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BGP

Configuring BGP on
Cisco Routers
Version 3.2

Lab Guide

CLS Production Servies: 12.29.05

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BGP

Lab Guide

Overview
This guide presents the instructions and other information concerning the lab activities for this
course. You can find the solutions in the lab activity Answer Key.

Outline
This guide includes these activities:
„ Lab 1-1: Initial Lab Setup
„ Lab 1-2: Configuring Basic BGP
„ Lab 2-1: Configuring a Transit AS
„ Lab 3-1: Using Multihomed BGP Networks
„ Lab 3-2: Employing AS-Path Filters
„ Lab 3-3: Filtering with Prefix-Lists
„ Lab 3-4: Implementing Changes in BGP Policy
„ Lab 4-1: Influencing BGP Route Selection with Weights
„ Lab 4-2: Setting BGP Local Preference
„ Lab 4-3: Understanding BGP Multi-Exit Discriminators
„ Lab 4-4: Addressing BGP Communities
„ Lab 6-1: Introducing Route Reflectors
„ Lab 6-2: Configuring and Monitoring Confederations
„ Lab 7-1: Limiting the Number of Prefixes Received from a BGP Neighbor
„ Lab 7-2: Implementing BGP Peer Groups
„ Lab 7-3: Using BGP Route Dampening
„ Answer Key

The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

The files or printed representations may not be used in commercial training. After completing this activity. Activity Objective In this activity. You have control over routers WGxR1 through WGxR4. have one serial link to the Frame Relay switch. for the sole use by Cisco employees for personal study. Cisco Systems. but you cannot configure them. BGP v3. you will be able to meet this objective: „ Prepare your workgroup to complete the lab activities in the Configuring BGP on Cisco Routers (BGP) course Visual Objective The figure illustrates what you will accomplish in this activity.2 © 2005. The PDF files and any printed representation for this material are the property of Cisco Systems. configure the interfaces on your routers. Inc. and Client). Lab 1-1: Initial Lab Setup Complete this lab activity to practice what you learned in the related module. Inc. Cheap. All rights reserved. All routers. . The first (Fast) Ethernet interface of each router is connected to the LAN segment. 2 Configuring BGP on Cisco Routers (BGP) v3. Visual Objective for Lab 1-1: Initial Lab Setup © 2005 Cisco Systems. and may not be distributed for purposes other than individual self-study. and establish IGP connectivity across your core backbone. You can also telnet to other routers that are shown in the figure.. you will perform initial router configuration. including the shared ones (Good. The first serial interface of each of your routers is connected to the Frame Relay switch. Inc.2—3 The figure displays the physical connectivity within your workgroup.

for the sole use by Cisco employees for personal study.) © 2005 Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables © 2005. . Required Resources These are the resources and equipment required to complete this activity. „ Two Ethernet 10BASE-T patch cables. Visual Objective for Lab 1-1: Initial Lab Setup (Cont. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. and may not be distributed for purposes other than individual self-study. Inc. BGP v3. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Inc. Cisco Systems. All rights reserved. Lab Guide 3 The PDF files and any printed representation for this material are the property of Cisco Systems. The files or printed representations may not be used in commercial training. The DCE side of the cable is connected to the Cisco 3660.2—4 The figure displays the logical connectivity of your workgroup. Frame Relay DLCIs are already configured on the Frame Relay switch to provide this topology. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter.. Inc.

Configures the OSPF network type for a specified broadcast | interface {point-to-multipoint [non- broadcast]}} ip host name [tcp-port-number] Eases configuration of the lab by defining a static host- address1 [address2. where your customer is connected „ Every workgroup has four routers. Inc. WGxR2. where two upstream service providers are located — Client ISP backbone. WGxR3. for the sole use by Cisco employees for personal study. Command List The table describes the commands that are used in this activity. Inc... „ The laboratory is organized as a number of workgroups that are connected to two common backbones: — ISP exchange point. Cheap.2 © 2005. Good. where x is the number of the workgroup. also called the provider backbone.. You will also configure an IGP in your workgroup. and WGxR4. serial interfaces. The files or printed representations may not be used in commercial training. „ You will perform initial router configuration and prepare the routers for further activities. Command Description interface type number Configures an interface type and places you in interface configuration mode no shutdown Administratively activates an interface ip address ip-address mask Sets a primary or secondary IP address for an interface [secondary] encapsulation frame-relay [ietf] Enables and specifies the Frame Relay encapsulation method frame-relay interface-dlci dlci Assigns a DLCI to a specified Frame Relay subinterface [protocol ip ip-address] on the router or access server show interfaces [interface-name] Displays the statistical information specific to an interface router ospf process-id Enables OSPF routing. During this procedure. The PDF files and any printed representation for this material are the property of Cisco Systems. which places you in router configuration mode network ip-address wildcard-mask Defines an interface on which OSPF runs. and may not be distributed for purposes other than individual self-study. There are also three shared routers. and IP addresses on each router in your workgroup. WGxR1. 4 Configuring BGP on Cisco Routers (BGP) v3. and defines area area-id the area ID for that interface ip ospf network {broadcast | non.address8] name-to-address mapping in the host cache—a suggestion would be to map to the loopback interface with the highest IP address of each router no ip domain-lookup Eases configuration of the lab by disabling the IP DNS- based host-name-to-address translation Job Aids These job aids are available to help you complete the lab activity. and Client. Cisco Systems. . configure passwords.

255.255.7. Lab Guide 5 The PDF files and any printed representation for this material are the property of Cisco Systems.6. and router Cheap has IP address 192.1 255.255. Task 1: Initial Lab Setup In this activity.8. configure the interfaces on your routers.x.20.5.x.x.x. subnet mask 255. © 2005.0 Loopback 1 197.168.1 255.3.20.1 255. They are shared by all workgroups.99 and is shared by all workgroups.1 255.x.20.255.255. Cisco Systems. Inc. Frame Relay DLCIs have the same value on both ends of the link.255.0 Note Router Good has IP address 192. The files or printed representations may not be used in commercial training.0 WGxR2 Loopback 0 197.x. and may not be distributed for purposes other than individual self-study.168.0 Loopback 1 197.0 WGxR3 Loopback 0 197.255.1 255.21.0 Loopback 1 197. Enable password Cisco VTY password Cisco WAN link encapsulation Frame Relay WAN link bandwidth 128 kbps (configured on the Frame Relay switch) Step 2 Configure two loopback addresses on each of your workgroup routers with the IP addresses from the following table.0 Step 3 Configure LAN IP addresses on WGxR1 and WGxR4 using parameters from the following table.255. subnet mask 255.168.255.2.x.255.1 255. for the sole use by Cisco employees for personal study.255.0 WGxR4 Loopback 0 197. Parameter Value Host name Use host names as shown in the second Visual Objective figure (x is the number of your workgroup).0 Loopback 1 197.255.1.21.1 255. Activity Procedure Complete these steps: Step 1 Perform initial configuration of your routers using the parameters in the following table. you will perform initial router configuration.x.1 255. Router Client has IP address 192.255.255.20. and establish IGP connectivity across your core backbone.168.255.4.x. Inc.22. . Router Interface Address Subnet Mask WGxR1 Loopback 0 197.168.255.0 Client ISP subnet 192.255.255. Parameter Value ISP exchange point subnet 192.255.255..x.

6/30 101 WGxR3 192.168.x. Cisco Systems.168.x.x.2/30 100 WGxR2 192.9/30 WGxR4 192. .168. for the sole use by Cisco employees for personal study.x. are shown in the following table.x. Step 6 Configure any IGP between your routers.x. Activity Verification You have completed this task when you attain these results: „ All router interfaces are active (line up. as well as the DLCI values for the Frame Relay virtual circuits. Step 4 Configure point-to-point Frame Relay subinterfaces on the Frame Relay links. and may not be distributed for purposes other than individual self-study. Inc. The IP addresses to be used on the link. The files or printed representations may not be used in commercial training. „ You can telnet and ping between all core routers.10/30 102 Step 5 Configure IP host mappings to ease Telnet hopping between routers..168.5/30 WGxR3 192. line protocol up).2 © 2005. for this step. Inc.168. 6 Configuring BGP on Cisco Routers (BGP) v3. Note It is preferred that you use a classless IGP.1/30 WGxR2 192.168. such as OSPF. Make sure that you do not use the IGP on the backbone LANs. The PDF files and any printed representation for this material are the property of Cisco Systems. First Router IP Address Second Router IP Address DLCI WGxR1 192.

Activity Objective In this activity. you will be able to meet these objectives: „ Configure initial BGP setup „ Configure BGP neighbors „ Announce local networks in BGP „ Redistribute routes into BGP „ Configure basic BGP route aggregation „ Monitor the status of the BGP routing process „ Monitor BGP neighbors „ Monitor the BGP table Visual Objective The figure illustrates what you will accomplish in this activity. Cisco Systems. for the sole use by Cisco employees for personal study. The files or printed representations may not be used in commercial training. All rights reserved. Lab Guide 7 The PDF files and any printed representation for this material are the property of Cisco Systems. Inc. and may not be distributed for purposes other than individual self-study. Lab 1-2: Configuring Basic BGP Complete this lab activity to practice what you learned in the related module. © 2005. BGP v3. you will configure BGP. Visual Objective for Lab 1-2: Configuring Basic BGP © 2005 Cisco Systems.2—5 The figure displays the BGP session that you will establish between WGxR1 and the Good service provider. .. Inc. Inc. After completing this activity.

. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Inc.2 © 2005. Required Resources These are the resources and equipment required to complete this activity. . The files or printed representations may not be used in commercial training. for the sole use by Cisco employees for personal study. Inc. „ Two Ethernet 10BASE-T patch cables. Cisco Systems. and may not be distributed for purposes other than individual self-study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables 8 Configuring BGP on Cisco Routers (BGP) v3. The DCE side of the cable is connected to the Cisco 3660. The PDF files and any printed representation for this material are the property of Cisco Systems. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter.

ensuring that all users in your network have Internet access. You will connect to a single service provider and statically announce the address space that the Internet Registry has assigned to you. Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address remote-as as. „ You must connect to the Internet using BGP. use the option always Job Aids These job aids are available to help you complete the lab activity. Lab Guide 9 The PDF files and any printed representation for this material are the property of Cisco Systems.. Cisco Systems. The files or printed representations may not be used in commercial training. Establishes a BGP session by using your workgroup number number as the AS number network network [mask mask] Announces IP prefixes in BGP ip route network mask … Configures a static IP route route-map name {permit | deny} seq Defines or modifies an existing entry in a route-map match ip address acl Matches routes in a route-map set origin igp Sets the origin in a route-map redistribute igp pid route-map Redistributes from your IGP into BGP name aggregate-address network mask Creates summary prefixes—use the summary-only [summary-only] keyword to suppress more-specific prefixes show ip bgp summary Verifies whether the BGP session is up show ip bgp neighbor Enables you to view detailed information about the neighbor show ip bgp Enables you to inspect the contents of the BGP table show ip bgp network Enables you to view detailed information about prefixes (aggregates) default-information originate Generates a default external route into an OSPF [always] routing domain—to enable advertising of the default route regardless of whether the software has a default route. and may not be distributed for purposes other than individual self-study. Command List The table describes the commands that are used in this activity. Inc. © 2005. Inc. for the sole use by Cisco employees for personal study. .

Remember that it may take up to a minute to establish a BGP session. WG1R1#show ip bgp summary BGP router identifier 192. 0 notifications. 24/0 paths. you will configure your network backbone for basic BGP connectivity with a service provider to establish BGP peering.1.199. Your display should resemble the following output.20.0/16 by configuring it in the BGP routing process.168. for the sole use by Cisco employees for personal study. Step 2 Configure the Good router to be your BGP neighbor using the parameters in the table.168.x.20 Service provider AS number 20 Step 3 Announce the IP prefix 197. 0 notifications. Activity Verification You have completed this activity when you attain these results: „ You can verify that you have established a BGP session.2 © 2005. Use your workgroup number as the AS number. remote AS 20. The PDF files and any printed representation for this material are the property of Cisco Systems. Parameter Value Service provider IP address 192. Also announce network 192. sent 0 10 Configuring BGP on Cisco Routers (BGP) v3.20..20.20. remote router ID 199. Inc. Activity Procedure Complete these steps: Step 1 Start the BGP process on WGxR1. local AS number 1 BGP table version is 25.0. scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxR 192. WG1R1#show ip bgp neighbor 192. Cisco Systems.20 4 20 9 4 25 0 0 00:01:31 24 WG1R1# „ You can view detailed information about the neighbor.20.199.0/24. hold time is 180.168. keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received Address family IPv4 Unicast: advertised and received Received 27 messages. 0 in queue Sent 22 messages.20 BGP neighbor is 192. external link BGP version 4.20.168. up for 00:19:50 Last read 00:00:50. Task 1: Configuring BGP In this task. . Your display should resemble the following output. Inc.x. Step 4 Ensure that WGxR1 is the exit point for your pod and is originating a default route for your IGP. main routing table version 25 24 network entries and 24 paths using 3192 bytes of memory 5 BGP path attribute entries using 260 bytes of memory 4 BGP AS-PATH entries using 96 bytes of memory 1 BGP community entries using 250 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 24/0 prefixes.168.199 BGP state = Established.168. and may not be distributed for purposes other than individual self-study. The files or printed representations may not be used in commercial training. 0 in queue Route refresh request: received 0.

0 192.168.20.168.0 192. d damped.20.168.12/30 192.2.0/16 192.0.26.11. local router ID is 192.168.51.168.8/30 192.168.37.1 0 0 1 i *> 197.0 192.20/30 192.20. Inc. Origin *> 192.20.3 0 20 3 ? Networks *> 192. h history.1 0 0 1 I © 2005.168.11. for the sole use by Cisco employees for personal study.214.168.0.3 0 20 3 ? because networks are *> 192.168.2.42.168. dropped 0 Last reset never Connection state is ESTAB.11.20 0 0 20 i *> 128.20 0 0 20 42 26 51 i *> 128.20 0 0 20 42 i *> 128.1.20. neighbor version 25 Index 1.20.168.20 0 0 20 213 i *> 128.16/30 192.20.168.incomplete Network Next Hop Metric LocPrf Weight Path *> 128.0 192.0 192. * valid.20.3 0 20 3 ? redistributed.20.0 192.2/32 192.0.11.168.3.3. Inc.0.20 0 0 20 42 26 i *> 128.0 192.51.0.20.1.168.0. depending on the progress of other pods.0 192.22 0 20 22 214 i Network *> 197. Local port: 179 Foreign host: 192.0 192.213.168. Offset 0.22 0 20 22 214 i *> 192.20.168. unread input bytes: 0 Local host: 192. and may not be distributed for purposes other than individual self-study.20. i .20.168.22.1.168.0.20 0 0 20 42 26 51 i *> 192.168.20 0 0 20 213 i *> 192.internal Origin codes: i .26.0 192.0.168.20.0.3. Lab Guide 11 The PDF files and any printed representation for this material are the property of Cisco Systems.1 Status codes: s suppressed.168.3.20.11.20 0 0 20 42 26 i *> 192.0.2 0 20 2 i *> 192. > best.20.20.37.3 0 20 3 ? “incomplete” *> 192. „ You can see a large number of networks being advertised by the Good provider when you inspect the contents of the BGP table on your router. The files or printed representations may not be used in commercial training.20. „ You can verify that you are receiving networks that are announced by other customers. Mask 0x2 24 accepted prefixes consume 864 bytes Prefix advertised 0.213.2 0 20 2 i in AS 2.0 192.168.0 192. *> 192.20 0 0 20 42 i *> 192.168.168.3.20.168.20. suppressed 0.0.EGP.3/32 192. WG1R1#show ip bgp BGP table version is 32. *> 192.168.42.168.22.0 0 32768 i *> 192.20.0 192.168.. e .20.168.1.168.20.20.168.3.168.0 0 32768 i originating *> 197.20 0 0 20 42 37 i *> 192.168.168.214.0 0.20.0 192.168.0/16 192. WG1R1# „ You can telnet from WGxR1 into the router Good and verify that it is receiving your networks over BGP.0 192.0 192.20 0 0 20 i *> 128.3.168.20. input: 0 mis-ordered: 0 (0 bytes) … rest deleted … Note The number of prefixes may vary.20.IGP. .168.1. ? . Cisco Systems.20.11.0.0/16 0.11.3 0 20 3 ? code is *> 192.20.3 0 20 3 ? originating in *> 192.20.20 0 0 20 i *> 192.4/32 192.20.168.20.20 0 0 20 i *> 192.20. Foreign port: 18395 Enqueued packets for retransmit: 0.0.0 192. Your display should resemble the following output.0 192.20 0 0 20 42 37 i *> 128. withdrawn 0 Connections established 1.11.3 0 20 3 ? AS 3.168. I/O status: 1.168.0. Minimum time between advertisement runs is 30 seconds For address family: IPv4 Unicast BGP table version 25.0.

. The files or printed representations may not be used in commercial training.168. Cisco Systems. Your display should resemble the following output.0/24 and 192. You will also use route-maps to set the origin of BGP routes to “IGP” instead of “incomplete. Step 3 Configure an access-list that permits all your networks except those that are shared among workgroups. Use the new access-list with a match command in the route- map. 12 Configuring BGP on Cisco Routers (BGP) v3.” Note Route-maps will be covered in detail in the module “Route Selection Using Policy Controls. „ You can perform ping and trace from WGxR4 to 192. Use the set command in the route-map to set the origin to “IGP.168.1 (an Internet destination that is announced by router Good). The PDF files and any printed representation for this material are the property of Cisco Systems.0/24 networks into BGP. you will remove all networks from your BGP definitions (from Task 1) and announce them by using redistribution from your IGP into BGP with a route-map. In this task. which sets the origin code to “IGP.11. Step 4 Configure a route-map. . for the sole use by Cisco employees for personal study. Activity Verification You have completed this activity when you attain these results: „ You can log in to the service provider router (Good) and verify that it receives proper networks from you.2 © 2005.” Make sure that you do not announce the 192. and may not be distributed for purposes other than individual self-study.20. you will use redistribution to announce a large number of networks into the BGP routing process.” Step 5 Configure redistribution from your IGP into BGP by using the previously configured route-map. Step 2 Telnet to router Good and verify that it no longer receives your networks. Inc.” In this task.21.20. Inc. and you can no longer rely on manually configuring your address space in the BGP process. Activity Procedure Complete these steps: Step 1 Remove all BGP network statements from the previous activity. Answer these questions: Q1) What do you need in order to propagate classful networks? Q2) What do you need in order to propagate classless networks (supernets or subnets)? Q3) Why do some networks that are received from router Good have a next-hop address pointing to other routers? Q4) What command would you use to see whether a neighbor is sending you any updates and how many? Task 2: Configuring Route Redistribution in BGP Your network has grown.

1.IGP.168.168.1 0 0 1 i .1 0 0 1 i Step 2 Use the aggregate command in your BGP process to aggregate the 197.0.20.incomplete Network Next Hop Metric LocPrf Weight Path .6.1.1.8/30 192.0 192.4. and may not be distributed for purposes other than individual self-study.20. you still need to announce the network 197.3. local router ID is 199.internal Origin codes: i . .168.7.20.168.1.168.1.168. . In this task. because of diagnostic needs. * valid.199.21.168. i .1.0 192.1 2297856 0 1 i *> 197. .1.20.168.20.20.168.168.1 0 0 1 i > 197.1.8. The files or printed representations may not be used in commercial training.0 192.8.0 192.168.1. .1 0 0 1 i > 197. Inc. d damped.0 192. © 2005. Individual subnets *> 192. However.4.0 192.0 192.168.20..0.0 192.5.x.168. e .0 192.0 192. Good> „ You can ensure that you are not originating networks 192.1.1.x.20. . Inc.0 192.20.6. > 197.5.20. Lab Guide 13 The PDF files and any printed representation for this material are the property of Cisco Systems.0.2.168.0 192. Answer these questions: Q1) What is the major difference between this implementation and the previous one? Which is better and why? Q2) What precautions do you have to take when using redistribution? Task 3: Configuring BGP Aggregation Your ISP has requested that you provide only summarized prefixes for your address range 197.168. h history.1 2809856 0 1 i *> 197.168.1 0 0 1 i no auto-summary”c *> 192. Activity Procedure Complete these steps: Step 1 Log in to the router Good.1 0 0 1 i > 197.168.1 0 0 1 i *> 197. verify that the ISP sees all your individual loopback networks. for the sole use by Cisco employees for personal study.1 2681856 0 1 i ommand is used in BGP.1.EGP.20.1.1 2809856 0 1 i *> 197.1 0 0 1 i > 197.1.1.20. *> 192. Cisco Systems.168.1 3321856 0 1 i *> 197.168. > best.199 Status codes: s suppressed.1.1.20.1 0 0 1 i > 197.0/30 192.1.0 192.1.20.199.8. Good>show ip bgp BGP table version is 70. you will configure BGP aggregation as requested.20.0 192.20.1 0 0 1 i > 197.168.1 2297856 0 1 i *> 197.20.20.0/24 and 192.168.0 192.168.1. „ You can verify that your networks are removed from the BGP table when they become unavailable (try shutting down one of the loopback interfaces).1 0 0 1 i are seen if *> 192.0/24.4/30 192.1.20.2.168.20. ? .20.0 192.1 3321856 0 1 i *> 197.1 0 0 1 i > 197.0 network as requested by your ISP. using the aggregate-address command.1.0.168.168.7.1 3193856 0 1 i *> 197.x.0 192.168.3.

