any locally connected routes in the 10. Example 8-6 displays the IP routing table on R2. Serial1/1 I 9. To configure redistribution.2. The ? tool is used to displays IGRP metrics.1. the IP routing table on R1 displays network connectivity to R2 and R3. Serial1/0 R 9.0/24 because you have yet to configure redistribution on R1. Also.0. Example 8-8 displays redistribution from RIP to IGRP.0. Serial1/0 10.0/24 is subnetted.1.0.0.2. Typically. Serial1/0 C 9. Serial1/1 R 10. notice that R1 assumes that the entire Class A network 10. you must perform the following tasks on R1: Step 1.0 [100/80225] via 9. 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 .1. R1 has full IP connectivity to R2 and R3.1.0.0. 3 subnets C 9. Example 8-6 show ip route on R2 R2#show ip route 9.1. 00:00:15.1. 00:00:31.2. Step 2. 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). Use the redistribute command on R1 to specify the routes to be redistributed.0 network.287 - .2. Serial1/0 Currently.0.0/24 is subnetted.0 [120/1] via 9.0/8 [120/1] via 9.0/24 is subnetted.1.3. 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. You set the metric for redistributing IGRP to RIP to a hop count of 1.0.1.1. Example 8-7 Redistributing IGRP into RIP on R1 R1(config)#router rip R1(config-router)#redistribute igrp 10 metric 1 At this stage.1.1.1. you haven't configured redistribution from RIP into IGRP so that R3 has full connectivity to R2.1.0. 00:00:27.2. Specify the metric to be assigned to any redistributed routes. 2 subnets C 9.0 is directly connected.

1/24 on R3 is successful because the remote network 10.0.0 R3(config-if)#router igrp 10 R3(config-router)#network 10.1/24.2.1.0/8 is reachable through the next hop address 9.1.2.0/24 is subnetted. Serial1/1 I 10.1 Type escape sequence to abort.1. Example 8-12 displays the IP routing table on R1 after an IGRP update is sent from R3 to R1. 100-byte ICMP Echos to 9.1.1.0.1.2. 3 subnets C 9. 00:00:09. Serial0 C 9. Serial1/0 C 9.288 - .0/24 is subnetted. round-trip min/avg/max = 28/29/32 ms Example 8-9 displays the remote network 9.0.1.0.1.1. 3 subnets C 9.0.0 [120/1] via 9.0 is directly connected. as defined by the redistribution command in Example 8-7. Example 8-11 Loopback Creation on R3 R3(config-if)#interface loopback 0 R3(config-if)#ip address 10.3.2. Remember from Example 8-5.1. Serial1/0 R 9.1.1.0 [100/80225] via 9.0. Next.1. Serial0 C 9.255.0 is directly connected.0. Sending 5.0 is directly connected.2.0/8 network advertised through RIP with an AD of 120 through R2 (RIP).0/24 is subnetted.0.2. Ethernet0/0 R2#ping 9.1. Serial1/0 10.3.1.0.1.1.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).2.0.2.1. Ethernet0 I 10.1.0.1.2.1.1. Example 8-12 show ip route on R1 R1#show ip route 9.0. Serial1/1 . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0.0. Serial0 R3#ping 10.3. 00:00:58.1.0.1.1 255. you configure a new subnet on R3 to make the networks a little more complex.1.0 [100/84000] via 9. 100-byte ICMP Echos to 10.0.3.1 as a loopback interface on R3 using a 24-bit subnet mask.1.1.0 [120/1] via 9. Serial1/0 R 9.1 as displayed in Example 8-9.1 or through R1.1.1.3.0.1. Serial1/1 I 9.1. Configure the address 10. as well as a ping request and reply to the remote network 9.0 R3 does not advertise the 10.1. 00:00:58.1.1/24 on R3 is successful.3.0 network.3. R1 had seen the 10.1.0/24 is subnetted. round-trip min/avg/max = 28/29/32 ms A ping to the remote address 10. Sending 5.0 is directly connected. and the metric is 1.0 reachable through the next hop address 9. 00:00:23. 00:00:23. Example 8-10 displays the IP routing table on R3.0.255.1. Example 8-9 IP Routing Table and Ping Request to 9.1. Example 8-10 IP Routing Table and Ping Request on R3 R3#show ip route 9.0. A ping to the remote address 10.1.1.1. 3 subnets I 9.0.0 is directly connected.1.1.0 is directly connected.0.0/8 [100/102000] via 9. Example 8-11 displays the loopback creation on R3 and the enabling of IGRP to advertise the loopback under IGRP.3.0 network to R1. 1 subnets C 10. 00:00:09.0/8 [100/80625] via 9.2.1.1.1.3.1.1.1. and enable IGRP on R3 to advertise the 10.2.1/24 on R2 R2#show ip route 9.2.1.0.CCNP Practical Studies: Routing Examine the IP routing tables on R2 and R3 to ensure IP connectivity by pinging the remote network 9.

2. timeout is 2 seconds: .0/24.CCNP Practical Studies: Routing R1 changes the path to 10. Example 8-16 displays the static route configuration on R1.0 through R3 because the AD of IGRP is 100.1.2. To solve this problem.0. NOTE Another method to overcome network connectivity problems is to configure static routes on R1 or enable an interface in the 10.1.0/8 is subnetted. when 10.1. which is 120.0. configure a static route on R1 with a more specific destination pointing to R3.2.1.0 range.255.0 range because the only trusted information for this Class A network is from the RIP domain. Sending 5.0.0/24 C 9. Success rate is 0 percent (0/5) R1#ping 10. as displayed in Example 8-14.0.0. Serial1/0 is directly connected.1. R1 has lost connectivity to the 10.0.2.0 network through R3.0.0..1.0 255.1. rejects all networks in the 10.1 Type escape sequence to abort.0 R 10. configure R1 to reject any networks in the 10.1 (R3's loopback interface). At this point.1.1 (R3's Ethernet interface) and 10.2.0 Serial1/1 . Sending 5.0. R1 does not accept the 10. 00:00:07. 100-byte ICMP Echos to 10.2.2.1.0.0/24 range on R1.0.0.1.0 networks configured on R2 and R3. but in this case. Serial1/1 [100/80225] via 9.0 network. compared to RIP.3.1. Serial1/1 [120/1] via 9. Example 8-13 displays a ping request to the IP address 10.0.1. Example 8-13 Ping Request on R1 R1#ping 10. In effect. does not permit the 10. this is not the desired solution because you have 10.1. 3 subnets is directly connected. Of course. 00:00:07.0.0.. Serial1/0 Any form of redistribution requires careful filtering. when configured on R1.0.1.1.1 Type escape sequence to abort. Example 8-14 configures a distribution list on R1.0 C 9.1.0.1.2.0 is advertised by R3 to R1.0.. 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. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). There are a number of different solutions to this. Therefore.0.255. R1 sends all traffic for the 10.0..1.0. Example 8-15 show ip route on R1 R1#sh ip route 9.0 R1(config)#access-list 1 permit any The distribute-list command.1. 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. Example 8-15 confirms the installation on the RIP-discovered route through R2.289 - .0.0.2. and accepts all other networks.1.0 I 9. Example 8-16 Static IP Route on R1 R1(config)#ip route 10.0. 100-byte ICMP Echos to 10.0.0 network.0.

255. 100-byte ICMP Echos to 10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5.1.1.2.0 is directly connected.1.3. 00:00:54. Serial1/1 10.2. Serial1/0 C 9. Example 8-17 displays the IP routing table on R1 and a successful ping request to 10.2.2.0 ! router igrp 10 redistribute rip metric 128 20000 255 1 1500 passive-interface Serial1/0 network 9.0 clockrate 128000 ! interface Serial1/1 ip address 9.1 Type escape sequence to abort. round-trip min/avg/max = 16/16/16 ms R1#ping 10.1.1.1. Serial1/1 R 10.1.1.0.0 is directly connected.0. Example 8-18 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Serial1/0 ip address 9. 2 subnets. because the AD of static routes is 1 and is lower then RIP at 120.2.2.2. Serial1/1 I 9. round-trip min/avg/max = 12/14/16 ms In a simple three router network.1 255.1.0.0. Serial1/0 R1#ping 10. send traffic for the more specific route through Serial 1/1 for hosts in the range 10.0 Serial1/1 ! access-list 1 deny 10.1.0/8 [120/1] via 9.1. 00:00:36.255.0 255.255.1.CCNP Practical Studies: Routing Cisco IOS routers. You also use the passive-interface command to ensure that a network running route redistribution is configured as efficiently as possible.0.0.255.1. Sending 5.1.0 distribute-list 1 in ip route 10.0.1.0 clockrate 128000 ! router rip redistribute igrp 10 metric 1 passive-interface Serial1/1 network 9.0.290 - .1.2. such as RIP and IGRP.0.0. In the scenarios that follow.0/24 is subnetted.2.1. Example 8-18 displays R1's full working configuration.1. you can determine that with even a few networks.0. redistribution causes routers to misinterpret information based on network configuration and classful behavior of routing protocols.1 255. 2 masks S 10.1 (to R3) Example 8-17 show ip route and Ping Request on R1 R1#show ip ro 9.255.2.0 [100/80225] via 9. 100-byte ICMP Echos to 10.0.255.1.1–254/24.2.0/24 is directly connected.1.0/8 is variably subnetted.1. 3 subnets C 9.1.0 access-list 1 permit any . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.1 (to R2) and 10.1 Type escape sequence to abort.1. you apply route maps instead of distribution lists to learn to use other filtering methods.

1.1.2.1.255.3.2 255.1 255.0.1 255.1 255.0.1.255.0 ! no ip classless line con 0 line aux 0 line vty 0 4 ! end .1.CCNP Practical Studies: Routing line con 0 line aux 0 line vty 0 4 end Example 8-19 displays R2's full working configuration. 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 10.0.0.0.0 interface Serial0 ip address 9.0 ! interface Serial1/0 bandwidth 128 ip address 9.255.0.255.255.1.255.0 network 10.0 bandwidth 125 router igrp 10 network 9.291 - .0 line con 0 line aux 0 line vty 0 4 end Example 8-20 displays R3's full working configuration.255.0.255.2 255.0 ! router rip network 9.0 network 10.1.0 ! interface Ethernet0 ip address 9.0. Example 8-20 R3's Full Working Configuration hostname R3 ! enable password cisco ! interface Loopback0 ip address 10.255.255.2.

Figure 8-3. bandwidth is not a major concern.CCNP Practical Studies: Routing Scenario 8-2: Migrating from RIP to OSPF in the Core In this scenario.0. you migrate a typical RIP network to OSPF in the core of the network and leave RIP on the edge of the network. network connectivity is maintained. R2. IP addressing and loopback address assignments have already been completed. Because all RIP-enabled routers have a local interface configured using a Class C mask. has been subnetted using a Class C mask throughout. RIP Topology Loopbacks have been configured in R1. The current IP routing table on R1 is displayed in Example 8-21.0. where typically. Figure 8-3 displays the current RIP network that you migrate to OSPF. and R3 to populate the IP routing tables. The Class B network. . 141.292 - . on LAN-based segments.108.

108.254.255.0 [120/1] via 141.0 is directly connected.14.4.108.21. Loopback4 R 141.254. 00:00:12.0 [120/1] via 141.0 [120/1] via 141.108.108.0 [120/1] via 141. Serial1/0 R 141.108.0 [120/1] via 141.254.0 is directly connected.255.108. Serial1/0 R 141.7.2.0 is directly connected.108.108.108. Serial1/1 R 141.1 ! interface Loopback5 255. 00:00:16.108.255.3.0 is directly connected.254.108.108. 00:00:12.255. Loopback5 C 141. Loopback2 C 141.108.0 is directly connected.0.20.255. Serial1/1 R 141.2. Loopback1 C 141.255. 00:00:12.108.108. 00:00:13. Loopback0 C 141.17. Serial1/0 R 141. 00:00:16.16.10.0 [120/1] via 141.0 [120/1] via 141.9.255.0 255. Serial1/1 R 141.2.5.108.2.1 ! interface Loopback2 ip address 141. Serial1/0 R 141.2. Serial1/0 R 141. 00:00:12.253. Serial1/1 R 141.0 [120/1] via 141.254.255.1 ! interface Loopback4 ip address 141.2.2.0 [120/1] via 141.254.1.255.2. 00:00:13.0 is directly connected.255.8.108.4.254. Example 8-22 R1's RIP Configuration hostname R1 ! enable password cisco ! ip subnet-zero ! interface Loopback0 ip address 141. Serial1/0 R 141.108.108.3. Ethernet0/0 C 141.108.13.0 [120/1] via 141.108. Serial1/0 C 141. 00:00:11.0 . Serial1/1 Example 8-21 displays over 25 different networks.255.108.0 [120/1] via 141.108. 00:00:15.255. Serial1/0 R 141.108.108. 00:00:17. 00:00:16.2.2.22.108.108. 00:00:13.2.2.108.108.0 [120/1] via 141. 26 subnets R 141. Loopback3 C 141. Serial1/0 [120/1] via 141.2.0 255. Serial1/1 C 141.108.0 [120/1] via 141.CCNP Practical Studies: Routing Example 8-21 show ip route on R1 R3#show ip route 141.108.255.108.293 - .2.108.19.108. Serial1/1 C 141.0 [120/1] via 141.1 ! interface Loopback3 ip address 141.255.254.108.108.1 ! interface Loopback1 ip address 141.0 255.108.255.255.255.23. Example 8-22 displays the current working configuration on R1 running RIP as the primary routing algorithm. 00:00:16.18. 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.108.108.108.0 [120/1] via 141.11.2.2. 00:00:16. 00:00:16. 00:00:17.5.0 255.6.254.254.2.2.108. Serial1/1 R 141.0 [120/1] via 141. Serial1/1 R 141. 00:00:12.108.255.0 is directly connected.108.255.0 [120/1] via 141.108.6.108.108.15.108.108.0/24 is subnetted.255.2.0 is directly connected.108.12. Serial1/1 R 141.0 is directly connected.108.2.

1 255.255.0 clockrate 128000 ! router rip network 141.12.255.1 255.294 - .1.108.255.255.1 255. Example 8-23 R2's RIP Configuration hostname R2 ! enable password cisco interface Loopback0 ip address 141.0.108.2 255.0 interface Serial1/0 ip address 141.0 ! interface Ethernet0/0 ip address 141.255.108.CCNP Practical Studies: Routing ip address 141.253.2 255.1 255.108.1 255.1 255.255.9.255.0.8.108.254.255.108.0 ! interface Serial1/0 bandwidth 128 ip address 141.13.0 ! interface Loopback3 ip address 141.255.0 router rip network 141.108.108.108.255.255.255.255.108.108.255.0 ! line con 0 end Example 8-23 displays R2's current working configuration.0 ! interface Loopback5 ip address 141.0 clockrate 128000 ! interface Serial1/1 ip address 141.1 255.11.255.10.14.255.108.108.255.255.0 ! interface Loopback2 ip address 141.255.108.255.1 255.1 255.255.255.255.7.1 255.0 ! interface Serial1/1 ip address 141.255.255.0 ! interface Ethernet0/0 ip address 141.0 ! interface Loopback4 ip address 141.255.255.15.255.108.0 ! ip classless ! .255.0 ! interface Loopback1 ip address 141.108.1 255.255.0 ! interface Loopback6 ip address 141.1 255.

Example 8-25 configures R1 for OSPF across the WAN to R1 and R2.108. Example 8-24 R3's RIP Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 141.1 255.255.255.0 ! interface Loopback6 ip address 141.0 ! interface Loopback2 ip address 141.108.0 ! end To start.255.108.255.1 255.22.108.0 bandwidth 125 clockrate 125000 ! router rip network 141.23.108.20.1 255.255.17. add OSPF to the center of the network.0 ! interface Loopback5 ip address 141.255.253. and place all the WAN interfaces in area 0.255.255.295 - .18.1 255. .108.0.0 ! interface Serial0 ip address 141.108.2 255.254.0 ! interface Loopback1 ip address 141.0 ! interface Loopback3 ip address 141.255.1 255.CCNP Practical Studies: Routing end Example 8-24 displays R3's current working configuration.255.255.16.0 bandwidth 125 ! interface Serial1 ip address 141.255.255. Maintain the Class C mask for now to make redistribution relativity easy to configure.1 255.255.0 ! interface Ethernet0 ip address 141.21.255.19.108.1 255.255. You take the same configuration steps on R2 and R3.108.108.255.1 255.108.255.0 ! interface Loopback4 ip address 141. This step is common when migrating from one protocol to another.1 255.255.255.

0 0.0 is directly connected.5.254. and R3 to advertise the RIP networks to the OSPF backbone.3. Example 8-27 also displays redistribution from OSPF to RIP to allow communication from R2/R3 Ethernet segments to R1's locally connected network. this configuration stops the sending of unnecessary updates across WAN links.0 [110/1562] via 141.0.0.108.0 0.0. Serial1/0 C 141.0.255 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).255 R1(config)#access-list 1 deny 141.108.5.255 R1(config)#access-list 1 deny 141.0.255 R1(config)#access-list 1 permit any . Loopback3 C 141. Loopback4 The only visible route on R1 is the locally connected routes and the WAN circuit between R2 and R3.108.2.0.0.108.6.255.0.108. Serial1/0 C 141.0.4.6. R2. is advertised by only RIP. Example 8-26 show ip route on R1 R1#show ip route 141. at the moment.108.0 is directly connected.255 R1(config)#access-list 1 deny 141.253.108.0 0.108.0 is directly connected.7.0 0.255.0 is directly connected.255 area 0 R1(config-router)#network 141.108.0 is directly connected.108.0 is directly connected.0.3. At this stage.7. Loopback1 C 141.0. 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 141.0 0.0.0 0.108.2.255.0 0. so there is no connectivity among the Ethernet and loopback interfaces.0.1. Example 8-27 displays the RIP to OSPF redistribution on R1.0.0/24 is subnetted.1. you have not configured any redistribution.108. 10 subnets O 141. Loopback2 C 141.0.108.0 is directly connected.108.254.108.0.0.0 0. Serial1/1 C 141. Next. configure redistribution on routers R1.108.0. Example 8-26 confirms the status of IP connectivity after the show ip route command is entered on R1. The ? tool is used to display the available options. Loopback0 C 141.108.0 is directly connected.0.255 R1(config)#access-list 1 deny 141.108.4.2.108.CCNP Practical Studies: Routing Example 8-25 OSPF Configuration on R1 R1(config)#router ospf1 R1(config-router)#network 141.296 - .0 0. 00:00:04.255 R1(config)#access-list 1 deny 141.255 R1(config)#access-list 1 deny 141.0 is directly connected. which.108.108. Ethernet0/0 C 141. Loopback5 C 141.

0.108. only classful networks would not be advertised.E1 .108.255. E2 .255 R3(config)#access-list 1 permit any Confirm IP routing connectivity from R1.0. This ensures that a routing loop cannot occur. can be replaced with the configuration in Example 8-28 to deny the range of networks 141.255 R1(config)#access-list 1 permit any Example 8-29 displays the redistribution and filtering required on R2.0.0/24 is subnetted.0 is directly connected.108. Example 8-28 replaces the seven-line access list with two lines of IOS configuration.0 [110/1562] via 141. Without this keyword.253.7.0 and permit all other networks.108.23.108.OSPF external type 1.2. Loopback1 C 141.0.0 is directly connected. Ethernet0/0 C 141.0 is directly connected.1. and the hop count for all redistributed OSPF networks into RIP is set to 3. 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. 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.OSPF external type 2.) Also. Typically.108.0–141. the distribution list on R1 denies any networks residing in 141. 26 subnets O 141. Example 8-27 displays the keyword subnets because the Class B network 141. Loopback3 C 141.108.7.1. (In this case.108.) Example 8-28 Access List Configuration on R1 R1(config)#no access-list 1 R1(config)#access-list 1 deny 141.0 0.108.5.0.7. Loopback2 .108. previously defined with seven statements.108.254.108. 00:00:51.255 from being advertised from OSPF to RIP.255.2.0.108. To ensure that networks residing on R1 are never advertised by the OSPF backbone. E .7.108.0 is directly connected.8.0 0. Example 8-31 show ip route and Pings on R1 R1#show ip route Codes: C .108.0 is directly connected.255 R2(config)#access-list 1 permit any Example 8-30 displays the redistribution and filtering on R3.0.4. Serial1/1 C 141. (The no access-list 1 command removes the configuration currently present for access list 1.297 - .0 is directly connected.CCNP Practical Studies: Routing R1 is now configured to redistribute from RIP to OSPF and vice versa.0 has been subnetted across the network.0 is directly connected. you are using classless networks on all routers.connected. Serial1/0 C 141. The access list 1. Loopback0 C 141.EGP 141. Serial1/0 C 141.7.108. networks have some other paths or back doors between any given routing topologies.3. the metrics have been set to 100 for all RIP-to-OSPF networks.108. Example 8-31 displays the IP routing table on R1 and some sample ping requests that conform IP connectivity.108.0–141.0 0.

Serial1/0 O E2 141. 00:00:51.108.0 [110/10] via 141.14.11. Example 8-32 show running-config (Truncated) on R1 router ospf 1 redistribute rip metric 100 subnets network 141. 00:00:52.108.0. 00:00:52.108. Serial1/1 O E2 141. 00:00:52. 00:00:52.2.0 is directly connected.108.108. 00:00:52.9. 00:00:51.255.255 access-list 1 permit any Example 8-33 displays the IP routing configuration on R2.0 [110/10] via 141. 00:00:52.1.21.16. 00:00:51.2.255.108.255.0 [110/10] via 141. Serial1/1 O E2 141. look at the routing configurations on Routers R1.255. 00:00:52. 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.108.22.2.0.298 - .108. .255.108.9.255.108.1 Type escape sequence to abort. Serial1/1 O E2 141.0 [110/10] via 141. Serial1/0 O E2 141.254.108.108.108.2.23.108.0.108. 100-byte ICMP Echos to 141.2.12.108.108.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).22. 00:00:51. Serial1/1 O E2 141. R2.13.108.2.CCNP Practical Studies: Routing C 141.255.255.2.7.1.2.0 [110/10] via 141. 00:00:51.0 [110/10] via 141.1 Type escape sequence to abort. 100-byte ICMP Echos to 141.108. round-trip min/avg/max = 16/16/16 ms R1#ping 141.0 distribute-list 1 out access-list 1 deny 141.108.15.0 [110/10] via 141.18.108.2.10. Serial1/0 O E2 141. Sending 5. Serial1/1 O E2 141.108.108.108. Serial1/0 O E2 141.108.0 0.254. Serial1/0 O E2 141.108.22. Serial1/1 R1#ping 141. 00:00:51.254.108.0.0.108.108.108.255 area 0 network 141.0 [110/10] via 141.0 [110/10] via 141.19.254.108.0.0 [110/10] via 141.254.108.108. 00:00:52.108. Serial1/0 O E2 141. Example 8-32 displays the IP routing configuration on R1.2. 00:00:51.108.0 [110/10] via 141.7. Sending 5.0 0. Serial1/1 O E2 141.108.2.108.254.108.108. Serial1/0 O E2 141. and R3. Loopback5 C 141.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.17.20.108.108.0 [110/10] via 141.0.8.254.0 [110/10] via 141.2.2.9.0 [110/10] via 141.0 [110/10] via 141. Serial1/0 O E2 141.2.254.0 [110/10] via 141. Serial1/1 O E2 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Loopback4 O E2 141. Before you complete this migration.2.0 is directly connected.0 0. 00:00:52.2.255.254.6.