Cisco Systems.2 © 2005.. for the sole use by Cisco employees for personal study. The PDF files and any printed representation for this material are the property of Cisco Systems. „ You can view detailed information about one of the aggregates. . Inc. Inc. and may not be distributed for purposes other than individual self-study. Answer these questions: Q1) Do you see all your prefixes on the provider router? Why? Q2) What do you need to be able to generate and propagate aggregate routes? 14 Configuring BGP on Cisco Routers (BGP) v3. The files or printed representations may not be used in commercial training. Note Use the keyword summary-only if you do not want to announce individual prefixes. Activity Verification You have completed this activity when you attain these results: „ You can verify that the correct routing information is present by checking the BGP table on your router WGxR1 „ You can log in to the service provider (Good) router and check its BGP table to see that suppressed networks should not be visible on router Good.

Lab Guide 15 The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. and may not be distributed for purposes other than individual self-study. you will be able to meet these objectives: „ Plan the migration of an existing backbone toward a fully meshed IBGP backbone that is designed for transit traffic „ Configure IBGP sessions between loopback interfaces „ Configure BGP synchronization to ensure successful IBGP operation of the transit AS „ Monitor IBGP operation Visual Objective The figure illustrates what you will accomplish in this activity. The files or printed representations may not be used in commercial training. Inc. After completing this activity. Inc.. Activity Objective In this activity. Cisco Systems. you will enable a service provider network with multiple BGP connections to other autonomous systems to behave as a transit AS. Visual Objective for Lab 2-1: Configuring a Transit AS © 2005 Cisco Systems.2—6 The figure displays the required BGP connectivity within your AS and the BGP sessions with your customer and your upstream ISPs. BGP v3. All rights reserved. Lab 2-1: Configuring a Transit AS Complete this lab activity to practice what you learned in the related module. Inc. . © 2005.

Cisco Systems. Inc. Uses the IP address of the specified interface as the source interface source address for the BGP session show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command neighbor ip-address next-hop. Inc. you will transform your network into a transit AS that runs BGP on all core routers. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. and may not be distributed for purposes other than individual self-study. Required Resources These are the resources and equipment required to complete this activity. The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address remote-as Establishes an IBGP session by using your workgroup as-number number as the AS number neighbor ip-address update. 16 Configuring BGP on Cisco Routers (BGP) v3. „ In this activity.2 © 2005. „ Two Ethernet 10BASE-T patch cables.. . and you already have your first customer. you decide to become an ISP. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. The files or printed representations may not be used in commercial training. The DCE side of the cable is connected to the Cisco 3660. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. Configures the router as the next hop for a BGP- self speaking neighbor no synchronization Disables synchronization of IGP and BGP routes Job Aids These job aids are available to help you complete the lab activity. „ With the rapid growth of the Internet.

168. Parameter Value Client IP address 192. Activity Verification You have completed this activity when you attain these results: „ You can check BGP on all core routers and the router Client and ensure that they have established the correct sessions with their peers. answering the no synchronization command.99 Client AS number 99 Step 6 Configure all routers in your workgroup as IBGP neighbors (IBGP full mesh).20 Step 5 Establish a BGP session with router Client on router WGxR4. Task 1: Configuring the BGP Transit AS In this task.1. and 192. Use the parameters from the following table. Inc. Use the parameters from the following table. You may also remove the access-list and route-map. Step 2 Start the BGP process on all routers in your workgroup.21.x.6.20. 197.0.1 4 1 1174 1196 52 0 0 13:34:58 0 197. you will configure your network backbone as a fully meshed IBGP backbone acting as a transit AS. and may not be distributed for purposes other than individual self-study.22 4 22 1195 1183 52 0 0 13:34:46 23 197. Step 3 Advertise your prefixes (loopbacks.0/16.1.168. Lab Guide 17 The PDF files and any printed representation for this material are the property of Cisco Systems. WG1R1#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.) Step 7 Ensure EBGP reachability by all IBGP-speaking routers within your transit AS without redistributing the connected interfaces of either external Ethernet. „ Configure a full mesh of IBGP sessions between all routers in your AS. Inc. Activity Procedure Complete these steps: Step 1 Clean up your BGP configuration by removing the BGP process and the default route from the IGP on WGxR1.168. Cisco Systems.x. Router AS Number IP Address Good 20 192.. Establish these BGP sessions between Loopback 0 interfaces.0/24) in BGP on routers WGxR1 and WGxR4. Your display should resemble the following output.20 4 20 1189 1200 52 0 0 13:34:45 23 192. Step 4 Re-establish the neighbor relationships to router Good without any filters on router WGxR1. for the sole use by Cisco employees for personal study.20.20.2. The files or printed representations may not be used in commercial training.1 4 1 1171 1183 52 0 0 13:34:58 13 © 2005. .168.1 4 1 1170 1188 52 0 0 13:35:17 0 197.1. (Make sure synchronization has been turned off.4. Use loopback interfaces to establish these IBGP sessions.168.

168.168.4.99.1 0 1 20 42 i *> 128.168.1 0 1 20 i *> 99.168. e .1.0.99.37.168.0..4.1 4 1 1173 1173 125 0 0 13:38:31 0 197.0.1 4 1 1183 1175 78 0 0 13:40:04 13 WG1R4#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.0.0.0.0/24 192.1 4 1 1175 1183 14 0 0 13:40:54 0 Client#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.X 4 1 1147 1146 18 0 0 13:42:01 2 „ You can check the BGP table on router Client and verify that it is correctly receiving BGP routes.111.168. .1 4 1 1176 1170 125 0 0 13:37:58 13 WG1R3#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 197.0 0 32768 i *> 197.1 4 1 1173 1179 14 0 0 13:40:54 0 197.6.1.213.1.1.0 192.1.0 0 32768 i *> 197. local router ID is 197.0.99.0.0/30 192.21.1/32 0.2 16 msec 16 msec 17 msec 18 Configuring BGP on Cisco Routers (BGP) v3.0.0 0 32768 i *> 197.0.21.1.0.1.0 192.1 0 0 1 i *> 192.21.20.0.0 0 32768 i *> 197.1 4 1 1175 1175 78 0 0 13:40:37 0 197. Cisco Systems. The files or printed representations may not be used in commercial training.0 192.99.0.21.0.22.0.1.0.21.internal Origin codes: i .1.0 0.1 0 1 20 42 37 i *> 128.0.168.1. The PDF files and any printed representation for this material are the property of Cisco Systems. Tracing the route to 197.168. Your display should resemble the following output.12.1 Status codes: s suppressed.0 0 32768 i *> 197.0 192.0.1 4 1 1200 1179 125 0 0 13:38:09 24 197.99.21.20.21.1 4 1 1193 1175 78 0 0 13:40:33 24 197.168.168.0 0.0.1).0 0 32768 i *> 197.21.0 0 32768 i *> 200.12.21.2 © 2005. Client#show ip bgp BGP table version is 119.1.0 0.1 0 1 20 213 i *> 192.213.0/20 0.1 0 1 20 i „ You can use traceroute from router WGxR1 to the loopback interface on router Client (197.21.0.0 0 32768 i *> 197.EGP.1.99.1.0 0.0 0 32768 i *> 197.99.99.11.0.99. i .1.0 192. Inc.1 0 1 20 i *> 192.128.168.0 0 32768 i *> 128.21.0 192.168. ? . WG1R2#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 197.0.1.1 Type escape sequence to abort.0.99 4 99 1191 1192 14 0 0 13:40:38 11 197.0 192.168.99.1 0 1 20 i *> 128.6.2. for the sole use by Cisco employees for personal study.21. You should see a path similar to this one: WG1R1# traceroute 197.0/16 192.99.20.0. * valid.11.1 0 1 20 42 i *> 192.99.IGP. Inc.2.168.1 1 192.0.21.0.incomplete Network Next Hop Metric LocPrf Weight Path *> 10. > best. and may not be distributed for purposes other than individual self-study.42.0 0.0.0 0.80.99.1 4 1 1190 1178 14 0 0 13:41:04 24 197.37.0.0 192. h history.168.12.20.168.1 0 1 20 213 i *> 197.0.42.120.1.1 0 1 20 42 37 i *> 192.99.0 0.0 0 32768 i *> 197.0.0/16 192. d damped.0 0.1.11.0 0.1.1.1 0 0 1 i *> 197.21.111.13.11.0.

Inc. Lab Guide 19 The PDF files and any printed representation for this material are the property of Cisco Systems. and may not be distributed for purposes other than individual self-study.99 48 msec * 44 msec Answer these questions: Q1) Check the BGP table on router Client.10 44 msec 40 msec 40 msec 4 192..168.21.1. Cisco Systems. The files or printed representations may not be used in commercial training. How many prefixes coming from your AS are in that BGP table? Q2) Is there any other way of discovering how many prefixes you have advertised to the router Client? Q3) Why did you have to disable synchronization? Q4) Why did you have to establish a full mesh of IBGP sessions? © 2005. .6 32 msec 32 msec 28 msec 3 192. 2 192.168.1. Inc.168. for the sole use by Cisco employees for personal study.

All rights reserved. After completing this activity.2 © 2005.2—7 The figure shows the connectivity that you need to establish for the second BGP session with the new provider router (Cheap). Inc. The PDF files and any printed representation for this material are the property of Cisco Systems. Activity Objective In this activity. for the sole use by Cisco employees for personal study. 20 Configuring BGP on Cisco Routers (BGP) v3. . and may not be distributed for purposes other than individual self-study. Inc. BGP v3. The files or printed representations may not be used in commercial training.. Cisco Systems. Lab 3-1: Using Multihomed BGP Networks Complete this lab activity to practice what you learned in the related module. you will configure BGP as part of a customer scenario where you must support connections to multiple ISPs. you will be able to meet these objectives: „ Configure BGP neighbors to support a multihomed customer scenario „ Monitor the status of the BGP routing process „ Monitor BGP neighbors in a multihomed customer scenario Visual Objective The figure illustrates what you will accomplish in this activity. Visual Objective for Lab 3-1: Using Multihomed BGP Networks © 2005 Cisco Systems. Inc. Required Resources These are the resources and equipment required to complete this activity. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed.

Because only WGxR1 is running BGP. „ Two Ethernet 10BASE-T patch cables. Task 1: Configuring Multihomed BGP Networks In this activity. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. Inc. Activity Procedure Complete these steps: Step 1 Remove BGP from routers WGxR2. and may not be distributed for purposes other than individual self-study. . The files or printed representations may not be used in commercial training. Cheap. using Cheap as your primary ISP and Good as your backup ISP. and WGxR4. Leave only the existing EBGP session on router WGxR1 to Good. for the sole use by Cisco employees for personal study. © 2005. enable synchronization and restore IGP default routing for your pod. you will configure BGP as part of a customer scenario where you must support connections to multiple ISPs. The DCE side of the cable is connected to the Cisco 3660. Lab Guide 21 The PDF files and any printed representation for this material are the property of Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. „ You have started to provide mission-critical e-commerce services. WGxR3. You decide to connect to a new ISP. and you must ensure their high availability. Inc. Cisco Systems.. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address remote-as Starts a BGP session with the neighboring AS as neighbor ip-address weight Assigns a weight to all updates that are received weight from the specified neighbor show ip bgp summary Verifies the state of BGP sessions show ip bgp Enables you to inspect the contents of the BGP table Job Aids These job aids are available to help you complete the lab activity.

20.168. ? .20.20.168. Inc.1.20.20. for the sole use by Cisco employees for personal study.168.168. local router ID is 197.168.20.168. * valid.incomplete Network Next Hop Metric LocPrf Weight Path *> 10. and may not be distributed for purposes other than individual self-study.12. Cisco Systems. Activity Verification You have completed this activity when you attain these results: „ You can verify that both BGP sessions are up.0 192. and 23 prefixes 16 BGP AS-PATH entries using 384 bytes of memory were received from 0 BGP community entries using 0 bytes of memory both neighbors.20.22 0 100 22 i * 192.22 0 100 22 i * 192.8.20 0 0 20 i *> 128.168.22 Step 3 Change the default weight on neighbor Cheap to 100 using the neighbor ip-address weight command to give preference to routes that are announced from router Cheap over those announced from router Good. main routing table version 122 35 network entries and 58 paths using 5483 bytes of memory Both sessions are 18 BGP path attribute entries using 936 bytes of memory up.22 4 22 45 34 122 0 0 00:07:11 23 WG1R1# „ You can check all the BGP prefixes with two paths to verify that your router prefers the one through router Cheap.IGP.0. Your display should resemble the following output.20. Your display should resemble the following output. scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxR 192. h history.22. The files or printed representations may not be used in commercial training.22. * 192.233 100 22 20 i * 192.20.233 0 0 20 i *> 128.168. i .168.0/24 192. > best.20.20.) Note BGP weights are covered in detail in the module “Route Selection Using Attributes” and its supporting lab activities. local AS number 1 BGP table version is 122. 95/37 paths.22 0 20 22 i *> 128.8.0.168. Inc. e .20 0 0 20 i *> 128.20 0 0 20 42 26 i 22 Configuring BGP on Cisco Routers (BGP) v3. The PDF files and any printed representation for this material are the property of Cisco Systems. 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 49/464 prefixes.internal Origin codes: i .22 0 100 22 i Both paths have * 192.20 100 22 20 i address.1.20. d damped.0 192.1. Service Provider Parameter Value Cheap AS number 22 IP address 192.20 4 20 411 412 122 0 0 00:07:10 23 192. WG1R1#show ip bgp summary BGP router identifier 197.168.2 © 2005.1 Status codes: s suppressed.0 192.0.20 0 0 20 i the same next-hop *> 128.20.0 192. (Do not forget to refresh your BGP routes.20.26..0. Step 2 Configure the second BGP neighbor on WGxR1 using the parameters in this table.20.20.0/24 192.168.12.168. wg1r1#show ip bgp BGP table version is 122.168.22 0 100 22 26 i * 192. .0.EGP.168.20.

20.20 0 0 20 i *> 192.0 192.20.0 192.213.20.20.168.0/30 192.22.11.20.22.168.20. *> 128.11.168.168.20.0.168.22 0 100 22 26 42 37 i * 192.22 0 20 22 i *> 192.11.20.20 0 0 20 42 i *> 128.20.22 0 100 22 26 51 i * 192. and may not be distributed for purposes other than individual self-study.37.22 0 100 22 26 i * 192.20 0 0 20 42 26 51 i Answer these questions: Q1) What can happen if a multihomed AS is passing routing information learned from one neighbor to another neighbor? Q2) Why do some prefixes have two paths but both use the same next-hop address? © 2005.22 0 100 22 i * 192.0 192.20.22 0 100 22 i * 192.42.20.20.0 192.168.20.168.12.0.22 0 100 22 26 42 i * 192.168.20.20.11.20.0 192.22 0 100 22 26 51 i * 192.214.20 0 0 20 42 26 i *> 192.168.42. Cisco Systems.20.168.20 0 0 20 42 37 i *> 192.168.168. .20 0 0 20 42 i *> 192.20 0 0 20 42 26 51 i *> 128.168.11.22 0 100 22 26 42 i * 192.168. Lab Guide 23 The PDF files and any printed representation for this material are the property of Cisco Systems. Inc.168.168.20.51..0 192. for the sole use by Cisco employees for personal study.22 0 100 22 214 i * 192.0.0 192.22 0 100 22 i * 192.20.168.0 192.20 100 22 20 213 i * 192.20 100 22 20 i * 192.51.20.20 0 0 20 213 i *> 128.0.20.168.168. Inc.37.20.20 0 0 20 i *> 192.11.168.20.20.168. The files or printed representations may not be used in commercial training.20 0 0 20 42 37 i *> 128.0/30 192.20.20.0 192.0 192.22 0 20 22 214 i *> 192.22 0 100 22 26 42 37 i * 192.168.20.26.168.20 0 0 20 i *> 192.20.168.0 192.168.0.168.12.

After completing this activity. Inc. The PDF files and any printed representation for this material are the property of Cisco Systems. Visual Objective for Lab 3-2: Employing AS-Path Filters © 2005 Cisco Systems. ..2 © 2005.2—8 The figure shows the structure of the autonomous systems beyond AS 20 and AS 22. 24 Configuring BGP on Cisco Routers (BGP) v3. Lab 3-2: Employing AS-Path Filters Complete this lab activity to practice what you learned in the related module. This information will assist you in your verification and any troubleshooting steps. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. Inc. Required Resources These are the resources and equipment required to complete this activity. Inc. Cisco Systems. BGP v3. for the sole use by Cisco employees for personal study. and may not be distributed for purposes other than individual self-study. All rights reserved. The files or printed representations may not be used in commercial training. you will configure BGP to influence route selection using AS-path filters where connections to multiple ISPs must be supported. Activity Objective In this activity. you will be able to meet these objectives: „ Identify where you can apply an AS-path filter when configuring a router to influence route selection „ Configure AS-path filters to influence route selection „ Monitor the operation of configured AS-path filters Visual Objective The figure illustrates what you will accomplish in this activity.

„ Select routes between the Good and Cheap service providers based on the following criteria: — Accept routes originating in AS 213 only from router Good. „ Customers in AS 214 request that you use only the provider Cheap to communicate with them because of security reasons. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. and may not be distributed for purposes other than individual self-study. „ You have also discovered that the service provider Cheap does not provide you with good connectivity to your users in AS 213. Lab Guide 25 The PDF files and any printed representation for this material are the property of Cisco Systems. Therefore. The DCE side of the cable is connected to the Cisco 3660.. Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address filter-list Filters incoming or outgoing updates with the as-path-filter {in | out} specified AS-path filter ip as-path access-list number Specifies the AS-path filter permit regexp show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command show ip bgp filter-list access. . you want to accept the routes originating in AS 213 only from the provider Good. „ Two Ethernet 10BASE-T patch cables. Enables you to check a filter list-number clear ip bgp neighbor Clears the BGP session Job Aids These job aids are available to help you complete the lab activity. © 2005. „ Your service providers complain that you propagate routes between them and that you could potentially become a transit network. The files or printed representations may not be used in commercial training. „ Use AS-path filters to filter incoming routes and to limit propagation of transit routes. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Inc. for the sole use by Cisco employees for personal study. Inc. Cisco Systems.

IGP.1 0 0 1 i * 197. Step 4 Configure an AS-path access-list to permit prefixes originating in your AS and deny all other prefixes. Task 1: Configuring AS-Path Filters In this activity.20.0 192.1 0 22 1 i *> 192.168.1 0 0 1 i * 192.168.20.168. — Ensure that you do not act as a transit AS between the two service provider routers (Good and Cheap). you will configure BGP to influence route selection using AS-path filters where connections to multiple ISPs must be supported.1. The BGP table showing prefixes that have 213 or 214 in their path (before applying the AS- path filters) should look like this: wg1r1#show ip bgp BGP table version is 122.2 © 2005. .168.0.213.1 0 20 1 i Configuring AS-path access-lists: Step 2 With the ip as-path access-list command.0 192.1 Status codes: s suppressed.0/16 192.20.0 192.internal Origin codes: i .1. ? .20 100 22 20 213 i * 192.1 0 22 1 i *> 192. Your display should resemble the following output.EGP.168. The filter should permit all other routes.20.20 100 22 20 213 i * 192.0 192.11. — Accept routes with AS 214 in the AS path only from router Cheap.0. Inc.20.incomplete Network Next Hop Metric LocPrf Weight Path *> 128.214.1 0 1 i Router Cheap: Network Next Hop Metric LocPrf Weight Path *> 192. Inc.1 0 20 1 i *> 197. The PDF files and any printed representation for this material are the property of Cisco Systems.20. Router Good: Network Next Hop Metric LocPrf Weight Path * 192. local router ID is 197.20.0 192.20.20.1 0 1 i * 192.168. Activity Procedure Complete these steps: Step 1 Log in to the Good and Cheap routers and verify the service provider claims that you propagate the routes between them.. e .1.0.0 192.168. d damped.20. The files or printed representations may not be used in commercial training.22 0 100 22 214 i 26 Configuring BGP on Cisco Routers (BGP) v3.22 0 100 22 214 i *> 192.168.168.20.214. Cisco Systems.1.11. for the sole use by Cisco employees for personal study.20. i . * valid. The filter should permit all other routes. Step 3 Configure another AS-path access-list to deny routes that contain number 214 as the last number in the AS path.0.168.168.20 0 0 20 213 i *> 192. and may not be distributed for purposes other than individual self-study.8.1.20. > best.168.20 0 0 20 213 i *> 128.168.168.168. configure an AS-path access-list to deny routes that have number 213 as the last number in the AS path.213.0/16 192.168. h history.20.

42.11.22 0 22 i * 128.1.0 192.168.20.20.8.22 0 22 i * 128.11.213.168.22 0 22 i * 192.20 0 20 i *> 192.168.0.0 192.20.168.168. * valid.22 0 22 26 i * 192.0 192. Inc.20 0 20 42 i *> 192. The files or printed representations may not be used in commercial training.199.20.42.0.22 0 22 214 I .IGP.213.20 0 20 i *> 192.22 0 22 26 42 37 i * 192.199 Status codes: s suppressed.0 192.20.168.22 0 22 214 i * 192. .0 192. * 192.168.20.168.22 0 22 i * 192.20 0 20 i *> 192. local router ID is 197.168. e .22 0 22 26 51 i *> 128.37.168.20 0 20 42 26 i *> 192.168. > best. .168.26. h history.168.26.22 0 0 22 214 i Applying AS-path access-lists: Step 5 Apply the AS-path access-lists that you configured in the previous steps to your BGP neighbors. Good> show ip bgp reg ^1_ BGP table version is 47.20. Cisco Systems.20.0.22 0 22 26 i * 128.20.11.EGP.20.20. local router ID is 199. Your display should resemble the following output.168.0.22 0 22 26 42 37 i * 128. .11.EGP.20 0 20 213 i *> 128.51.0.20.168.168.20 0 20 42 37 i *> 192.168.20 0 20 42 26 51 i *> 192.168.168..20. e .214.0 192.20. Lab Guide 27 The PDF files and any printed representation for this material are the property of Cisco Systems.incomplete Network Next Hop Metric LocPrf Weight Path *> 192.20 0 20 42 37 i *> 192.1 Status codes: s suppressed.20 0 20 i *> 192. i . WG1R1#show ip bgp BGP table version is 84.20.0 192.20.20 0 20 42 26 i *> 192.20.20. . i .20 0 20 213 i *> 192.22.168.0.11.168.20.20.20.168. d damped.20.20.20.0 192.20 0 20 42 i *> 192.internal Origin codes: i .0 192.168.1.11. Your display should resemble the following output.168.20.168.0. ? .11. ? .0 192. Inc.168. Activity Verification You have completed this activity when you attain these results: „ You can verify that all paths containing AS 213 are received only from router Good and that all paths containing AS 214 are received only from router Cheap.20.incomplete Network Next Hop Metric LocPrf Weight Path * 128.168.168.168.168. WG1R1# „ You can verify that routers Good and Cheap are not receiving any prefixes that do not originate in your AS. > best.0.22. d damped.1 0 0 1 i © 2005.0 192. and may not be distributed for purposes other than individual self-study.0 192.20.0 192.0 192.20 0 20 42 26 51 i *> 192. * valid. for the sole use by Cisco employees for personal study.214.22 0 22 26 42 i * 128.11.0 192.internal Origin codes: i .22 0 22 26 42 i * 192.0 192.22 0 22 26 51 i .37.51.168.20.0 192.20.20.20.IGP. h history.199. . * 192.20.

Cisco Systems. .2 © 2005. The PDF files and any printed representation for this material are the property of Cisco Systems.168. Inc. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study.20. the BGP table should contain a large number of prefixes. *> 197.0/16 192.1 0 1 i Answer these questions: Q1) By this time.0. for the sole use by Cisco employees for personal study. Inc..1. What regular expression would you use with the show ip bgp command on WGxR1 to view the prefixes that are originated by your AS? Q2) What regular expression would you use on router Good or Cheap to view the prefixes that originate in your AS? Q3) What regular expression would you use on router Good or Cheap to view the prefixes that are received from your AS? Q4) How can you test your AS-path filters before applying them and clearing BGP neighbors? 28 Configuring BGP on Cisco Routers (BGP) v3.

you will be able to meet these objectives: „ Configure filtering of inbound or outbound updates with prefix-lists „ Modify configured prefix-list filters „ Monitor the operation of configured prefix-list filters Visual Objective The figure illustrates what you will accomplish in this activity. The files or printed representations may not be used in commercial training.. and may not be distributed for purposes other than individual self-study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. © 2005. BGP v3. Lab Guide 29 The PDF files and any printed representation for this material are the property of Cisco Systems. you will configure BGP to influence route selection using prefix-list filters where you must support connections to multiple ISPs. Inc. . Lab 3-3: Filtering with Prefix-Lists Complete this lab activity to practice what you have learned in the related module.2—9 The figure shows the connectivity that is established between your AS and the two service providers Good and Cheap. Activity Objective In this activity. All rights reserved. Required Resources These are the resources and equipment required to complete this activity. Cisco Systems. After completing this activity. Visual Objective for Lab 3-3: Filtering with Prefix-Lists © 2005 Cisco Systems. Inc. Inc. for the sole use by Cisco employees for personal study.

„ In this activity. The DCE side of the cable is connected to the Cisco 3660.. Inc. Command Description router bgp as-number Places you in BGP configuration mode ip prefix-list name [seq seq] Enables you to create an entry in a prefix-list {permit | deny} network/length [ge length | le length] neighbor ip-address prefix-list Filters incoming prefixes prefix-list in show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command show ip bgp prefix-list prefix. — Do not accept any private networks (RFC 1918) from either neighbor. — Do not accept class C networks or their subnets from router Good. The files or printed representations may not be used in commercial training. The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. „ Two Ethernet 10BASE-T patch cables. 30 Configuring BGP on Cisco Routers (BGP) v3. „ The memory consumption on WGxR1 has increased because of the large BGP tables that have been received from your service providers. Inc. „ Your analysis shows that you must perform the following tasks to minimize the size of the BGP table on router WGxR1: — Do not accept any subnets of class B networks from router Cheap. Displays a BGP routing table based on the contents list-name of the prefix-list Job Aids These job aids are available to help you complete the lab activity. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. you will minimize the size of the BGP table on your router with inbound filters that are implemented with prefix-lists. Some of the announced prefixes are also in the private IP (RFC 1918) address space.2 © 2005. Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. and may not be distributed for purposes other than individual self-study. You realize that the service providers announce a large number of very small prefixes to you. . You will also filter any prefixes in the private IP address space that you might receive from your service providers.

local router ID is 197. and may not be distributed for purposes other than individual self-study.20. Inc.168.0.20.168.20.22 0 100 22 26 42 i * 192.20.20 0 0 20 42 26 51 i *> 192.168. d damped.20 0 0 20 42 i *> 192. ? .168.11.37. The files or printed representations may not be used in commercial training.168.0 0 32768 i *> 192.20. Inc. h history.22 0 20 22 i *> 192.20 0 0 20 213 i *> 128.0/24 192.0.EGP.22 0 100 22 214 i * 192.20.20.0/30 192.1.20.20.0 192.20.20.168. Lab Guide 31 The PDF files and any printed representation for this material are the property of Cisco Systems.20.0 192.0 32768 i * 200.20. .168.168.11.168. Cisco Systems.168.20. Task 1: Filtering with Prefix-Lists In this activity.0 192.214.20.1.0.22 0 100 22 i * 192.22 0 100 22 i * 128.22 0 100 22 26 51 i *> 128.20 0 0 20 i *> 192.0 192.233 0 0 20 i *> 192.20.0 192.168.168.22 0 100 22 i * 128.12.168.20 100 22 20 i * 192.20.168.incomplete Network Next Hop Metric LocPrf Weight Path * 10.22. Activity Procedure Complete these steps: Step 1 Verify that your current BGP table looks somewhat like the following: wg1r1#show ip bgp BGP table version is 44.22.168.22 0 100 22 26 42 37 i * 128.11.20.22 0 100 22 26 51 i *> 192.168.0 192.168.42.20 0 0 20 i *> 192.0.0. for the sole use by Cisco employees for personal study.233 100 22 20 i * 128.0/16 0.22 0 100 22 i Configuring prefix-lists: Step 2 Based on your analysis.22 0 100 22 26 42 i * 128.22 0 100 22 i * 192.22 0 100 22 26 i * 128.213.20.168.20 100 22 20 i * 200.168.0 192.12.168.20. create prefix-lists to filter incoming updates from routers Good and Cheap.20.26.20 0 0 20 i *> 192.51.0 192.168.20 0 0 20 42 26 51 i *> 192..0.0 192.20.0.0 192.22 0 20 22 i *> 192.168.22.51.20 0 0 20 42 37 i *> 192. * valid.168.0.20 0 0 20 i *> 192.168.42.22 0 100 22 26 42 37 i * 192.168.20.168.11.168.0.20.0 192.0 192.22 0 100 22 i * 128.0.22 0 100 22 214 i *> 197.0.0 192.20.168.0.20.0 0.20.20.20.20 100 22 20 i * 128.20.168. © 2005.20.37.20 0 0 20 i *> 192.11.22 0 100 22 26 i * 192.26.20 0 0 20 213 i *> 192.20.20.20.12. e .11.0 192. — Use prefix-lists to perform these tasks.22.20.168.20.20 0 0 20 42 26 i *> 192.168.20 0 0 20 42 i *> 192.0.0 192.20.168.168. > best.0.168.20 0 0 20 42 26 i *> 192.20.20 0 0 20 42 37 i *> 192.213.22 0 100 22 i * 192.20.168.214.0 192.22.0/16 192.11.0 192. i .22 0 20 22 i *> 192.168.0/16 192.168.internal Origin codes: i .0.168.0.20 0 0 20 i *> 192.0/24 192.20 0 0 20 i *> 192.20.1.168.20.20.8.168. you will configure BGP to influence route selection using prefix-list filters where you must support connections to multiple ISPs.20.20.168.20.0/30 192.IGP.11.168.1 Status codes: s suppressed.20.168.12.0.20.

22 0 100 22 i *> 192.20. you can also issue the show ip bgp prefix-list prefix-list-name command.0.168.20.168.20 0 0 20 i *> 128.20.20. for the sole use by Cisco employees for personal study.0.0 192.20. * valid.IGP.0 192.0/24 192.0.168.IGP.20.20.0/30 192.168.0 0 32768 i 32 Configuring BGP on Cisco Routers (BGP) v3.20.8.20 0 0 20 i * 128.22 0 20 22 i *> 128.0 192.26. The PDF files and any printed representation for this material are the property of Cisco Systems.20.22 0 100 22 26 42 i * 192. ? .0 192.22 0 100 22 i *> 192. i . > best. h history.0 192.0 192.11.168.168.1 Status codes: s suppressed.168.20.20. (Don’t forget to refresh your BGP routes.20.20.20.168.22 0 100 22 i * 192.0.168.20 0 0 20 42 i *> 128.20.0 192.20..20.2(11)T or later.11.168.22.20.168.0 192.168.26.20 0 0 20 i * 200.168.20.20 0 0 20 42 26 i *> 128. The files or printed representations may not be used in commercial training. ? . If your Cisco IOS software version is Release 12.22 0 100 22 26 i * 192.20.20.37.20.1.1 Status codes: s suppressed.20.20.11.22 0 100 22 i *> 192.0 192.0.22. Your display should resemble the following output.0 192.22 0 100 22 214 i *> 192.20.20. d damped.20.0 192.12.168.26.168.20 0 0 20 42 i * 128. d damped.20.20 0 0 20 213 i *> 128.168.42. Inc.20.0. Cisco Systems.20.20.22.0 192.20.22 0 100 22 26 42 i *> 192.20.1.0.42.214.22 0 100 22 26 42 37 i *> 192.EGP.0.EGP.22 0 100 22 26 51 i * 192.12.0. .168.20 0 0 20 42 26 51 i *> 128.168. local router ID is 197.0/24 192.22 0 100 22 26 42 37 i * 192.42.0.0.20 0 0 20 42 26 51 i *> 128.0 192.22 0 20 22 i wg1r1# Full BGP table: wg1r1#show ip bgp BGP table version is 50.20 0 0 20 i *> 128.12.20.51.20.20 0 0 20 42 37 i *> 128.20.20. e .20 0 0 20 i *> 128.168.8.11.0/24 192.11.20 100 22 20 i *> 192.20 0 0 20 213 i * 200.0.20 0 0 20 i *> 128.0.20.0/30 192.213. e .incomplete Network Next Hop Metric LocPrf Weight Path *> 128.12. wg1r1#show ip bgp reg ^20_ BGP table version is 50.168. > best.0 192.11.168.168.20.2 © 2005.168. * valid.213.168.0/16 192.20 0 0 20 i *> 128.168.0 192.12.22 0 100 22 i * 192.0/24 192.0 0.22 0 100 22 26 i *> 192.internal Origin codes: i .0 192. i .168.37.0/16 192.51.168.0 192.22 0 20 22 i * 128. and may not be distributed for purposes other than individual self-study.168.20.20.168.20 0 0 20 42 37 i * 128.0.22.0 192. Applying prefix-lists: Step 3 Apply the prefix-lists that you have created to updates coming from routers Good and Cheap.168.168.0 192.20.22 0 100 22 26 51 i *> 192.0.0.37.0.168.12.168.0. h history.168.internal Origin codes: i . Inc.incomplete Network Next Hop Metric LocPrf Weight Path * 128.0.) Activity Verification You have completed this activity when you attain these results: „ You can inspect your BGP table and check the proper operation of your prefix-list filters.22.1.22.0 192.51.20 0 0 20 42 26 i * 128.168.0 192.168.22. local router ID is 197.

22 0 100 22 214 i *> 197.168.0/16 192.22.22 0 20 22 i Answer these questions: Q1) Are neighboring workgroups still reachable? Q2) Why does router WGxR1 still accept class B networks from router Cheap? © 2005.214.0.0 192.0 32768 i *> 200. Cisco Systems.1.20 100 22 20 i * 192.0.11..0/16 192.20 0 0 20 i *> 200. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study.168.0.168.0/16 0.20.168.20.20. Inc. Lab Guide 33 The PDF files and any printed representation for this material are the property of Cisco Systems.168. for the sole use by Cisco employees for personal study.20.0.20.0. Inc.22 0 100 22 i * 192. . *> 192.20.

. If a router is running an earlier version of Cisco IOS software. The PDF files and any printed representation for this material are the property of Cisco Systems. Visual Objective for Lab 3-4: Implementing Changes in BGP Policy © 2005 Cisco Systems. All rights reserved. 34 Configuring BGP on Cisco Routers (BGP) v3. then it is necessary to configure the soft reconfiguration feature to minimize the impact of expediting BGP policy updates. Inc. you will configure the soft reconfiguration feature to minimize the impact of expediting BGP policy updates in a network scenario where you must support connections to multiple ISPs. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study. Inc. as well as the BGP sessions with two different service providers. for the sole use by Cisco employees for personal study. you will be able to meet these objectives: „ Configure and perform a soft reconfiguration „ Monitor the operation of a soft reconfiguration Visual Objective The figure illustrates what you will accomplish in this activity. Lab 3-4: Implementing Changes in BGP Policy Complete this lab activity to practice what you learned in the related module.2 © 2005.2—10 The figure displays the required BGP connectivity within your workgroup. Cisco Systems. After completing this activity.. In this activity. Activity Objective Note The latest versions of Cisco IOS software include a route refresh capability using the clear ip bgp command. Inc. BGP v3. however.

The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. Cisco Systems. Command Description router bgp as-number Places you in BGP configuration mode clear ip bgp {* | address | peer. The DCE side of the cable is connected to the Cisco 3660. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. Inc.. Enables inbound soft reconfiguration group name} in show ip bgp Enables you to inspect the contents of the BGP table show ip neighbor ip-address Shows detailed information about a specific neighbor show ip neighbor ip-address Enables you to view all updates that are received received-routes from the specified neighbor (before filters) show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command © 2005. and may not be distributed for purposes other than individual self-study. Lab Guide 35 The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. The files or printed representations may not be used in commercial training. Required Resources These are the resources and equipment required to complete this activity. Inc. „ Two Ethernet 10BASE-T patch cables. . „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations.

wg1r1#show ip bgp neighbor 192.1 or later releases support the route refresh capability and dynamic soft resets. The PDF files and any printed representation for this material are the property of Cisco Systems.20. Routers running Cisco IOS Software Release 12. check to ensure that soft reconfiguration is not configured. The files or printed representations may not be used in commercial training.168. you will configure the soft reconfiguration feature to minimize the impact of expediting BGP policy updates in a network scenario where you must support connections to multiple ISPs.” Job Aids These job aids are available to help you complete the lab activity..20. use the show ip bgp neighbors command. Your display should resemble the following output. and may not be distributed for purposes other than individual self-study. If a router supports the route refresh capability. the following message is displayed: “Received route refresh capability from peer. .20 received-routes % Inbound soft reconfiguration not enabled wg1r1#show ip bgp neighbor 192. 36 Configuring BGP on Cisco Routers (BGP) v3.22 received-routes % Inbound soft reconfiguration not enabled Step 2 Enable inbound soft reconfiguration on WGxR1 to both neighbors Good and Cheap.1 do not support the route refresh capability and must clear the BGP session using the neighbor soft-reconfiguration command. for the sole use by Cisco employees for personal study. Unfortunately. To determine whether a BGP router supports this capability. and can use the clear ip bgp {* | address | peer- group name} in command to clear the BGP session. Inc. Note Using the neighbor soft-reconfiguration command may require your router to have much more memory than normally needed. Clearing the BGP session using the neighbor soft-reconfiguration command has a negative effect on network operations and should only be used as a last resort. Activity Procedure Complete these steps: Step 1 Before you begin. You suspect that the frequent changes in your BGP routing policies might be the reason. „ In this activity. Task 1: Configuring Soft Reconfiguration In this activity. your service providers run a Cisco IOS release that does not support BGP route refresh functionality. Cisco Systems. Inc.168. and you would like to implement a mechanism that enables you to perform nondisruptive changes in routing policies. Note Routers running Cisco IOS software releases prior to Release 12. „ Your customers complain that they are sometimes unable to reach your e-commerce servers. you will configure soft reconfiguration to enable nondisruptive changes in BGP routing policies.2 © 2005.