0 0.255 access-list 1 permit any Example 8-34 displays the IP routing configuration on R3.254.0.0.7.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.108.0.CCNP Practical Studies: Routing Example 8-33 show running-config (Truncated) on R2 router ospf 1 redistribute rip metric 10 subnets network 141.0 0.108.299 - .0.8.0.0.0. Example 8-34 show running-config (Truncated) on R3 router ospf 1 redistribute rip metric 10 subnets network 141. .108.0 distribute-list 1 out ! access-list 1 deny 141.108.0.108.255 access-list 1 permit any Figure 8-4 displays the OSPF area assignment to complete the RIP to OSPF migration.255 area 0 network 141.0 0.253.0 distribute-list 1 out ! ip classless ! access-list 1 deny 141.108.0 0.0.0.255 area 0 network 141.255 area 0 ! router rip redistribute ospf 1 metric 3 passive-interface Serial0 passive-interface Serial1 network 141.7.16.0 0.255.0 0.0.253.108.108.0.

300 - . Also.255.255.255.7.2 255.108.255.255.252 R2(config-if)#interface s1/1 R2(config-if)#ip address 141.255.0 0.255.255.7.108.0 0.252 Example 8-36 displays the removal of RIP on R2 and the OSPF and IP address assignment on R2. 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.255.255 area 0 R1(config-router)#network 141. 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 141.252 R1(config-if)#interface s1/1 R1(config-if)#ip address 141. note the new IP address assignment for the WAN links with /30 subnets.255 area 0 R2(config-router)#network 141.255.5 255.0 0.0.108.255.255.255 area 2 R2(config-router)#exit R2(config)#interface s1/0 R2(config-if)#ip address 141.10 255.0.108.255 area 1 R1(config)#interface s1/0 R1(config-if)#ip address 141. 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 141.255.0.252 .108.108.8.0.108.1 255.0 0.CCNP Practical Studies: Routing Figure 8-4.0.0.108. Example 8-35 displays the removal of RIP on R1 and the OSPF and IP address assignment on R1.255.0.

00:00:28.108.108. 00:00:27.108.108.108.0 0.2.3. OSPF can support VLSM and network summarization.108.255.1.0.108. 00:00:28.301 - .2. Serial1/0 O IA 141.108.0/24 is directly connected.108. Example 8-38 displays R1's IP routing table. 00:00:28.108. 1.255.9. Loopback1 C 141.6.252 R3(config-if)#interface serial1 R3(config-if)#ip address 141.108.11.255. 00:00:28.0/24 is directly connected. 00:00:28.108.5.6. 3 masks O 141.15.1/32 [110/782] via 141.255.1/32 [110/782] via 141.108.255.108.1/32 [110/782] via 141.108.108.255. Serial1/1 O IA 141.2.255. 00:00:28. Serial1/1 O IA 141.1/32 [110/782] via 141. Loopback5 C 141. Loopback2 C 141.14.0.0/24 is directly connected. Serial1/1 C 141.0/24 is directly connected.108.8/30 [110/1562] via 141.0. Serial1/0 O IA 141.255 area 0 R3(config-router)#exit R3(config)#interface serial0 R3(config-if)#ip address 141.108. 00:00:28.0/24 [110/791] via 141. IA . Serial1/1 O IA 141. 00:00:28.108.0/24 is directly connected.108.255.108.17.255.108. 00:00:27.) Example 8-39 displays the summarization for .108.1/32 [110/782] via 141.22.255.108. Loopback0 C 141. Serial1/1 O IA 141.OSPF inter area 141.2. 2.connected.6.2.255. Serial1/1 In Example 8-32.108.255.108.1/32 [110/782] via 141.19.1/32 [110/782] via 141.1/32 [110/782] via 141.12.255.7.2.2.6. 00:00:27.108. 26 subnets.108.255. Example 8-37 Removal of RIP on R3 and OSPF/IP Address Assignment R3(config)#router ospf 1 R3(config-router)#network 141.4/30 is directly connected. and R3 causes the Cisco IOS to remove any redistribution between RIP and OSPF automatically. Example 8-38 R1's IP Routing Table R1#show ip route Codes: C . 00:00:28.23.1/32 [110/782] via 141.0/24 is directly connected.255. manual removal of redistribution is not required on Routers R1. O . so configure each router in Figure 8-4 to summarize locally connected routes.6 255.108.0/30 is directly connected.255.2.CCNP Practical Studies: Routing Example 8-37 displays the removal of RIP on R3 and the OSPF and IP address assignment on R3.108.108. Serial1/0 O IA 141. Serial1/1 O IA 141. Serial1/0 O IA 141.7. view the IP routing table on R1.108. Serial1/1 O IA 141. Serial1/0 O IA 141.6. .23.1/32 [110/782] via 141.255.255.6. and R3.2.255. 00:00:28.13.9 255.1/32 [110/782] via 141.108.8.18.255.16.1/32 [110/782] via 141.0/24 [110/791] via 141. the redistributed routes appear as E2 (External Type 2) and OSPF is configured across all three routers.2.108.255. (All routers are ABRs because each router resides in areas 0.108. The OSPF type route is displayed as O IA in Example 8-38.255.108.0/16 is variably subnetted.4.21.108. Serial1/0 C 141. which are contiguous.108.1/32 [110/782] via 141.OSPF. Loopback3 C 141. Serial1/0 O IA 141. Ethernet0/0 C 141.108.10.0/24 is directly connected. 00:00:28.108.108. Serial1/1 O IA 141.0 0. R2. 00:00:27. Serial1/0 C 141. Therefore.252 NOTE Removing RIP from Routers R1.108. Serial1/0 O IA 141. Now that OSPF is configured across all routers.1/32 [110/782] via 141.255.255.108. R2.108.6.108.6.108. 00:00:27.108. 00:00:27.20. Loopback4 O IA 141. or 3.255.0. Serial1/0 O IA 141.255.255 area 3 R3(config-router)#network 141.108.255.6.

0–141.0.302 - .0 Example 8-42 displays the summarization required on R3 to encompass the networks 141. With large IP networks.2.0.255.0.8/30 [110/1562] via 141. (These networks reside in area 2.108. You may ask yourself why you are not using 141.16.6.0.0/16 is variably subnetted.108. Serial1/0 O IA 141.CCNP Practical Studies: Routing networks 141. The mask.248.15. 3 masks O 141.D IP mask for address R1(config-router)#area 1 range 141.108. To summarize internal OSPF routes.) Example 8-41 Area Summary on R2 R2(config)#router ospf 1 R2(config-router)#area 2 range 141.108.108.108.255.0 Example 8-41 displays the summarization required on R2 to encompass the networks 141.D IP address to match R1(config-router)#area 1 range 141.108. (These networks reside in area 3.) Example 8-42 Area Summary on R2 R3(config)#router ospf 1 R3(config-router)#area 3 range 141.0 Example 8-43 displays the OSPF IP routing table on R1. (Initially.108.1 255. Serial1/1 .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. you had 17 RIP entries. you must configure the global ip subnet-zero command on R1.0.255.8.0– 141. the network IP designer should always use all the address space available.7.255. 00:01:13.108. To enable subnet zero.0.0 255.0.0–141.16. Example 8-40 enables the use of zero subnets on R1.255.0 255.255.255.0 The ? tool is used to display the various options. as displayed in Example 8-21. when RIP was the primary routing algorithm.108.0 on R1 or subnet zero.108.108. The loopback addresses on R1 reside in OSPF area 1. 255.0/21 [110/782] via 141.255. 00:04:57.108.255. 00:04:57.0 255.248.108. encompasses the seven networks ranging from 141.255.0–141.B.8.23. 13 subnets.108.C.0. the area area-id range network subnet mask IOS command is required.255.108.108.C.2.B.0. Serial1/0 O IA 141.0/21 [110/791] via 141.) Example 8-43 show ip route ospf on R1 R1#show ip route ospf 141.108.248. Example 8-40 Subnet Zero Enabling on R1 R1(config)#ip subnet-zero R1(config-if)#interface loopback 6 R1(config-if)#ip address 141.16.108. Example 8-39 displays the area summary command on R1.248.108.108. subnet zero is a perfect example.8.255.0 ? A.7.

255.4.0 ! interface Loopback3 ip address 141.255 area 1 network 141.108.1 255.0.255. Now.255.255.0 ! interface Loopback4 ip address 141.108.5 255.255.255.255.255.255.255.248.0 ! interface Loopback2 ip address 141.255.255.0 ! interface Loopback5 ip address 141.0.255.1 255.255.1 255.255. such as OSPF.252 no ip mroute-cache no fair-queue clockrate 128000 ! interface Serial1/1 ip address 141.CCNP Practical Studies: Routing R1 has 3 OSPF network entries as opposed to 17 using RIP.108. .255.1 255.0 ! interface Loopback1 ip address 141.108.252 clockrate 128000 ! router ospf 1 area 1 range 141.1 255. such as RIP.0.0 ! interface Serial1/0 ip address 141. view the full working configurations of all three routers in Figure 8-4.0 0. Before looking at another scenario.7.1 255.0 network 141.255.108.303 - .0. The migration in this scenario demonstrates the powerful use of redistribution and what you should be aware of when configuring metrics.255. you can see why networks are converted from classful routing protocols.255.2.108.5.108.108.0. Example 8-44 R1's Full Working Configuration Hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.255 area 0 ! ip classless end Example 8-45 displays R2's full working configuration.255.1 255.0.0 255.1 255.108. to classless protocols.0 ! interface Loopback6 ip address 141.3.0 ! interface Ethernet0/0 ip address 141.108.255.255.108.0 0.1 255.108.108.1. Example 8-44 displays R1's full working configuration.255.6.255.7.

108.1 255.13.255.255.9.2 255.255.252 ! interface Serial1/1 ip address 141.10 255. .108.0 ! interface TokenRing0/0 no ip address shutdown ring-speed 16 ! interface Serial1/0 bandwidth 128 ip address 141.0.0 ! interface Loopback1 ip address 141.0 255.255.108.108.255.108.0 ! interface Loopback5 ip address 141.248.255.0 ! interface Ethernet0/0 ip address 141.0 ! interface Loopback4 ip address 141.108.255.108.255.255.108.1 255.0 0.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 141.1 255.255.304 - .8.255.8.252 ! router ospf 1 area 2 range 141.255.255.1 255.255 area 0 ! ip classless ! end Example 8-46 displays R3's full working configuration.108.0.255.0 ! interface Loopback2 ip address 141.255.255.7.0.11.108.255.14.255 area 2 network 141.255.255.1 255.108.1 255.108.255.12.15.8.255.0 network 141.1 255.0 ! interface Loopback6 ip address 141.10.108.1 255.0 0.255.255.255.0 ! interface Loopback3 ip address 141.

255.255.255.108.1 255.108.0.255.255.9 255.108.21.0 ! interface Loopback2 ip address 141.20.108.255.16.0 ! interface Loopback4 ip address 141.255.0 ! interface Loopback5 ip address 141.7.108.255.255.108.255 area 3 network 141.0 media-type 10BaseT ! interface Ethernet1 no ip address ! interface Serial0 ip address 141.0 ! interface Loopback6 ip address 141.17.1 255.255.0.255.108.19. The end design goal of this scenario is to ensure full IP connectivity among all interfaces.108.255. The internetwork in Figure 8-5 has an OSPF domain and three EIGRP domains.0 0.255 area 0 area 3 range 141.252 bandwidth 125 ! interface Serial1 ip address 141.255.1 255.0.0 255.22.0 ! interface Loopback3 ip address 141.255.0 ! end Scenario 8-3: Redistributing Between EIGRP and OSPF In this scenario.0 ! interface Loopback1 ip address 141.255.1 255.305 - .1 255.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 141.6 255.16.23.108.108.255.16.108.255.0 ! interface Ethernet0 ip address 141.1 255.18.255.0 0. you configure a five-router topology with four different autonomous systems using two IP routing algorithms: OSPF and EIGRP.108. .252 bandwidth 125 clockrate 125000 ! router ospf 1 network 141.1 255.255.248.255.255.255.255.255.1 255.108.

Figure 8-5 depicts a simple OSPF network with one area. you can use one IOS command to place all R1's interfaces in OSPF area 0 or the backbone.0. Start by enabling the routing protocols in use. Also. the backbone.0 area 0 The inverse mask. the backbone network in OSPF.2 0.255.CCNP Practical Studies: Routing Figure 8-5. OSPF and EIGRP Domains Routers R1. hence.255.0. you must carefully consider any route redistribution to avoid routing loops. All of Router R1's interfaces reside in area 0.0.2 into area 0.255 area 0 Routers R2 and R3 reside in OSPF and EIGRP domains.108. (Remember that OSPF has a process ID that is only locally significant. Example 8-48 R2's OSPF Configuration R2(config)#router ospf 1 R2(config-router)#network 141.0.) R4 is configured in EIGRP domain 1. The WAN link between R4 and R5 resides in EIGRP domain 3.306 - . . 0.108. Therefore. notice that a redundant path exists between R4 and R5. Example 8-48 configures R2's serial link to R1 to reside in area 0.0 255. configures the IP address 141. and R3 are configured in OSPF process 1. Figure 8-5 displays the OSPF area assignments required for this topology. Example 8-47 R1's OSPF Configuration R1(config)#router ospf 1 R1(config-router)#network 0. Figure 8-5 details the IP address assignment.255. and R5 is configured in EIGRP domain 2.0.0. namely OSPF on Routers R1–R3. Example 8-47 places all interfaces on R1 in area 0.255.0. R2.

Before you configure redistribution. configure the EIGRP domains on R4 and R5.307 - . Also on R4.255. in EIGRP domain 3. The peers on R4 confirm that EIGRP is configured on R3.0 area 0 R1 should now have full OSPF adjacency to R2 and R3. you need to apply the passive interface command to ensure that no routing updates are sent. Example 8-49 R3's OSPF Configuration R3config)#router ospf 1 R3config-router)#network 141. There is no EIGRP peer to R5 because EIGRP is not enabled on R5 yet. Similarly.255.108.108.255. Example 8-50 shows ip ospf neighbor on R1 R1#show ip ospf neighbor Neighbor ID 141.255.0.0. only one network resides in EIGRP 3.6 0.0.CCNP Practical Studies: Routing Example 8-49 configures R3's serial link to R1 to reside in area 0. Example 8-51 EIGRP Configuration on R4 R4(config)#router eigrp 1 R4(config-router)# passive-interface Serial1 R4(config-router)# network 141.108.108. . 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. Example 8-51 configures R4 in EIGRP domains 1 and 3.100.0 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. so you can apply some summary commands later.255.17 141. Example 8-50 confirms that OSPF has formed a full relationship to R2 and R3.0 R4(config-router)# no auto-summary Automatic summarization is disabled on R4.2 141. Example 8-52 confirms the EIGRP interfaces in domains 1 and 3.108. 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).0 R4(config-router)#network 161.13 Pri 1 1 State FULL/ FULL/ Dead Time 00:00:38 00:00:38 Address 141.108.0. Example 8-53 configures R5 in EIGRP 2 and EIGRP 3.108.0.6 Interface Serial1/0 Serial1/1 R1 is fully adjacent (Full) to R2 and R3. for interfaces in EIGRP domain 1. the WAN link to R5.

Redistributing from one EIGRP AS to another does not require you to define a metric because EIGRP conserves the metric.0/17.18. you redistribute only networks using the metric from the original AS or domain.255. the core routers in the network.100.128.20/30 [90/21024000] via 141.100.100. Example 8-55 Redistribution on R5 R5(config-router)#interface Serial0 R5(config-if)# ip summary-address eigrp 2 160.128.0 [170/21049600] via 141.0/16 is variably subnetted.308 - . Serial1/1 D EX 141.255.108.0. Serial1/1 D EX 160.0 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. You configure route maps on R2 and R3.18. Example 8-56 show ip route eigrp on R2 R2#sh ip route eigrp 141.108. later in this chapter.0 R5(config-router)# no auto-summary At this stage.108.0. Example 8-54 Redistribution on R4 R4(config)#interface s0 R4(config-if)#ip summary-address eigrp 1 160.108. Example 8-56 displays the IP routing table (EIGRP only) on R2.108. 2.0 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.128.100. 13 subnets. advertising the subnet 160.0 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 141.0/17.0. advertising the subnet 160.0/17 is subnetted.255.18. 2 masks D 141.255.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 141.18.0.0 [90/20537600] via 141.100.255. 00:01:26.108. you have not configured any redistribution. You do have to ensure that route maps or distribution lists are used to avoid loops.108. Serial1/1 160.12/30 [170/22016000] via 141. The second summary route redistributed from domain 3 to 2 appears as an external EIGRP (D EX) route. 00:01:26.0 255. 2 subnets D 160.128.0.255.108.108.128.0. . and 3. 00:01:26. Start by configuring redistribution in the EIGRP domains 1. Therefore. Serial1/1 R2 has the summary route from R4 appearing as an internal EIGRP route (D) because the network resides in the same AS.100. display the IP routing tables on R2 and R3. 00:01:26. Example 8-54 configures redistribution from EIGRP domain 1 to 3 on Router R4 and also configures a summary route on R4.255.100.0.0 255.0 R5(config-router)# network 160.0.255.

0.255.0 [170/21529600] via 141. 00:07:27.255.108.255 access-list 1 permit any ! Networks in Access-list 2 reside in the OSPF domain access-list 2 deny 141.255.255 and also the WAN subnets 141.309 - .108.0 0.14.4 0.108.0. 2 subnets D EX 160.14.128.0/16 is variably subnetted.0 0. 00:10:12.100.CCNP Practical Studies: Routing Example 8-57 displays the IP routing table (EIGRP) in R3. Serial1 D EX 141.108.255 access-list 2 deny 141. 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 160.128.108.0) and external summary route (D EX 160.108.3 access-list 2 permit any R2 is configured to redistribute OSPF networks with a route map named allowintoeigrp. by using route maps. 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 [90/21017600] via 141.255. 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.16/30 [170/22016000] via 141. Similarly.0.0.100.0.100.100. indicating that only networks matching access list 1 are allowed into OSPF.108. 2 masks D 141.255.4/30 (Link R1/R3). Because OSPF and EIGRP use different metrics for routing.108.7.0. as shaded in Example 8-58.0–141.255.108. this prevents erroneous routing information and routing loops from occurring.0. Serial1 141.108.0 0.108. Example 8-58 configures R2 for redistributing OSPF routes into EIGRP and EIGRP routes into OSPF.255.7. you must assign metrics when redistributing and ensure.100. the route map named allowintoospf permits all networks matching access-list 2.3 access-list 2 deny 141. Example 8-57 show ip route eigrp on R3 R3#show ip route eigrp 160.108. that no redistributed information causes a routing loop.0. 00:10:12.14.255.0/30 (Link R1/R2) and 141.0.0.108. Serial1 D 160. when redistributing EIGRP networks into OSPF. respectively. 00:06:21.0.255.20/30 [90/21504000] via 141.0.255.0/17 is subnetted.0) for the remote Ethernet segments on R4 and R5. Serial1 Similarly.100. R3 has an internal (D 160.0.14. R2 is configured not to permit any routes from R4 advertising networks in the range 141.255. .108. 13 subnets.

1 Type escape sequence to abort.100.100.255.1.108. Serial1/1 160.6.20/30 [110/100] via 141. 01:16:02.100.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. Serial1/1 O E2 141. Sending 5.108.255 access-list 2 deny 141. examine some IP routing tables starting from the core router R1 in OSPF area 0. or the backbone. round-trip min/avg/max = 28/31/32 ms R1# Example 8-61 displays the IP routing table on R4. 2 subnets O E2 160. Serial1/0 O E2 160.108.1/25 and 150.255. Example 8-60 show ip route ospf and Pings on R1 R1#show ip route ospf 141.0. 100-byte ICMP Echos to 160.0. 01:16:11.108.100.255.4 0.12/30 [110/100] via 141.6. Serial1/1 O E2 141.100.0 as part of the access list.255. R4 won't be able to get to the networks connected to R5 because the 160.0 0.1.3 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.100.255.108.7.108.255 access-list 1 permit any ! Networks in Access-list 2 reside in the OSPF domain access-list 2 deny 141. .100.0.128.1. Serial1/1 R1#ping 160.108.255.6.255.100.108.1 Type escape sequence to abort.108.100. Now that redistribution is completed and filtered on core routers. For the purposes of this exercise. 01:16:02. 100-byte ICMP Echos to 160.0.255. 01:16:02. 13 subnets.255. To fix this.0.0/17 is subnetted.0.255. A common technique to ensure network connectivity is to ping IP interfaces.108.6.0.0.100. Sending 5.100.0 0. In other words.128. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).3 access-list 2 deny 141. assume the back-to-back serial connections between R4 and R5 never fail. you can add the network 160.0.1.0. Example 8-60 displays the IP routing table (OSPF routes only) on R1 and some sample pings to the remote EIGRP networks 160.0.0/16 is variably subnetted.1.108.2.1.129/25.16/30 [110/100] via 141. round-trip min/avg/max = 28/30/32 ms R1#ping 160.310 - .0.128. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0. 01:16:02.100.0 network is denied from being redistributed into EIGRP from OSPF.0 [110/100] via 141.0 0.255. EIGRP domain 3 is isolated. 2 masks O E2 141.0 [110/100] via 141.108.

108.2.22.255.108.108.3. Serial1 141. Serial1 141.1. timeout is !!!!! Success rate is 100 percent (5/5).2.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. 01:42:27.0/24 [170/22016000] via 141. Serial0 141. 100-byte ICMP Echos to 141.0.22.255.108.13. 01:21:46.108.255.100.0/24 [170/22016000] via 141. 01:21:46. 2 subnets 160.108.108.0. timeout is !!!!! Success rate is 100 percent (5/5).0/24 [170/22016000] via 141.1.255.108. timeout is !!!!! Success rate is 100 percent (5/5). 13 subnets.255.108. round-trip min/avg/max R4#ping 141.108.0/16 is variably subnetted. Serial1 141. (These routes are the loopback interfaces on R1.20/30 is directly connected.0/24 [170/22016000] via 141.108.2.255.255.1.4.1 Type escape sequence to abort.0 is directly connected.108.7. Serial1 141. 01:21:46.5.255.100.7.100.108.108.5.0/17 is subnetted. Serial1 141. Serial1 141.1 Type escape sequence to abort. Serial1 141.255.3.22.108.108. Serial0 141. 100-byte ICMP Echos to 141.0.108.0. 01:21:47.0 [170/21017600] via 141.22. timeout is !!!!! Success rate is 100 percent (5/5).108.0.12/30 is directly connected. 01:42:25.108.6.0/24 [170/22016000] via 141.108.1 Type escape sequence to abort.1.108.255.1.108. Serial1 141. Serial1 141. Serial1 160. 01:21:46.311 - .108.6. timeout is !!!!! Success rate is 100 percent (5/5).1. Example 8-62 Pinging Loopbacks from R4 R4#ping 141.255.16/30 [90/21504000] via 141.255. round-trip min/avg/max R4#ping 141.22. Serial1 141. Sending 5.22.108.108.108. Ethernet0 EX EX EX EX EX EX EX EX EX D EX C Full connectivity is displayed on R4.108.0/24 [170/22016000] via 141. 100-byte ICMP Echos to 141.108.4. 100-byte ICMP Echos to 141.) 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.1 Type escape sequence to abort.108.108. 01:21:46.4/30 [90/21504000] via 141. and notice that the shaded routes in Example 8-61 encompass all the routes from 141.22.255.255.108.5.108.108. 01:42:51.1.255. 2 masks 141.108. 01:42:25. round-trip min/avg/max R4#ping 141. round-trip min/avg/max R4#ping 141.0/30 [170/22016000] via 141.0/24 [170/22016000] via 141.108.108. round-trip min/avg/max R4#ping 141.22. Sending 5.1.255. Sending 5.22.0/24 [170/22016000] via 141. timeout is !!!!! Success rate is 100 percent (5/5).0– 141. 100-byte ICMP Echos to 141.108.255.255.3.22.22. 01:21:46. round-trip min/avg/max R4#ping 141.4. 100-byte ICMP Echos to 141.0.1 Type escape sequence to abort. Serial1 160. Sending 5. Sending 5. Sending 5.0.108.1 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 .1. 01:21:46.128.108.1 Type escape sequence to abort.108.108.