0 192.20.0/24 192.20.20.0 192.0. local router ID is 197. > best.168.0 192.168.20.0.0 192.11.42.20 0 0 20 42 26 51 i * 192.20.20 0 0 20 42 i * 192.11.20.0/30 192.168.168.0. h history.20.168.168.EGP.20 0 0 20 i * 200.22 0 100 22 i *> 192.11.42.0.internal Origin codes: i .22 0 20 22 i * 128.11.20 0 22 20 i *> 128.26.internal Origin codes: i .12.incomplete Network Next Hop Metric LocPrf Weight Path * 10.0 192.22.20.1.0 192.22 0 100 22 i *> 192.22 0 100 22 214 i *> 192.20.0 192.20.0 192.168.168.20.20 0 0 20 213 i * 192.0 192.22 0 100 22 i * 128.IGP. d damped.20.0 192.20.0 192.168.0.11.0/16 192.168.12.0 192.0.11. * valid.20. h history.0/16 192.22.20.168.0/30 192.42.37.22. e . Inc.20.1.168.22.213.168.20.1 Status codes: s suppressed.0 192.0 192. i . The files or printed representations may not be used in commercial training.11.168.11.0. ? .20.168.20 100 22 20 i *> 200.51.0 192.0 192.20 0 0 20 42 37 i * 192. ? .168.0 192.37.20.22 0 100 22 i *> 192.0 192.168.0 192..168.0/16 192.20.20 0 22 20 213 i *> 192.20 0 0 20 42 26 i * 128.0.213.22.0 192.22 0 20 22 i * 192.0 192.20 0 0 20 42 37 i * 128.214.0.11.8.168. Activity Verification You have completed this activity when you attain these results: wg1r1#show ip bgp neighbor 192.0.168.0.51.20.1 Status codes: s suppressed.168.22 0 100 22 26 42 i *> 192.22 received-routes BGP table version is 50.EGP.20.22.0 192.214.0 192.8. local router ID is 197.20 0 0 20 42 26 i * 192.0.168.20. Cisco Systems.20.0 192.26.0.12.0/24 192.20 0 0 20 i * 192.168.IGP. Lab Guide 37 The PDF files and any printed representation for this material are the property of Cisco Systems. .0.168.214.168.20.214.0 192.168.0.22 0 100 22 214 i *> 200.51.20.20 0 0 20 i * 192.0 192.11.20.233 0 22 20 i *> 128.20.0.37.168.213.20.168. i .168.233 0 0 20 i * 128. e .20.51.20.168.20.11.0 192.20.22 0 20 22 214 i * 200.26.20 0 0 20 i *> 128.20 100 22 20 i *> 192.22.11.20.0.22 0 100 22 26 42 37 i *> 128.11. for the sole use by Cisco employees for personal study.20 0 0 20 i *> 128.0.168.22.0.20.22 0 100 22 26 42 37 i *> 192.168.20.0/24 192.20.26.20.0 192.168.20 0 0 20 42 26 51 i *> 128.0.11.20.0/24 192.168.22 0 100 22 26 42 i *> 128.213.0 192.168.168.22 0 100 22 i © 2005.37.22 0 100 22 i * 128.0.22 0 100 22 26 51 i * 128.20.20.0.12.168.168.incomplete Network Next Hop Metric LocPrf Weight Path * 10.168.0/30 192.20.168.20.20.22 0 100 22 26 51 i * 192.0 192.0/16 192.20 0 0 20 i * 192.12.20.11.0 192.20 0 22 20 213 i *> 128.0.168.12. Inc.20.20.20.0/30 192.11.22.20.20.0 192.12. d damped.0 192.168.168.20.42.20. * valid.168.0.168.22 0 20 22 214 i * 192.20.168.22 0 100 22 26 i *> 192.20 0 0 20 i * 128.22 0 0 22 i *> 128.20 received-routes BGP table version is 50.168.20.20. and may not be distributed for purposes other than individual self-study.20.20 0 0 20 213 i * 128.22.0 192.20 0 0 20 42 i * 128.168.20.20.22 0 100 22 26 i *> 128.22 0 20 22 i Total number of prefixes 23 wg1r1#show ip bgp neighbor 192.12. > best.

The PDF files and any printed representation for this material are the property of Cisco Systems. and may not be distributed for purposes other than individual self-study. Inc. The files or printed representations may not be used in commercial training. Inc. for the sole use by Cisco employees for personal study. . Total number of prefixes 23 Answer these questions: Q1) What command do you use to show which entries in the BGP table of the local router have been propagated to a specific neighbor? Q2) What command do you use to display which of the routes in the local BGP table have been received and accepted from an indicated neighbor? 38 Configuring BGP on Cisco Routers (BGP) v3. Cisco Systems..2 © 2005.

2—11 The figure shows the connectivity that is established between your AS and the two service providers Good and Cheap. you will configure BGP to influence route selection by using the weight attribute in a situation where you must support connections to multiple ISPs. The files or printed representations may not be used in commercial training. Cisco Systems. and may not be distributed for purposes other than individual self-study. BGP v3. Lab 4-1: Influencing BGP Route Selection with Weights Complete this lab activity to practice what you learned in the related module.. Visual Objective for Lab 4-1: Influencing BGP Route Selection with Weights © 2005 Cisco Systems. © 2005. . for the sole use by Cisco employees for personal study. Inc. Inc. All rights reserved. After completing this activity. Activity Objective In this activity. Lab Guide 39 The PDF files and any printed representation for this material are the property of Cisco Systems. Inc. you will be able to meet these objectives: „ Influence the BGP route selection process by configuring per-neighbor weights „ Influence the BGP route selection process by configuring BGP weights with route-maps „ Monitor BGP route selection and weights Visual Objective The figure illustrates what you will accomplish in this activity.

„ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. for the sole use by Cisco employees for personal study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. „ Two Ethernet 10BASE-T patch cables. . Inc. The DCE side of the cable is connected to the Cisco 3660. and may not be distributed for purposes other than individual self-study. Cisco Systems. Inc. The PDF files and any printed representation for this material are the property of Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. The files or printed representations may not be used in commercial training.2 © 2005. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. Commands Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address weight Assigns a weight to all updates that are received weight from the specified neighbor neighbor {ip-address | peer. Applies a route-map to incoming or outgoing routes group-name} route-map map-name {in | out} route-map name {permit | deny} Defines or modifies an existing entry in a route-map seq match as-path list-number Specifies route-map matching criteria to match an AS-path access-list set weight weight Sets the weight in a route-map show ip bgp summary Verifies that both BGP sessions are up show ip bgp Enables you to inspect the contents of the BGP table clear ip bgp Clears the BGP session with your neighbor 40 Configuring BGP on Cisco Routers (BGP) v3.. Required Resources These are the resources and equipment required to complete this activity.

Job Aids
These job aids are available to help you complete the lab activity.
„ Currently, you are using the service provider Cheap as your primary provider for Internet
connectivity and the service provider Good as your backup provider. As a result of this
policy, the link toward the Good service provider is underused, while the link toward the
provider Cheap is overloaded.
„ An analysis of the Internet structure beyond your service providers indicates that you can
improve the link use if you send traffic toward AS 213 and AS 37 directly to the Good
service provider.
„ In this activity, you will improve the simple routing policy that you created in the lab
activity “Using Multihomed BGP Networks” by specifying BGP weights with route-maps.
„ You must implement the following routing policy:
— Prefer routes announced from router Cheap over those announced from router Good.
— Prefer routes going through or originating in AS 213 or AS 37 from router Good.

Task 1: Influencing BGP Route Selection with Weights
In this activity, you will configure BGP to influence route selection by using the weight
attribute in a situation where you must support connections to multiple ISPs.

Activity Procedure
Complete these steps:

Configuring AS-path access-lists:
Step 1 Create an AS-path access-list that permits either AS number 213 or 37 in the AS
path (one is sufficient).

Setting per-neighbor default weights:
Step 2 (Optional) Set default weights for both neighboring routers. For example, use 100
for Good and 200 for Cheap as weights.

Step 3 Inspect your BGP table to verify that you prefer routes coming from Cheap to routes
coming from Good.

Using AS-path filters within route-maps to set weights:

Step 4 Create a new route-map. Use the previously configured AS-path access-list as the
match condition in one of the route-map statements, and set the weight of matched
routes as needed. Remember that routes matching this AS-path access-list from
Good should give the highest weight; therefore, you might use 300 for the weight.
Step 5 Apply the route-map to incoming updates from router Good.

Activity Verification
You have completed this activity when you attain these results:
„ You can verify your BGP table to see that all prefixes with two paths prefer the one
through router Cheap. Your display should resemble the following output.

© 2005, Cisco Systems, Inc. Lab Guide 41
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

wg1r1#show ip bgp
BGP table version is 43, local router ID is 197.1.8.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 128.20.0.0 192.168.20.20 0 100 20 i
*> 192.168.20.22 0 200 22 i
*> 128.20.12.0/24 192.168.20.20 0 100 20 i
* 128.22.0.0 192.168.20.20 0 100 20 i
*> 192.168.20.22 0 200 22 i
*> 128.22.12.0/24 192.168.20.22 100 20 22 i
* 128.26.0.0 192.168.20.20 0 100 20 42 26 i
*> 192.168.20.22 0 200 22 26 i
*> 128.37.0.0 192.168.20.20 0 300 20 42 37 i
* 192.168.20.22 0 200 22 26 42 37 i
* 128.42.0.0 192.168.20.20 0 100 20 42 i
*> 192.168.20.22 0 200 22 26 42 i
* 128.51.0.0 192.168.20.20 0 100 20 42 26 51 i
*> 192.168.20.22 0 200 22 26 51 i
*> 128.213.0.0 192.168.20.20 0 300 20 213 i
*> 128.214.0.0 192.168.20.22 0 200 22 214 i
*> 192.20.11.0 192.168.20.22 0 200 22 i
*> 192.20.12.0/30 192.168.20.20 200 22 20 i
*> 192.22.11.0 192.168.20.22 0 200 22 i
*> 192.22.12.0/30 192.168.20.22 0 200 22 i
*> 192.26.11.0 192.168.20.22 0 200 22 26 i
*> 192.37.11.0 192.168.20.22 0 200 22 26 42 37 i
*> 192.42.11.0 192.168.20.22 0 200 22 26 42 i
*> 192.51.11.0 192.168.20.22 0 200 22 26 51 i
*> 192.168.1.0 0.0.0.0 0 32768 i
*> 192.214.11.0 192.168.20.22 0 200 22 214 i
*> 197.1.0.0/16 0.0.0.0 32768 i
* 200.20.0.0/16 192.168.20.20 0 100 20 i
*> 192.168.20.20 200 22 20 i
* 200.22.0.0/16 192.168.20.22 100 20 22 i
*> 192.168.20.22 0 200 22 i

Answer these questions:

Q1) Did all paths automatically get a weight of 100 or 200? Why not? What did you have to
do?

Q2) Name some parameters and attributes that are used for best-path selection.

42 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

Lab 4-2: Setting BGP Local Preference
Complete this lab activity to practice what you learned in the related module.

Activity Objective
In this activity, you will configure BGP to influence route selection using the local preference
attribute in a situation where you must support multiple connections to an ISP. After
completing this activity, you will be able to meet these objectives:
„ Configure BGP local preference using route-maps
„ Monitor BGP local preference

Visual Objective
The figure illustrates what you will accomplish in this activity.

Visual Objective for Lab 4-2:
Setting BGP Local Preference

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—12

The figure shows the new physical connectivity, BGP sessions, and the expected traffic flow in
the network.

Required Resources
These are the resources and equipment required to complete this activity.

Your workgroup requires the following components:
„ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software
installed.

© 2005, Cisco Systems, Inc. Lab Guide 43
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

you will establish a second link toward the Good service provider and use the local preference attribute to select the newly established link as the preferred exit point from your network. „ Two Ethernet 10BASE-T patch cables. „ The additional link that you establish will connect WGxR2 and the Good router through the Frame Relay network. The DCE side of the cable is connected to the Cisco 3660. . The files or printed representations may not be used in commercial training. you must use local preference in your AS to ensure consistent AS-wide routing policy. Inc. and may not be distributed for purposes other than individual self-study. The PDF files and any printed representation for this material are the property of Cisco Systems. All traffic from your AS toward Good should flow over this link. Cisco Systems. Inc. „ In this activity. for the sole use by Cisco employees for personal study.2 © 2005. You will configure an EBGP session between WGxR2 and Good over this link. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. Applies a route-map to incoming or outgoing routing group-name} route-map map-name updates {in | out} set local-preference number Sets the local preference attribute within a route- map show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command clear ip bgp Restarts the BGP session with your BGP neighbor Job Aids These job aids are available to help you complete the lab activity.. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. 44 Configuring BGP on Cisco Routers (BGP) v3. „ You want to have two links with the Good service provider to increase the reliability of your Internet service. With several links that connect you to the same service provider. Commands Command Description router bgp as-number Places you in BGP configuration mode no synchronization Disables BGP synchronization neighbor{ip-address | peer. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations.

set the local preference higher than the default value of 100 (for example. Parameter Value Service provider IP address 192. The other side of this PVC is connected to router Good. © 2005. Step 6 Create a new route-map on router WGxR2. Within the route map.1/30 for the Frame Relay link connection.2 Service provider AS number 20 Establishing full-mesh IBGP: Step 3 Establish IBGP sessions between all routers in your pod with disabled synchronization. Step 7 Apply the route-map to incoming updates from router Good. Using local preference to ensure AS-wide routing policy: Step 5 On WGxR1. remove neighbor weight statements and any route-map statements that modify the weight attribute on WGxR1 for the routers Good and Cheap.1/30 20x Establishing EBGP peering between WGxR2 and router Good: Step 2 Configure the router Good as the EBGP neighbor by using the parameters from the following table.3x. . Lab Guide 45 The PDF files and any printed representation for this material are the property of Cisco Systems.168. Activity Procedure Complete these steps: Configuring additional IP connectivity: Step 1 Create another point-to-point subinterface on WGxR2 using the parameters from the following table.. Cisco Systems. The files or printed representations may not be used in commercial training. Task 1: Setting BGP Local Preference In this activity.168. for the sole use by Cisco employees for personal study. which is already configured. „ On WGxR2. use DLCI 20x and IP address 192. Remember. „ The BGP routing design contains the following items: — AS x should prefer AS 20 as the upstream service provider. Router WGxR2 should be used as the exit point under normal circumstances.3x. the networks need to be advertised in the IGP. Step 4 Remember that external networks are not carried in your IGP.168. you will configure BGP to influence route selection using the local preference attribute in a situation where you must support multiple connections to an ISP. Router IP Address DLCI WGxR2 192. Inc. 200). and may not be distributed for purposes other than individual self-study. Inc.3x. Remember to use the good practice of implementing a stable loopback interface address for peering. — Peering to AS 20 through WGxR1 should be used only if the primary link fails.

WG1R4#traceroute 192. Inc.3.0/24 192.1 0 100 0 i *> 192. > best.2 0 200 0 20 42 26 51 i * i192.2 © 2005.31.168.12.168. wg1r2#show ip bgp BGP table version is 29.168.168.0.0 192.0. Cisco Systems.1.20.0 192.168.0 192.168.51.168. and may not be distributed for purposes other than individual self-study.11.12.1 1 192.0.168.31.2 0 200 0 20 i *> 192.168. Tracing the route to 192.11.2 0 200 0 20 i *> 128.31.11.1.0.0 192.51.31.168.168.0.168. Activity Verification You have completed this activity when you attain these results: „ On WGxR2.0.11.2 200 0 20 22 I „ You can use the traceroute command from router WGxR4 and WGxR1 to 192.1 100 0 i *>i197.31.168.168.. d damped. The PDF files and any printed representation for this material are the property of Cisco Systems.1.0.11.0.31.0. i .213.31.0 192.22.2 0 200 0 20 42 37 i *> 128.2 0 200 0 20 i *> 128.168.1 Type escape sequence to abort. Tracing the route to 192.5 32 msec 45 msec 40 msec 3 192.1.0 192.168.214.1.20.0 192.incomplete Network Next Hop Metric LocPrf Weight Path *> 10.2 0 200 0 20 i *> 128.11.0. Step 8 Perform clearing of the BGP session between the routers by using the clear ip bgp * command.168.0/16 192.0/30 192. Your display should resemble the following output.0 192.2 0 200 0 20 42 i *> 192.0 192.31.213.168.1 Status codes: s suppressed.0.22.31.0/16 192.168.11.0 192.1. e .2 0 200 0 20 42 26 51 i *> 128.IGP. Inc.2 0 200 0 20 i *> 128.31.8.2 200 0 20 22 214 i *>i197.31.31.0.37.11.0 192.31.0/30 192.168.12.31.168.2 200 0 20 22 214 i *> 192.0 192.0 192.0 192.2 0 200 0 20 42 37 i *> 192.1.0 192.31.2 0 200 0 20 213 i *> 192.168.0.31.11.22.1.0/21 192. .168.20.1 Type escape sequence to abort.22.31.1 1 192.1 100 0 i *> 200.31.0 192.168.168.31.2 0 200 0 20 213 i *> 128.42.168.31. ? .168.2 0 200 0 20 i *> 192.37.1 0 100 0 i *> 0.42.26.0 192.0 0 32768 i *>i192.2 200 0 20 22 i *> 192.2 0 200 0 20 42 i *> 128.2 56 msec * 52 msec wg1r1#traceroute 192.20. Use a soft clearing of WGxR1 if you still have soft inbound reconfiguration enabled.20.168. The files or printed representations may not be used in commercial training. * valid.0 192.20.2 0 200 0 20 42 26 i *> 128.9 32 msec 24 msec 20 msec 2 192.2 40 msec 28 msec 24 msec 2 192.20.0/22 192.20.2 12 msec * 16 msec 46 Configuring BGP on Cisco Routers (BGP) v3.11.168.0/24 192.168.1.12.1.0/16 192.168.26.11.31.2 0 200 0 20 42 26 i *> 192.168.168.31.31.22.168.20.0 192. local router ID is 197.0.0.11.214. h history.31.1.31.1. you can verify that the local preference has been changed and also note the IBGP routes.2 0 200 0 20 i *> 192.EGP.0.1.168.internal Origin codes: i .31. Your display should resemble the following output.1 100 0 i *>i197.20.2 200 0 20 22 i *> 128. for the sole use by Cisco employees for personal study.11.2 0 200 0 20 i *> 200.1.

1.8.1. Inc.168.1.1 1 wg1 (192. (Note that this result might depend on the age of the EBGP sessions from Step 8 above [oldest EBGP path that was selected] and necessitate clearing of the router Good peer with WGxR2 to demonstrate asymmetrical routing. Lab Guide 47 The PDF files and any printed representation for this material are the property of Cisco Systems. Answer these questions: Q1) Is routing between router WGxR1 and Good symmetrical? Q2) Which routers receive the local preference attribute? © 2005. .168.1 Type escape sequence to abort. Use the command traceroute 197. and may not be distributed for purposes other than individual self-study.1) 4 msec 0 msec 4 msec 2 192. „ You can use traceroute from router Good to interface loopback0 on routers WGxR4 and WGxR1. The files or printed representations may not be used in commercial training.20.7.1.168.1 1 wg1 (192. Cisco Systems. Tracing the route to 197. Inc.20.7.7.1) 4 msec * 0 msec „ You can compare the two outputs of the traceroute command to determine whether the routing is symmetrical. Good#traceroute 197.168. Your display should resemble the following output.1 source lo 0.) Note You may need to use an extended traceroute from router Good.1 Tracing the route to 197.22.1 Type escape sequence to abort.1.2 [AS 1] 20 msec 28 msec 24 msec 3 192. Both traceroute commands should show router WGxR2 in the path.168. The next lab will address these issues.1. for the sole use by Cisco employees for personal study.1.11.6 [AS 1] 40 msec 45 msec 36 msec 4 192. Packet sent with a source address of 192.8.1..10 [AS 1] 52 msec * 48 msec Good#traceroute 197.

The files or printed representations may not be used in commercial training. All rights reserved. Cisco Systems. Visual Objective for Lab 4-3: Understanding BGP Multi-Exit Discriminators © 2005 Cisco Systems. BGP sessions. Inc. for the sole use by Cisco employees for personal study. 48 Configuring BGP on Cisco Routers (BGP) v3. Inc.2 © 2005. and traffic flow in the network.. and may not be distributed for purposes other than individual self-study. Activity Objective In this activity. Required Resources These are the resources and equipment required to complete this activity.2—13 The figure shows the physical connectivity. . BGP v3. you will be able to meet these objectives: „ Configure the BGP MED using route-maps „ Monitor the BGP MED Visual Objective The figure illustrates what you will accomplish in this activity. Inc. Lab 4-3: Understanding BGP Multi-Exit Discriminators Complete this lab activity to practice what you learned in the related module. The PDF files and any printed representation for this material are the property of Cisco Systems. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. you will configure BGP to influence route selection using the MED attribute in a situation where you must support multiple connections to an ISP. After completing this activity.

„ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. Applies a route-map to incoming or outgoing routing group-name} route-map map-name updates {in | out} route-map name {permit | deny} Defines or modifies an existing entry in a route-map seq set metric metric Sets the MED in a route-map clear ip bgp * Resets the BGP peer show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command Job Aids These job aids are available to help you complete the lab activity. Note This activity is a continuation of the previous lab activity. „ The implementation should ensure symmetrical routing. You should use backup peering only when the primary link is down. Inc. Use the MED to influence neighboring AS 20 to choose the preferred return path. . The DCE side of the cable is connected to the Cisco 3660. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study. You will use the MED to indicate to the Good router the exit point that it should use. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. Inc. © 2005. „ Two Ethernet 10BASE-T patch cables. for the sole use by Cisco employees for personal study. Commands Command Description router bgp as-number Places you in BGP configuration mode neighbor {ip-address | peer. resulting in asymmetrical routing.. „ You have noticed that the traffic from router Good toward your AS sometimes passes through the router WGxR1. Cisco Systems. Lab Guide 49 The PDF files and any printed representation for this material are the property of Cisco Systems.

20.0.0. you will configure BGP to influence route selection using the MED attribute in a situation where you must support multiple connections to an ISP.20.2 © 2005. Configuring WGxR2 to set the MED: Step 3 Create a new route-map.22.0.0.0.199.20.11.51.168.0. ? .0 192.168.0.22 0 0 22 214 i * 192.incomplete Network Next Hop Metric LocPrf Weight Path *> 10.168.199 Status codes: s suppressed.11. e .0.0 0 32768 i * 128.0.0 0 32768 i *> 128.168. Apply the route-map to outgoing updates toward the router Good. which sets the BGP MED to a low value (for example.0.0.0 0 32768 i *> 128.168.0 0 32768 i * 128. Activity Verification You have completed this activity when you attain these results: „ You can check the BGP table on router Good to see whether the MED is present in BGP updates that are received from WGxR1 and WGxR2.22 0 0 22 26 i *> 0.0.0 0 32768 i * 192.0 192.0 0 32768 i * 128.168.0 0 32768 i * 128.22 0 0 22 i *> 0.20. * valid.20.12.20.22 0 0 22 i *> 0. i . for the sole use by Cisco employees for personal study. The PDF files and any printed representation for this material are the property of Cisco Systems.0 0 32768 i *> 128.0 192.0.0.22 0 0 22 i *> 0. d damped.168.26.internal Origin codes: i .12.22 0 0 22 26 42 37 i *> 0.0 192. Good#show ip bgp BGP table version is 46.22 0 0 22 i *> 0.20.0.0 0..22 0 0 22 26 42 i *> 0.0 192.20.0 0 32768 i *> 128.168.0/24 0.20. . 200). check the BGP table for router Good to see whether the MED is present in BGP updates that are received from WGxR1 and WGxR2.168. Apply the route-map to outgoing updates toward the router Good. h history. Task 1: Configuring BGP Multi-Exit Discriminators In this activity.199. local router ID is 199.22 0 0 22 i * 128.IGP.168.0. Configuring WGxR1 to set the MED: Step 2 Create a new route-map.20. Inc.20.0 192.0/30 0.0.20.22 0 0 22 26 51 i *> 0.0.0 192.0. which sets the BGP MED to a high value (for example.0.12.0.0.168.0.0.37.0.20.214. Activity Procedure Complete these steps: Step 1 Before starting the activity.22.233 0 32768 i * 128.0. Note Remember to advertise your networks.0.0.0.22.0 192.EGP.0 0 32768 i *> 192. Cisco Systems.42.213.0 192. Your display should resemble the following output. Inc. > best.0 0 32768 i 50 Configuring BGP on Cisco Routers (BGP) v3.0/24 192. 100). and may not be distributed for purposes other than individual self-study.0.0.20.20.0 192.0. The files or printed representations may not be used in commercial training.

0.168.168.22 0 0 22 26 42 37 i *> 0.0 192.1 100 0 1 i * 192.20.0 0 32768 i * 192.0.0.31.1 1 192.1 [AS 1] 36 msec 28 msec 24 msec 2 192.168.0.11.22.22 0 0 22 26 51 i *> 0.37.20.0 0 32768 i *> 192.20.0 192. Your display should resemble the following output.7. Tracing the route to 197. Lab Guide 51 The PDF files and any printed representation for this material are the property of Cisco Systems.1 1 192.11.168.11.2 60 msec 64 msec 56 msec wg1r1#traceroute 192.0.0 0 32768 i * 192. Your display should resemble the following output.0. Inc.1 0 22 1 i * 192.1 200 0 1 i *> 200.0 192.1 [AS 1] 36 msec 28 msec 24 msec 2 192.1.20.7. for the sole use by Cisco employees for personal study.42.1.20..168.1. Inc.168.20.20. Cisco Systems.0 192.12.1.22.168.5 28 msec 44 msec 41 msec 3 192.20. Tracing the route to 192.20.22 0 0 22 214 i * 197.168.0/16 192.168.0.1 1 192.31.1. and may not be distributed for purposes other than individual self-study.0. *> 192.168.168.31.168.1 1 192.1.0 0 32768 i * 192.11. The files or printed representations may not be used in commercial training.0 192.20.0/16 0.11.22 0 0 22 26 i *> 0.0/16 192. .0 192.8.0. wg1r4#traceroute 192. © 2005.213.168. Good#traceroute 197.1.0 0.1 source lo 0 Type escape sequence to abort.1.20.0.168.1 source lo 0 Type escape sequence to abort.26.31.11.168.0 0 32768 i * 192.20.31.168.1 100 0 1 i * 192.168.51.214.9 32 msec 24 msec 20 msec 2 192.2 40 msec 28 msec 20 msec 2 192.0. Tracing the route to 192.1.22 0 0 22 I „ You can use the traceroute command from routers WGxR4 and WGxR1 to 192.22 0 0 22 i * 192.1.11.1 0 22 1 i *> 192.0.11. Tracing the route to 197.168.31.1.2 32 msec * 36 msec „ You can use the traceroute command from router Good to interface loopback1 on routers WGxR4 and WGxR1.1.0 192.168.0.1 Type escape sequence to abort.20.168.6 [AS 1] 32 msec 36 msec 36 msec 3 192.168.20.168.168.8. Both traceroute commands should show router WGxR2 in the path.0 0 32768 i *> 200.20.1.10 [AS 1] 52 msec * 48 msec Good#traceroute 197.1 200 0 1 i *> 192.168.11.168.31.0.0.1 0 22 1 i *> 192.20.11.20.168.31.1 200 0 1 i *> 192.20.168.22 0 0 22 26 42 i *> 0.168.1 [AS 1] 40 msec * 36 msec „ You can compare the two outputs of the traceroute command to determine whether the routing is symmetrical.1 Type escape sequence to abort.1 100 0 1 i * 192.11.20.0/30 192.

. Inc. for the sole use by Cisco employees for personal study. Answer these questions: Q1) Which parameters and attributes have to be equal before the MED is compared to select the best path? Q2) What is the default value of the MED? 52 Configuring BGP on Cisco Routers (BGP) v3. Cisco Systems. The PDF files and any printed representation for this material are the property of Cisco Systems. Inc. . The files or printed representations may not be used in commercial training.2 © 2005. and may not be distributed for purposes other than individual self-study.

you will configure BGP to influence route selection by using the BGP community attribute in a situation where you must support multiple connections to an ISP. Activity Objective In this activity. Cisco Systems. Lab 4-4: Addressing BGP Communities Complete this lab activity to practice what you learned in the related module. After completing this activity. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. and may not be distributed for purposes other than individual self-study. Visual Objective for Lab 4-4: Addressing BGP Communities © 2005 Cisco Systems. you will be able to meet these objectives: „ Configure route tagging by using BGP communities „ Configure BGP community propagation „ Monitor BGP communities Visual Objective The figure illustrates what you will accomplish in this activity.. and traffic flow in the network. Inc.2—14 The figure shows the physical connectivity. for the sole use by Cisco employees for personal study. BGP v3. Inc. All rights reserved. Required Resources These are the resources and equipment required to complete this activity. BGP sessions. . Inc. © 2005. Lab Guide 53 The PDF files and any printed representation for this material are the property of Cisco Systems. The files or printed representations may not be used in commercial training.

„ Two Ethernet 10BASE-T patch cables. for the sole use by Cisco employees for personal study.. Inc. Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. Inc. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. The PDF files and any printed representation for this material are the property of Cisco Systems.2 © 2005. and may not be distributed for purposes other than individual self-study. 54 Configuring BGP on Cisco Routers (BGP) v3. The DCE side of the cable is connected to the Cisco 3660. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. The files or printed representations may not be used in commercial training. .

Inc. Lab Guide 55 The PDF files and any printed representation for this material are the property of Cisco Systems. Commands Command Description router bgp as-number Places you in BGP configuration mode neighbor {ip-address | peer. Inc. Applies a route-map to incoming or outgoing routing group-name} route-map map. for the sole use by Cisco employees for personal study. Enables community propagation to BGP neighbors community neighbor ip-address shutdown Disables communication with a BGP neighbor © 2005. and may not be distributed for purposes other than individual self-study. Cisco Systems. The files or printed representations may not be used in commercial training. updates name {in | out} route-map name {permit | Defines or modifies an existing entry in a route-map deny} seq match community c-acl Matches communities in a route-map by using a community-list set community community Sets community attributes in a route-map—use the [additive] keyword additive to append communities instead of replacing them set local-preference num Sets local preference attribute ip bgp-community new-format Configures BGP communities using as:nn format ip community-list num Creates a community access-list {permit | deny} community show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command show ip bgp community Enables you to view BGP routes that have at least one [community [community …]] community attribute or those that are specified in the [exact-match] command show ip bgp community-list Enables you to view BGP routes that are permitted by c-list [exact-match] the specified community-list neighbor ip-address send. ..

.x.1 [AS 1] 16 msec 16 msec 16 msec 2 192. Inc.3x.10 [AS 1] 44 msec * 40 msec Step 2 Remove the BGP neighbor statement on WGxR1 for router Good or simply disable communication via the neighbor shutdown command.6 [AS 1] 28 msec 32 msec 28 msec 3 192.7. The trace should match this display (where x is your workgroup number): Good#traceroute 197.x. Activity Procedure Complete these steps: Step 1 Before starting this lab. for the sole use by Cisco employees for personal study. Job Aids These job aids are available to help you complete the lab activity. As a result of the new service that is available from Cheap. you still wish to use the primary connection to Good for return traffic should the link to provider Cheap fail.168. Inc. „ You wish for all outgoing traffic to continue using the link to Good. Configuring outbound filters on WGxR2: Step 5 Create a route-map to set the community attribute on all BGP updates that are sent from WGxR2 to the provider Good.x.7. You decide to change your route selection policy to use the newly updated link from Cheap. Step 6 Apply the route-map to the BGP neighbor Good in the outbound direction. and may not be distributed for purposes other than individual self-study.1. and you solicit assistance from provider Good.168.x. „ Your second service provider Cheap has upgraded its link to your network to match that of the provider Good.168. Cisco Systems. 56 Configuring BGP on Cisco Routers (BGP) v3. Tracing the route to 197. Configuring BGP community propagation: Step 3 Configure BGP community propagation on router WGxR2.1 1 192. you decide to remove the backup link to provider Good because you can now achieve both link and provider redundancy. Step 4 Enable your WGxR2 router to configure communities using the as:nn format.x.1 source lo 0 Type escape sequence to abort. Knowing that you have a connection to the provider Good. The PDF files and any printed representation for this material are the property of Cisco Systems. „ You cannot influence return path selection across multiple providers. Set the community attribute to x:20.2 © 2005. . where x is your workgroup number. use the traceroute command from router Good to 197.7. you will configure BGP to influence route selection by using the BGP community attribute in a situation where you must support multiple connections to an ISP. The files or printed representations may not be used in commercial training. Provider Good agrees to set local preference for any routes that you mark as follows: — Local preference of 50 for routes marked with a community attribute of x:20 Task 1: Configuring BGP Communities In this activity. but all return traffic should use the newly updated link from Cheap.

31. the next hop is not changed. Cisco Systems.199 Status codes: s suppressed. * valid.168. Activity Verification You have completed this activity when you attain these results: „ You can log in to the router Good and verify that the BGP community attribute has been correctly set.1) Origin IGP. you would expect to see that the first line of the traceroute shows Cheap as the first hop.incomplete Network Next Hop Metric LocPrf Weight Path * 192.1. Answer these questions: Q1) What do you have to do to enable community propagation? © 2005.168.22 (192.1.168.1 1 wg1 (192.1.1.8.1.168.. Inc. (aggregated by 1 197. version 22 Paths: (2 available.1. However. external.11. Your display should resemble the following output. because the routers Good. the next hop has not been changed. because local preference is a stronger route-selection tool.1. Your display should resemble the following output.199. is the bottom route. atomic-aggregate. but because of the shared media.31. (aggregated by 1 197. Your display should resemble the following output. and may not be distributed for purposes other than individual self-study.6 [AS 1] 28 msec 28 msec 36 msec 4 192.10 [AS 1] 44 msec * 44 msec Note Normally. > best.2 [AS 1] 16 msec 16 msec 16 msec 3 192. Good>show ip bgp community 1:20 Good#show ip bgp community 1:20 BGP table version is 61.1 0 50 0 1 i * 197. atomic-aggregate Community: 1:20 22 1. table Default-IP-Routing-Table) Advertised to peer-groups: students2 1. and WGxR1 share a common Ethernet segment.168.1 from 192.1.3. e .20.0.1) 192. Good#traceroute 197.7. Cheap. The next-hop rule applies even when there is no BGP connection between Good and WGxR1.0/21 192.20.168.internal Origin codes: i .1) 192.1 (197.1.0 192. for the sole use by Cisco employees for personal study.0. valid. localpref 100.168. the BGP next-hop rule states the following: If the current BGP next hop is in the same IP subnet as the receiving router.7. .168.0/21.EGP. valid.8.1. „ On router Good.IGP. i .1. Lab Guide 57 The PDF files and any printed representation for this material are the property of Cisco Systems. you can execute the command: show ip bgp 197.168.20. Good#show ip bgp 197. best #2.1 BGP routing table entry for 197. This result is true even though the AS-path length is longer. it is changed to the IP address of the sending router.1) Origin IGP.1.1) 0 msec 0 msec 0 msec 2 192. Inc.1 from 192.168. ? . h history. external.22 (Cheap).7.199.1 50 0 1 i You can log in to router Good and perform the same traceroute that was done before you started the configuration in this lab. d damped. localpref 50.168. otherwise.7.1 Type escape sequence to abort. Tracing the route to 197. because of local preference. local router ID is 199.31. best Note that the best path.31.20. and the next hop is 192.1.20.168. The files or printed representations may not be used in commercial training.1.

for the sole use by Cisco employees for personal study. Cisco Systems. Inc. . The PDF files and any printed representation for this material are the property of Cisco Systems. The files or printed representations may not be used in commercial training.. and may not be distributed for purposes other than individual self-study.2 © 2005. Q2) What mechanisms can you use to match or set communities? 58 Configuring BGP on Cisco Routers (BGP) v3. Inc.

. Inc. . Inc. for the sole use by Cisco employees for personal study. Activity Objective In this activity. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. Required Resources These are the resources and equipment required to complete this activity. The DCE side of the cable is connected to the Cisco 3660.2—15 The required IBGP sessions and the cluster structure are outlined in the figure. and may not be distributed for purposes other than individual self-study. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. Inc. Lab Guide 59 The PDF files and any printed representation for this material are the property of Cisco Systems. After completing this activity. Cisco Systems. The files or printed representations may not be used in commercial training. BGP v3. Lab 6-1: Introducing Route Reflectors Complete this lab activity to practice what you learned in the related module. © 2005. you will be able to meet these objectives: „ Plan the migration of an existing IBGP backbone to a backbone with route reflectors „ Configure BGP route reflectors on a BGP backbone „ Monitor a BGP backbone that contains route reflectors Visual Objective The figure illustrates what you will accomplish in this activity. All rights reserved. you will enable route reflectors to modify IBGP split-horizon rules in a transit AS. Visual Objective for Lab 6-1: Introducing Route Reflectors © 2005 Cisco Systems.

and WGxR1 is its client. Within this cluster. 60 Configuring BGP on Cisco Routers (BGP) v3. Commands Command Description router bgp as-number Places you in BGP configuration mode bgp cluster-id id Specifies the cluster-ID neighbor ip-address route. — WGxR2 is the route reflector in cluster 2. you will replace the IBGP full mesh with a hierarchy of BGP route reflectors. Cisco Systems. and may not be distributed for purposes other than individual self-study. router WGxR3 is the route reflector. . — Router WGxR4 is not participating in any cluster and needs to be in IBGP full mesh with top-level route reflectors. Establishes an IBGP session by using your workgroup reflector-client number as the AS number show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command Job Aids These job aids are available to help you complete the lab activity.2 © 2005. for the sole use by Cisco employees for personal study. The PDF files and any printed representation for this material are the property of Cisco Systems. „ In this activity. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. Inc.. and WGxR2 is the client. Inc. „ Two Ethernet 10BASE-T patch cables. „ Configure IBGP sessions in your AS according to this design: — Cluster 1 is your top-level cluster. The files or printed representations may not be used in commercial training.

Your display should resemble the following output.4.1 4 1 4053 4035 1028 0 0 00:01:26 25 © 2005.2. Cisco Systems.1. Lab Guide 61 The PDF files and any printed representation for this material are the property of Cisco Systems.2.20.168. Activity Verification You have completed this activity when you attain these results: „ You can check your BGP connections on the core routers and ensure that they are connected only to the peers. WG1R1#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.20.22 4 22 1720 1705 138 0 0 01:11:03 23 197. .168. Remember that the external network is not announced in your IGP. Configuring the top-level route reflector WGxR3: Step 4 Configure cluster-ID 101 on the top-level route reflector WGxR3. Remember to remove next- hop-self because EBGP is no longer configured. Activity Procedure Complete these steps: Cleaning up your BGP configurations: Step 1 Remove the EBGP session on WGxR2 to router Good.168. Task 1: Configuring Route Reflectors In this activity. and may not be distributed for purposes other than individual self-study. Removing unnecessary BGP neighbors from your AS: Step 6 Remove the IBGP sessions that are no longer needed from routers in your pod.1.1. Configuring the second-level route reflector WGxR2: Step 5 Configure cluster-ID 102 on WGxR2. Step 3 Configure EBGP from WGxR4 to router Client as 192. as shown in the lab diagram. you will enable route reflectors to modify IBGP split-horizon rules in a transit AS.1. Inc. Configure the client on WGxR2 and remove unnecessary IBGP sessions from WGxR2.1 4 1 1665 1703 138 0 0 00:02:52 11 WG1R2#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 197. Inc. for the sole use by Cisco employees for personal study.21. Configure the client on WGxR3 and remove unnecessary IBGP sessions. Step 2 Enable the shutdown neighbor from WGxR1 to Good or reconfigure if the neighbor statement was removed.1.1 4 1 4035 4053 1074 0 0 00:01:05 13 WG1R3#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 197.1 4 1 4149 4053 1074 0 0 00:03:19 25 197.99 with AS 99..20 4 20 5923 4224 138 0 0 01:11:00 23 192. Option: WGxR1 filters to Good and Cheap can be removed or left intact. The files or printed representations may not be used in commercial training.

table Default-IP-Routing-Table) Advertised to non peer-group peers: 192. metric 0.0. WG1R1#show ip bgp 197.0.168.20.1 0 1 22 i *> 192.0.0.0.1 0 1 22 i *> 128.0. > best.1 0 1 22 i *> 192.0.168.1.0 192.168.21.168.0.1 0 1 i *> 192.0 0 32768 i *> 197. Cisco Systems.0.99.168.1 4 1 1674 1745 225 0 0 01:27:19 23 „ You can check to see whether router Client is receiving networks from your network.1 Status codes: s suppressed.26.99.51.1 0 1 22 26 51 i *> 128.12.0/24 192. for the sole use by Cisco employees for personal study. Client#show ip bgp BGP table version is 210.0 192.7.0 0 32768 i *> 128. e .21.1.0 0.0 0 32768 i *> 197. Your display should resemble the following output.1/32 0.1. local router ID is 197.80.0.111.168.0.0 0.21.0 0 32768 i *> 197.12.0 0.99. 0.2.0 0 32768 i *> 197.0/16 192.168.99.1 0 1 22 i *> 192. and may not be distributed for purposes other than individual self-study.1 0 1 20 i *> 128.0/20 0.1 0 1 22 26 i *> 128.21.0.13.0 0 32768 i *> 200.21.1 0 1 20 42 37 i *> 128.0.168.1 0 1 22 26 51 i *> 192.1.168.20.168.0.214.1 0 1 22 26 42 37 i *> 192.12.0.11.0.168.37.0.22.37. The files or printed representations may not be used in commercial training.168.0 192.0.1 0 1 20 213 i *> 128.168. best Originator: 197.21.12.0.0.22.21.12.1) Origin IGP.22.0 0. 197.1 0 1 20 42 i *> 128..213. i .0/16 192.21.1 0 1 22 20 i *> 192.168.IGP.168.1 0 1 22 26 42 i *> 192.168.0 0.22 99 192.168.7.0.1.1 0 1 22 i *> 128.0. Your display should resemble the following output.0 192.0 0 32768 i *> 197. .0 192.21.0 0.6.1 (197. version 129 Paths: (1 available.99.1.0 192. localpref 100.99.1 0 1 20 22 i *> 128.0 192.99.0.22.0.0 192.0 192.0.11.0 0.21.20 192.0.20.1 0 1 22 26 i *> 192.0.21.0.11.internal Origin codes: i .21. h history.0 0.1.0.0 0 32768 i *> 197.incomplete Network Next Hop Metric LocPrf Weight Path *> 99.20.21.0.168.4.168.21.102.168.0 0.EGP.0/30 192.0.0/24 192.99.99.21.21.21.21.51.0. Inc. valid.11.99.42.0.1 0 1 20 i *> 200.0/16 192.21.128.0 192.1 0 1 22 214 i *> 192.0 192.21.99 (metric 202) from 197.0 0 32768 i *> 197.0 0 32768 i *> 197. ? .0 192. The command output will vary depending on filters.168.168.99.120.22.21.1.214.11.26.0/24.1 0 1 22 i „ You can check to see whether the cluster-list attribute is applied to routes passing through the AS.11.0 0 32768 i *> 197.0 192.20.2 © 2005.0.168.168. Inc. d damped.99.168.1.21.111.1. best #1.0.21.21.0 BGP routing table entry for 197.22. Cluster list: 0.101 62 Configuring BGP on Cisco Routers (BGP) v3.0.0 192.168.42.1 0 1 i *> 197.0.21.1 4 1 4171 4068 1028 0 0 01:27:02 13 WG1R4#show ip bgp summary … Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.0 192.0 192.0/30 192.0.20.168.20.20. internal.99.1.99 4 99 1744 1713 225 0 0 00:46:07 11 197. The PDF files and any printed representation for this material are the property of Cisco Systems. * valid.168.1 0 1 22 214 i *> 197.11.11.0.