4/30. FD is 22016000 via Redistributed (22016000/0) via 141.255. 1 successors. R .108. Ethernet0 P 141.108.Reply.2.13 (26112000/6826496). Example 8-63 show ip eigrp topology on R4 R4#show ip eigrp topology IP-EIGRP Topology Table for AS(1)/ID(160. Serial0 P 141. 1 successors. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255.108.1) Codes: P . FD is 22016000 via Redistributed (22016000/0) via 141.13 (21504000/20992000).255. Serial1 via Reconnected (20992000/0) P 141.108. 1 successors.1.255.0/17. Serial0 P 141. Sending 5. FD is 22016000 via Redistributed (22016000/0) via 141. Serial0 IP-EIGRP Topology Table for AS(3)/ID(160.312 - . 1 successors. Serial0 P 141.0/24.0/24.13 (26112000/6826496).6. 1 successors. FD is 281600 via Connected.108.Active.Query. 1 successors.255.108.108.0/24.108.108.255.108.128. 1 successors.255.Reply status P 141.100.0/24. A .4.108.108.13 (26112000/6826496). FD is 20992000 via Connected.20/30. Serial0 P 160. U .255.0/30. FD is 22016000 via Redistributed (22016000/0) via 141. Serial0 P 141. FD is 22016000 via Redistributed (22016000/0) via 141. r . the EIGRP topology table on R4 and R5 displays feasible successors.Update. round-trip min/avg/max = 36/38/40 ms Because R4 and R5 have a redundant path to the OSPF backbone.108. Serial1 P 141.16/30.1. FD is 22016000 via Redistributed (22016000/0) via 141.13 (26112000/6826496).255. 1 successors.255.13 (26112000/6826496). Q .13 (26112000/6826496).0.20/30.1. FD is 21017600 via Redistributed (21017600/0) via 141.255.0/17.108.108. 1 successors.100.1.255. Example 8-63 displays the output from the show ip eigrp topology command on R4.100.108.Passive. 1 successors.7.255. 1 successors.255.0/24.0/24. FD is 22016000 via Redistributed (22016000/0) via 141.16/30. FD is 20992000 via Connected.255.0/24.108. Serial0 P 141.22 (21504000/2169856). FD is 21504000 via Redistributed (21504000/0) P 141.100. 100-byte ICMP Echos to 141.1) P 141.108.13 (26112000/6826496). 1 successors. 1 successors. 1 successors.108. FD is 21504000 via 141. 1 successors. Serial0 P 141.13 (26112000/6826496).255. FD is 21504000 via 141. Serial0 P 141.108.255.0.13 (26112000/6826496).255.13 (26112000/6826496).108.3.108.5. 1 successors.12/30.255.0/24.108. Serial0 P 141.108. Serial1 . 1 successors.108. FD is 20992000 via Connected. FD is 22016000 via Redistributed (22016000/0) via 141.CCNP Practical Studies: Routing Type escape sequence to abort.108. Serial0 P 141. FD is 22016000 via Redistributed (22016000/0) via 141. Serial0 P 160.108.6.108.

0/24. 1 successors. 1 successors.255. for example.100.108. Serial1 P 141.7.108.255. FD is 22016000 via 141. Serial1 via Redistributed (26112000/0) P 141. Example 8-65 confirms the IP routing table.255. FD is 22016000 via 141.0/24. 1 successors. Serial0 via Reconnected (20992000/0) P 141.22 (22016000/2730496). 1 successors.0/24 is through Serial 1. Serial1 via Redistributed (26112000/0) P 141.22 (22016000/2730496). FD is 22016000 via 141.0/17.108.12/30.108.108. R4 has a number of dual paths to remote networks. 1 successors.0.255. 1 successors.255.22 (22016000/2730496).108.108.255.255. Serial1 via Redistributed (26112000/0) P 141.255.255.108. Serial1 via Redistributed (26112000/0) P 141. 1 successors.108.255.0/30.3.108. Serial1 via Redistributed (26112000/0) P 141.0/24.5.108. Serial1 via Redistributed (26112000/0) P 141.108.0/24.108. FD is 22016000 via 141.128.22 (22016000/2730496).0/17. . FD is 21504000 via Redistributed (21504000/0) via 141.255. Next.0/24.108.108. changed state to down The IP routing table on R4 displays the path to the remote loopbacks and OSPF network through Serial 0.0. 1 successors.255. 1 successors. Serial1 via Redistributed (26112000/0) P 160.108. FD is 22016000 via 141.CCNP Practical Studies: Routing P 141. which is higher than through Serial 1 to R5 (22016000 compared to 26112000).22 (22016000/2730496). FD is 22016000 via 141.22 (22016000/2730496).6. simulate a network failure by shutting down the serial link to R5 on R4. the chosen path to the remote network 141. 1 successors.108. Example 8-64 disables the link to R5. FD is 22016000 via 141.108.313 - .22 (22016000/2730496).0/24.108.4/30.0/24. FD is 22016000 via 141.255.6. FD is 20992000 via Connected.108. Serial1 P 160.22 (22016000/21024000). as shaded in the output.2.255. Serial1 via Redistributed (26112000/0) In Example 8-63. 1 successors. note the EIGRP composite metric.108.0/24.22 (22016000/2730496). Serial1 via Redistributed (26112000/0) P 141. 1 successors. 1 successors. FD is 22016000 via 141.22 (21017600/281600). FD is 281600 via Redistributed (281600/0) P 141. Because the metric is lower through Serial 1.1.4. FD is 21017600 via 141. changed state to administratively down 04:02:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1.100.108.22 (22016000/2730496). Example 8-64 Shut Down S1 on R4 R4(config)#interface serial 1 R4(config-if)#shutdown 04:02:11: %LINK-5-CHANGED: Interface Serial1.108.

255.108.0 ip ospf network point-to-point ! interface Loopback3 ip address 141.0 ip ospf network point-to-point ! interface Loopback6 ip address 141.0/16 is variably subnetted.255.108.6. 00:02:07.4.1 255.108.1 255.0.0/24 [170/26112000] via 141. Example 8-66 displays R1's full working configuration.0/24 [170/26112000] via 141.13.6.255.0/24 [170/26112000] via 141. 00:02:07.CCNP Practical Studies: Routing Example 8-65 show ip route eigrp on R4 R4#show ip route eigrp 141.255. Serial0 D EX 141.255.255.108.0 ip ospf network point-to-point ! interface Loopback1 ip address 141.108.1 255.1 255.13.255.3.1 255.108.100.108.108.314 - .255.1 255.13. You must pay particular attention to the metric and avoid any routing loops.108.0/24 [170/26112000] via 141.0 ip ospf network point-to-point ! interface Loopback2 ip address 141.128.255.1.255.0/24 [170/26112000] via 141.0.108.108.4/30 [90/21504000] via 141.0.108.108.108.1 255.108. 00:02:07. Serial0 D EX 141.1. Serial0 D EX 141. 00:02:07.1 255.13. Serial0 D EX 141. 2 subnets D EX 160.255.255. 00:02:08.255. Serial0 D EX 141.255. 02:53:02. Serial0 D EX 141. Serial0 D EX 141.255.5.255. 2 masks D 141.255. 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.108.108.7. Serial0 D EX 141. Serial0 D EX 141. 00:02:07. 00:02:08.255.0/24 [170/26112000] via 141.255.255.0/17 is subnetted.0 ip ospf network point-to-point ! interface Ethernet0/0 ip address 141.100.0 ip ospf network point-to-point ! interface Loopback5 ip address 141.13.255.108.255. Example 8-66 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Loopback0 ip address 141.0.255.255.1 255.255.108.252 . Serial0 160.108.108.0 ip ospf network point-to-point ! interface Loopback4 ip address 141.108.255.5.108.255.108.255.2.0/24 [170/26112000] via 141.13.13.13.255.108.2.13.0 [170/26112000] via 141.0/30 [170/26112000] via 141.108. 00:02:08.255.255.4. 00:02:08.0/24 [170/26112000] via 141.108.0 ! interface Serial1/0 ip address 141.108. 11 subnets.108.13. 00:02:08.7.13.108.108.3.255.

255.255 access-list 1 permit any access-list 2 deny 141.255.255.0 area 0 access-list 1 deny 160.0.17 255.255.0.2 0. 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 141.108.255.0.255.0 0.0 redistribute eigrp 2 metric 100 subnets route-map allowintoospf redistribute eigrp 1 network 141.3 access-list 2 deny 141.0.108.0.108.252 ! router eigrp 2 redistribute ospf 1 metric 1500 2000 255 1 1500 route-map allowintoeigrp passive-interface Serial1/0 network 141.255.108.252 no ip mroute-cache ! interface Serial1/1 ip address 141.0.100.5 255.255.0.108.0.255.255.255 area 0 ! end Example 8-67 displays R2's full working configuration.108.0.7.315 - .0.255.0.0.3 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.2 255.0 255.0.CCNP Practical Studies: Routing clockrate 128000 ! interface Serial1/1 ip address 141.0 no auto-summary ! router ospf 1 summary-address 141.255.0 0.248.255.255.255 access-list 2 deny 141.252 clockrate 128000 ! router ospf 1 redistribute connected subnets network 0.0 0.108.255.4 0.0.0 255.108.108.255. .

255.255.128.255.255 access-list 1 permit any access-list 2 deny 141.0.6 0.0.255.108.0 5 ! interface Serial1 bandwidth 125 ip address 141. Example 8-69 R4's Full Working Configuration hostname R4 ! enable password cisco ! interface Ethernet0 ip address 160.108.252 bandwidth 125 clockrate 125000 ! router eigrp 1 redistribute ospf 1 metric 1500 20000 255 1 1500 route-map allowintoeigrp passive-interface Serial0 network 141.0.21 255.0.0 0.255.255.108.255.100.0.0.0 0.255.0.255.3 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 8-69 displays R4's full working configuration.316 - .255.4 0.100.6 255.252 clockrate 125000 ! .255 access-list 2 deny 141.108.252 bandwidth 125 ! interface Serial1 ip address 141.108.128.108.0 0.1.0 no auto-summary ! router ospf 1 redistribute eigrp 1 metric 100 subnets route-map allowintoospf network 141.14 255.255.255.7.1 255.0 area 0 access-list 1 deny 160.255.0 255.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 141.255.0.0.0.255.255.108.255.108.3 access-list 2 deny 141.0.13 255.252 ip summary-address eigrp 1 160.0 ! interface Serial0 bandwidth 125 ip address 141.108.255.0.100.

252 ip summary-address eigrp 2 160.255 access-list 2 permit 160.0.252 no ip directed-broadcast ! router eigrp 3 redistribute eigrp 2 passive-interface Ethernet0 passive-interface Serial0 network 141.255.0.0 no auto-summary ! router eigrp 3 redistribute eigrp 1 passive-interface Ethernet0 passive-interface Serial0 network 141.0 no auto-summary access-list 1 permit 160.CCNP Practical Studies: Routing router eigrp 1 redistribute eigrp 3 passive-interface Serial1 network 141.108.255.1 255.0.0 0.255.0 network 160.108.100.0 clockrate 125000 ! interface Serial1 ip address 141.22 255.128.0 0.0 ! interface Serial0 ip address 141.255.108.0 255.18 255.0.0 no auto-summary ! ip classless ! end .0.128.128.108.0 network 160.255.100.255. Example 8-70 R5's Full Working Configuration hostname R5 ! enable password cisco interface Ethernet0 ip address 160.0 no auto-summary ! router eigrp 2 redistribute eigrp 3 passive-interface Serial1 network 141.0.127.255 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.128.108.0.127.255.100.100.108.100.0.100.255.0.317 - .0.

0.128 R1(config-if)#interface Loopback3 R1(config-if)# ip address 131. The ability to configure networks from a classless and classful domain and vice versa is critical.108.4.1 0.2.4.129 0.128 R1(config-if)#interface Loopback2 R1(config-if)# ip address 131.1 255.108.255.0.1 0.0.0. Router R1 has a number of interfaces in OSPF area 333.3.0 area 333 R1(config-router)#network 131.129 255.108.3.248 R1(config)#router ospf 1 R1(config-router)#network 131.0.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.108. 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).0.108. To ensure that routing resources are not wasted.1 0. Figure 8-6. and R2 is running RIP only.108.3. To do this.318 - .248 R1(config-if)#interface Loopback4 R1(config-if)# ip address 131.1 255.0.255.255. Example 8-71 R1 Configuration R1(config)#interface Loopback0 R1(config-if)# ip address 131.108. This scenario uses static routes to ensure connectivity between the classless (RIP) domain to the classful (OSPF) domain.255.108.255. You configure R1 for redistribution between RIP and OSPF.108.0 area 333 R1(config-router)#network 131. because OSPF advertises these routes. Example 8-71 configures R1 for IP addressing and enables OSPF and RIP.1 255.0. This scenario contains only two routers. so you can easily replicate this network with your own set of Cisco IOS routers. even on the loopbacks.0 R1(config-if)#interface Loopback1 R1(config-if)# ip address 131.5.255.0 area 333 . you apply passive interfaces where required.1 255.255.255. Ensure that RIP updates are sent to only the Ethernet interfaces on R1 by configuring R1 with passive interfaces.255.255. Routing IP Between RIP and OSPF The end goal of this scenario is to ensure full IP connectivity between the two different IP networks. allow only one routing algorithm to advertise each interface.2.0 area 333 R1(config-router)#network 131.3.

1.255.255.0 255.255. which is a Class C subnetted route.2. . The first is to use static routes.3.128 131.1.0.0.1 0.108.108. Example 8-75 Static Route Configuration on R2 R2(config)#ip R2(config)#ip R2(config)#ip R2(config)#ip route route route route 131.108.1 131. Ethernet0/0 The only IP network in Example 8-74 is the subnet 131.1.CCNP Practical Studies: Routing R1(config-router)#network 131.255. Because R2 is configured with a classful routing protocol.0 255. Example 8-74 show ip route R1 R2#show ip route 131.1 R2 is configured with static routing information.0 To enable R2 to learn the OSPF loopback interfaces on R1 dynamically.255.108.2 255.0 [120/1] via 131. Ethernet0/0 C 131.108.4.108. even though the remote networks are not Class C subnets.1.255.1. enable RIP-to-OSPF redistribution on R1. Example 8-72 RIP Configuration on R2 R2(config)#interface ethernet 0/0 R2(config-if)#ip address 131.1 131.108.248 131. 2 subnets R 131. and the second method uses summarization techniques on R1.128 255. Example 8-74 displays the IP routing table on R1.0 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 R2.0 is directly connected.108.0. by setting the metric to 1 (hop count).108.108.108. Configure R2 with static routes and ensure network connectivity to R1 loopback interfaces.0 R2(config-if)#exit R2(config)#router rip R2(config-router)#network 131.1.108. Example 8-75 configures R2 with four static routes pointing to the next hop destination to R1's Ethernet IP address of 131.0/24 is subnetted.0.108.1.108.1.0.255.0 255.248 131.108.1.255.1.319 - . Example 8-73 displays the redistribution on R1 from RIP to OSPF.3.128 131. You can use two methods to solve this scenario.108.0 area 333 R1(config-router)#router rip R1(config-router)#network 131.0.255.5.108. Example 8-76 displays R2's IP routing table and five ping requests to all R1's loopback interfaces. Confirm network connectivity by viewing the IP routing table on R2 and pinging all remote loopback interfaces on R1.5.255. 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 R2.108. only 24-bit networks are advertised by R1 and accepted by R2.2. 00:00:06.1 131.

108. round-trip min/avg/max = 1/3/4 ms R2#ping 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0 ! interface Loopback1 ip address 131. 100-byte ICMP Echos to 131.3.4. Sending 5. you can use static routes to overcome the limitations of routing between VLSM networks or fixed-length subnet mask (FLSM) networks.0/16 is variably subnetted.108.0/29 [1/0] via 131.108.108.1.R .108.255.0/24 [120/1] via 131.1 S 131.4. 100-byte ICMP Echos to 131.1.2.108. round-trip min/avg/max = 1/3/4 ms R2#ping 131.1. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.1.5.5.108.255. 100-byte ICMP Echos to 131.1 Type escape sequence to abort.3.1 Type escape sequence to abort. Example 8-77 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 131.255.129 Type escape sequence to abort.1 S 131.108.CCNP Practical Studies: Routing Example 8-76 show ip route and ping on R2 R2#show ip route Codes: C . 6 subnets.1 S 131.255.1 255.108.108.128/25 [1/0] via 131.1.108. 100-byte ICMP Echos to 131.1. 3 masks S 131.108.1.3. Sending 5. Example 8-77 displays R1's full working configuration.108. you configure routing between VLSM and FLSM networks without using static routing. Sending 5.5.255.1 255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).connected.108.1.129 255.108.0/29 [1/0] via 131.4. round-trip min/avg/max = 1/3/4 ms R2#ping 131.4.1 R 131.2.128 interface Loopback3 ip address 131.1 255.108. 00:00:13.129.RIP 131.3. S . Ethernet0/0 R2#ping 131.1 Type escape sequence to abort.108.1. Ethernet0/0 C 131.static.108. Sending 5.108.108.3. In the next scenario.108. round-trip min/avg/max = 1/2/4 ms R2# Example 8-76 displays IP networks installed in the routing table.3.0/24 is directly connected. Sending 5. round-trip min/avg/max = 1/2/4 ms R2#ping 131.108.108.0.128 interface Loopback2 ip address 131.108.3.108. Even though RIP is classful.3.255.0/25 [1/0] via 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108.248 .1.2.1.2.255.320 - .

0 ! ip route 131.0.128 255.0.1 131.1 255.4.0.0 255.108.255.0 area 333 network 131. 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 131.1.1 0.128 131.108.255.108.255.0.321 - .1 ip route 131.0.3.2.1 0.255.108.248 131.108.4.255.255.255.108.0 ! router rip network 131.108.0 255.1 end Scenario 8-5: Route Summarization Without Using Static Routes In this scenario.108.108.0 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 131.108.128 131.0 area 333 network 131.1.5.1.255.108.1.255.0 255.1 0.1.1 ip route 131.1.108.255.108.5.2 255.255.128 131.0 ! end Example 8-78 displays R2's full working configuration.108.1.1.255. you revisit the topology in Figure 8-6 and use dynamic routing to insert the non-class C networks into R2's routing table.1 ip route 131.1 131.255.248 131.255.3.4.255.108.248 131.255.1 0.0 255.0.108.1. 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 131.3.248 ! interface Ethernet0/0 ip address 131.108.129 0.CCNP Practical Studies: Routing ! interface Loopback4 ip address 131.0.108.108.0 area 333 network 131.0 router ospf 1 network 131.5.1.0.255.0 255.128 131.108.0 area 333 network 131.255. Example 8-79 removes the static route configuration on R2.5.1 255.0.0.108.128 255.255.3.108.1 131.108.108.108.1 .255.3.255.108.255.0.0.3.0 255.248 131.

R1 is an ASBR. [120/1] via 131. 00:00:06.3. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 R2 assumes all 131. To ensure that routing loops cannot occur.4. 00:00:06. 00:00:06.2.0 R 131.1.108.255. the loopbacks on R1) are redistributed to R2. so you do not need to add this interface. Example 8-80 summary-address Command on R1 R1(config)#router ospf 1 R1(config-router)#summary-address 131.1.255.5.0/24 network. To ensure that R1 never accepts routes that are locally reachable. you can apply the summary-address network-mask command.0 networks are subnetted as 24-bit networks.108.108.1.0 R1(config-router)#summary-address 131.1. Example 8-80 configures summarization on R1 for the four loopbacks.255.108.108. as displayed in Example 8-81.108. 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 802.5.1. you can advertise all loopbacks on R1 as Class C subnets to R2.1.1.1.4.0 255. Example 8-81 displays the IP routing table on R2.108. 00:00:06.322 - . called allowout. Example 8-82 configures a route map. configure a distribution list that allows only the loopbacks configured on R1.0 R 131.CCNP Practical Studies: Routing The IP routing table on R2 now contains only the 131.255.0 C 131. that permits only the non-class C networks to be advertised to R2. as displayed in Example 8-74. Example 8-81 show ip route on R2 R2#show ip route 131. is directly connected. To redistribute the networks in R1's network. R1 sends only the loopbacks interfaces and R2 accepts only routes that are not locally connected.0 255. Loopback 0 is a Class C subnet route.0 R 131.108.0 255.108.255.2.108.108.3.0 R1(config-router)#redistribute connected subnets The last command in Example 8-80 ensures that all connected routes (in this case. [120/1] via 131.0.0/24 R 131.0 is subnetted.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. so you can use the summary command to send an update to RIP with any mask you need.108.108. .1.108. 5 subnets [120/1] via 131.108. [120/1] via 131.0.255.0 R1(config-router)#summary-address 131. Because all Cisco IOS routers always choose a path with a more specific route.

1 0.0 ! router ospf 1 summary-address 131.2.1.108.255.255.255.255.0 R2(config)#access-list 1 permit 131. Example 8-84 show ip route rip on R2 R2#show ip route rip 131.0 summary-address 131.0 area 333 network 131.108.5.108.CCNP Practical Studies: Routing Example 8-83 configures a distribution list on R2 permitting only loopbacks 0–4 into R2's IP routing table.1 255.0 255.1.108.3.108.128 ! interface Loopback3 ip address 131.1 255.0.108.0 [120/1] via 131.255.0.1 255.255.0/24 is subnetted.1.108.5. 00:00:00.255.0 area 333 .255. 00:00:00.5.108.255.248 ! interface Loopback4 ip address 131.0 summary-address 131.0 255.0. 00:00:00.128 ! interface Loopback2 ip address 131. Example 8-85 R1's Full Working Configuration hostname R1 ! enable password cisco ! interface Loopback0 ip address 131.4. R 131.108.108.129 255.108.0 [120/1] via 131.108. all other networks are rejected.1 255.0.255.108.255.108.0.1.2. Example 8-85 displays R1's full working configuration. R 131.255.255. Ethernet0/0 Ethernet0/0 Ethernet0/0 Ethernet0/0 The same principles applied here can be applied to any number of routers.0.3.3.1 0.0 area 333 network 131.5.108.0.4.0.255.1.108.5.1 255.4.248 interface Ethernet0/0 ip address 131.108.255.4.108. and as long as route maps and filtering are applied.2. 5 subnets R 131.1.108.108.3.108.0 redistribute connected subnets route-map allowout network 131.0 R2(config)#access-list 1 permit 131.0 [120/1] via 131.255. 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 131.3.255.108. 00:00:00.0 area 333 network 131.0 255.0.3.0 Example 8-84 confirms the IP routing table on R2. the network should be free of routing loops and maintain full network connectivity.0 [120/1] via 131.255.108.1 0.1.0 area 333 network 131.1.108.2.108.129 0.3.0 R2(config)#access-list 1 permit 131.0. R 131.108.4.0 ! interface Loopback1 ip address 131.1 0.323 - .1.108.0.