Answer these questions: Q1) Did this design require you to configure a cluster-ID? Q2) What is the default cluster-ID? Q3) When do you have to configure a cluster-ID? © 2005. Cisco Systems.. Lab Guide 63 The PDF files and any printed representation for this material are the property of Cisco Systems. and may not be distributed for purposes other than individual self-study. . Inc. The files or printed representations may not be used in commercial training. for the sole use by Cisco employees for personal study. Inc.

as well as the BGP sessions that must be established. you will be able to meet these objectives: „ Plan the migration of an existing IBGP backbone toward BGP confederations „ Configure BGP confederations on a BGP backbone „ Monitor a BGP backbone containing BGP confederations Visual Objective The figure illustrates what you will accomplish in this activity. for the sole use by Cisco employees for personal study. BGP v3. you will enable confederations to modify IBGP AS-path processing in a transit AS. Cisco Systems. The files or printed representations may not be used in commercial training. After completing this activity.2 © 2005.2—16 The AS numbers that will be used in the confederation.. Inc. The sessions should be established on the routers between Loopback0 interfaces as shown in the figure. Inc. are shown in the figure. Lab 6-2: Configuring and Monitoring Confederations Complete this lab activity to practice what you learned in the related module. Routers in member autonomous systems should originate their own networks. The PDF files and any printed representation for this material are the property of Cisco Systems. Visual Objective for Lab 6-2: Configuring and Monitoring Confederations © 2005 Cisco Systems. 64 Configuring BGP on Cisco Routers (BGP) v3. . Inc. Activity Objective In this activity. and may not be distributed for purposes other than individual self-study. All rights reserved.

. © 2005. Lab Guide 65 The PDF files and any printed representation for this material are the property of Cisco Systems. Inc. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10-BASE-T patch cables Command List The table describes the commands that are used in this activity. The files or printed representations may not be used in commercial training. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. Inc. for the sole use by Cisco employees for personal study. and may not be distributed for purposes other than individual self-study. Required Resources These are the resources and equipment required to complete this activity. Cisco Systems. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. The DCE side of the cable is connected to the Cisco 3660. . „ Two Ethernet 10BASE-T patch cables.

Also announce network 192..0/24.2 © 2005. WGxR3 AS 65002 WGxR4 AS 65003 „ AS 99 should receive only prefixes that originate in your AS x and AS 37. Inc. Inc. The files or printed representations may not be used in commercial training. Configures an EBGP session between neighbors that multihop are not directly connected Job Aids These job aids are available to help you complete the lab activity. 66 Configuring BGP on Cisco Routers (BGP) v3. „ To successfully complete this activity. You should accept only prefixes that originate in AS 99 from router Client.168. . Task 1: Configuring Confederations In this activity. Configures the source interface of a BGP session source interface neighbor ip-address ebgp. Activity Procedure Complete these steps: Perform the following steps on all routers in your workgroup: Step 1 Remove the BGP process and start a new BGP process with the proper member-AS number. and may not be distributed for purposes other than individual self-study. you must remove all BGP processes and start new processes with private AS numbers according to this table. Step 2 Announce networks that originate in this subautonomous system. The PDF files and any printed representation for this material are the property of Cisco Systems.x. Commands Command Description router bgp as-number Places you in BGP configuration mode bgp confederation identifier x Specifies the real AS number bgp confederation peers as1 Lists the neighboring intra-confederation autonomous [as2 [as3] …] systems show ip bgp Enables you to inspect the contents of the BGP table show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command neighbor ip-address remote-as Configures a BGP neighbor as-number neighbor ip-address update. Cisco Systems. Router Member-AS Number WGxR1 AS 65001 WGxR2. you will enable confederations to modify IBGP AS-path processing in a transit AS. for the sole use by Cisco employees for personal study.

Activity Verification You have completed this activity when you attain these results: „ Check to see whether router Client is receiving only your networks and those originating in AS 37. ? . Note The filter that permits networks that originate in your AS needs to be changed to permit all prefixes that originate in all intra-confederation autonomous systems. configure router Client as your BGP neighbor. Inc. Cisco Systems. * valid. Step 7 On WGxR4.0 192.0 192. apply AS-path filters to incoming and outgoing updates toward router Client.0 192.168. .168.21.21.4. local router ID is 197. Client#show ip bgp regexp ^1_ BGP table version is 319. The files or printed representations may not be used in commercial training.8.168.0. configure routers Good and Cheap as your BGP neighbors.11.1 0 1 i *> 197. Answer these questions: Q1) What additional command did you have to use to establish intra-confederation EBGP sessions between loopback interfaces? Q2) Why was it necessary to change the AS-path filters? © 2005. Your display should resemble the following output.6.5.1 0 1 i Note Another way to verify filters is to enter the following command on WGxR4: WGxR4#show ip bgp neighbors 192.1.0 192.EGP.21.21.1.99.0 192.1 0 1 i *> 197.1.1.99 advertised-routes.1 0 0 1 i *> 197.111. i . for the sole use by Cisco employees for personal study.2.1 Status codes: s suppressed. Inc. e .1 0 1 i *> 197.21. Step 3 Set the confederation identifier by using your real AS number.7..168. Step 4 Establish intra-confederation EBGP sessions and IBGP sessions within the member- AS. and may not be distributed for purposes other than individual self-study.168.168.21. d damped.0 192.37.IGP.1.0 192.3. > best.1.168.168.168.incomplete Network Next Hop Metric LocPrf Weight Path *> 128. Perform the following steps only on the specific router that is indicated in each step: Step 5 On WGxR1.1.1 0 1 20 42 37 i *> 192. h history. List all intra- confederation neighboring autonomous systems by using the bgp confederation peers command.internal Origin codes: i . „ Use the show ip route ospf command to make sure that your IGP carries only your internal networks.0 192.21.21.1. Step 6 On WGxR4.0 192.21.0 192.1 0 1 i *> 197.1 0 0 1 i *> 197.168.168. Use loopback interfaces for all BGP sessions.168.0 192.1.1 0 1 i *> 197.1 0 0 1 i *> 197.21.1.21.21. Lab Guide 67 The PDF files and any printed representation for this material are the property of Cisco Systems.1 0 1 20 42 37 i *> 192.37.168.

BGP v3.2—17 The figure shows the connectivity that is established between your AS and the two service providers Good and Cheap. Inc. Lab 7-1: Limiting the Number of Prefixes Received from a BGP Neighbor Complete this lab activity to practice what you learned in the related module. 68 Configuring BGP on Cisco Routers (BGP) v3. After completing this activity. The files or printed representations may not be used in commercial training. Inc. Visual Objective for Lab 7-1: Limiting the Number of Prefixes Received from a BGP Neighbor © 2005 Cisco Systems. All rights reserved. you will configure BGP to limit the number of prefixes that are received from a neighbor.. Inc. Activity Objective In this activity. Required Resources These are the resources and equipment required to complete this activity.2 © 2005. The PDF files and any printed representation for this material are the property of Cisco Systems. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. . for the sole use by Cisco employees for personal study. Cisco Systems. you will be able to meet these objectives: „ Configure the BGP maximum-prefix function „ Monitor the BGP maximum-prefix function Visual Objective The figure illustrates what you will accomplish in this activity. and may not be distributed for purposes other than individual self-study.

Cisco Systems. The DCE side of the cable is connected to the Cisco 3660. „ Two Ethernet 10BASE-T patch cables. Commands Command Description router bgp as-number Places you in BGP configuration mode neighbor ip-address maximum. „ Your analysis shows that you must perform the following tasks to minimize the size of the BGP table on router WGxR1: — Create a warning log whenever your service provider (Cheap) sends you more than 15 prefixes. . The service provider is asking for evidence that you are receiving more prefixes than you should. for the sole use by Cisco employees for personal study. „ In this activity. Inc. © 2005. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. you will configure logging on your router to warn you if you receive more BGP prefixes than you should from your service provider. Inc.. Lab Guide 69 The PDF files and any printed representation for this material are the property of Cisco Systems. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. and you would like to be protected against these problems. and may not be distributed for purposes other than individual self-study. „ You have noticed that one of your upstream service providers occasionally announces a very large number of BGP prefixes. which results in memory and CPU overload on your router (WGxR1). Specifies the allowed maximum number of prefixes prefix maximum [threshold] [warning-only] [restart restart-interval] show ip bgp Enables you to inspect the contents of the BGP table show ip neighbor neighbor Shows detailed information about a specific neighbor show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command Job Aids These job aids are available to help you complete the lab activity. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. The files or printed representations may not be used in commercial training. You suspect that the service provider might have internal problems.

22 (afi 0) reaches 12.168.20.1. BGP-4-MAXPFX: No.2 © 2005..20. 0 in queue Sent 1073 messages. keepalive interval is 60 seconds Received 1123 messages.22 BGP neighbor is 192.168. remote router ID 0. and may not be distributed for purposes other than individual self-study. of prefix received from 192.20. local AS number 1 BGP table version is 72. for the sole use by Cisco employees for personal study. of prefix received from 192.0 BGP state = Idle Last read 00:04:48. Task 1: Limiting the Number of Prefixes Received In this activity.0.20. Your display should resemble the following output.22. scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168. you will configure BGP to limit the number of prefixes that are received from a BGP neighbor.22 (afi 0): 16 exceed limit 15 BGP-5-ADJCHANGE: neighbor 192.8.20.168. 0 in queue Route refresh request: received 0.20. 1 notifications. Do not disable BGP. 522/469 paths. Inc. Activity Verification You have completed this activity when you attain these results: „ You can verify that both neighbors are up.168. Inc.168. you can find out why. remote AS 22. 0 notifications.0. Configure your router such that the BGP session is terminated if your router (WGxR1) receives more than the agreed number of prefixes.168.20.22 3/1 (update malformed) 0 bytes WG1R1#show ip bgp summary BGP router identifier 197. . hold time is 180. max 15 BGP-3-MAXPFXEXCEED: No.20 4 20 1504 1451 72 0 0 00:26:44 10 192.22 4 22 1123 1073 0 0 0 00:00:37 Idle (PfxCt) WG1R1#show ip bgp neighbor 192. of prefix received from 192. but instead create a warning message in the router log.168. Step 2 Check your console for the following two messages: 22:46:40: %BGP-4-MAXPFX: No.168. Cisco Systems.20. If not. sent 0 Minimum time between advertisement runs is 30 seconds 70 Configuring BGP on Cisco Routers (BGP) v3.168. The PDF files and any printed representation for this material are the property of Cisco Systems.1. Activity Procedure Complete these steps: Configuring the maximum-prefix function: Step 1 Set a limit to the number of prefixes that your router WGxR1 accepts from router Cheap.20. of prefix received from 192.22 (afi 0) reaches 12. main routing table version 72 41 network entries and 41 paths using 5453 bytes of memory 18 BGP path attribute entries using 936 bytes of memory 10 BGP AS-PATH entries using 256 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 5 BGP filter-list cache entries using 60 bytes of memory 16 received paths for inbound soft reconfiguration BGP activity 300/2803 prefixes.22 (afi 0): 16 exceed limit 15 Step 3 After showing the service provider your logs. you have decided to take administrative action by implementing a BGP policy that will terminate the neighbor session between you and your upstream provider (Cheap) should it continue to violate your agreement on the number of prefixes that are advertised to your network. external link BGP version 4. max 15 22:49:00: %BGP-3-MAXPFXEXCEED: No.22 Down BGP Notification sent BGP-3-NOTIFICATION: sent to neighbor 192.20. The files or printed representations may not be used in commercial training.

internal Origin codes: i .168. You can clear the neighbor session between your WGxR1 router and router Cheap afterward..0 192. WG1R1#show ip bgp nei 192.0.20.0 192.22 0 0 22 i *> 128.0 192. ? – incomplete Network Next Hop Metric LocPrf Weight Path * 10.0.22 to restore peering No active TCP connection WG1R1# „ You can increase the number of allowed prefixes to continue testing.20.20.20.42.11.168. Inc.26.20.37.0.0. no.22 0 0 22 26 i * 128. neighbor version 0 Index 2.168.20 0 22 20 i *> 200.20.11.20.20.0/30 192.168.22 0 0 22 214 i * 200.12.0 192.168.22.22 routes BGP table version is 249.22 0 0 22 i * 128.20.168.12.20.20.168.EGP.168. local router ID is 197.20. The files or printed representations may not be used in commercial training.0 192.20.12.214.213.IGP.0.12.20.0/16 192.22.22.22 0 0 22 26 42 i *> 192.22 0 0 22 26 51 i * 128.22 0 0 22 26 i * 192.0/16 192. maximum limit 15 Threshold for warning message 75% Connections established 6.0.22 0 0 22 214 i * 192. of prefix and clear ip bgp 192. dropped 6 Last reset 00:04:48.26.0/24 192.0.0/24 192.37.20. h history.168.51. Default weight 200 For address family: IPv4 Unicast BGP table version 72.11.22 0 0 22 i *> 192. Inc. * valid. i .168. of prefixes configured.168.168.0 192. Cisco Systems.42.0 192.22 0 0 22 i * 192. „ You can clear the neighbor session (configuration done in this activity) between your WGxR1 router and router Cheap afterward and ensure that the neighbor session remains active.1. Offset 0.0.11.0 192.0.168.20.20.0 192.20.1 Status codes: s suppressed.20 0 22 20 i * 192.20.0/30 192.0 192. Mask 0x4 Inbound soft reconfiguration allowed Inbound path policy configured Outbound path policy configured Incoming update prefix filter list is FromCheap Incoming update AS path filter list is 2 Outgoing update AS path filter list is 3.168.11.214.168.0.0 192.20.22 0 0 22 26 42 i *> 128.168.22 0 0 22 26 42 37 i * 192.22 0 0 22 i *> 192.0 192.0 192. > best.0 192.11.20 0 22 20 213 i *> 192.168.233 0 22 20 i * 128.20. .213.8.20.168.20.20 0 22 20 213 i *> 128.22 0 0 22 i *> 128.22 0 0 22 26 42 37 i * 128.168.20.0.168.20. © 2005.0 192. and may not be distributed for purposes other than individual self-study. due to Error during connection collision Peer had exceeded the max. Your display should resemble the following output.51.0 192.22.22 0 0 22 26 51 i * 192. for the sole use by Cisco employees for personal study.168.20.20.168. Lab Guide 71 The PDF files and any printed representation for this material are the property of Cisco Systems.168.168.22 0 0 22 i Total number of prefixes 23 „ You can increase the number of allowed prefixes so that all of the prefixes coming from Cheap will be allowed and the session will not be terminated.20.0 192. d damped.20 0 22 20 i * 128.0.11.22. Reduce the no.20.168. „ You can inspect the prefixes that your router is receiving from Cheap with the show ip bgp neighbors command and the routes keyword.11. e .20.

The files or printed representations may not be used in commercial training. Answer this question: Q1) What can you configure on your router to allow the BGP session to restart automatically if the received number of prefixes exceeds the configured maximum? 72 Configuring BGP on Cisco Routers (BGP) v3. . Inc. Inc. The PDF files and any printed representation for this material are the property of Cisco Systems. and may not be distributed for purposes other than individual self-study. Cisco Systems. for the sole use by Cisco employees for personal study.2 © 2005..

The files or printed representations may not be used in commercial training. you will use BGP peer groups to share common configuration parameters between multiple BGP peers. Inc. for the sole use by Cisco employees for personal study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. BGP v3. and may not be distributed for purposes other than individual self-study. Activity Objective In this activity. All rights reserved. Lab Guide 73 The PDF files and any printed representation for this material are the property of Cisco Systems. Visual Objective for Lab 7-2: Implementing BGP Peer Groups © 2005 Cisco Systems. Lab 7-2: Implementing BGP Peer Groups Complete this lab activity to practice what you learned in the related module. Required Resources These are the resources and equipment required to complete this activity. Inc. Cisco Systems.. Inc. © 2005. . After completing this activity.2—18 The figure shows the connectivity that is established between your AS and the two service providers Good and Cheap. you will be able to meet these objectives: „ Configure BGP peer groups „ Monitor the operation of BGP peer groups Visual Objective The figure illustrates what you will accomplish in this activity.

. Inc. Cisco Systems. Creates a BGP or multiprotocol BGP peer group group neighbor ip-address peer-group Configures a BGP neighbor to be a member of a peer peer-group-name group neighbor peer-group-name Specifies the allowed maximum number of prefixes maximum-prefix maximum [threshold] [warning-only] [restart restart-interval] show ip bgp Enables you to inspect the contents of the BGP table show ip bgp neighbors neighbor Shows detailed information about a specific neighbor show ip bgp peer-group [peer. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations. you will configure router WGxR1 to terminate the neighbor session between you and your upstream providers if you receive more than 50 BGP prefixes from them. You have decided to increase the number of prefixes that are allowed and to make prefix limiting a universally applied policy for all peers. The PDF files and any printed representation for this material are the property of Cisco Systems. „ After working with the Cheap provider. „ Two Ethernet 10BASE-T patch cables. Commands Command Description router bgp as-number Places you in BGP configuration mode neighbor peer-group-name peer. „ In this activity. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study. you have finally resolved the maximum-prefix violation problem that your network was experiencing. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. for the sole use by Cisco employees for personal study. The DCE side of the cable is connected to the Cisco 3660. „ You will use BGP peer groups to implement the policy to ease administration when more peers are added and to minimize router CPU utilization. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter.. 74 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005. Inc. Enables you to display information about BGP peer group-name] [summary] groups Job Aids These job aids are available to help you complete the lab activity.

scan interval 15 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192. replicated 13 © 2005. Assigning a neighbor into a peer group: Step 2 Configure the neighbor connections for the service provider routers Good and Cheap to be members of the peer group.1. you will use BGP peer groups to share common configuration parameters between multiple BGP peers. local AS number 65001 BGP table version is 355.20..168. 319/253 paths. Your display should resemble the following output. you can use the show ip bgp peer-group command to verify that the parameters of the peer group have been properly configured. you can use the show ip bgp peer-group peer-group-name command with the summary keyword to verify that you have configured the correct neighbors as members of the peer group.22 Index 1. Lab Guide 75 The PDF files and any printed representation for this material are the property of Cisco Systems. WG1R1#show ip bgp peer-group SvcPro summary BGP router identifier 197. Mask 0x2 Inbound soft reconfiguration allowed Update messages formatted 38.20. Inc.20. . members: 192. Activity Procedure Complete these steps: Creating a BGP peer group: Step 1 Create a BGP peer group on your WGxR1 router to set a limit to the number of prefixes that your router accepts. BGP sessions should be terminated if the number of received prefixes exceeds 50. Note BGP sessions with Good and Cheap must be up in case you forgot to reestablish the disabled session with Cheap by increasing BGP prefix limit (as suggested at the end of the previous lab).168. Your display should resemble the following output. Task 1: Configuring BGP Peer Groups In this activity. The files or printed representations may not be used in commercial training. Cisco Systems.20 4 20 13979 8418 355 0 0 00:15:29 23 192. Offset 0. main routing table version 355 43 network entries and 66 paths using 6547 bytes of memory 20 BGP path attribute entries using 1040 bytes of memory 19 BGP AS-PATH entries using 456 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 84/1135 prefixes.20 192. peer-group external.8.1. Inc.20. WG1R1#show ip bgp peer-group BGP peer-group is SvcPro BGP version 4 Default minimum time between advertisement runs is 30 seconds For address family: IPv4 Unicast BGP neighbor is SvcPro. and may not be distributed for purposes other than individual self-study.168.22 4 22 412 397 355 0 0 00:07:38 23 „ On WGxR1. Activity Verification You have completed this activity when you attain these results: „ On WGxR1.168. for the sole use by Cisco employees for personal study.