0 distribute-list 1 in access-list 1 permit 131.0 access-list 1 deny 160.3.0 ! route-map allowout permit 10 match interface Loopback1 Loopback2 Loopback3 Loopback4 ! end Example 8-86 displays R2's full working configuration.108.0 access-list 1 permit 131.0.108.108.108.255.100.1.0.4.255.108.0 access-list 1 permit 131.5.0 0.0.0.324 - . 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.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 131.0 ! router rip network 131.0 access-list 1 permit 131.2 255.108.255 end .255.2.108.

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

255.2.108.255.0 ! interface Loopback3 ip address 141. You can. All other networks are allowed into R1's IP routing table.6.255.0 ! interface Loopback6 ip address 141. Example 8-87 R1's Full Working Configuration hostname R1 ! enable password cisco ! ip subnet-zero interface Loopback0 ip address 141.255.0 clockrate 128000 ! router eigrp 1 redistribute rip metric 128 20000 255 1 1500 network 151.CCNP Practical Studies: Routing The following configurations provide a sample working solution to the network topology in Figure 8-7.255. however.255.255.255.108.255.108. The shaded portions in Example 8-87 are key configuration commands for filtering.255.0 clockrate 128000 ! interface Serial1/1 bandwidth 128 ip address 151.0 ! ip classless .0 distribute-list 1 in ! router rip passive-interface Serial1/0 passive-interface Serial1/1 network 141.255. R1 is configured for RIP and EIGRP.0.108.3. Static routes are not used in this design.0 ! interface Serial1/0 bandwidth 128 ip address 151. The redistribution on R1 is filtered to deny any locally sourced networks on R1.255.1 255.1 255.255.0 ! interface Loopback5 ip address 141.108.0. Example 8-87 displays R1's full working configuration.1 255.255.1 255.108.7.255.108.1 255.0 ! interface Loopback1 ip address 141.1.108.0 ! interface Ethernet0/0 ip address 141.1 255.0 ! interface Loopback2 ip address 141.0.4.0 ! interface Loopback4 ip address 141.255.1 255.255.1 255.1 255.5.255.108. configure this network many different ways.255.108.254.1 255.255.108.108.326 - .255.

1 255.255.1 255.0 ! interface Loopback4 ip address 141.108.9.255.108.0 interface Serial1/1 bandwidth 128 ip address 151.255.255.0 ! router eigrp 1 network 151.0 ! interface Loopback3 ip address 141.108.255.0 ! interface Loopback1 ip address 141.0 distribute-list 1 in ! router igrp 1 passive-interface Serial1/0 passive-interface Serial1/1 network 141.255.108. Example 8-88 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero ! interface Loopback0 ip address 141.0 ! interface Ethernet0/0 ip address 141.255.0 ! interface Loopback6 ip address 141.255.255.108.255.1 255.255.1 255.255.255.108.1 255.255.0 0.13.15.12.1 255.108.108.255.CCNP Practical Studies: Routing ! access-list 1 deny 141.0 ! interface Loopback2 ip address 141.255 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.255.255.108.2 255.108.253.108.327 - .255.2 255.8.0.0 ! interface Loopback5 ip address 141.0 ! ip classless .14.255.255.11.0.1 255.1 255.108.0.0.10.255.0 ! interface Serial1/0 bandwidth 128 ip address 151.108.7.

108.255.1 255.255.1 255.255.254.108.255.0 ! interface Loopback2 ip address 141.255.7.255.255.0 0.255.255.1 255.108.23.255.0 ! interface Loopback6 ip address 141.255.108.21.108.255 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.108. Example 8-89 R3's Full Working Configuration hostname R3 ! enable password cisco ! no ip domain-lookup ! interface Loopback0 ip address 141.253.1 255.0.CCNP Practical Studies: Routing ! access-list 1 deny 141.1 255.18.17.255.0 ! interface Loopback4 ip address 141.255.8.108.255.1 255.1 255.16.255.108.328 - .0 ! interface Loopback5 ip address 141.1 255.0.1 255.108.0 bandwidth 128 ! interface Serial1 ip address 151.255.20.255.0 bandwidth 128 clockrate 128000 ! router eigrp 1 redistribute ospf 1 metric 128 20000 1 1 1500 network 151.108.108.19.255.255.0 ! interface Loopback1 ip address 141.255.22.0 media-type 10BaseT ! interface Ethernet1 no ip address ! interface Serial0 ip address 151.0 ! interface Loopback3 ip address 141.108.2 255.0 ! interface Ethernet0 ip address 141.0 .

00:06:22. 00:06:22.108.108. Serial1/0 C 151.2.0 [170/20640000] via 151. 00:06:22.15. 00:06:22.0 0.0 is directly connected. 00:06:20.0. Serial1/0 D EX 141. Loopback3 C 141.254.108.2. Example 8-91 displays the EIGRP topology table on R1. Also.0/24 is the same.255. Loopback2 C 141.254. Serial1/1 D EX 141.108. Serial1/1 151.6.108.108.254. Serial1/0 D EX 141.108.2.108.2.108.0 is directly connected. Serial1/1 D EX 141.0/24 is subnetted.108.0. Serial1/0 R1# The redistributed networks from R2 and R3 appear as external EIGRP routes (D EX).108.0 is directly connected. Serial1/1 [90/21024000] via 151.108.0.4. Serial1/0 D EX 141.108.255.108. 00:06:22.8.108.108.23.253.0.254.2. The shaded portions display the dual path to 151.108.108.0 [170/25632000] via 151.108.2.0.254. 00:06:21.10.255. Serial1/1 D EX 141.16.254.2. 00:06:21. EIGRP is load balancing. The EIGRP topology table on R1 confirms the same composite metric.2.22.253.108.255 area 100 ! ip classless access-list 1 deny 141.2.108.108. Serial1/1 D EX 141.0 is directly connected.0 [170/25632000] via 151.9.5.17. 00:06:21.19.255. 00:06:22.108.108.108.108.254.108.255.2. Serial1/0 D EX 141.254.108. Serial1/0 D EX 141.2.108. 00:06:21. Loopback4 D EX 141.0 [170/20640000] via 151.108.2.108.254.20. 00:06:22.108.CCNP Practical Studies: Routing distribute-list 1 in ! router ospf 1 network 141.0 [170/20640000] via 151.108.0. Example 8-90 show ip route on R1 R1#show ip route 141. Serial1/1 D 151. 24 subnets C 141.255.3.255.108.108.0 [170/25632000] via 151. Serial1/0 D EX 141.108.2.255. Serial1/1 D EX 141.7.108.21.108.0 [170/25632000] via 151.0 [170/20537600] via 151. 00:06:21. 00:06:22.253.0 is directly connected.108.254.108.2.0 [170/25632000] via 151.108. Serial1/1 D EX 141. Loopback5 C 141. 00:06:21.255 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 R1.108. 00:06:22.2. Loopback0 C 141.2.0 is directly connected.2.7.0 [170/25632000] via 151.11.12.108. Serial1/1 D EX 141. Ethernet0/0 C 141.0/24 is subnetted.2.0 0.329 - .0 [170/20640000] via 151.255.0 [170/20640000] via 151.14. 3 subnets C 151.0 [170/20640000] via 151.0 [90/21024000] via 151.0 [170/25632000] via 151.13.255.18.16.0 is directly connected. Serial1/0 D EX 141. .1.108.0 is directly connected.108.108.108.0 [170/25632000] via 151.108.0 is directly connected.16.2.0 [170/20640000] via 151.108. because the composite metric to the WAN network 151.108. 00:06:21. Serial1/0 D EX 141.108.7. Loopback1 C 141. Loopback6 C 141. 00:06:22. demonstrating full network connectivity.0 is directly connected.

254.Reply. 1 successors.15.108.108. Q .2 (20640000/128256).17.255.13.108. 1 successors.2 (25632000/25120000).108.108.254.254.255.2 (25632000/25120000).108.2 (20640000/128256).108.108. FD is 20640000 via 151. FD is 25120000 via Redistributed (25120000/0) P 141. 1 successors. U . 1 successors.0/24. FD is 20640000 via 151. 1 successors.0/24.108.0/24.2 (20640000/128256). FD is 20640000 via 151. 1 successors.108.0/24. 1 successors.0/24.11.0/24. 1 successors. 1 successors. 1 successors. Serial1/1 . 1 successors.0/24.9. FD is 21024000 via 151.254.255. FD is 20512000 via Connected. Serial1/0 P 141. Serial1/0 P 141. Serial1/0 P 141.108.108.108.108.108.0/24.Active.108.0/24. FD is 25632000 via 151.0/24.108. FD is 25120000 via Redistributed (25120000/0) P 141.108.4. FD is 25632000 via 151.108. 1 successors. 1 successors.1.0/24.2 (25632000/25120000).108.0/24.254.0/24. 1 successors.0/24.10.7. FD is 25120000 via Redistributed (25120000/0) P 141.108.2 (21024000/20512000).108.14. FD is 20640000 via 151. FD is 20537600 via 151.0/24. 1 successors. FD is 25632000 via 151. 1 successors.108.0/24. 1 successors.2 (25632000/25120000).2 (20640000/128256).Update.0.330 - . r . 2 successors. FD is 25632000 via 151.0/24.0/24.108.2 (25632000/25120000).19.2 (21024000/20512000). Serial1/0 via 151. FD is 25120000 via Redistributed (25120000/0) P 141.108.0/24.23.108. FD is 20640000 via 151.108. R .3. FD is 25632000 via 151.254.12.255.8.108. Serial1/0 P 141. Serial1/1 P 141.21.255. 1 successors. FD is 25120000 via Redistributed (25120000/0) P 141. FD is 25632000 via 151.2 (20640000/128256).0/24.254.0/24.2 (20640000/128256).108.20.108. FD is 20512000 via Connected.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 .22. FD is 25120000 via Redistributed (25120000/0) P 141.5.253. Serial1/0 P 141.255. Serial1/0 P 141.0/24.108.108. FD is 25632000 via 151. Serial1/1 P 141. Serial1/0 P 151.255. 1 successors. Serial1/1 P 151.108. Serial1/1 P 141. 1 successors. FD is 25120000 via Redistributed (25120000/0) P 141. Serial1/1 P 141. Serial1/0 P 141.0/24. Serial1/1 P 141. Serial1/1 P 141. 1 successors.2 (25632000/25120000).2 (25632000/25120000).0/24.18.0/24.108.Passive. Serial1/1 P 141. FD is 20640000 via 151. 1 successors. 1 successors. FD is 25632000 via 151. 1 successors.2 (25632000/25120000). Serial1/1 P 141.0/24. FD is 20640000 via 151.108. FD is 25120000 via Redistributed (25120000/0) P 141. 1 successors.108.108.6.2.108.108. Serial1/0 P 141. 1 successors.108.2 (20537600/281600).16.108.108.254.2 (20640000/128256).255.Reply status P 151.254.254.108.255.108.Query.255.108. A .0/24.

1 Type escape sequence to abort. 100-byte ICMP Echos to 141. 100-byte ICMP Echos to 141.108. 100-byte ICMP Echos to 141.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 141.1 Type escape sequence to abort.17.108.108. round-trip min/avg/max = 16/16/17 ms R1#ping 141. round-trip min/avg/max = 16/16/16 ms R1#ping 141.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).CCNP Practical Studies: Routing R1# Example 8-92 confirms network IP connectivity by pinging all the remote networks from R1.1 Type escape sequence to abort.331 - .1. Sending 5. Sending 5.108.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 12/14/16 ms R1#ping 141. Sending 5.15. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 141.13.1 Type escape sequence to abort. Sending 5.1.1.1 Type escape sequence to abort. round-trip min/avg/max = 16/16/16 ms R1#ping 141.108.1 Type escape sequence to abort.8.108.11.1 Type escape sequence to abort. Sending 5. 100-byte ICMP Echos to 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort. round-trip min/avg/max = 16/16/16 ms R1#ping 141.16. Sending 5. 100-byte ICMP Echos to 141.108.1.10.18.1 Type escape sequence to abort. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. 100-byte ICMP Echos to 141.108.12.17. Sending 5.16.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! .108.11.15.108.108.14.108.108.1.1. Sending 5.1. round-trip min/avg/max = 16/16/16 ms R1#ping 141.9.1.13. round-trip min/avg/max = 16/17/20 ms R1#ping 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).108. 100-byte ICMP Echos to 141.1. Sending 5. Example 8-92 Pinging Remote Networks on R1 R1#ping 141.18.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/16 ms R1#ping 141.108.108. Sending 5.8.108.108.9. round-trip min/avg/max = 12/14/16 ms R1#ping 141.1 Type escape sequence to abort.14. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1. 100-byte ICMP Echos to 141.10.12. round-trip min/avg/max = 16/16/16 ms R1#ping 141.

21. 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.108. round-trip min/avg/max = 12/13/16 ms R1#ping 141. round-trip min/avg/max = 12/14/17 ms R1#ping 141.1.20.1 Type escape sequence to abort.1 Type escape sequence to abort.1 Type escape sequence to abort.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).21.108. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).23. "Answers to Review Questions.332 - .22.108. 100-byte ICMP Echos to 141. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.22.108. Sending 5.19. round-trip min/avg/max = 16/16/16 ms R1#ping 141. Sending 5.108.1.108. 100-byte ICMP Echos to 141. Sending 5.108.1 Type escape sequence to abort. Sending 5.108. 100-byte ICMP Echos to 141." 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. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).20.1.108. round-trip min/avg/max = 16/16/16 ms R1# Review Questions The answers to these question can be found in Appendix C. 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? . round-trip min/avg/max = 16/16/16 ms R1#ping 141.1 Type escape sequence to abort. Sending 5. round-trip min/avg/max = 12/15/17 ms R1#ping 141.108.23. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 141. 100-byte ICMP Echos to 141.19.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).

Table 8-3. 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.CCNP Practical Studies: Routing Summary Redistribution from one routing protocol to another has been extensively covered in this chapter.333 - . "CCNP Routing Self-Study Lab. known as the autonomous domain. Useful for determining other paths available on an EIGRP router. static routing. Tests IP connectivity. Disables updates sent outbound but still listens to updates." Table 8-3 summarizes the most important commands used in this chapter. Enables EIGRP routing under a common administrative control. The issues of routing loops and metric conversion from one routing protocol to another have been demonstrated. Enables redistribution. You can have more than one OSPF process ID running. Displays the EIGRP topology table. and you should now have the skills necessary to enable any form of route redistribution. Mastering distribution lists. . 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. Enables OSPF routing. Displays the complete IP routing table. Enables or disables an interface. The process ID is local to the router. In such a situation. Routing between classless and classful domains is one of the major learning tools you must master quickly in any IP network. Disables automatic summarization. All hardware interfaces are shut down by default. information can be controlled to ensure that the network is routing IP as correctly and efficiently as possible. See Table 8-2 for a complete listing of available options. and route maps enables you to avoid routing loops and ensure that full IP connectivity still exists.

.

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.

- 335 -

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.

- 336 -

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.

- 337 -

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).

- 338 -

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.)

- 339 -

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.

- 340 -

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

- 341 -

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

- 342 -

0.0.1 ip host R4 133.33.0.1.33.0.0.1.0.206.0 access-list 1 permit 9.0 access-list 1 permit 4.1.33.1 ip host R1 133.33.202.206.255.33.1.1 peer-group ibgpnetwork neighbor 133.5 weight 200 no auto-summary ! ip classless ip ospf name-lookup ! access-list 1 permit 1.33.1 ip host R2 133.0.33.1 ip host R3 133.1 peer-group ibgpnetwork neighbor 133.201.1 route-map setattributes in neighbor 171.0.202.0 access-list 1 permit 6.0 ip ospf network point-to-point .33.0 access-list 1 permit 2.0 access-list 1 permit 8.1.108.202.0 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.0.204.0.255. Example 9-3 R2's Full Working Configuration hostname R2 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.1 ip host R5 133.108.33.33.0.1 peer-group ibgpnetwork neighbor 133.1.205.203.0.203.204.108.0.205.0 access-list 1 permit 5.0.1 remote-as 1024 neighbor 171.108.33.1 peer-group ibgpnetwork neighbor 171.0.5 remote-as 1024 neighbor 171.0.1 255.0.5 route-map setattributes in neighbor 171.CCNP Practical Studies: Routing neighbor 133.108.1 weight 100 neighbor 171.1 peer-group ibgpnetwork neighbor 133.0 access-list 1 permit 7.1 ! interface Loopback0 ip address 133.343 - .33.0 access-list 1 permit 3.108.0.

33.255.255.255.255.344 - .33.33.33.33.33.255.255.33.255.1 255.0 ip ospf network point-to-point ! interface Loopback7 ip address 133.3.33.1 255.255.255.7.1 255.255.255.33.29.33.30.255.26.255.128 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 133.28.0 ip ospf network point-to-point ! interface Loopback6 ip address 133.31.1 255.0 ip ospf network point-to-point ! interface Loopback3 ip address 133.255.252 ! interface Serial1/2 no ip address shutdown .CCNP Practical Studies: Routing ! interface Loopback1 ip address 133.7.255.255.0 ip ospf network point-to-point ! interface Loopback2 ip address 133.9 255.24.0 ip ospf network point-to-point ! interface Loopback5 ip address 133.0 ip ospf network point-to-point ! interface Loopback4 ip address 133.1 255.0 ip ospf network point-to-point ! interface Ethernet0/0 description VLAN 200 (OSPF Area 200) ip address 133.255.252 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 133.1 255.33.1 255.255.255.255.255.1 255.0 ip ospf network point-to-point ! interface Loopback8 ip address 133.1 255.255.27.2 255.25.

0.255.0 network 133.1 0.255.1 ! interface Loopback0 ip address 133.1 0.0.202.1 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.205.345 - .0 255.255.33.3.0 area 0 ! router bgp 1 no synchronization neighbor 133.2 0.201.206.33.0.7.33.33.4.1 ip host r2 133.0 area 0 network 133.202.33.33.1 ip host r4 133.33.33.0 ip ospf network point-to-point ! interface Ethernet0 description VLAN 300 (OSPF Areas 300) ip address 133.1 ip host R6 133.1 255.33. Example 9-4 R3's Full Working Configuration hostname R3 ! enable password cisco ip subnet-zero no ip domain-lookup ip host r1 133.202.203.33.0 area 0 network 133.33.0.248.0 0.CCNP Practical Studies: Routing ! interface Serial1/3 no ip address shutdown ! router ospf 1 router-id 133.128 no ip directed-broadcast ip ospf priority 255 ip policy route-map sendtraffic media-type 10BaseT ! interface Ethernet1 no ip address .0.204.33.0.33.24.0 area 200 network 133.1 ip host R5 133.33.0.1 ip host R3 133.1 remote-as 1 neighbor 133.1 area 0 authentication message-digest area 200 stub area 200 range 133.0.24.33.1 255.255.203.255 area 200 network 133.7.33.255.201.0.7.201.9 0.33.

255.0.0.203.0 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 .13 0.255.7.201.0.203.33.33.7.0.33.6 255.7.6 0.346 - .1 update-source Loopback0 ! ip local policy route-map sendtraffic ip ospf name-lookup ! access-list 1 permit 0.0 area 350 network 133.0 area 300 network 133.7.255.1 area 0 authentication message-digest network 133.0.255.201.252 no ip directed-broadcast fair-queue 64 256 0 clockrate 2000000 ! interface Serial2 description Serial Link to R1 S1/1 ip address 133.0 area 0 ! router bgp 1 no synchronization neighbor 133.7.252 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 133.0.255.1 0.0.0.13 255.0.4.10 0.33.33.33.CCNP Practical Studies: Routing no ip directed-broadcast shutdown ! interface Serial0 description Serial Link to R2 S1/1 bandwidth 125 ip address 133.33.33.10 255.255.0.252 ip ospf authentication-key ccnp ip ospf hello-interval 25 clockrate 125000 ! interface Serial3 shutdown ! router ospf 1 router-id 133.1 0.1 remote-as 1 neighbor 133.33.0 area 0 network 133.33.0.33.0 area 0 network 133.0.7.

11.255.33.5.0 ip ospf network point-to-point ! interface Ethernet0 description VLAN 400 (OSPF Area 400) ip address 133.255.202.1 255.206.7.1 ip host R5 133.1 255.10.14 255.255.204.255.2 255.255.33.255.204.347 - .1 ip host r4 133.224 ! interface Serial0 no ip address shutdown ! interface Serial1 description Serial Link to R3 S1 ip address 133.33.1 ip host r3 133.33. Example 9-5 R4's Full Working Configuration hostname R4 ! enable password cisco ip subnet-zero no ip domain-lookup ip host R6 133.33.1 ip host R1 133.0.33.205.33.1 ! cns event-service server ! interface Loopback0 ip address 133.33.203.255.33.33.255.252 ! interface Serial2 description Serial Link to R5 S0 ip address 133.2 255.0 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 133.255.33.1 ip host R2 133.201.0 ! interface Serial3 description Serial Link to R6 S1 ip address 133.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.255.0 distribute-list 3 out ! .33.

205.0 access-list 6 permit 133.0 access-list 3 permit any access-list 4 permit 133.0 area 350 network 133.1.0 Null0 ip route 133.0 255.0.33.201.255.0.255.0 access-list 1 deny 133.255.0 255.0 255.0.1 0.4.0 access-list 4 permit 133.33.33.0 access-list 6 permit 133.1 0.0 Null0 ip route 133.0 access-list 5 deny 133.33.33.0 access-list 3 deny 133.0 255.33.255.206.33.0 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 133.5.33.0.33.255.14 0.33.10.0 Null0 ip route 133.33.255.0.204.0 access-list 1 deny 133.0 255.9.33.33.33.0 access-list 2 permit 133.CCNP Practical Studies: Routing router ospf 1 router-id 133.33.255.33.10.1 remote-as 1 neighbor 133.204.33.33.6.33.204.1 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 133.205.11.1 update-source Loopback0 ! ip classless ip route 133.206.0 access-list 3 deny 133.0.255.3.0 Null0 no ip http server ip ospf name-lookup ! access-list 1 deny 133.33.0 distribute-list 1 out ! router bgp 1 no synchronization neighbor 133.8.7.0 Null0 ip route 133.0 access-list 5 deny 133.348 - .33.33.0 route-map igrpnets permit 10 match ip address 2 ! route-map eigrpnets permit 10 match ip address 4 .8.33.11.0 access-list 6 permit 133.5.6.0 access-list 2 permit 133.206.33.33.0 access-list 2 permit 133.0.7.0 access-list 5 permit any access-list 6 permit 133.0 area 350 network 133.33.0 access-list 3 deny 133.33.9.7.0 access-list 1 permit any access-list 2 permit 133.12 access-list 6 permit 133.201.33.6.255.33.255.5.33.33.

1 255.33.201.1 ! interface Loopback0 ip address 133.255.33.33.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.8.0 ! interface Ethernet0 description VLAN 500 (EIGRP AS 1) ip address 133.201.1 ip host R2 133.33.1 255.255.0.202.33.203.204.1 remote-as 1 neighbor 133.1 ip host R1 133.349 - .255.205.205.0 clockrate 125000 ! interface Serial1 shutdown ! router igrp 1 network 133.33.33.33.201. Example 9-6 R5's Full Working Configuration hostname R5 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.255.255.33.255.33.1 ip host R4 133.1 ip host R5 133.33.255.0 ! interface Serial0 description Serial Link to R4 S2 ip address 133.1 255.33.1 255.0 ! interface Ethernet1 description VLAN 550 (EIGRP AS 1) ip address 133.255.10.206.1 update-source Loopback0 ! .1 ip host R3 133.9.33.0 ! router bgp 1 no synchronization neighbor 133.

255.33.1 ip host R2 133.205.206.1 255.0 ! router eigrp 1 redistribute eigrp 2 route-map allowout passive-interface Ethernet0 passive-interface Loopback0 passive-interface Serial0 network 133.6.255.33.255.0 ! interface Ethernet0 description VLAN 600 (EIGRP AS 2) ip address 133.1 remote-as 1 neighbor 133.201.33.33.33.203.0 255.33.33.1 ! interface Loopback0 ip address 133.16.255.33.255.1 255.1 ip host R3 133.1 ip host R5 133.1 255.0.11.201.0 ! router bgp 1 no synchronization neighbor 133.201.255.0 distance eigrp 90 90 ! router eigrp 2 passive-interface Serial1 network 133.CCNP Practical Studies: Routing ip classless ip route 133.1 ip host R4 133.204.0.1 ip host R1 133.255.202.33.206.350 - .33.33.33.33.0 ! interface Serial0 shutdown ! interface Serial1 description Serial Link to R4 S3 ip address 133.33.206.240.0 Serial0 ! line con 0 line aux 0 line vty 0 4 ! end Example 9-7 displays R6's full working configuration.1 update-source Loopback0 ! ip classless ! access-list 2 permit 133.0 . Example 9-7 R6's Full Working Configuration hostname R6 ! enable password cisco ! ip subnet-zero no ip domain-lookup ip host R6 133.33.

0.0 255.0 Null0 ip route 100.0 255.0.0 ! interface Serial0 description Serial Link to R1 S1/2 ip address 171.0 Null0 .0.0.255.0.0 Null0 ip route 5.0.0.0.0.0.100.0.0.0.0 255.0.108.100.6.0.0 255.0.100.2 remote-as 1 neighbor 171.0 Null0 ip route 6.0.0 0.0.0 255.0.0.0 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.255.0.0.255.0.0 Null0 ip route 11.0.0 255.0.2 remote-as 1024 neighbor 171.0.255.0.0 255.255.0.0 255.0.0 255.1.0.0 Null0 ip route 3.0 Null0 ip route 8.0.0.0 Null0 ip route 4.0.255.108.0.0.0.CCNP Practical Studies: Routing access-list 2 permit 133.0.0 255.0.0.100.0 255.0.0 Null0 ip route 101.252 clockrate 125000 ! interface Serial1 shutdown ! router bgp 1024 redistribute static neighbor 141.255. 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 141.108.0 255.0.1 255.0 Null0 ip route 7.0 255.2 default-originate no auto-summary ! ip classless ip route 0.0 Null0 ip route 141.0 Null0 ip route 102.0 Null0 ip route 2.0 255.0.108.0 Null0 ip route 10.0.255.0 Null0 ip route 142.0.108.0.1 255.1.0.0.0.0.0.1.0.0.0 255.0.1.108.0 255.0.0 255.33.0.0.0 Null0 ip route 144.0.0.0 255.0 Null0 ip route 1.0.0.1.0.255.0.0 Null0 ip route 141.0 Null0 ip route 143.0.0.351 - .0.0.

0 0 0 0 4 255.0.252 ! interface Serial0 description Serial Link to R1 S1/3 ip address 171.0.252 ! interface Serial1 shutdown ! interface Serial2 shutdown ! interface Serial3 shutdown ! router bgp 1024 bgp log-neighbor-changes redistribute static neighbor 141.0 255.0.0.0 255.255.0.0 0.1.0.0 Null0 ip route 1.255.255.0.255.0 Null0 ip route 6.0.108.0 Null0 ip route 4.0.0.0 255.1.0 255.5 255.0 255.0 148.0 Null0 ip route 11.0.2 255.0.0.0.0 255.0 Null0 .0 Null0 ip route 5.0 255.6 default-originate ! ip classless ip route 0.0 Null0 ip route 7.0.0.0.0 147.1.0.0.0.0.0.0.0.255.0.6 remote-as 1 neighbor 171.0.100.0.0.0.100.0 255.0.0 255.0.255.108.0.0.0.0 255.0.0.0. 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 141.0.0.0 255.0.255.0 Null0 ip route 2.1 remote-as 1024 neighbor 171.1.0 149.0.100.0.0 255.255.100.0.0.0 146.0.0 Null0 Null0 Null0 Null0 Null0 Example 9-9 displays ISP2's full working configuration.100.108.0.352 - .108.1.0 255.0.0 Null0 ip route 10.108.0 Null0 ip route 8.0.0 Null0 ip route 3.CCNP Practical Studies: Routing ip route ip route ip route ip route ip route ! line con line aux line vty ! end 145.0.0.255.0.0.0 255.0.0.

255.0.0.0.255.0.0.0. (The following configuration is also truncated.0 255.100.0.0.0 255.0 255.0 Null0 0 0 0 4 Example 9-10 displays the full working configuration of the Catalyst 6509 switch.0 Null0 141.0.0.0.100.0.7 set ip route 0.0 255.0 Null0 142.255.100.33.0.0 255.100.0.5-5-4.0.0 255.0 133.0 Null0 145.0.0 Null0 141.100.0 255.0/0.0.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 100.0 Null0 143.2/255.255.353 - .0 255.0 255.255.255.255. 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 100 133.0.0.0 255.100.0.0 Null0 144.0.0.33.0 Null0 148.1.0 Null0 102.0 Null0 147.1.0.0.bin ! #mls set mls enable ipx ! # default port status is enable ! #module 1 : 2-port 1000BaseX Supervisor .0 Null0 101.0.108.255.33. the #s are comment lines in Catalyst 6500 series software placed by Catalyst IOS).0 255.0.0.0 255.0.0.0.100.255.0.255.1.100.0.0 Null0 146.1 ! #set boot command set boot config-register 0x102 set boot system flash bootflash:cat6000-sup.100.0 255.255.0.0.248 133.0.0.0 Null0 149.255.

33.6.0/24 [110/1000] via 133.6. Serial1/1 O E2 133.6. 00:13:18.33. 00:03:35. Serial1/0 O 133. Serial1/1 .7. Serial1/1 O E2 133. 00:03:35. Any network designer must use common verification tools to ensure that IP connectivity is achieved.33. Serial1/1 O IA 133.2. debug.7.0/24 [110/1601] via 133.33.33.33. Serial1/1 [110/1600] via 133.33.6.0/24 [110/801] via 133. OSPF. and telnet commands.33. 00:13:17.33. 00:03:34.33. Serial1/0 O E2 133.2.33. show ip route.6.7. Cisco IOS contains bugs and caveats.33.0/16 is variably subnetted.7. 00:03:34.0/24 [110/100] via 133.4.203.204. BGP tables are presented to display BGP attributes and next hop path taken from each router. so even correct configurations do not always guarantee connectivity.33.205. Serial1/1 O IA 133.0/25 [110/810] via 133.202.7. 00:03:35. 00:13:17.7. Example 9-11 displays the IP (OSPF) routing table on R1.6. ping.33.354 - .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. Some ping and telnet requests from each router are also shown.0/24 [110/801] via 133. Finally.33. 6 masks O IA 133.7.6.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 3/11.8. The first command used. You should familiarize yourself thoroughly with the common show.33.33.33.33. Serial1/1 O 133.33. 28 subnets. ping. 00:03:34.2. Serial1/1 O IA 133.7. 00:13:18.5.33.8/30 [110/1600] via 133.33. 00:03:34.0/25 [110/1000] via 133.3. This section starts by looking at the IGP network namely.6. and IGRP. 00:03:34. Sample show.7.206.0/24 [110/1000] via 133.7. Example 9-11 show ip route ospf on R1 R1#show ip route ospf 133. and telnet Commands The following displays are presented here to demonstrate IP connectivity among all six routers.33.6.6.7.0/24 [110/100] via 133.7. Serial1/0 O 133. as displayed in Example 9-10. Serial1/1 O E2 133. EIGRP.0. is the most widely used command on Cisco IOS routers.0/27 [110/1610] via 133.7.33.

33.1 Type escape sequence to abort. Sending 5.10.) .206. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133.33.33. 100-byte ICMP Echos to 133.33.33.2 133. 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 133.33. as required.33.1.7.7.206.6.7.0/24.33.6.205.33.7.206.1. 00:03:36.7.203.1 Type escape sequence to abort.1 Type escape sequence to abort.0/24 [110/100] via 133. 00:02:42.7. round-trip min/avg/max = 1/1/4 ms R1#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5. 133.6.204.33. The loopbacks in Table 9-2 are used to ping from R1.205. round-trip min/avg/max = 28/31/32 ms R1#ping 133.202.0/24 [110/20] via 133.6. Sending 5. 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. round-trip min/avg/max = 16/16/20 ms R1#ping 133.9.0/24 as 1000.0/24. 100-byte ICMP Echos to 133.33.33.33. 00:03:36.1 Type escape sequence to abort.1 Type escape sequence to abort.203.33.33. Sending 5.201. and 133.7.1. round-trip min/avg/max = 32/32/32 ms Example 9-14 displays IP connectivity to the remaining IP interfaces as described in Table 9-1.0/21 [110/801] via 133. The OSPF adjacency on R1 is displayed in Example 9-12.33.202.201.0/24 [110/20] via 133.7.6. Serial1/1 133. (Note the local interfaces on R1 are not displayed or pinged from R1. the remote neighboring routers are listed as R2 and R3 in Example 9-12.33.33.33.33.33.33.33. Serial1/1 133. Serial1/1 133.2.1. 100-byte ICMP Echos to 133. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 00:02:41. Example 9-13 Pinging Local Loopbacks on R1 R1#ping 133.24. Sending 5. Serial1/1 133.11. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5. round-trip min/avg/max = 32/32/36 ms R1#ping 133. Serial1/0 R1 has an OSPF cost metric to networks 133.6 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. 00:03:35.1.1 Type escape sequence to abort.33.355 - . round-trip min/avg/max = 16/16/16 ms R1#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.3.204.CCNP Practical Studies: Routing O O O O O E2 E2 E2 IA IA 133.12/30 [110/1600] via 133.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).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 = 28/29/32 R1#ping 133.2. Sending 5. 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/16/20 R1#ping 133.13 Type escape sequence to abort.10.10.11. Sending 5. Sending 5.3.2. Sending 5.14 Type escape sequence to abort.3.33. round-trip min/avg/max = 32/32/36 R1#ping 133.33.1 Type escape sequence to abort.7. round-trip min/avg/max = 16/16/20 R1#ping 133.33.7.4.33.33.33. round-trip min/avg/max = 16/20/28 R1#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.33.33.6.1. Sending 5.2 Type escape sequence to abort.33.1. round-trip min/avg/max = 32/32/33 R1#ping 133.13. round-trip min/avg/max = 16/16/20 R1#ping 133.10.2 Type escape sequence to abort. round-trip min/avg/max = 28/30/32 R1#ping 133.33.33. Sending 5.33. round-trip min/avg/max = 28/30/32 R1#ping 133.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).10 Type escape sequence to abort.11. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133. 100-byte ICMP Echos to 133.33. Sending 5.33. timeout is 2 seconds: !!!!! ms ms ms ms ms ms ms ms ms ms ms . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).7.1.2.1 Type escape sequence to abort.7.2 Type escape sequence to abort. Sending 5.7. 100-byte ICMP Echos to 133.10.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Sending 5. Sending 5.7.7.1.356 - . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133.33.9. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.11.33. Sending 5. 100-byte ICMP Echos to 133.10.1 Type escape sequence to abort.33.33.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).11.7. 100-byte ICMP Echos to 133.7.6 Type escape sequence to abort.CCNP Practical Studies: Routing Example 9-14 Pinging LAN/WAN Interfaces from R1 R1#ping 133. 100-byte ICMP Echos to 133.14.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/16/16 R1#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.7. round-trip min/avg/max = 28/29/32 R1#ping 133. Sending 5. 100-byte ICMP Echos to 133.4.33.9 Type escape sequence to abort. 100-byte ICMP Echos to 133.

1.33. Sending 5.1/29. Hello 10. Network Type POINT_TO_POINT. line protocol is up Internet Address 133.1.33. Retransmit 5 Hello due in 00:00:05 Neighbor Count is 0.10.33. Sending 5. round-trip min/avg/max = 16/16/16 R1#ping 171.357 - .8.1 No backup designated router on this network Timer intervals configured. Hello 10. 100-byte ICMP Echos to 171. Retransmit 5 Hello due in 00:00:04 Neighbor Count is 1. Wait 40. Adjacent neighbor count is 1 . 100-byte ICMP Echos to 133.201. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1/0 is up. Router ID 133.10. round-trip min/avg/max = 32/32/36 R1#ping 133.108.33.33.201.1 Type escape sequence to abort.2.33.1 Type escape sequence to abort. Router ID 133. 100-byte ICMP Echos to 133.33.8. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Area 100 Process ID 1.5 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 0 percent (5/5) R1#ping 133. Sending 5. 100-byte ICMP Echos to 133.1. Cost: 10 Transmit Delay is 1 sec.1.33.1.33.108. Dead 40.10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.2.8. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Dead 40.1.33. Sending 5.9.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. round-trip min/avg/max = 32/37/48 R1#ping 133. Interface address 133.1 Type escape sequence to abort.5. 100-byte ICMP Echos to 133.7.33.CCNP Practical Studies: Routing Success rate is 100 percent (5/5).1/30.1.10.2 Type escape sequence to abort. round-trip min/avg/max = 16/17/20 R1#ping 133.9. Network Type BROADCAST. State DR. 100-byte ICMP Echos to 133. Sending 5. Sending 5. round-trip min/avg/max = 16/16/20 R1#ping 171.108. Priority 1 Designated Router (ID) r1. 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. Sending 5.8.2 Type escape sequence to abort. 100-byte ICMP Echos to 171. Cost: 800 Transmit Delay is 1 sec. Area 0 Process ID 1.108. Wait 40.1. Timer intervals configured.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. line protocol is up Internet Address 133.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 32/32/33 R1#ping 133.33. State POINT_TO_POINT.1 Type escape sequence to abort.33.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).

358 - .1. Wait 40. line protocol is up Internet Address 133. Network Type POINT_TO_POINT. line protocol is up Internet Address 133. Cost: Transmit Delay is 1 sec.33. Router ID 133.33. Cost: Transmit Delay is 1 sec. Cost: Transmit Delay is 1 sec.1/24. Timer intervals configured.201. State POINT_TO_POINT. Network Type POINT_TO_POINT. Dead 40.16. line protocol is up Internet Address 133. Area 100 Process ID 1. Hello 25. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Dead 40.18. Timer intervals configured.33.201. State POINT_TO_POINT. using default key id 0 Loopback1 is up. Cost: Transmit Delay is 1 sec. Area 100 Process ID 1. Area 0 Process ID 1. State POINT_TO_POINT.33.1/24. Router ID 133. Network Type POINT_TO_POINT.1. Timer intervals configured.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback4 is up.1.1/24. Timer intervals configured. Router ID 133.20.201.1.33.1/24. Hello 10.201. Area 100 Process ID 1.5/30.33. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Network Type POINT_TO_POINT. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0.1/24. State POINT_TO_POINT. line protocol is up Internet Address 133. Router ID 133. Cost: Transmit Delay is 1 sec. Area 100 Process ID 1. Wait 40. Cost: 800 1 1 1 1 1 1 .7.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback2 is up. using default key id 0 Serial1/1 is up. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback5 is up. Wait 40.33. Router ID 133. Network Type POINT_TO_POINT. Network Type POINT_TO_POINT. Wait 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback3 is up. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Network Type POINT_TO_POINT. Dead 40. line protocol is up Internet Address 133. Hello 10.201. Retransmit 5 Hello due in 00:00:18 Neighbor Count is 1. Dead 40. Area 100 Process ID 1.33. Cost: Transmit Delay is 1 sec.1. using default key id 0 Loopback0 is up. Retransmit 5 Hello due in 00:00:00 Neighbor Count is 0. Wait 100. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. State POINT_TO_POINT. Dead 40.19. line protocol is up Internet Address 133. Timer intervals configured.33. Hello 10. Wait 40.33.1/24. Router ID 133.33. Hello 10.33.201.1. Hello 10. Timer intervals configured. line protocol is up Internet Address 133.1. Dead 100. State POINT_TO_POINT. Area 0 Process ID 1. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.CCNP Practical Studies: Routing Adjacent with neighbor r2 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured.201.201.17. Router ID 133.

206. . Network Type POINT_TO_POINT. 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. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback6 is up.7.10. State POINT_TO_POINT.10.10. Router ID 133. Serial1/1 O E2 133. Serial1/1 O IA 133. 00:05:29. Retransmit Hello due in 00:00:00 Neighbor Count is 0. and whether authentication is in use. Timer intervals configured. Wait 40. such as Hello and dead intervals.33.33. 00:06:22. Serial1/1 O E2 133.33.0/24 [110/100] via 133. Hello 10.33. 17:03:37.10.7. 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. Serial1/1 O E2 133.33. Wait 40.33.359 - . Serial1/1 O IA 133.33.11.7. Dead 40. 00:05:29.0/24 [110/20] via 133.10.0/21 [110/801] via 133. 17:03:37.10.7. Hello 10.33.0/24 [110/1601] via 133.10.7. Wait 40.0/24 [110/801] via 133.CCNP Practical Studies: Routing Transmit Delay is 1 sec. Example 9-16 show ip route ospf on R2 R2#show ip route ospf 133.7. Wait 40.201.33.33.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0.33.21. with the same command (show ip ospf interface). Serial1/1 O E2 133.22.1. Transmit Delay is 1 sec.1/24.201.0/16 is variably subnetted. 00:06:22.16.33. Timer intervals configured.33. the OSPF neighbor states.203. Serial1/1 O E2 133.1/24.7.33. 00:06:23.33. 00:06:21. line protocol is up Internet Address 133.10.7.4/30 [110/864] via 133.7.33.0/24 [110/100] via 133.33. Serial1/1 O IA 133.1/24.33.33.0/24 [110/1000] via 133. line protocol is up Internet Address 133. Hello 10.0/24 [110/20] via 133.33.23.33. 17:03:37.33. 00:06:21. 00:06:22.33. line protocol is up Internet Address 133. 00:06:22.1. 37 subnets.0/24 [110/1000] via 133.1. State POINT_TO_POINT.0/27 [110/1610] via 133. Dead 40. State POINT_TO_POINT.0/25 [110/810] via 133.201.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback7 is up.10. Serial1/1 O E2 133.4.7.0/24 [110/801] via 133.1. 00:06:21.10. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback8 is up. Serial1/0 O 133.5. Network Type POINT_TO_POINT.33. Transmit Delay is 1 sec.10. Router ID 133.0.33. Serial1/1 O 133.10.7. Example 9-16 displays the IP OSPF routing table on R2.7.7.33. 00:06:23.33.33. 6 masks O IA 133.205. Transmit Delay is 1 sec.7. Serial1/0 O 133. Serial1/1 O IA 133.10.33.0/24 [110/100] via 133. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Dead 40.12/30 [110/1600] via 133.201.1. Network Type POINT_TO_POINT.9. 00:06:22.33. Timer intervals configured. Retransmit Hello due in 00:00:00 Neighbor Count is 0.6.7.33.33.1.10. Timer intervals configured. Hello 10.8.33. Dead 40.7.33. Area 100 Process ID 1. Area 100 Process ID 1.7.33. Router ID 133.204. Area 100 Process ID 1.33. Serial1/1 O E2 133.1. 00:06:21.0/29 [110/810] via 133. Serial1/1 O IA 133.33.7. You can verify OSPF area assignments and other details. State POINT_TO_POINT.

360 - . timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Dead 40.206.33.1. 100-byte ICMP Echos to 133.204. Dead 40. Area 0 Process ID 1.1. State DR. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Area 200 Process ID 1.33.1. Example 9-18 show ip ospf interface on R2 R2#show ip ospf interfac Ethernet0/0 is up.1. line protocol is up Internet Address 133. Router ID 133.33.33.1 Type escape sequence to abort.33.33. round-trip min/avg/max = 1/2/4 ms R2#ping 133.CCNP Practical Studies: Routing Example 9-17 Ping Request on R2 to Remote Networks R2#ping 133. 100-byte ICMP Echos to 133.202. line protocol is up Internet Address 133. Cost: 800 Transmit Delay is 1 sec.33.7. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).205.1 Type escape sequence to abort. round-trip min/avg/max = 16/16/20 ms R2#ping 133. Interface address 133. line protocol is up Internet Address 133.203.33.202. round-trip min/avg/max = 16/16/16 ms R2#ping 133. Sending 5. Priority 1 Designated Router (ID) 133. Retransmit 5 Hello due in 00:00:08 Neighbor Count is 1. Sending 5. Adjacent neighbor count is 1 Adjacent with neighbor r1 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Sending 5. Wait 40.33.1/25. Sending 5.202.3.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Router ID 133. round-trip min/avg/max = 16/16/20 ms R2#ping 133.1.206. Network Type BROADCAST. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).9/30. Retransmit 5 Hello due in 00:00:09 Neighbor Count is 0.1 Type escape sequence to abort. using default key id 0 Serial1/1 is up.2/30. 100-byte ICMP Echos to 133.33. 100-byte ICMP Echos to 133.7.33.1. State POINT_TO_POINT.202.33.201. Timer intervals configured.1. Hello 10.201.33.2. Hello 10. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Area 0 . Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1/0 is up. 100-byte ICMP Echos to 133.204.1.203. Sending 5. 100-byte ICMP Echos to 133.1 Type escape sequence to abort.1 No backup designated router on this network Timer intervals configured.33.33.3. Wait 40.1 Type escape sequence to abort. Cost: 200 Transmit Delay is 1 sec.205. round-trip min/avg/max = 32/32/32 ms Example 9-18 displays the output from the IOS show ip ospf interface command.33.33. round-trip min/avg/max = 32/32/36 ms R2#ping 133.202. Network Type POINT_TO_POINT.33.33.

Retransmit Hello due in 00:00:00 Neighbor Count is 0. line protocol is up Internet Address 133. Dead 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback2 is up. Timer intervals configured. line protocol is up Internet Address 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback6 is up. State POINT_TO_POINT. Area 200 Process ID 1. Retransmit Hello due in 00:00:00 Neighbor Count is 0.202.27. using default key id 0 Loopback1 is up.33. Router ID 133.1. Dead 40.1/24.33.33.33. Wait 40. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Router ID 133. Network Type POINT_TO_POINT. Hello 10.1. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback4 is up.25. Area 200 Process ID 1. Area 0 Process ID 1.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Wait 40. Transmit Delay is 1 sec.1/24. line protocol is up Internet Address 133. Transmit Delay is 1 sec. Dead 40.33.1.1.33.1/24. Transmit Delay is 1 sec. Router ID 133. Area 200 Process ID 1. Wait 40. Area 200 Process ID 1.202.1. 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 . Network Type POINT_TO_POINT. Transmit Delay is 1 sec. Network Type POINT_TO_POINT. Timer intervals configured.202. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Router ID 133.202. Timer intervals configured. State POINT_TO_POINT. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Router ID 133.361 - . Router ID 133. State POINT_TO_POINT. State POINT_TO_POINT. State POINT_TO_POINT. Hello 10.33.1/24. Hello 10. Wait 40. Network Type POINT_TO_POINT. Network Type POINT_TO_POINT. line protocol is up Internet Address 133.1/24. Wait 40.202. Hello 10.1. Wait 40. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback3 is up. Timer intervals configured. Dead 40. State POINT_TO_POINT. Timer intervals configured.33. Retransmit Hello due in 00:00:08 Neighbor Count is 1. State POINT_TO_POINT. Dead 40. line protocol is up Internet Address 133.33.202.33.202. Hello 10.26.202. Hello 10. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Dead 40.CCNP Practical Studies: Routing Process ID 1. line protocol is up Internet Address 133. Hello 10.33. Transmit Delay is 1 sec. Transmit Delay is 1 sec.28. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback5 is up.24. Timer intervals configured.1. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Wait 40. Router ID 133. using default key id 0 Loopback0 is up. Transmit Delay is 1 sec. Network Type POINT_TO_POINT. Area 200 Process ID 1. Timer intervals configured.1/24.33. Network Type POINT_TO_POINT. Dead 40.