20 0 0 20 i *> 128.20 0 0 20 42 37 i *> 192.20.0/24 192.11.20.11.20.20.0.214.20 0 0 20 i * 192.0 192..37.42.20.0.20.0 192.20 0 0 20 i *> 192.20.168.20. Inc.20 0 0 20 213 i * 192.20.20.12.20. „ You can use the show ip bgp neighbors command and the received-routes keyword to inspect the prefixes that your router is receiving from both Good and Cheap.20 0 0 20 42 26 51 i *> 192.0 192. Cisco Systems. The PDF files and any printed representation for this material are the property of Cisco Systems.0 192.0.20.11.20 0 0 20 213 i * 128.0/30 192.0 192. i .1.22 0 20 22 214 i *> 192.2 © 2005.168.20.incomplete Network Next Hop Metric LocPrf Weight Path *> 10.0/16 192.20.168.20.0 192.0/30 192.168.20.0 192.37.11.20.20.26.EGP.168.20.20. ? . The files or printed representations may not be used in commercial training.20 0 0 20 i * 128.20 0 0 20 42 i * 192.0 192.20 0 0 20 42 37 i *> 128.0.0. wg1r1#show ip bgp neighbors 192. > best.20.22.20.168.0. . Your display should resemble the following output.168.0.0.20 0 0 20 i *> 128.internal Origin codes: i .0 192. h history.20 0 0 20 i * 200.0/16 192.20.0 192.168.168.168.20.0.168.12.0 192.42.20.11.8.0 192.168.20 0 0 20 42 26 51 i *> 128.11.0.168.51.22 0 20 22 i Total number of prefixes 23 „ You can clear the neighbor session between your WGxR1 router and router Cheap afterward and ensure that the neighbor session remains active.168.11.213.20.22 0 20 22 i * 192.168.51.168. what single command can you use to reset the BGP sessions on both routers? 76 Configuring BGP on Cisco Routers (BGP) v3.22 0 20 22 i * 128.233 0 0 20 i *> 128.0.0/24 192.20 0 0 20 42 i * 128.168.0 192.12.0 192.11.20 0 0 20 i *> 192.12. Answer this question: Q1) If the number of prefixes that are received from both providers exceeds 50. local router ID is 197.20.168. d damped.22.168.26.22 0 20 22 214 i *> 200.20 received-routes BGP table version is 355.1 Status codes: s suppressed.0 192.0 192. e . and may not be distributed for purposes other than individual self-study. * valid.0 192.168.22.168.20 0 0 20 42 26 i *> 128.168. Inc.22.20.IGP.0.20. for the sole use by Cisco employees for personal study.20 0 0 20 42 26 i *> 192.213.22.168.214.168.

© 2005.2—19 The figure shows the connectivity that is established between your AS and the Client router. you will be able to meet these objectives: „ Configure BGP route dampening „ Release dampened routes „ Monitor BGP route dampening Visual Objective The figure illustrates what you will accomplish in this activity. and may not be distributed for purposes other than individual self-study. Your workgroup requires the following components: „ Four Cisco 2610 routers with a WIC-1T and BGP-capable operating system software installed. Required Resources These are the resources and equipment required to complete this activity. Activity Objective In this activity. Cisco Systems. The DCE side of the cable is connected to the Cisco 3660. Lab Guide 77 The PDF files and any printed representation for this material are the property of Cisco Systems. Inc. . After completing this activity. Inc. Visual Objective for Lab 7-3: Using BGP Route Dampening © 2005 Cisco Systems. All rights reserved. Inc.. The files or printed representations may not be used in commercial training. Lab 7-3: Using BGP Route Dampening Complete this lab activity to practice what you learned in the related module. you will use route dampening to minimize the impact of unstable routes. BGP v3. for the sole use by Cisco employees for personal study. „ Four CAB-X21FC + CAB-X21MT DTE-DCE serial cable combinations.

for the sole use by Cisco employees for personal study. and may not be distributed for purposes other than individual self-study. Inc. Commands Command Description router bgp as-number Places you in BGP configuration mode bgp dampening route-map route. Specifies BGP dampening parameters by using a route- map map match community c-acl Matches BGP communities in a route-map by using a community-list set dampening half-life reuse Sets the BGP route-dampening factors suppress max-suppress-time ip community-list num {permit | Creates a community access-list deny} community show ip bgp Enables you to inspect the contents of the BGP table show ip bgp flap-statistics Enables you to view prefixes that have previously flapped show ip bgp dampened-paths Enables you to view prefixes that are currently suppressed show ip bgp regexp regexp Enables you to use a regular expression to filter the output of the show ip bgp command show ip bgp community Enables you to view BGP routes that have at least one [community [community …]] BGP community attribute or those that are specified in [exact-match] the command show ip bgp community-list Enables you to view BGP routes that are permitted by c-list [exact-match] the specified community-list debug ip bgp dampening Enables you to see major events that are related to route dampening 78 Configuring BGP on Cisco Routers (BGP) v3. Cisco Systems. The lab backbone requires the following components (supporting up to eight workgroups): „ One Cisco 2610 router with a WIC-1T and BGP-capable operating system software installed „ Two Cisco 2610 routers with BGP-capable operating system software installed „ One Cisco 3640 router with an installed NM-8A/S „ Two Cisco Catalyst 2924M XL Ethernet switches „ Three Ethernet 10BASE-T patch cables Command List The table describes the commands that are used in this activity. The PDF files and any printed representation for this material are the property of Cisco Systems. „ IBM PC (or compatible) with Windows 95/98 and an installed Ethernet adapter. „ Two Ethernet 10BASE-T patch cables. . The files or printed representations may not be used in commercial training.2 © 2005. Inc..

Cisco Systems. Activity Procedure Complete these steps: Creating filters for the dampening route-map: Step 1 Create a community-list that matches prefixes that carry a BGP community of x:300 (where x is your real AS number. Inc. and may not be distributed for purposes other than individual self-study. Step 6 The third statement should match prefixes that are longer than /8. Step 5 The second statement should match prefixes that are longer than /23. Lab Guide 79 The PDF files and any printed representation for this material are the property of Cisco Systems. — Prefixes between /0 and /8 should have a half-life of 10 minutes. Step 2 Create a prefix-list that matches all prefixes that are longer than /23. The first statement of the new route-map should match prefixes that carry a BGP community of x:300. The files or printed representations may not be used in commercial training. suppress 2000). „ Service providers usually use BGP route dampening to minimize the impact that route flaps in the Internet can have on the stability of their networks. Inc. In this activity. Step 3 Create a prefix-list that matches all prefixes that are longer than /8.. for the sole use by Cisco employees for personal study. Task 1: Using BGP Route Dampening In this activity. . then the prefix should not be dampened. „ Configure graded route dampening for routes that are received from the Client router according to the following design: — If a prefix contains a community attribute of x:300. © 2005. — Maximum suppression time should be changed to four times the half-life time for all prefixes. Set the half-life parameter to 20 minutes and max-suppress-time to 80 minutes. No route-dampening parameters need to be set. you will use route dampening to minimize the impact of unstable routes. BGP route dampening also reduces the CPU load on the routers that are running BGP. and use default values for other parameters (reuse 750. Creating a route-map for route dampening: Step 4 Create a new route-map. — Prefixes longer than /23 should have a half-life of 20 minutes. Job Aids These job aids are available to help you complete the lab activity. Set the half-life parameter to 15 minutes and max-suppress-time to 60 minutes. not your member-AS number). and use default values for other parameters (reuse 750. — Prefixes between /9 and /22 should have a half-life of 15 minutes. suppress 2000). you will minimize the impact of flapping routes on your AS and upstream autonomous systems by implementing BGP route dampening.

for the sole use by Cisco employees for personal study.0.168.20 0 100 0 (65002 65001) 20 42 i *> 128.incomplete Network From Reuse Path *d 99.22 0 100 0 (65002 65001) 22 26 51 i 80 Configuring BGP on Cisco Routers (BGP) v3.0 BGP routing table entry for 99.EGP.42.51.21.12.internal Origin codes: i .12.21. Set the half-life parameter to 10 minutes and max-suppress-time to 40 minutes.20. e .7.0.21.37.1.0.0.. using the bgp dampening route-map route-map command.0/8.0/24 192.168.0 192.99 00:40:30 99 i Note This command is being replaced with the show ip bgp dampening dampened-paths command.99. * valid. valid. The files or printed representations may not be used in commercial training.168.99. local router ID is 197.1) Origin IGP. d damped.IGP.0 192.99 6 00:09:25 00:40:20 99 Note This command is being replaced with the show ip bgp dampening flap-statistics command. > best.20 0 100 0 (65002 65001) 20 i *> 128.2 © 2005. i . Step 8 Enter BGP configuration mode and.0.168. e .incomplete Network From Flaps Duration Reuse Path *d 99.168.0 192.22.0.20. h history. Inc. Inc.1. local router ID is 197.20.EGP.internal Origin codes: i .20.20.20.26. and may not be distributed for purposes other than individual self-study.168.22.168.0.99 0 0 99 i *> 128.0.168. . (suppressed due to dampening) 192.168.22 0 100 0 (65002 65001) 22 26 i *> 128. WGxR4#show ip bgp 99. reuse in 00:03:30 WGxR4#show ip bgp BGP table version is 89.0.0.IGP.IGP.21. ? . and use the show ip bgp flap-statistics and show ip bgp dampened-paths commands to verify the operation of route dampening on your WGxR4 router.0/24 192.20 0 100 0 (65002 65001) 20 i *> 128.20. d damped.168.0/20 192.99. Activity Verification You have completed this activity when you attain these results: „ You can shut down interface Loopback55 on router Client several times to create flaps.7. flapped 6 times in 00:31:20. Your display should resemble the following output.EGP. localpref 100.incomplete Network Next Hop Metric LocPrf Weight Path *> 10.168. version 80 Paths: (1 available.168. suppress 2000).0. h history.20 0 100 0 (65002 65001) 20 i *> 128.21.168.99 (197.20 0 100 0 (65002 65001) 20 42 37 i *> 128.111. no best path) Not advertised to any peer 99.20. e . start BGP route dampening based on the created route-map.0 192. The PDF files and any printed representation for this material are the property of Cisco Systems.0/20 192.20.168.1. WGxR4#show ip bgp flap BGP table version is 89.0.22 0 100 0 (65002 65001) 22 i *> 128.1 Status codes: s suppressed.20. metric 0. > best. * valid.1 Status codes: s suppressed. and use default values for other parameters (reuse 750.168. Step 7 The last statement should match all other prefixes (no match command). i .7.99 00:25:20 99 i *d 197. WGxR4#show ip bgp damp BGP table version is 89.0 192. Try it as well.128. d damped.0 192.internal Origin codes: i .20.0. * valid. h history. ? . i .0.21.99 from 192.0 192.128.21. external Dampinfo: penalty 958.0.0 192.99 6 00:09:25 00:25:20 99 *d 197.0.233 0 100 0 (65002 65001) 20 i *d 99. local router ID is 197.0 192.0.1 Status codes: s suppressed.168. Try it as well.0 192. ? . Cisco Systems. > best.0.

1.20.51.1.22.20.0 0.4.0.1.168.0/30 192.0 0 32768 i *> 197. Lab Guide 81 The PDF files and any printed representation for this material are the property of Cisco Systems.168.12.20 0 100 0 (65002 65001) 20 i *> 192.1.12.168.20.120.168.11.214.20.1.0.20 0 100 0 (65002 65001) 20 i *> 192.213.20.0 192.21.111.42.99 0 0 99 i *> 197.22.80.0/16 192. The files or printed representations may not be used in commercial training.21.1.99 0 0 99 i *d 197.0 192.213.0.168.22 0 100 0 (65002 65001) 22 i Answer these questions: Q1) What is the purpose of route dampening? Q2) Which routes are affected by route dampening? © 2005.20.20.0 192.7.20.0 192. Cisco Systems.20.168.0 192.0 192.13.168.168.11. *> 128.21.0.0.6.1.22 0 100 0 (65002 65001) 22 26 i *> 192.21.99.11.1.168.99.21.11.1.168.26.21.0 0..2.168.1 0 100 0 (65002 65001) i *> 197.2.99 0 0 99 i *> 197.20 0 100 0 (65002 65001) 20 213 i *> 192.21.3. Inc.37.20.0/16 192.0 0.99 0 0 99 i *> 200.20.99.168.1.20 0 100 0 (65002 65001) 20 i *> 200.168. and may not be distributed for purposes other than individual self-study.22 0 100 0 (65002 65001) 22 i *> 192.0 0 32768 i *> 192.1. for the sole use by Cisco employees for personal study.20.0 192.20 0 100 0 (65002 65001) 20 42 i *> 192.0 192.12.0 197.99 0 0 99 i *> 197. .99.1.11.1 0 100 0 (65002 65001) i *> 197.20.1 0 100 0 (65002) i *> 197.168.99 0 0 99 i *> 197.21.168.0 192.0 0 32768 i *> 197.11.4.99 0 0 99 i *> 197.99.21.0.168.22.168.99 0 0 99 i *> 197.168.168. Inc.5.1.0 197.0 192.0 197.99.0 192.0.1/32 192.1.168.20 0 100 0 (65002 65001) 20 i *> 192.1.0 192.20.22 0 100 0 (65002 65001) 22 214 i *> 192.0.22 0 100 0 (65002 65001) 22 26 51 i *> 192.4.20.1.20.99 0 0 99 i *> 197.22.168.0 197.0/20 192.1.128.0 197.20 0 100 0 (65002 65001) 20 213 i *> 128.168.214.0 192.8.20.99.99.1 0 100 0 (65002) i *> 197.0.0.2.11.20.11.99 0 0 99 i *> 197.0/30 192.0 197.0 192.21.22 0 100 0 (65002 65001) 22 214 i *> 197.1 0 100 0 (65002) i *> 197.99.1 0 100 0 (65002) i *> 197.0 192.11.20 0 100 0 (65002 65001) 20 42 37 i *> 192.168.0 192.1.0 192.1.168.99.0 192.168.

1 ip host good 192. .168.255.3 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname wg1r1 ! boot-start-marker boot-end-marker ! enable password cisco ! no aaa new-model ip subnet-zero ip cef ! no ip domain lookup ip host wg1r2 197.1 197. Cisco Systems. Current configuration : 1257 bytes ! version 12.168.20 ip host cheap 192.168.1 255.1.255.1 255.2. for the sole use by Cisco employees for personal study. The files or printed representations may not be used in commercial training.5.6.20.4.3.1.1. and may not be distributed for purposes other than individual self-study.22 ip host client 192.20. Inc. Answer Key The correct answers and expected solutions for the activities that are described in this guide appear here.0 half-duplex ! interface Serial0/0 bandwidth 128 no ip address encapsulation frame-relay frame-relay lmi-type cisco ! interface Serial0/0.20.1 255. with differences that are specific to your device or workgroup: wg1r1#sh run Building configuration..255.1 ip host wg1r3 197..255.1.255.1.1 197.0 ! interface Loopback1 ip address 197. Lab 1-1 Answer Key: Initial Lab Setup When you complete this activity.7.168.1.1.0 ! interface Ethernet0/0 ip address 192.168.99 ! interface Loopback0 ip address 197.255.255.255.100 point-to-point ip address 192.8.1.252 ip ospf network point-to-point 82 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005.1. your router configuration will be similar to the following. The PDF files and any printed representation for this material are the property of Cisco Systems.1 197.21.1 255.1.1 ip host wg1r4 197. Inc..

0.168.3 area 0 network 197. Cisco Systems.8.0 0. Lab Guide 83 The PDF files and any printed representation for this material are the property of Cisco Systems.0. for the sole use by Cisco employees for personal study.1. frame-relay interface-dlci 100 ! interface Ethernet0/1 no ip address shutdown half-duplex ! router ospf 1 log-adjacency-changes network 192.0 0.0.255 area 0 ! ip http server ip classless ! line con 0 line aux 0 line vty 0 4 password cisco login ! end wg1r1# © 2005. and may not be distributed for purposes other than individual self-study.. Inc.0. .0. Inc.1.255 area 0 network 197.1. The files or printed representations may not be used in commercial training.0 0.1.0.

0 WGxR1(config-router)#exit WGxR1(config)#ip route 197. your router configuration will be similar to the following.0. the command sequence to use is as follows: WGxR1#configure terminal WGxR1(config)#router ospf process-id WGxR1(config-router)#default-information originate always Answers to Review Questions Q1) What do you need in order to be able to propagate classful networks? There must be at least one subnet in the routing table.0. with differences that are specific to your device or workgroup.0 255. Cisco Systems. and the network must be listed in the BGP process with no mask attached to it. . Q2) What do you need to be able to propagate classless networks (supernets or subnets)? The prefix must be listed in the BGP process together with its proper mask.0.20.x.255.x..0 null 0 250 WGxR1(config)#end Also. The PDF files and any printed representation for this material are the property of Cisco Systems. Lab 1-2 Answer Key: Configuring Basic BGP When you complete this activity.0 mask 255. The files or printed representations may not be used in commercial training. Q3) Why do some networks that are received from router Good have a next-hop address pointing to other routers? Router Good performs next-hop processing and sets the next hop to router Cheap for routes that are received from Cheap and propagated to you. Q4) What command would you use to see whether a neighbor is sending you any updates and how many? You would use the show ip bgp neighbor command. Inc. and may not be distributed for purposes other than individual self-study.255.168. Task 1: Configuring BGP Use the following command sequence on your router WGxR1 (replace x with your workgroup number): WGxR1#configure terminal WGxR1(config)#router bgp x WGxR1(config-router)#neighbor 192. Inc. The exact corresponding entry must also be present in the IP routing table.0. make sure that you announce a default route into your network. 84 Configuring BGP on Cisco Routers (BGP) v3. If you are running OSPF in your network.20 remote-as 20 WGxR1(config-router)#network 192.0 WGxR1(config-router)#network 197.168.2 © 2005. for the sole use by Cisco employees for personal study.x.

Task 2: Configuring Route Redistribution in BGP Use the following command sequence on your router WGxR1 (replace x with your workgroup number): WGxR1#configure terminal WGxR1(config)#router bgp x WGxR1(config-router)#no network 192.x.0 WGxR1(config-router)#no network 197. Task 3: Configuring BGP Aggregation Use the following command sequence on your router WGxR1 (replace x with your workgroup number): WGxR1(config)#router bgp x WGxR1(config-router)#aggregate-address 197.168.0 WGxR1(config)#access-list 1 permit any WGxR1(config)#route-map SetOrigin permit 10 WGxR1(config-route-map)#match ip address 1 WGxR1(config-route-map)#set origin igp WGxR1(config-route-map)#end WGxR1# Answers to Review Questions Q1) What is the major difference between this implementation and the previous one? Which is better and why? The previous implementation is better for service provider environments because it is more controlled.0.255.0 mask 255.0 255. and may not be distributed for purposes other than individual self-study.0.168. Inc. Inc.0 255..x.0 WGxR1(config)#access-list 1 deny 192.x. This implementation is better for enterprise networks because it is more dynamic. Cisco Systems. Q2) What precautions do you have to take when using redistribution? You should always filter redistributed routes with a route-map to make sure that unwanted networks are not announced into BGP.0.255. for the sole use by Cisco employees for personal study. Lab Guide 85 The PDF files and any printed representation for this material are the property of Cisco Systems.x. The files or printed representations may not be used in commercial training.21.0.0 summary-only WGxR1(config-router)#end WGxR1# © 2005.248.255.8.20.168.0 summary-only WGxR1(config-router)#aggregate-address 197.0 WGxR1(config-router)#redistribute <igp> <pid> route-map SetOrigin WGxR1(config)#access-list 1 deny 192. .