00:07:08.1 133.7. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback8 is up. Network Type POINT_TO_POINT.0/29 [110/74] via 133.7.9. Serial2 O 133.201.7.33.202. Timer intervals configured.5.0.14.7.33. Serial1 O E2 133. State POINT_TO_POINT.5. Router ID 133.33.33.1.33.0/24 [110/100] via 133.7.33. Hello 10. Serial1 O 133.33. .7.33.1/24. Area 200 Process ID 1. Serial0 O 133. (Refer to the full configuration in Example 9-4).33.0/30 [110/864] via 133.6. Serial0 O E2 133.7.7. 00:06:10.10.5.33.33.9.14.33. Serial2 O IA 133.0/24 [110/100] via 133.5.33.7.0/25 [110/1000] via 133. Serial1 O E2 133.7. 29 subnets. Transmit Delay is 1 sec.33. Transmit Delay is 1 sec.33. Hello 10.33.0/24 [110/801] via 133.0/24 [110/65] via 133.33.33.33. Area 200 Process ID 1. Hello 10. 00:07:09.1.1/24. Dead 40.0/21 [110/801] via 133.202.33.33.1.10 Interface Serial1/0 Serial1/1 Example 9-20 displays the IP (OSPF) routing table on R3.30.33. Router ID 133.33. Retransmit Hello due in 00:00:00 Neighbor Count is 0. 17:04:09.33. Wait 40. 00:07:08.33. Network Type POINT_TO_POINT.7.11.33. State POINT_TO_POINT. Area 200 Process ID 1.7. Retransmit Hello due in 00:00:00 Neighbor Count is 0. Serial1 O E2 133.0/24 [110/801] via 133.0/24 [110/100] via 133.33.9.14.0/24 [110/20] via 133. 6 masks O 133.14.24. 00:07:08.16.202. 17:04:09. Serial0 Example 9-21 displays a successful ping request to all routers by using the names configured on R3. Retransmit Hello due in 00:00:00 Neighbor Count is 0.33.33. Router ID 133.1.362 - .9. Wait 40. Transmit Delay is 1 sec.7. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) R2# Example 9-19 displays the OSPF neighbors on R2.7.7. 00:07:08.3.14.33. 00:07:08.205. Wait 40.33. line protocol is up Internet Address 133.206. line protocol is up Internet Address 133. Example 9-20 show ip route ospf on R3 R3#show ip route ospf 133.14.202.14.33.14.33.7.0/24 [110/20] via 133.7.33. Timer intervals configured.1/24.33.33.33.33. 00:07:09. 00:07:08.0/24 [110/1000] via 133. Serial1 O 133.33.5. Serial2 O IA 133.0/16 is variably subnetted. 00:07:08. Dead 40. Serial1 O E2 133.8.0/27 [110/810] via 133.7. 00:07:08.33.7. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback7 is up. Serial2 O IA 133.CCNP Practical Studies: Routing Internet Address 133.33.29.0/21 [110/65] via 133.204. Network Type POINT_TO_POINT. 00:07:08. Serial1 O E2 133. Serial1 O IA 133. State POINT_TO_POINT.0/24 [110/1000] via 133.31. Serial1 O E2 133. 17:04:10. 00:06:10. Timer intervals configured.14. Dead 40. 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.

Sending 5. Network Type BROADCAST. Router ID 133. 100-byte ICMP Echos to 133. maximum is 0 msec Neighbor Count is 0.CCNP Practical Studies: Routing Example 9-21 Pinging All Loopbacks Using Names on R3 R3#ping r1 Type escape sequence to abort.203. Sending 5. line protocol is up Internet Address 133. Priority 255 Designated Router (ID) r3. line protocol is up Internet Address 133.1 No backup designated router on this network Timer intervals configured.1.4. Router ID 133. Retransmit 5 Hello due in 00:00:04 Index 1/1. Hello 10. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0.363 - . Example 9-22 show ip ospf interface on R3 R3#show ip ospf interface Ethernet0 is up.33.205.1.33.33.204. 100-byte ICMP Echos to 133. round-trip min/avg/max = 16/16/16 ms R3#ping r3 Type escape sequence to abort. Network Type POINT_TO_POINT. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).203.1. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1. Cost: 10 Transmit Delay is 1 sec. Hello 10.1.33.201. Sending 5.33. maximum is 0 Last flood scan time is 0 msec.1/24.33.33.1. 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. 100-byte ICMP Echos to 133. Sending 5.33. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/17/20 ms R3#ping r5 Type escape sequence to abort. Sending 5. Sending 5. round-trip min/avg/max = 1/2/4 ms R3#ping r4 Type escape sequence to abort. Wait 40. Retransmit 5 Hello due in 00:00:00 Index 3/5.1/25.202. Dead 40. round-trip min/avg/max = 32/33/36 ms R3#ping r6 Type escape sequence to abort. Area 300 Process ID 1. Interface address 133.203. Wait 40. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).4. 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.1. Cost: 1 Transmit Delay is 1 sec. State POINT_TO_POINT. Timer intervals configured. Dead 40.206.203.33. State DR. Area 0 Process ID 1.33.1. 100-byte ICMP Echos to 133.33. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). flood queue length 0 Next 0x0(0)/0x0(0) .

State POINT_TO_POINT. Area 350 Process ID 1. Dead 100. Cost: 64 Transmit Delay is 1 sec. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. maximum is 0 msec Neighbor Count is 0. Hello 10. Network Type POINT_TO_POINT. Retransmit 5 Hello due in 00:00:02 Index 1/4. .7.203. Cost: 800 Transmit Delay is 1 sec. maximum is 0 msec Neighbor Count is 1.6/30.33. maximum is 9 Last flood scan time is 0 msec.7. Router ID 133. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1. Retransmit 5 Hello due in 00:00:01 Index 1/2. Network Type POINT_TO_POINT. Adjacent neighbor count is 1 Adjacent with neighbor r1 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. line protocol is up Internet Address 133. Cost: 800 Transmit Delay is 1 sec.1. Area 0 Process ID 1. Wait 100. IGRP.33. maximum is 0 Last flood scan time is 0 msec. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1.33. maximum is 0 msec Neighbor Count is 1. Area 0 Process ID 1.1.33.10/30. using default key id 0 Serial0 is up.7. and EIGRP. Example 9-23 displays the full IP routing table on R4 including the BGP routes. Wait 40. Retransmit 5 Hello due in 00:00:02 Index 2/3. maximum is 9 Last flood scan time is 0 msec. line protocol is up Internet Address 133.CCNP Practical Studies: Routing Last flood scan length is 0. Dead 40. Dead 40. Timer intervals configured.364 - . using default key id 0 Serial1 is up.33. State POINT_TO_POINT.203. Router ID 133. Timer intervals configured. Timer intervals configured. Hello 25. using default key id 0 R4 is configured for three interior routing protocols: OSPF.1. line protocol is up Internet Address 133.33.203. State POINT_TO_POINT. Adjacent neighbor count is 1 Adjacent with neighbor r4 Suppress hello for 0 neighbor(s) Serial2 is up. Network Type POINT_TO_POINT. Adjacent neighbor count is 1 Adjacent with neighbor r2 Suppress hello for 0 neighbor(s) Message digest authentication enabled No key configured. Wait 40.13/30. maximum is 9 Last flood scan time is 0 msec. maximum is 0 msec Neighbor Count is 1. Router ID 133. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1. Hello 10.

13.201.0/30 is subnetted.33.OSPF external type 2. EX . Null0 S 133.1.0.33.108.33.4 [200/0] via 133.10. 00:19:02.33.201.1. N2 .33.33. Serial2 I 133.0.7.201.7.33. Serial3 O IA 133.100.1.0/27 is directly connected.202.7.33.33.0 [200/0] via 133.0.0.0/8 [200/0] via 133.33.13. 00:19:02.6.100.201.IS-IS inter area * .33. Serial1 O IA 133.33.201.0.0.33.201.201.201. 01:12:20 171. O . 01:12:21 B 146.0/29 [110/138] via 133. 01:12:20 B 8. Serial1 O IA 133.33.0.periodic downloaded static route Gateway of last resort is 133.201.205.201.201.33.8.1.7. Ethernet0 D 133.33.0.0.0/24 [100/8976] via 133. Serial1 O IA 133.7.IS-IS level-1. 01:12:20 B 3.0/24 [100/8576] via 133.33.EIGRP external.0.10. 34 subnets. 00:19:02. Serial2 C 133. L2 .100.0/8 [200/0] via 133.33.0.0/24 is directly connected. Serial1 S 133.0/24 is directly connected.33.1. Loopback0 I 133. 01:12:20 B 1.33.201. 6 masks C 133.1.33.33.201.33.33. 00:01:05.201.IS-IS.0/24 [110/129] via 133.33. Serial2 C 133.4.13.0/16 [200/0] via 133.33.1.1.201.33.8/30 [110/864] via 133.33.1.0/24 is directly connected.0/24 is directly connected.0/24 [90/2297856] via 133.0/8 [200/0] via 133.1.4. L1 .0.201.0/16 [200/0] via 133. 00:19:02. 01:12:04 B 2.0/16 [200/0] via 133. R .0/8 [200/0] via 133.33. ia .0/16 [200/0] via 133.0.33.0/30 [110/928] via 133.33.IS-IS level-2.0.201.33.33.11.100. I . Serial1 S 133. 01:12:21 B 149.0/24 [110/865] via 133.108.0.4/30 [110/128] via 133. Serial1 S 133.OSPF NSSA external type 1.IGRP.0/16 [200/0] via 133. B .33.33.1.100.0.33.203.per-user static route.33.OSPF NSSA external type 2 E1 . 01:12:21 B 11.33.static.mobile.0/24 [90/2195456] via 133.EGP i .0/16 [200/0] via 133. Null0 O IA 133.0/24 is directly connected.7.204.0 B 102.33.7.13.0/16 [200/0] via 133.RIP.201.0. 01:12:20 B 4.0. M .0.ODR P . 01:12:21 133. 01:12:20 B 5. 01:12:20 B 7.1. Null0 O IA 133. 01:12:20 B 100.0.10.0/8 [200/0] via 133.0/8 [200/0] via 133.1. 01:12:21 B 147.33.CCNP Practical Studies: Routing Example 9-23 show ip route on R4 R4#show ip route Codes: C .1.1.33.0.1.0.0/8 [200/0] via 133.0.1.1.365 - .13.7. E2 .0.1.0/16 [200/0] via 133. S .10.0.100.13.9. 2 subnets B 171.201. 00:01:05.1.0/16 [200/0] via 133.33.7.1.1.3.108. 00:01:04. 00:19:02.0/25 [110/74] via 133.connected.0/8 [200/0] via 133.5.0/8 [200/0] via 133. 01:12:20 B 101.0/8 [200/0] via 133.OSPF external type 1. Null0 C 133.0.1.201.33. U . Serial2 D 133. 00:19:02.OSPF.33. 02:53:59. 01:12:04 B 171. IA . Serial1 S 133. Serial1 I 133. 00:19:02.13. 01:12:20 B 141.0.7.33.0/25 [110/1064] via 133.0. 01:12:21 B 148.13.0.12/30 is directly connected. 00:19:02.33.7. 02:53:58.0/8 [200/0] via 133.0/24 [110/65] via 133.33.201.201.7.3.0. Null0 O IA 133.candidate default.1.108.33.33.1 to network 0.7.0. 01:12:21 B 10.1.1.1. 01:12:20 B 144.BGP D .201.0/24 [100/8576] via 133.1.0/24 is directly connected.201.0/8 [200/0] via 133.0/8 [200/0] via 133.201.100. 01:12:20 B 142.1.201.201. 01:12:20 B 145.0.7.0.0.33.33.33.13. Serial3 O IA 133.0/16 [200/0] via 133.5.33.0.33.33.33.0.100.0.33.33. 00:19:03. 01:12:20 B 143.1. o .33.0.33.1.EIGRP.33.1. Serial1 O IA 133.33.11. 01:12:20 B 141.OSPF inter area N1 .0.33. E . 01:12:20 B 6. Serial1 .1.0.206.1.0/24 is directly connected.100.0/16 is variably subnetted.33.

State POINT_TO_POINT.33.1. 01:12:23 R4's IP routing table has entries for OSPF.33.0/0 [200/0] is directly connected. Timer intervals configured. 01:12:07 [200/0] via 133.1 No backup designated router on this network Timer intervals configured. and EIGRP. Retransmit 5 Hello due in 00:00:00 Index 3/3. 01:12:07 [200/0] via 133. Cost: 1 Transmit Delay is 1 sec.22.33.0/24 B 133. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Loopback0 is up. 00:19:03.33.201.0. maximum is 10 Last flood scan time is 0 msec.1/24.13. 01:12:07 [200/0] via 133. Area 350 Process ID 1. and hence.33. BGP is supplied a default route from R1. Adjacent neighbor count is 1 Adjacent with neighbor r3 Suppress hello for 0 neighbor(s) .33. Timer intervals configured.33. Dead 40.5. Router ID 133. 01:12:07 [200/0] via 133. IGRP. Wait 40.0/24 B 133.1.33. Hello 10. State POINT_TO_POINT.33.204. Priority 1 Designated Router (ID) r4.33.1.33.11. Retransmit 5 Hello due in 00:00:03 Index 1/1. Hello 10. State DR.33. Serial1 via 133.7. 01:12:07 [200/0] via 133.33. Retransmit 5 Hello due in 00:00:02 Index 2/2.33. Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Serial1 is up. Hello 10.201. Wait 40.0/24 B 133. maximum is 0 Last flood scan time is 0 msec.33.33. the gateway of last resort is set.201. Network Type POINT_TO_POINT. Cost: 10 Transmit Delay is 1 sec.0/24 B 133.33. Router ID 133.33. line protocol is up Internet Address 133.204.1/27.CCNP Practical Studies: Routing C 133.16.16. Serial3 [200/0] via 133. line protocol is up Internet Address 133.33. Router ID 133.201.20. Area 350 Process ID 1.33. Network Type BROADCAST. Area 350 Process ID 1. 01:12:07 [110/129] via 133.33.23.33.24.201.1.21.201.0.0/24 O IA 133. maximum is 0 msec Neighbor Count is 0.0/21 B 133. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1.33.17.5. maximum is 0 msec Neighbor Count is 0.204. maximum is 0 Last flood scan time is 0 msec.0/24 B 133.33. maximum is 4 msec Neighbor Count is 1.0/24 B 133.33.1. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0. Dead 40.0/24 O IA 133.7.1. Serial1 [200/0] via 133. Example 9-24 displays the output from the IOS show ip ospf interface command.204. Cost: 64 Transmit Delay is 1 sec.33.19.1.0/24 B 133. 01:12:07 [200/0] via 133.7. Wait 40.1. Dead 40.18.1.33. line protocol is up Internet Address 133. Network Type POINT_TO_POINT.1. flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0.366 - .1.1. Interface address 133.13.14/30.201.201.0/21 B* 0.33.33. 01:12:07 [110/865] via 133.201. 00:19:03. Example 9-24 show ip ospf interface on R4 R4#show ip ospf interface Ethernet0 is up.

202. Sending 5.1 Type escape sequence to abort. Sending 5. round-trip min/avg/max = 16/16/20 ms R4#ping 133. Sending 5.33.33.11. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.205.33.33.1 Type escape sequence to abort.1 Type escape sequence to abort.205.202. 100-byte ICMP Echos to 133.201. Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.1 Type escape sequence to abort.204. 100-byte ICMP Echos to 133. 100-byte ICMP Echos to 133.201.33.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 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. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort.1.1.33. Sending 5.33.1 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.CCNP Practical Studies: Routing Example 9-25 displays the output from the IOS show ip ospf neighbor command on R4. Example 9-28 Pinging Loopbacks on R4 R4#ping 133. 100-byte ICMP Echos to 133.13 Interface Serial1 Example 9-26 displays the output from the IOS show ip eigrp interfaces command.33.1 Type escape sequence to abort. round-trip min/avg/max = 16/17/20 ms R4#ping 133.1.33.7. round-trip min/avg/max = 1/2/4 ms R4#ping 133.33.204.203.33. Example 9-27 show ip eigrp neighbors on R4 R4#show ip eigrp neighbors IP-EIGRP neighbors for process 1 H Address Interface 0 133.203. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. 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 133.33. 100-byte ICMP Echos to 133.1.206. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).367 - .206. round-trip min/avg/max = 16/16/20 ms . 100-byte ICMP Echos to 133. Sending 5. round-trip min/avg/max = 16/16/20 ms R4#ping 133.

33.10.203.2. as displayed in Example 9-29.202.10.10.1.33.1 Type escape sequence to abort.0/24 [100/100125] via 133. 00:00:45.33. 00:00:44.33.1 Type escape sequence to abort. 34 subnets.CCNP Practical Studies: Routing Example 9-29 displays the IGRP IP routing table on R5. Sending 5.0 with a Class C mask.202.33.0.10.2.204. round-trip min/avg/max = 28/32/36 ms R5#ping 133.3.33.3.33.11. and because the local interfaces are configured with the Class B network 133.2. 00:00:45.10. Serial0 I 133.33.33.33. Sending 5. 100-byte ICMP Echos to 133.10. 00:00:44.1.2. R4 has been configured to send all networks as /24.1.206. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. 00:00:44.33. Sending 5.33.33.201. Serial0 I 133.10. Serial0 I 133.33. round-trip min/avg/max = 32/32/32 ms R5#ping 133.33. Serial0 I 133.33. 00:00:44.204.201.0/24 [100/100125] via 133.1.0/24 [100/10476] via 133.0/24 [100/100125] via 133.1.10.1.33.33. round-trip min/avg/max = 1/2/4 ms R5#ping 133. Serial0 I 133.206.33.204. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0/24 [100/100125] via 133.10. round-trip min/avg/max = 32/32/36 ms R5#ping 133. 7 masks I 133.6.0/24 [100/100125] via 133. 00:00:45.33. such as the subnets 133.7. round-trip min/avg/max = 32/32/32 ms R5#ping 133. Sending 5.1. 00:00:45. 100-byte ICMP Echos to 133.7.33.2.2.0/24 [100/8976] via 133.33. . Serial0 I 133.201. Serial0 I 133.10.2.1.206. Sending 5. 00:00:45.0/29. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0 and 133.1 Type escape sequence to abort. 00:00:44.2.33.33.0/24 [100/10976] via 133.1 Type escape sequence to abort.0/24 [100/10576] via 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). Example 9-29 IGRP IP Routing Table on R5 R5#show ip route igrp 133. Serial0 I 133.202.33.2.33.33.1 Type escape sequence to abort. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1 Type escape sequence to abort. Sending 5.203.0/16 is variably subnetted. Serial0 I 133. round-trip min/avg/max = 16/16/16 ms R5#ping 133.33.33.33.0/24 [100/100125] via 133.33. Serial0 I 133.4.10.2. 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.33.33.10.33.1 Type escape sequence to abort. Serial0 R5 is running only IGRP. 100-byte ICMP Echos to 133. 00:00:45. Example 9-30 Pinging All Loopbacks on R5 R5#ping 133.33.33. Serial0 I 133.0/24 [100/100125] via 133.2. 100-byte ICMP Echos to 133.205.0. 100-byte ICMP Echos to 133.205. 00:00:44.368 - .2.203.5.1.33.0/24 [100/100125] via 133.33.33.

Serial1 D 133.11.0/21 [90/25632000] via 133.7.0/24 [90/25632000] via 133.7.33.2. Serial1 D EX 133.2.11. 00:02:35. round-trip R5#ping 133.0/24 [90/2169856] via 133. Serial1 D 133.0.0/24 [90/25632000] via 133.4.2.33. Serial1 D EX 133. Serial1 D EX 133. 00:00:35.2.2. 00:00:36.7. Serial1 D EX 133.11. 00:00:35.3.1.33.24.33. 00:02:34.33.2 Type escape sequence to abort.2.33. Serial1 D EX 133. 00:02:35. 6 masks D 133.11.7.5.202. which is running EIGRP in two domains: 1 and 2. 00:02:35.7. 00:02:35. 26 subnets.7.33. 00:00:35.3.33.33.33.33.9. Serial1 D 133.11.0/24 [90/2707456] via 133.11.11.33.2. Serial1 D 133.33.33. Serial1 D EX 133.2. 00:00:35. Serial1 Example 9-32 displays the interfaces configured in EIGRP 1 and 2. Serial1 D EX 133.201.33. 00:00:36. 00:00:35. Serial1 D EX 133.2.0/24 [90/2169856] via 133.0/24 [90/2681856] via 133.33.0/30 [90/25632000] via 133. Serial1 D EX 133.205.11.7. 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 R6.11. 100-byte ICMP Echos to 133.33.0/25 [90/25632000] via 133.7.0/24 [90/2297856] via 133.33. Serial1 D 133. 00:00:35.33.11.11.0/21 [90/25632000] via 133. !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 133.33.CCNP Practical Studies: Routing Sending 5.16.12/30 [90/2681856] via 133.33.11. Sending 5.33. Serial1 D EX 133.7. round-trip R5#ping 133. 00:00:37.2. !!!!! Success rate is 100 percent (5/5).2.2. !!!!! Success rate is 100 percent (5/5).11.33. 00:02:35. 00:00:35.33.11.33. .11.0/29 [90/25632000] via 133.33.33.2.204. 00:02:35.33.0/24 [90/2169856] via 133.33.33.1. Serial1 D EX 133.2. round-trip R5#ping 133.33.2.7. 00:02:35.8. 00:00:36.2.0/16 is variably subnetted.10.11. Serial1 D 133. 00:02:35.33.0/27 [90/2195456] via 133.203.11.7.33. 100-byte ICMP Echos to 133.33.33.33.1.8/30 [90/25632000] via 133.4. Serial1 D 133.0/24 [90/2169856] via 133.2. 100-byte ICMP Echos to 133.33.11.11.33. !!!!! Success rate is 100 percent (5/5).0/24 [90/2169856] via 133. Example 9-31 show ip route eigrp on R6 R6#show ip route eigrp 133.11.2.5 Type escape sequence to abort.33.5.1 Type escape sequence to abort.33.33.0/24 [90/2707456] via 133.0/24 [90/25632000] via 133.11.33. Sending 5.33. Serial1 D EX 133.33.2.11.1.33. Sending 5. 00:02:35. Serial1 D 133.0/25 [90/25632000] via 133.2.33.33.0/24 [90/2809856] via 133.33. 00:02:35.4/30 [90/25632000] via 133.33.1.33.33. 00:02:34. Serial1 D EX 133.2.2.33.11.5.2.33. Serial1 D EX 133.2.33.369 - .

Sending 5. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33. 100-byte ICMP Echos to 133.1.206.33. round-trip min/avg/max = 32/32/32 ms R6#ping 133. 100-byte ICMP Echos to 133.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).33.1 Type escape sequence to abort. Sending 5. Sending 5. round-trip min/avg/max = 32/32/36 ms R6#ping 133.33.2 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 R4.1.205.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 = 32/32/36 ms R6#ping 133.205.33. 100-byte ICMP Echos to 133.33.204.203.1 Type escape sequence to abort.33. Sending 5. 100-byte ICMP Echos to 133.11.201.33.1 Type escape sequence to abort. round-trip min/avg/max = 1/2/4 ms R6# . Sending 5.202. round-trip min/avg/max = 32/32/32 ms R6#ping 133. 100-byte ICMP Echos to 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). round-trip min/avg/max = 16/16/16 ms R6#ping 133. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).203. 100-byte ICMP Echos to 133.1 Type escape sequence to abort. Sending 5.33.1 Type escape sequence to abort. No EIGRP routers exist in domain 2. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).206.202. Example 9-34 displays a successful ping request to all loopback interfaces in Figure 9-1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).1.1 Type escape sequence to abort.1.370 - .1. 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 0 133.204.33.33.33. Example 9-34 Pinging Loopbacks on R6 R6#ping 133.201.33.

33.1 closed R5>telnet 133.33.1 Trying 133.33. users on connected interfaces routed throughout this network also have full IP connectivity.1 .1 .33.204.1 Trying 133. Example 9-35 displays an executive user telneting from R5 to all remote routers using the loopback interfaces in Table 9-2.33.33.. Open R4>quit [Connection to 133.371 - ..203.1 . Routers R2–R6...204. R4.202.202.206.202.33. and R6 from R5. only R2's BGP table is presented here for your reference.33..1 .1 closed R5>telnet 133.1 closed R5>telnet 133.206. so if you can telnet from the router.204.33.206.1 Trying 133.1 .1 Trying 133.201. Example 9-35 Telnet into R1.. Open R2>quit [Connection to 133.33. Open R1>quit [Connection to 133. Open R6>quit [Connection to 133. R3.. the BGP tables on R3–R6 are exactly the same as R2.1 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..201.33.204.1 closed R5>telnet 133..CCNP Practical Studies: Routing Telnet from the classful domain on R5 and ensure that you can telnet to all five remote routers..203. R5>telnet 133.33.33.33..1 .33.201.204.204.. View the BGP tables on R1 and R2.1 .1 closed R5>telnet 133.1 Trying 133.203. Open R6>quit [Connection to 133.1 Trying 133. Therefore.33.1 closed R5>telnet 133.33.206. .33.206.1 Trying 133. Open R4>quit [Connection to 133.. Example 9-36 displays the BGP table on R1.33. Because IBGP is running among R1 (route reflector) and route reflector client.33.33. R2.206. Open R3>quit [Connection to 133..

7.7.7.1.1.5.0.7.23.0 171.4/30 0.0.6 801 32768 ? *> 133.108.1 0 100 1024 ? *> 133.108.1.0.1.33.1.3.33.1.0/21 133.1.33.24.0.0 0 32768 ? Network Next Hop Metric LocPrf Weight Path *> 133.33.2 801 32768 ? *> 133.108.0.21.0.5 0 200 400 300 200 1024 ? * 171.5 0 200 1024 ? * 171.201.7.1.108.1.0/25 133.0.0 171.0.108. e .internal Origin codes: i .7.2 801 32768 ? *> 133.108.7.108.1.0.0/24 0.33. * valid.1.0.0.33.108.33.5 0 200 400 300 200 1024 ? * 171.12/30 133.0/24 0.0 0 32768 ? *> 133.1.0.108.0.33.5 0 200 1024 ? * 171.18. ? .1.7.1.1 100 1024 i *> 1.0.1 0 100 400 300 200 1024 ? *> 3.0.33.8/30 133.5 0 200 400 300 200 1024 ? * 171.108.0.0 0 32768 ? *> 133.108.0.0.0 0 32768 ? *> 133.1 0 100 1024 ? *> 101.108.4.5 0 200 1024 ? * 171.33.0 171.108.33.6 810 32768 ? *> 133.incomplete Network Next Hop Metric LocPrf Weight Path *> 0. local router ID is 133.0.108.0/30 0.0/24 0.0.1 0 100 1024 ? *> 102.33.108.108.0.7.2 1600 32768 ? *> 133.33.33.1.0 171.0 0 32768 ? *> 133.108.33.1 0 100 400 300 200 1024 ? Network Next Hop Metric LocPrf Weight Path *> 10.0.0.33.19.0.0 0 32768 ? *> 133.0/24 0.0/24 0.0/25 133.16.5 0 200 400 300 200 1024 ? * 171.108.0.1 0 100 1024 ? *> 141.EGP.202.7.33.0/29 0.0/24 0.0/24 0.0 171.108.33.0 0 32768 ? *> 133.0 171.1. d damped.108.1.5 0 200 1024 ? * 171.0/24 133.6 1601 32768 ? *> 141.0.0.372 - .108.6 1610 32768 ? *> 133.5 0 200 400 300 200 1024 ? * 171.108.33.0.1.CCNP Practical Studies: Routing Example 9-36 show ip bgp on R1 R1#show ip bgp BGP table version is 77.0 171.0/27 133.1.201.1.108.0 171.0.0/24 133.0.108.33.1 0 100 400 300 200 1024 ? *> 7.5 0 200 1024 ? * 171.33.0.0/24 0.108.1.0.1.0.33.0.7.1 0 100 400 300 200 1024 ? *> 5.0.1 0 100 400 300 200 1024 ? *> 6.0.33.5 200 1024 i * 171.108.0.0 0 32768 ? *> 133.0.0/24 133.0 171.5 0 200 400 300 200 1024 ? * 171.1.0.1 0 100 1024 ? *> 11.108.203.1 Status codes: s suppressed.0 171.IGP.0.1.1.20.0/24 0.33.0.5 0 200 400 300 200 1024 ? * 171.33.33.108.1.1 0 100 400 300 200 1024 ? *> 8.1.22.0 171.5 0 200 1024 ? .0.0 0 32768 ? *> 133.204. i .0.33.0.0 171.6 1600 32768 ? *> 133.17.1.0.108.1.1.0 0 32768 ? *> 133.7.5 0 200 400 300 200 1024 ? * 171.0 171.100.1.0.0.1 0 100 400 300 200 1024 ? *> 4.108.0 0 32768 ? *> 133.1.33.33.5 0 200 1024 ? * 171.0.0. h history.2 1000 32768 ? *> 133.0.108.0.1 0 100 1024 ? *> 100.0 171.1 0 100 400 300 200 1024 ? *> 2.0 171.0.108. > best.0.0 171.0 0 32768 ? *> 133.33.33.7.0.

0.0.201.33.0 *>i101.33.0 *>i102.201.33.201.0 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 R2.1.201.201.0.33.1 133.100.1 133.100.33.33.201. * valid.0 143.201.201.0.33.0 *>i11.33.108.16.0.33.0.0.1 133.0.1.108.33.100.1 133.5 171.33.0/25 *>i133.108.7.internal Origin codes: i . Example 9-37 show ip bgp on R2 R2#show ip bgp BGP table version is 370.5.33.33.0.0.5 171.108.108.33.0/30 171.4.1.1 171.33.1.EGP.0 148.0. h history. d damped.0.12/30 *>i133.1 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 ? ? ? ? ? ? ? ? .33.1 133.108.0/24 *>i133.108.100.0.1 171.108.1 133.0.201.108.1. ? .1 133.0 *>i8.33.33.0/24 *>i133.201.0 *>i133.33.1 133.201.1 133.0/27 Network *>i133.100.0.17.0.19.202.CCNP Practical Studies: Routing * *> * *> * *> * *> * *> * *> * *> * *> * *> *> 142.33.5 171.0.7.1 133.1 Next Hop 133.33.201.1 171.108.0/29 *>i133.201.0/24 *>i133.33.1 0.1.1.0.108.201.5 171.18.0 *>i2.33.3.1.0.201.1 133.0/25 *>i133.33.0.33.0 146.33. e .1 133.33.1 133.1 133.0 *>i1.201.20.33.0 0.1.4/30 *>i133.1 133.5 171.201.0.0 *>i4.1 171.100. local router ID is 133.4/30 171.0/24 *>i133.1.33.108.201.1 133.21.0.0/30 *>i133.1 133.0.IGP.0 *>i5.201.1.201.5 171.33.1 171.201.7.0.0 *>i7.33.1.33.1 171.33.1 171.33.1.0.108.373 - .1 171.33.0.5 Next Hop 171.201.0.0 *>i10.100.1.1.201.5 171.108.201.0.0.100.0.0 Network 147.0.0 171.33.1.201.201. > best.0.0.1 133.33.1 133.1 133.0 149.33.incomplete Network *>i0.7.33.1 133.1 133.0 *>i100.108.0 *>i3.1 133.1.108.0 145.0 *>i6.1 Status codes: s suppressed.33.0 144.0.0.0.108.8/30 *>i133.33.108.1.0/24 *>i133.0.201.0.33.0/24 Next Hop 133. i .1 133.108.1.33.1.0.1 133.1 133.0.201.

33.0/24 *>i141.201.201.33.1 133.0/24 *>i133. Example 9-39 show tcp brief on R1 R1#show tcp brief TCB Local Address 812F0240 171.5 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 R1.201.1 133.33.1.1 133.0 *>i143.201.1 133.11069 812F1A94 r1.108.33.201.1.0 *>i149.1. local AS number 1 BGP table version is 77.1 133.0 *>i141.5.179 r3.100. 533/462 paths Neighbor 133.1 133. 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.33.1 133.CCNP Practical Studies: Routing *>i133. (BGP uses TCP port 179.11001 R5.33.108.0.33.201.33.1 133.0.201.33.0/24 *>i133.201.108.11073 8130B85C r1.201.1 133.201.201.0 *>i171.100.1 133.100.201.0.33.201.0.23.33.6.33.179 171.1 133.204.201.1.1 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. and Example 9-39 confirms that BGP is configured with the TCP port number 179.179 r2.0.33.205.0.203.1 Next Hop 133.22.201.108.1 133.0 Network *>i145.33.0 *>i148.0.2.1 133.201.0/24 *>i133.1.179 81308298 r1.) .0/21 *>i133.11071 812F1F10 r1.33.11070 813029BC r1.1.108.203.100.0.100.33.11074 812EFDC4 171.108.0 *>i147. Example 9-38 show ip bgp summary on R1 R1#show ip bgp summary BGP router identifier 133.33.374 - .0 *>i144. Example 9-39 displays the TCP sessions on R1 with the IOS show tcp brief command.179 R6.4/30 R2# 133.204.33.108.201.1.0.33.33.0 *>i146.108.33.33.100.1 133.0.1.24.1 133.0/24 *>i133.1.179 R4.202.0/30 *>i171.33.0/24 *>i133.33.33.201.33.100.33.1 133.1 133.1 133.11068 Foreign Address 171.1 133.202.108.33.1 133.179 (state) ESTAB ESTAB ESTAB ESTAB ESTAB ESTAB ESTAB R1 is configured with seven BGP TCP peers.1 171.33.201.1 171.33.201.33.201.100.0 *>i142.1 133.206.1.33.100.

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

.

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

Always attempt a question even if you are unsure of the correct answer. CIM is a virtual IOS simulator that enables you to configure a set number of IOS features without having to purchase expensive Cisco routers. and CCNA engineers will tell you that hands-on experience with Cisco routers and switches is the most valuable learning tool. so you can take advantage of your adrenaline rush if you arrive early. even if you passed. provide tuition and virtual labs. the time. The testing center provides a pen and some form of writing paper. Try to stay calm.html Strategies for the Exam This section covers some simple things you can do the day before and during the exam. you can go in early.CCNP Practical Studies: Routing Hands-On Experience Almost all CCIE. Ensure that you have the correct directions for the testing center.378 - . Have a relaxing evening. try answering the question by a process of elimination. Allow at least an extra hour for any traveling involved. you can study any routing algorithm using loopback interfaces. On the day before the exam. On the exam day. you can use the exam to your advantage by remembering the topics that are not your strengths. During the exam. You are not allowed anything in the exam room. Confirm that your photo ID will be accepted. Leave all those heavy books at home. typically an erasable sheet. it's best to take your passport so you will not have any problems. Immediately after the examination. The following link provides more details about this virtual lab program: www. Take advantage of this free access to try new configurations and get expert advice from local Cisco engineers.) You can hire and actually configure Cisco IOS routers and switches for a set fee. are real Cisco devices. so even if you are struggling. so you can view the technology and spend time configuring Cisco IOS features for free. By building a small practice lab. Sometimes. Use the materials provided to work out the logic of some questions. What makes you a CCNP is passing a couple of exams. Contact your Cisco representative for more information. so you need to be on your guard mentally. as discussed in several scenarios in this book. Typically.com/warp/public/710/cim/index. two answers will stand out. Cisco virtual labs. ensure that you utilize your daily access to view how the network is functioning using the techniques presented in this guide.cisco. . Wear loose. except a refreshment and the provided writing materials. too many to mention here. do the following things: • • • If you do not know the answer to a question. CCNP. Point your search engine toward the keywords. park and take a few moments to relax before the exam. Some candidates attempt to cram in too much learning the night before at the cost of a good night's sleep. even with just two routers. do the following things: • • • • Leave plenty of time to get to the testing center. so try and eliminate the two obviously incorrect answers as soon as you can. write down the topics you were not comfortable with and the source materials you need to acquire that knowledge. in fact. Cisco provides an excellent product called Cisco Interactive Mentor (CIM). and the location of the exam. The examination questions are written by folks who want you to pick the first answer that looks good. If you work daily with routers in your present job. comfortable clothing and take a sweater in case the room is too cold. Remember that you can take the exam multiple times. Various Internet sites. (These labs are called virtual but. Cisco Systems even provides lab access at various Cisco sites around the world. but what makes you a quality CCNP is the desire to extend your ability with every passing moment. do the following things: • • • • Call Sylvan Prometrics or whomever is hosting your examination and confirm your seat. 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 sends these transcripts to you. . In addition.CCNP Practical Studies: Routing Cisco Certification Status As soon as you pass all tests for a given Cisco certification.galton.379 - . you receive a login ID and password. so you can track your status of any certification path at www. Cisco certification logos. You can also download Certification logos for use on your business cards. Tracking Cisco Certification Online Cisco also provides online tracking. you attain that Cisco certification status. Cisco also generates transcripts that indicate which exams you have passed and your corresponding test scores.com/~cisco/. and more (sometimes even a free shirt). and you can keep your demographic information up to date so you are always informed of any changes. This Web site takes about seven days from your examination date to be updated.

.

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

To pass the lab exam.cisco. 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.com/warp/customer/625/ccie/certifications/sample_routing. and if you book the test. signaling. Cisco announces a beta trial for the Routing and Switching qualification test.html CCIE Lab Exam Test Format Passing the qualification examination is the easier part of the CCIE exam journey.cisco.com/warp/customer/625/ccie/ccie_program/whatsnew. After you pass the qualification test.html. although it is a little more difficult with many more indepth questions.382 - .com/warp/customer/625/ccie/certifications/rsblueprint. and so on) LAN Security Multiservice The blueprint for this examination is located at www. You can view some sample questions at www. 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). you pay only a small fee compared to the standard fee of approximately $250. The following link has more information: www. The good news is that the format of the lab examination has changed from two full days to one day only.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 . and you need to study on routers full time for at least three to six months.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.html. your life needs to change dramatically. The two-hour. This reduces the effectiveness of eliminating obviously incorrect answers and choosing from the remaining answers. you are eligible to sit for the lab examination. framing. computer-based examination is similar to other Cisco certifications.com/CCIE/Schedule_Labhttps://www.scribd.com/jsp/login. You can book your lab examination online at the following address: http://tools. What makes some of questions more difficult on the exam is that more than five answer choices are listed for all or most questions.cisco. you are now required to configure only a set number of features.cisco. NOTE Occasionally.

Europe. Nova Scotia. Belgium Johannesburg. and fully understand what each IOS command actually enables. 5710 Fax: +86 10 8518 2096 E-mail: ccie_apt@cisco. 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 2001.383 - . and Africa San Jose. and Bangalore. California Research Triangle Park. Brazil Brussels. South Africa E-mail: ccie_ucsa@cisco. NSW. Anyone can configure a Cisco router. Japan . contact the following: • For lab locations in North America. Australia.com • For lab locations in Chatswood. South America. instead of relying on limited experience with certain commands. Canada Sao Paulo. and Singapore Tel: +86 10 6526 7777 Ext.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. North Carolina Halifax.CCNP Practical Studies: Routing Ensure that you practice with and understand these devices. but the ability to understand the full consequence of a command is crucial to passing the CCIE Lab Examination. 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.com • For lab locations in Tokyo. Practice configuring almost every IOS feature. All CCIE certification labs around the world are testing candidates in the new one-day format.

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

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

.

88.11111111. Which routing protocols do not support VLSM? IGRP and RIP I. Given the subnet in binary notation 1111111.40. Which subnet mask provides approximately 1022 hosts? 2n-2 = 1022.11111100.10 255.0 and a subnet mask of 255.255. the subnet mask 255. What is the broadcast address for the subnet 131.254.24 255.145.0 and broadcast address 151.255.80.255.192 A: Performing a logical AND reveals the following: • • • • Subnet 131. Cisco routers drop broadcasts unless you configure bridging.100.88.1.100.255 where 255 represents all binary 1s.88.100.127 Subnet 171. These routing protocols support VLSM because the routing protocols send the subnet mask as part of any routing update.199.1. The number of bits required in the subnet mask is 10 bits.40.108.56.0/24? 5: A: 6: A: 7: A: 8: A: 9: .1. or the subnet mask 255.255.254.00000000) What is the equivalent subnet mask for the notation 131.0 and broadcast address 131.100. EIGRP.255 Subnet 151.255. The only way to overcome this is to use a combination of static IP routes or a default route.387 - .0/24? The broadcast address is 131. determine the subnet address and broadcast addresses: • • • • 131.0 borrows nine (or n) bits from the subnet mask. or 2n=1024. and BGP.255.00000000. how many hosts are available on this subnet? Using the formula 2n-2 = 29-2 = 512 hosts. The answers are in bold.108. 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. OSPF. Which routing protocols support VLSM and why? RIPv2.255.252.CCNP Practical Studies: Routing Appendix C.1. IS-IS. Answers to Review Questions This appendix contains the answers to each chapter's review questions.108. what is the decimal equivalent? The decimal equivalent is 255.255.1.40.54 255.63 2: A: 3: A: 4: A: Given the network 141.1.199.100.224 161.255.0 (1111111.0 and broadcast address 171.255.0.11111111.128 171. or a Class B address.31 Subnet 161. The original questions are included for your convenience.00000000.67 255.108.255.0 and broadcast address 161.108.108.18.199.0.255.0.0 151.1. Chapter 1 1: Given the following host address and subnet mask combinations.45.

0. the slash bit notation represents the number of bits assigned to the subnet mask: /24 means 24 bits.255.388 - .CCNP Practical Studies: Routing A: The slash notation is common in today's documentation and on Cisco IOS.0/24 are all successful because the 5 ICMP packets are all reachable as displayed by the five ! characters.255.108. 131. Is the ping test successful or not? Explain why or why not? The ping tests to remote networks 131. 6: A: 7: A: 8: A: . From R1. Which command do you use to view only RIP routes? show ip route rip or sh ip ro r. and 131.255. 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.11111111. Why is the command version 2 configured on each router? Because you are using two types of masks.255 Class C:192.0/24.0/16? There are nine subnets using two 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).255 Class B: 172. and 1 represents the hop count to reach the remote network. Each remote routing entry is labeled with the following information: [120/1].0. 255.255.0-172.255.7.16.0. Identify the private address ranges defined in RFC 1918? RFC 1918 defines three major classes for private use. which are address ranges that are not routable in the Internet.11111111.0 (or /24) and 255. How many subnets are known by R1 using the Class B network 131.8. Which command do you use to view only connected routes? show ip route connected or sh ip ro c.255.252 (or /30).255. a ping test is sent to three remote networks.16. 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.168.255.255.00000000 or 255. so RIPv2 has been enabled to cater to the 30-bit mask between the routers.255.0/24. Besides a ping test. In this case.0-10. The following are the three private ranges: 10: A: • • • Class A: 10.0.108.168.9. all the remote networks are 1 hop count away.108.0.1-192. What does the 120 represent and what does the 1 represent? The 120 is the default administrative distance or trustworthiness of the information. or VLSM. In binary this is 11111111.108. RIPv1 does not understand VLSM.

In other words. 2: A: 3: A: 4: A: . What path does the packet sent to the IP subnet 171.108.0.108. Mel is contained within one area only and because that area is the backbone.108.2. What path is taken to the remote network 141. packets to this network are dropped.0/24 take? Because this network is not listed in Sydney's IP routing table.108. as well as a router that performs route redistribution (an ASBR). The gateway of last resort is also set to 141. This is commonly referred to as the Gateway of Last Resort (GOLR).0/16 and 141.100.1.0/32 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).1/24? R1's routing table has no entry for the network 141. How many subnets are known by R1 using the Class B networks 131.6. The actual hop count is set by the ASBR (router Simon) in Figure 4-8.255.108. Mel is a backbone router. This is typically Internet-based traffic.0/16? There are eight subnets using three masks for the Class B address 141.100.4.4.0. and SanFran? Simon is a backbone OSPF router in area 0.33.1.108. Why is the remote network 141.108.0. In Example 4-64.4 (router Simon).108.1.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.0.108.108. the packet is sent to the default routing entry or the next hop address of 141. 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. what is the hop count or metric to the remote network 141.0/24 [110/74]? The cost is 74 and the administrative distance is 110.1. this is an intra-area OSPF route. and because there is no default network or gateway of last resort. Simon is configured to set all networks with a hop count of 2 by using the command redistribute ospf 1 metric 2. What is the cost associated with the remote network 131. What type of OSPF routers are the Routers Simon. There are nine subnets using three different masks for the Class B network 131. which can be truncated as sh ip ro os. Mel. but it supplies a default router and can also be classed as an ASBR.108.108. SanFran is also a backbone router.0. Which command do you use to view only OSPF routes? show ip route ospf.0.108.389 - .0/24? The RIP metric is set to 2.

108.108.2 Interface Serial2 Serial3 Two methods are used in OSPF to summarize IP networks. Null0 141. the longest match rule is used to route packets to the remote networks.108.108.255.108.255.108.0. 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. Example 4-66 displays the OSPF neighbors on the router Simon.2.255.390 - .108.0/25 is directly connected.255. 171.0/24 is a summary. What are they and what IOS command is used to provide summarization? Inter-area summarization with area area id range mask command.0/24 is directly connected.3.108.6.3. 00:12:23.2. namely 141.1/29 and 141.0/29 [110/74] via 141.4.108.255. Null0 141.108.0. Null0 141. 00:31:46. 5 masks 141.0/24 is a summary. . Ethernet1 141.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.108.2.0/28 [110/74] via 141. Configure the command ip ospf domain-lookup in global configuration mode to allow OSPF to assign a name to an IP address. Changes are less likely to occur within a small group of routers than in a large group. 00:31:47. reduces the topology table. as seen by the router SanFran along with a successful ping to the remote networks. Example 4-65 displays the IP routing table on Simon. 00:12:23. External summarization with the IOS command summary network mask command.0/30 is directly connected.3. Serial2 141. 10 subnets.255.3.1.0/24.4/30 is directly connected.108.108.0. Example 4-65 Simon's IP Routing Table Simon#show ip route Gateway of last resort is 141. Serial3 141.109.109. 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. Ethernet0 141.0/24 is directly connected. Serial2 141.108.0/24 is directly connected.108.108. Serial3 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.2 to network 0.4.108. Null0 141. leading to fewer SPF calculations as well. Chapter 5 Example 5-79 displays the detailed paths to the three remote networks.109.2. 00:12:23. 171.6 141.0.0. Because Simon has more specific routing entries. and 171.0/16 is variably subnetted.1.255.0 C O C C S O C S O O O 6: A: 141. in turn.108.255.4.1/28.108.2.0/24 is a summary.

2 on Ethernet0/0. via Ethernet0/0 Route metric is 409600. Example 5-80 show ip route 171. minimum bandwidth is 10000 Kbit Reliability 255/255. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5).0. Sending 5. Sending 5.4.2.391 - . 00:13:26 ago.108. metric 409600. type internal Redistributing via eigrp 1 Last update from 131.1. 00:13:32 ago. metric 409600.1.1.109.2.0.0 Routing entry for 171.2 on Ethernet0/0.0/22 Known via "eigrp 1". .1. metric 409600.3.108.2.108.109.1. from 131.1. minimum MTU 1500 bytes Loading 1/255.109.1 Type escape sequence to abort.1.109. from 131. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). 100-byte ICMP Echos to 171.2.2. Hops 1 SanFran#ping 171.0 Routing entry for 171.109.109. 00:13:38 ago. 100-byte ICMP Echos to 171. and 3.2.0/22 Known via "eigrp 1".108. traffic share count is 1 Total delay is 6000 microseconds. Hops 1 SanFran#ping 171.0/22 Known via "eigrp 1". round-trip min/avg/max = 1/3/4 ms If you perform a show ip route of the network 171. minimum MTU 1500 bytes Loading 1/255.4. via Ethernet0/0 Route metric is 409600. minimum MTU 1500 bytes Loading 1/255.108.0.109.0/24 on SanFran.109. type internal Redistributing via eigrp 1 Last update from 131.108.1. timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5). from 131.1.2.109.108. traffic share count is 1 Total delay is 6000 microseconds.1. 00:13:26 ago Routing Descriptor Blocks: * 131.3.109.CCNP Practical Studies: Routing Example 5-79 show ip route and ping on SanFran SanFran#show ip route 171. distance 90.1.1.2.109. 100-byte ICMP Echos to 171. 2. distance 90.0 % 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 on Ethernet0/0.109. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171.108.1. Sending 5.109.109. via Ethernet0/0 Route metric is 409600.3.2. minimum bandwidth is 10000 Kbit Reliability 255/255. you see the output displayed in Example 5-80. Hops 1 SanFran#ping 171.108.109. round-trip min/avg/max = 1/2/4 ms SanFran#show ip route 171. minimum bandwidth is 10000 Kbit Reliability 255/255.1 Type escape sequence to abort.1 Type escape sequence to abort. 00:13:32 ago Routing Descriptor Blocks: * 131.0 Routing entry for 171.1. traffic share count is 1 Total delay is 6000 microseconds.1. distance 90.4. 00:13:38 ago Routing Descriptor Blocks: * 131.0 on SanFran SanFran#show ip route 171. type internal Redistributing via eigrp 1 Last update from 131.

Notice. 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. 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. Which IOS command is used to enable BGP4 on a Cisco router? router bgpas. and 3 (00000011).CCNP Practical Studies: Routing 1: A: Example 5-79 displays the IP routing table of the Router SanFran. which is more trusted than OSPF at 110. under the EIGRP process. 171. What is the variance command used for? The variance command. and it disables automatic summarization of subnet routes into network-level routes. is used to allow additional paths to a remote destination when the composite metric is not the same.392 - . . When is the EIGRP topology table updated? Whenever a change occurs in the network.255. Which networks does the entry 171. Cisco IOS developers figure that their own routing protocol is more trustworthy than OSPF.2.3.0. In the end.0/24 on SanFran.0 when applied to the Class B address 171. an industry standard. the EIGRP neighbors are reset. What is the default administrative distance for EIGRP internal routes? The default value is 90. 2 (00000010). such as a network failure. the last two are not the same.0. resulting in network down times and the loss of IP data. Manual redistribution is required between different autonomous systems or routing domains. the EIGRP topology table is updated by update packets sent to all EIGRP routers in the same AS.0. The last three bits includes the networks 1 (00000001). 252 is 1111 11100. Why does EIGRP need to be manually configured to redistribute into another autonomous system? EIGRP manually redistributes only between IGRP in the same AS.109.0/24.1. In binary.108. 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: 131.252.109.0/22 embrace? The /22 indicates a mask of 255.109.0. but the first six are (11111100 is 252).109. 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 *.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. and 171. a failure to reply leaves the router in an active state.1.109. Example 5-79 confirms connectivity by displaying detailed IP route entries for the remote networks 171.

2.108.255. local AS number 2 BGP table version is 21. Example 6-83 displays the BGP table on a Cisco BGP router. What is the BGP autonomous system that R2 resides in? How many BGP sessions are active.108.0/24 131.0/24 in Example 6-83? Use Example 6-83 to answer questions 4-6.101.1.108.1.108.1.5 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. Example 6-83 show ip bgp R2>show ip bgp BGP table version is 21.0/24 131.101. or AS 1.108. Example 6-84 displays the output from the show ip bgp summary command for a Cisco BGP-enabled router.255.255. * valid.393 - .5 100 200 200 1 ? *> 131.255.255.5 100 200 200 1 ? *> 131. Port 23 (local port) is used by Telnet.1 Status codes: s suppressed.11008 611654BC 161. i internal Origin codes: i .108.23 A: 4: Foreign Address 131. How many BGP sessions are in use? Example 6-82 show tcp brief R2>show tcp brief TCB Local Address 613EE508 131. 119/80 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 131. Which path is chosen to the remote network 131. The version of BGP in use is 4.1 100 200 200 1 ? * 131. h history.1 100 200 200 1 ? *> 161. > best.108.0.1 4 1 2755 2699 21 0 0 1d20h 19 131.101.108.CCNP Practical Studies: Routing 3: Example 6-82 displays the output from the show tcp brief command.179 131.255. ? .108.108. .11051 (state) ESTAB ESTAB ESTAB There are two BGP TCP sessions (the foreign TCP port number is 179).108.1.1.108.255.5.0/24? The metric is set to 100 (lower is preferred) and the local preference is 200 (higher values preferred).179 131.1.108.0 0 32768 i A: 5: A: 6: A: 7: The path chosen is indicated by > on the left side of the BGP table.108.108. which indicates the next hop address 131.108. Which autonomous system does the network 131.255.108.IGP.1.108. What is the metric and local preference for the remote network 131. 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.1. 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 161.1. e . local router ID is 161.0. d damped.255. the default setting.1.6.108.255.108.0/24 originate from? The path is indicated by 1 ?.11009 613ED584 131.incomplete Network Next Hop Metric LocPrf Weight Path * 131.1.108.255.EGP.255.0/24 0.

neighbor peer ip -address default-originate. View the following BGP table. you would only need 999 peers (use the formulae (n-1) where n is the number of routers). > best.2 percent of the same fully meshed network.108. where n is the number of BGP routers. if any? To view route reflectors. * valid. which show command(s) can you use. and the range of values for weight is 0–294967295. All other peers must be fully meshed.0.0. and AS path. higher or lower weight. local router ID is 131.IGP.4 Status codes: s suppressed. ? . Which IOS command is used to display the following output? 3: A: 4: BGP table version is 61. What is the originating AS for the remote preferred path to the remote network 6: A: 7: A: 8: .EGP. and the second is to view the running configuration with the IOS show running-config command. What is the BGP table? The BGP table is a collection of local and remote network entries describing the next hop address.0 *> 141.108. weight. To display route reflector clients.0. Route reflectors are used in IBGP networks only.254. i internal Origin codes: i . which is only 0. With the use of route reflectors.5 0.0/24 A: 5: A: Next Hop 171. you can use two methods on the route reflector: one is to use the IOS show ip bgp neighbors command.1. How is a route reflector client configured for IBGP? Route reflector clients are configured for normal IBGP peering.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.394 - . What are the terms peer or neighbor used to describe in BGP? A peer or neighbor indicates a TCP session between two BGP routers. what value is preferred. Based on these entries. and what is the range of values for weight? Higher weight values are preferred. 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. with 1000 BGP routers. What is a BGP cluster? Cluster is a term used to describe a router reflector and the configured route reflector clients. e . For example.incomplete Network *> 0. the number of peers is 1000(999)/2 = 499500. Provide the IOS command syntax to enable a default route to be sent to a remote peer. d damped. local preference. networks are inserted into the IP routing table.CCNP Practical Studies: Routing 8: A: 9: A: 10: A: On a Cisco router. h history.108. The default value is 0. 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)/2.0.1. The route reflector has additional commands to ensure that updates are reflected from one route reflector client to another.

B . The next-hop-self attribute is used for IBGP peers only.RIP. 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.candidate default U .OSPF external type 1. which IOS command sets the weight and local preference attribute to 100? First.EIGRP.0/24? R5#show ip bgp BGP table version is 22.108. d damped.CCNP Practical Studies: Routing 141.1. Using a route map. . o .mobile. e . you must apply it to remote BGP peers on the inbound or outbound direction required. 10: A: Can you set the BGP attribute next-hop-self to both EBGP and IBGP peers? No.0/24 *> 151. EIGRP AD is 90 and OSPF is 110.OSPF inter area N1 .OSPF.0.395 - . E .BGP D .EGP i .EIGRP external.OSPF external type 2.108. IA .0.IGP. and originating from AS 300. > best. 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.1.1. then 100. ? . local router ID is 171. For example.static. The lower AD is more trustworthy. * .1.1 Metric LocPrf Weight Path 200 2000 100 300 i 0 32768 i 200 2000 100 ? Cisco IOS always displays the AS path taken.EGP. EX .1 0. S .IS-IS level-1. M . O . so the Cisco IOS chooses EIGRP.2 Status codes: s suppressed.IS-IS level-2.1.IS-IS.0 is through the AS 2000.1.IGRP.108. I . h history. R . N2 . L1 .0.per-user static route.0 A: Next Hop 171. which can include routing information dynamically discovered using OSPF or RIP. E2 . L2 .108.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.108.OSPF NSSA external type 2 E1 . i internal Origin codes: i . The IOS command to set this attribute to remote peers is neighbor ip-address next-hop-self. You can change the default AD values by using the IOS distance command. and in this example.OSPF NSSA external type 1.0 171.0/24 *> 171. the path traversed to reach the remote network 141.incomplete Network *> 141.1.108. the following indicates all the possible routing methods on a Cisco router: Codes: C .108.108.connected. * valid.

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

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

25 Hours) NOTE Not all CCIE labs require a communication server to be configured.398 - . . Communications Server (0. 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.CCNP Practical Studies: Routing Figure D-1.

Set the hello time on VLAN_B to 10 seconds. R2. respectively. a CCIE candidate is not required to cable the lab network physically. Catalyst Ethernet Switch Setup I (0. R9 is a Catalyst 6509 switch with a Multilayer Switch Feature Card (MSFC) module installed.25 Hours) Configure the Ethernet switch for five VLANs: • • • • • VLAN 2. 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. configure the management interface SC0 with the address 131. is connected to R1 and R2. You network is already physically patched. Construct your network as shown in Figure D-1. . named VLAN_A. Set all Ethernet ports to forward data immediately after a device is plugged in or activated. Routers R1. 2001 onward.CCNP Practical Studies: Routing Configure the communication server so that when you type the host name of a router on the server. named VLAN_D. is connected to R3. and R7 are connected to the Catalyst Ethernet switch (Catalyst 6509 series switch). Configure R1 as the communication server by using the ip host command. Therefore. Communication server port 10 connects to the Catalyst Token Ring switch. Ensure that the switch is configured in the VTP domain Cisc0_vTp and the switch can create and delete VLANs in the future. named VLAN_B. Using VLAN_A. no time allocation is given to this section.0. is connected to R4. R5.2/25. VLAN 4.25 Hours) Configure the following spanning-tree parameters on the Catalyst 6509: • • • • Ensure that the switch never becomes the root bridge on VLAN_D. VLAN 6. R4. Communication server port 9 connects to the Catalyst Ethernet switch. All serial links between routers are connected through a Frame Relay switch. Ensure that all devices in your network can telnet to the switch even if R1 or R2 is down. Catalyst Ethernet Switch Setup II (0. Routers R1 and R4 are connected to an ISDN service with the switch type defined as basic-5ess. and R8 are connected to the Catalyst Token Ring switch (Catalyst 3900 series switch). named VLAN_E. Physical Connectivity (No Time) NOTE From October 1. This section is added for completeness only. VLAN 3. is connected to R7. R6. Routers R1. and R4 connects to number plan 0296307050. you are connected across the console port to that router: • • • • • • Set up the routers as shown in Figure D-1. R1 connects to number plan 0298017705.108. R3. Ensure that the switch has the best possible chance of becoming the root bridge in VLAN_E. is connected to R6 and R9. VLAN 7. named VLAN_C. Communication server ports 2 through 8 are connected to routers R2 through R8.399 - .

25 Hours) Configure R9 (6509 with an MSFC card) for IP routing. 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.---1 1 15 1 3 3 9 9 Mod --1 15 3 9 Mod 1 (enable) show module Ports Module-Type ----.1 1. 12.5(4) 4.4 1.----------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. If any ports become disabled because of hardware errors.CCNP Practical Studies: Routing Configure the following miscellaneous parameters: • • • • • • • Disable Cisco Discovery Protocol on ports 3/1-8.24)V 5.2(0. configure the MSFC for IP routing in VLAN 6 using RIPv2 only. Do not route between any other interfaces. Therefore. no time is projected for this section.1 2.400 - . Catalyst Ethernet MSFC Setup (0. Ensure that any IP phones installed or connected to Card 3 are supplied inline power.3(1) Sw 5. 5. Example D-1 show module on R9 (MSFC) Cat6509> Mod Slot --. ensure that the switch automatically enables the affected ports after 10 minutes. 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. Ensure that the switches get a clock source from R1 using NTP. Example D-1 displays the hardware profile on the Catalyst 6509 switch.1(1)E.------------------------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 ------------------.5(4) 12.1 1 By using the information displayed in Example D-1.3 Fw 5. IP Configuration and IP Addressing (No Time) NOTE Because of recent changes to the CCIE exam. Disable power redundancy on the switch. .1(1)E. however. the subject is presented here to ensure potential CCIE candidates have a good understanding of IP address spaces and subnetting.3(1) 5. the candidate is not required to configure IP addressing.

No subinterfaces are allowed on any router. Use a subnet with the least number of hosts for the ISDN link. Ensure that you can also ping the local interface from each router configured for Frame Relay. all routers must have full IP connectivity between every routing domain. Use a 29-bit mask for all Frame Relay connections running classless IP routing protocols. Use a 24-bit mask for VLAN E. Configure IP addresses on your remaining interfaces: • • • • • • • • Use a 25-bit mask for VLAN 2. Use a 28-bit mask for VLAN D. Use a 27-bit mask for VLAN 3. You may assign a subnet from your Class B range. Use LMI type to Cisco only.0 to 131.5 Hours) Configure RIP on Routers R6 and R9 only: • • • • • Configure RIP on R6 E0 and R9 E0. Redistribute the RIP route into IGRP domain. All router interface types are DTE.108.255. IGP Routing (3 Hours) After this section is completed. IGRP Configuration (0. Frame Relay Setup (0. Use a most efficient subnetwork for IP addresses on the Frame cloud. Ensure that only unicast updates are sent and received. Assign each router a 24-bit subnet for the loopback address to use. The Frame port type is DCE. Ensure that you read the entire paper before designing your IP address space. You must use this address space for all addresses unless a different address space is specified in a particular question.5 Hours) Configure IP across your Frame Relay network as displayed in Figure D-2: • • • • • • • You have to use static maps for each protocol. including the ISDN backup interfaces when operational.255 to design your network. Do not use the keyword broadcast for the Frame Relay link between R6 and R7 when mapping IP. Use a 26-bit mask for all Token Ring networks. Set the enable password for all routers and switches to ccieToBe. it must be possible to reach all your routers and switches.CCNP Practical Studies: Routing Use the Class B subnetted IP address 131.5 Hours) Configure IGRP on Routers R6 and R7 only: . RIP Configuration (0. It must be possible to ping and telnet from any one router using the loopback address. and do not rely on autosensing the LMI type on any routers.108. Make sure you can see distributed RIP routes throughout your topology. 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. Authenticate any RIP packets. No dynamic mapping is permitted. Use a 24-bit mask for all Frame Relay connections running classful IP routing protocols. After your IP address space and IP routing are complete.401 - .0.

0. Redistribute the OSPF and external EIGRP routes with an administrative distance of 199 in the EIGRP domain. Redistribute the IGRP routes into OSPF domain. and EIGRP domains. Redistribute the EIGRP routes into OSPF domains with a cost metric of 1000 seen on all OSPF routers. Ensure that R4 is the DR in the OSPF backbone network.0. Ensure that R3 never sends any updates across the Ethernet (E0) segment. R7. All routers must be able to see all other IPX routes and must be able to IPX ping each router.0. acting as an IPX server. RIP. except Router R3. do not enable EIGRP IPX. Ensure that all OSPF routes are redistributed and reachable in the IGRP. Ensure that all IPX-enabled routers can reach these two server SAPs. You can use IPX EIGRP as your routing protocol. . OSPF Configuration (1. Set the hello interval on R2 Ethernet segment to 20 seconds.0.40 is configured so that excessive CPU resources are not consumed on Router R4. You can assume no other areas or routers are attached to this segment. Ensure that EIGRP is authenticated across the Frame Relay connections.40. Ensure that all loopbacks appear as /24 bit networks on all IP routing tables. Ring 500 is in area 500. and R7. and Ring 800. Make sure you can see distributed IGRP routes throughout your topology as Type 1 OSPF routes. Do not use the redistribute connected command on any router to accomplish this.0.5 Hours) Configure OSPF as described in Figure D-1. and R8 only: • • • • • Configure EIGRP in domain 333 between the serial link on R7 to R8. acting as a printer server. Ensure that area 0. The Ethernet segment between R1 and R2 resides in area 1. Ensure that you can IPX ping across your network. The Ethernet segment on R4 resides in area 0. You cannot configure IPX addressing on the Frame Relay link. The ISDN link between R1 and R4 resides in the area 0. but ensure that all routes appear in the IGRP and RIP domains. Configure NLSP between R6 and R7.0.0. Ensure that R1 will never be the DR on all segments. Between R6 and R7. Summarize as much as possible to reduce the redistributed routes into OSPF. EIGRP Configuration (0. Do not create any unspecified OSPF areas: • • • • • • • • • • • • • • • • • Configure the OSPF backbone over the Frame Relay network between the three routers: R2.402 - .5 Hours) Configure EIGRP on Routers R3. Set the hello interval between the link R1 and R4 to 25 seconds. 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. R3 to R8.CCNP Practical Studies: Routing • • • • • Use 10 as the AS number for IGRP. Ensure that the router ID of all OSPF-enabled routers is the loopback address. and IPXPrn1. Configure two IPX services on R1 named IPXServ1. Ring 100 is in area 100. R4. Do not create any additional areas. IGRP covers the link between R6 and R7 only. The link between R4 and R5 is in area 4. Ensure that the OSPF backbone in the Frame cloud is authenticated. Disable IPX RIP wherever possible.

Ensure that the IOS image is restored to the Flash on R1 and then reload R1. Configure a filter that blocks NetBIOS packets with the destination name SimonisaCCIE from leaving R5 and R8. R3. ensure that all exec users can use the IOS clear in exec mode on Router R1 only. Use a different virtual ring group on each router.0200. DLSw+ peers should be active only when user-based traffic (SNA/NetBIOS) is sent or received.5 Hours) ISDN switch information: • • ISDN switch type: basic-5ess ISDN numbering: . and 800 should have connectivity to VLAN 2 and 3. ensure that DLSw+ remains established. Ensure that VLAN 2 can reach hosts on Ring 100. R1 should place an outgoing call to R4.75 Hours) Configure DLSw+ on R1.20 Hours) Your customers accidentally erased router R1's system image in Flash memory. and R8: • • • • • • • • • • • Rings 100. Use PPP encapsulation and the strongest authentication available.CCNP Practical Studies: Routing Basic ISDN Configuration (0. When the Frame Relay link is restored. When the ISDN is active. To allow nonprivileged users access to R1 and the ability to clear terminal server lines. They don't have Cisco IOS Software or an TFTP server on hand. R1 and R2 are running the same IOS code and are the same router hardware type (Cisco 2503 routers). R4 cannot call R1 under any circumstances. They also have no Internet access. DLSw+ Configuration (0. Administrators must still use the enable password ccieToBe on all routers to access privilege mode.0200 on Ring 100 or VLAN 2. bring down the ISDN link after 25 minutes. R5. . Flash Configuration (0. Configure the ISDN interfaces on R1 and R4 as follows: • • • • • • Only when S0 of R1 goes down.R4: 0296307050 • SPIDS are not required. Hosts on Ring 500 are used only when Ring 100 is not reachable. Ensure that all routers peer to R1 and only in a network failure do DLSw+ circuits terminate on R5. SNA hosts reside on Rings 100 and 500.R1: 0298017705 . VTY Changes (0.20 Hours) Configure all VTY lines so that network administrators do not require local authentication. 500. Ensure that remote DLSW+ peers do not send too many queries for the destination MAC address 0200. all routers must be able to ping and telnet the local ISDN interfaces on R1 and R4. Ensure that the only SAPs enabled on R3 are null SAPs and SAP 08. Permit all other NetBIOS traffic starting with the name Simonis?***. Ensure that you never bring up more than one B channel to keep costs to a minimum.403 - . If IP connectivity exists.

Private Address Space Allocation (0.110. Ensure that the remaining network can access the host with the IP address 10.1.255 with the following attributes: • • • Ensure that BGP origin is set to IGP. Set all routes in the range 110. EBGP Configuration (0. Using the network command only.100. R8's remote peer is 191.2/30 and remote AS is 4345. Configure R5 and R8 as route reflectors.20 Hours) The enable password on the 6509 switch has been modified. ensure that all networks are advertised to the route reflectors R5 and R3. set the enable password to ccie and the access password to cisco. Make sure your have full BGP connectivity.10. Prepend with paths with the AS paths 1000 999 100. Do not disable BGP synchronization.10. ISP1 and ISP2 are advertising the full Internet routing table.255. . Ensure that the Class A address is never present in any routing table except R1.200.0. Assuming you have access to the switch using password recovery on the switch.2/24 and remote AS is 1024.20 Hours) Configure R1 to act as an HTTP server.5 Hours) Configure IBGP on all routers in your network: • • • • • • • • • • Do not use any WAN IP interfaces for IBGP sessions. Ensure that all routers have entries in their IP routing tables. Do not change the administrative distance on any interior routing protocol.0.10. as your network is prone to failures across the Frame Relay cloud. As long as there is IP connectivity in your network. even in the event of network failure of any one router.0 to 121.25 Hours) Configure EBGP on R5 and R8 as follows: • • • • R5's remote peer is 171. Set the weight to 1000 for all even networks and 2000 for all odd networks.0 to 121. and allow the users to access the rest of the network.75 Hours) After finishing each of the following sections.1.255.1. BGP Routing Configuration (0. ensure BGP is active in all routers.108. Minimize IBGP configurations as much as possible.100.1. Catalyst 6509 Password Recovery (0.100/24. Basic IBGP Configuration (0.255/24. make sure all configured interfaces/subnets are consistently visible on all pertinent routers. Ensure that the only route accepted is a default route and routes of the form 110.1 to 10.404 - .110.1. Use AS 2002 on all IBGP routers.255.20 Hours) Some users on VLAN_A have configured their PCs with the Class A addresses ranging from 10.CCNP Practical Studies: Routing HTTP Server (0. but only allow clients from Ring 500. and ensure that all traffic uses a preferred path through router R5.