1 0 0 1 i > 197.20.1 0 0 1 I After aggregation: *> 197.20. and a prefix within the aggregate range has to be present in the BGP table.x.1 0 0 1 i > 197..168. Inc.1 0 0 1 i > 197.168.0 192.x.1 0 0 1 i > 197.20.7.20.168.1 0 0 1 i > 197. The files or printed representations may not be used in commercial training.0 192.3.2 © 2005.2.168.1 0 1 i *> 197.20.x. All the other routes should be suppressed.20. Cisco Systems.1 0 0 1 i > 197.0/21 192.0 192. Before aggregation: > 197.x.x.1 0 0 1 i > 197.x.0 192.20.4.8. and may not be distributed for purposes other than individual self-study.0 192.6. .x.0.1 0 1 I 86 Configuring BGP on Cisco Routers (BGP) v3.x.8.0 192. Inc.168. Answers to Review Questions Q1) Do you see all your prefixes on the provider router? Why? You should see only the configured aggregates and the routes that are not within the aggregation range on the provider router.168.168. for the sole use by Cisco employees for personal study. Q2) What do you need to be able to generate and propagate aggregates? The aggregate address has to be configured in the BGP process.0 192. The PDF files and any printed representation for this material are the property of Cisco Systems.168.1.168.x.20.5.20.20.x.0 192.168.0 192.

2.x.1.1 update-source loopback 0 WGxR1(config-router)#neighbor 197.1 next-hop-self WGxR1(config-router)#neighbor 197.x.x.168.21.x.1 next-hop-self WGxR4(config-router)#neighbor 197.0 WGxR1(config-router)#network 197. .1.x.1 remote-as x WGxR3(config-router)#neighbor 197.x.0. and may not be distributed for purposes other than individual self-study.0.1 remote-as x WGxR4(config-router)#neighbor 197.1 update-source Loopback0 WGxR2(config-router)#end Use the following command sequence on your router WGxR3: WGxR3(config)#router bgp x WGxR3(config-router)#no synchronization WGxR3(config-router)#neighbor 197.0 255. Cisco Systems.248.1 remote-as x WGxR3(config-router)#neighbor 197.1 update-source Loopback0 WGxR3(config-router)#neighbor 197.255.0 WGxR1(config)# ip route 197.1 remote-as x WGxR2(config-router)#neighbor 197.1.x.1 update-source Loopback0 WGxR3(config-router)#neighbor 197.6.1 update-source Loopback0 WGxR3(config-router)#end Use the following command sequence on your router WGxR4: WGxR4(config)#router bgp x WGxR4(config-router)#no synchronization WGxR4(config-router)#neighbor 192. your router configuration will be similar to the following.99 remote-as 99 WGxR4(config-router)#network 192.1 update-source Loopback0 WGxR2(config-router)#neighbor 197.x.x.x.0.1 remote-as x © 2005.4.0 null 0 WGxR1(config-router)#end Use the following command sequence on your router WGxR2: WGxR2(config)#router bgp x WGxR2(config-router)#no synchronization WGxR2(config-router)#neighbor 197.x.x.1 update-source Loopback0 WGxR2(config-router)#neighbor 197.0 WGxR4(config-router)#neighbor 197.x..255.1 update-source Loopback 0 WGxR1(config-router)#neighbor 197.x.x.x.x.6.1 update-source loopback 0 WGxR1(config-router)#neighbor 197.x. Task 1: Configuring the BGP Transit AS Use the following command sequence on your router WGxR1: WGxR1(config)#router bgp x WGxR1(config-router)#no synchronization WGxR1(config-router)#no aggregate-address 197.0.x.6.1 next-hop-self WGxR1(config-router)#network 192.4.20 remote-as 20 WGxR1(config-router)#neighbor 197. Lab Guide 87 The PDF files and any printed representation for this material are the property of Cisco Systems.6.168.x.0.x.6. Lab 2-1 Answer Key: Configuring a Transit AS When you complete this activity.2.1.x.2.1 update-source Loopback 0 WGxR4(config-router)#neighbor 197.x.1 remote-as x WGxR1(config-router)#neighbor 197.x.0 255.1 remote-as x WGxR1(config-router)#neighbor 197. Inc.x.0 mask 255.0.0.1 remote-as x WGxR3(config-router)#neighbor 197.4.8. The files or printed representations may not be used in commercial training.4.x. for the sole use by Cisco employees for personal study.0 mask 255.0 WGxR4(config-router)#network 197.0 summary-only WGxR1(config-router)#no aggregate-address 197.6.2.1.1 remote-as x WGxR2(config-router)#neighbor 197.0 summary-only WGxR1(config-router)#neighbor 192.x.0. Inc.1 next-hop-self WGxR1(config-router)#neighbor 197.1.168.20.2.x.255.0 255.1 remote-as x WGxR2(config-router)#neighbor 197.x.255.6.x.1.255.168.1 remote-as x WGxR1(config-router)#neighbor 197.4.x. with differences that are specific to your device or workgroup.x.2.

2. Cisco Systems.2. for the sole use by Cisco employees for personal study. How many prefixes coming from your AS are in that BGP table? 20 Q2) Is there any other way of discovering how many prefixes you have advertised to the router Client? show ip bgp neighbor ip-address advertised Q3) Why did you have to disable synchronization? You should use BGP synchronization only in networks where BGP routes are redistributed in IGP. The files or printed representations may not be used in commercial training. .1 next-hop-self WGxR4(config-router)#exit WGxR4(config-)#end Answers to Review Questions Q1) Check the BGP table on router Client.1 update-source loopback 0 WGxR4(config-router)#neighbor 197. Inc.4. This design is no longer viable for service provider networks because of the large number of routes that are advertised in the Internet. The PDF files and any printed representation for this material are the property of Cisco Systems.. Inc. 88 Configuring BGP on Cisco Routers (BGP) v3.4. WGxR4(config-router)#neighbor 197. Q4) Why did you have to establish a full mesh of IBGP sessions? IBGP split-horizon rules require a full mesh of IBGP sessions within the AS.x.1 next-hop-self WGxR4(config-router)#neighbor 197.2 © 2005.x.x.x.1 update-source loopback 0 WGxR4(config-router)#neighbor 197.x.1 remote-as x WGxR4(config-router)#neighbor 197. and may not be distributed for purposes other than individual self-study.4.

.168.168. . Use the following command sequence on your router WGxR1 (replace x with your workgroup number): WGxR1(config)#router bgp x WGxR1(config-router)#neighbor 192. for the sole use by Cisco employees for personal study. your router configuration will be similar to the following.20. Cisco Systems. and may not be distributed for purposes other than individual self-study. The files or printed representations may not be used in commercial training. with differences that are specific to your device or workgroup. Lab Guide 89 The PDF files and any printed representation for this material are the property of Cisco Systems. Lab 3-1 Answer Key: Using Multihomed BGP Networks When you complete this activity. Inc. Q2) Why do some prefixes have two paths but both use the same next-hop address? Both service providers are connected to the same subnet as all the customers.22 weight 100 WGxR1(config-router)#end WGxR1# Answers to Review Questions Q1) What can happen if a multihomed AS is passing routing information learned from one neighbor to another neighbor? The multihomed AS that is passing routes between BGP neighbors can become a transit AS.22 remote-as 22 WGxR1(config-router)#neighbor 192. © 2005.20. Inc. and the BGP next-hop processing optimizes the data flow.

Inc.IGP.0. Good#show ip bgp regexp ^1_ BGP table version is 111.199. Good# show ip bgp regexp _1$ BGP table version is 111.0 0. * valid.22 filter-list 2 in WGxR1(config-router)#neighbor 192. local router ID is 199.* WGxR1(config)#ip as-path access-list 3 permit ^$ WGxR1(config)#router bgp x WGxR1(config-router)#neighbor 192.incomplete Network Next Hop Metric LocPrf Weight Path *> 192. The PDF files and any printed representation for this material are the property of Cisco Systems.20.168.8. h history. with differences that are specific to your device or workgroup. e .inter Origin codes: i .20.1 0 22 1 i *> 192.1. ? .1.168. Inc.0.168.199 Status codes: s suppressed.0.199.0.20. ? .EGP.IGP.1.20. What regular expression would you use with the show ip bgp command on WGxR1 to view the prefixes that are originated by your AS? Use show ip bgp regexp ^$. h history. e . local router ID is 197.20 filter-list 1 in WGxR1(config-router)#neighbor 192.20.0.20.168. .1 Status codes: s suppressed.168.0/16 0. Lab 3-2 Answer Key: Employing AS-Path Filters When you complete this activity. d damped.20 filter-list 3 out WGxR1(config-router)#neighbor 192.1 0 1 i Q3) What regular expression would you use on router Good or Cheap to view the prefixes that are received from your AS? Use show ip bgp regexp ^x_. and may not be distributed for purposes other than individual self-study.0/16 192.168.199. local router ID is 199. AS is 1. Use the following command sequence on your router WGxR1 (replace x with your workgroup number): WGxR1(config)#ip as-path access-list 1 deny _214_ WGxR1(config)#ip as-path access-list 1 permit . i .incomplete Network Next Hop Metric LocPrf Weight Path * 192. d damped.1 0 0 1 i * 197. > best.EGP. The files or printed representations may not be used in commercial training.168.1.internal Origin codes: i . your router configuration will be similar to the following.0 0 32768 i *> 197.0 32768 i Q2) What regular expression would you use on router Good or Cheap to view the prefixes that originate in your AS? Use show ip bgp regexp _x$.20.2 © 2005. > best..199 90 Configuring BGP on Cisco Routers (BGP) v3.168.* WGxR1(config)#ip as-path access-list 2 deny _213$ WGxR1(config)#ip as-path access-list 2 permit .0 192.199.1. the BGP table should contain a large number of prefixes. wg1r1#show ip bgp regexp ^$ BGP table version is 44.0. Cisco Systems.168. * valid. for the sole use by Cisco employees for personal study.22 filter-list 3 out WGxR1(config-router)#end WGxR1#clear ip bgp * Answers to Review Questions Q1) By this time.1 0 22 1 i *> 192.168.20. i .

168.1.20.0/16 192.168.0 192.1.. > best.IGP. .incomplete Network Next Hop Metric LocPrf Weight Path *> 192. i .168. Status codes: s suppressed. Inc.0. d damped. Lab Guide 91 The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. The files or printed representations may not be used in commercial training. ? .1 0 1 i Q4) How can you test your AS-path filters before applying them and clearing BGP neighbors? You can test the AS-path filters with the show ip bgp filter-list filter command. * valid.EGP.internal Origin codes: i .1 0 0 1 i *> 197. e . Inc.20. and may not be distributed for purposes other than individual self-study. h history. © 2005. Cisco Systems.

Lab 3-3 Answer Key: Filtering with Prefix-Lists
When you complete this activity, your router configuration will be similar to the following,
with differences that are specific to your device or workgroup.

Use the following command sequence on your router WGxR1 (replace x with your workgroup
number):
WGxR1(config)#ip prefix-list FromGood deny 192.0.0.0/3 ge 24
WGxR1(config)#ip prefix-list FromGood deny 192.168.0.0/16 le 32
WGxR1(config)#ip prefix-list FromGood deny 172.16.0.0/12 le 32
WGxR1(config)#ip prefix-list FromGood deny 10.0.0.0/8 le 32
WGxR1(config)#ip prefix-list FromGood permit 0.0.0.0/0 le 32
WGxR1(config)#ip prefix-list FromCheap deny 128.0.0.0/2 ge 17
WGxR1(config)#ip prefix-list FromCheap deny 192.168.0.0/16 le 32
WGxR1(config)#ip prefix-list FromCheap deny 172.16.0.0/12 le 32
WGxR1(config)#ip prefix-list FromCheap deny 10.0.0.0/8 le 32
WGxR1(config)#ip prefix-list FromCheap permit 0.0.0.0/0 le 32
WGxR1(config)#router bgp x
WGxR1(config-router)#neighbor 192.168.20.20 prefix-list FromGood in
WGxR1(config-router)#neighbor 192.168.20.22 prefix-list FromCheap in
WGxR1(config-router)#end
WGxR1#clear ip bgp *

Answers to Review Questions
Q1) Are neighboring workgroups still reachable?

Yes, they are still reachable.

Q2) Why does router WGxR1 still accept class B networks from router Cheap?

Only subnets of class B networks are filtered, not the class B networks themselves.

92 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

Lab 3-4 Answer Key: Implementing Changes in BGP Policy
When you complete this activity, your router configuration will be similar to the following,
with differences that are specific to your device or workgroup.

Use the following command sequence on your router WGxR1 (replace x with your workgroup
number):
wg1r1#show ip bgp neighbor 192.168.20.20 received-routes
% Inbound soft reconfiguration not enabled

wg1r1#show ip bgp neighbor 192.168.20.22 received-routes
% Inbound soft reconfiguration not enabled

wg1r1(config)#router bgp x
wg1r1(config-router)#neighbor 192.168.20.20 soft-reconfiguration inbound
wg1r1(config-router)#neighbor 192.168.20.22 soft-reconfiguration inbound
wg1r1(config-router)#exit
wg1r1(config)#exit

Answers to Review Questions
Q1) What command do you use to show which entries in the BGP table of the local router
have been propagated to a specific neighbor?

show ip bgp neighbors ip-address advertised

Q2) What command do you use to display which of the routes in the local BGP table have
been received and accepted from an indicated neighbor?

show ip bgp neighbors ip-address routes

© 2005, Cisco Systems, Inc. Lab Guide 93
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

Lab 4-1 Answer Key: Influencing BGP Route Selection with
Weights
When you complete this activity, your router configuration will be similar to the following,
with differences that are specific to your device or workgroup.

Use the following command sequence on your router WGxR1 (replace x with your
workgroup number):
WGxR1(config)#ip as-path access-list 10 permit _37_|_213_
WGxR1(config)#route-map SetWeight permit 10
WGxR1(config-route-map)#match as-path 10
WGxR1(config-route-map)#set weight 300
WGxR1(config-route-map)#exit
WGxR1(config)#route-map SetWeight permit 20
WGxR1(config-route-map)#exit
WGxR1(config)#router bgp x
WGxR1(config-router)#neighbor 192.168.20.20 weight 100
WGxR1(config-router)#neighbor 192.168.20.22 weight 200
WGxR1(config-router)#neighbor 192.168.20.20 route-map SetWeight in
WGxR1(config-router)#end
WGxR1#clear ip bgp *
WGxR1#

Answers to Review Questions
Q1) Did all paths automatically get a weight of 100 or 200? Why not? What did you have to
do?

The BGP sessions had to be reset in order to apply newly configured weights to
incoming BGP routes.

Q2) Name some parameters and attributes that are used for best-path selection.

The following BGP parameters and attributes are used for BGP best-path selection in
the order specified: weight, local preference, AS-path length, origin code, MED.

94 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.
The PDF files and any printed representation for this material are the property of Cisco Systems, Inc.,
for the sole use by Cisco employees for personal study. The files or printed representations may not be
used in commercial training, and may not be distributed for purposes other than individual self-study.

255.255..3x. because the router Good prefers more stable EBGP routes received from WGxR1 and the router WGxR1 prefers routes received from WGxR2.3x.168. Inc.20. © 2005. Lab Guide 95 The PDF files and any printed representation for this material are the property of Cisco Systems.0 WGxR2(config-router)#neighbor 192.168.0 null 0 WGxR2(config)#exit Configuration of router WGxR1: WGxR1(config)router bgp x WGxR1(config-router)#no neighbor 192. your router configuration will be similar to the following. Q2) Which routers receive the local preference attribute? Only routers within the AS receive the local preference attribute.x.168. and may not be distributed for purposes other than individual self-study. Inc. .168.168.1 255.22 weight 200 WGxR1(config-router)#no neighbor 192. the routing is not symmetrical.20.2 route-map SetLP in WGxR2(config-router)#neighbor 192.255.2 remote-as 20 WGxR2(config-router)#neighbor 192.20 route-map SetWeight in WGxR1(config-router)#end Answers to Review Questions Q1) Is routing between router WGxR1 and Good symmetrical? Initially.168.168.3x. Lab 4-2 Answer Key: Setting BGP Local Preference When you complete this activity.x. The files or printed representations may not be used in commercial training. Use the following command sequence on your workgroup routers as indicated (replace x with your workgroup number): Configuration of router WGxR2: WGxR2(config)#route-map SetLP WGxR2(config-route-map)#set local-preference 200 WGxR2(config-route-map)#exit WGxR2(config)#router bgp x WGxR2(config)#router# no synchronization WGxR2(config-router)#network 192.168.2 next-hop-self WGxR2(config-router)#exit WGxR2(config)#int s0/0.0 255.20.252 WGxR2(config-subif)#frame-relay interface-dlci 20x WGxR2(config-fr-dlci)#exit WGxR2(config-subif)#exit WGxR2(config)#ip route 192.255. with differences that are specific to your device or workgroup. for the sole use by Cisco employees for personal study.200 point-to-point WGxR2(config-subif)#ip address 192.20 weight 100 WGxR1(config-router)#no neighbor 192.3x. Cisco Systems.168.

The PDF files and any printed representation for this material are the property of Cisco Systems. Cisco Systems. Lab 4-3 Answer Key: Understanding BGP Multi-Exit Discriminators When you complete this activity. your router configuration will be similar to the following.20 route-map SetMED out WGxR1(config-router)#end WGxR1# WGxR1#clear ip bgp * Configuration of router WGxR2: WGxR2(config)#route-map SetMED WGxR2(config-route-map)#set metric 100 WGxR2(config-route-map)#exit WGxR2(config)#router bgp x WGxR2(config-router)#neighbor 192. with differences that are specific to your device or workgroup. For transit networks.3x. local preference. for the sole use by Cisco employees for personal study. 96 Configuring BGP on Cisco Routers (BGP) v3. Inc. the MED is removed by the router in outgoing EBGP updates. Inc.. Q2) What is the default value of the MED? For networks that originated in the local AS. Use the following command sequence on your router WGxR1 (replace x with your workgroup number): Configuration of router WGxR1: WGxR1(config)#route-map SetMED WGxR1(config-route-map)#set metric 200 WGxR1(config-route-map)#exit WGxR1(config)#router bgp x WGxR1(config-router)#neighbor 192.2 route-map SetMED out WGxR2(config-router)#end WGxR2# WGxR2#clear ip bgp * Answers to Review Questions Q1) Which parameters and attributes have to be equal before the MED is compared to select the best path? The MED is used only to compare routes that are received from the same AS that have equal weight.168. AS-path length.168.2 © 2005. the default MED value is the IGP metric from the IP routing table. .20. The files or printed representations may not be used in commercial training. and origin code. and may not be distributed for purposes other than individual self-study.

© 2005. Cisco Systems. your router configuration will be similar to the following. with differences that are specific to your device or workgroup.2 route-map SetCommunity out WG1R2(config-router)#neighbor 192. Lab 4-4 Answer Key: Addressing BGP Communities When you complete this activity. Inc.20.3x. The files or printed representations may not be used in commercial training.168. . and may not be distributed for purposes other than individual self-study. Inc..168. for the sole use by Cisco employees for personal study.2 send-community WG1R2(config-router)#exit WG1R2(config)#ip bgp-community new-format WG1R2(config)#exit WG1R2#clear ip bgp * Use the following command sequence on your router WGxR1 (replace x with your workgroup number): Configuration of router WGxR1: WG1R1(config-router)#neighbor 192. Use the following command sequence on your router WGxR2 (replace x with your workgroup number): Configuration of router WGxR2: WG1R2(config)#route-map SetCommunity WG1R2(config-route-map)#set community x:20 WG1R2(config-route-map)#exit WG1R2(config)#router bgp x WG1R2(config-router)#neighbor 192. Lab Guide 97 The PDF files and any printed representation for this material are the property of Cisco Systems.168. Q2) What mechanisms can you use to match or set communities? Only route-maps allow matching or setting of BGP communities.20 shutdown Answers to Review Questions Q1) What do you have to do to enable community propagation? Enable BGP community propagation with the neighbor send-community command.3x.

20.1 remote-as x WGxR4(config-router)#no neighbor 197.1 route-reflector-client WGxR2(config-router)#end Use the following command sequence on your router WGxR3: WGxR3(config)#router bgp x WGxR3(config-router)#bgp cluster-id 101 WGxR3(config-router)#no neighbor 197.1. Q3) When do you have to configure a cluster-ID? You need to configure a cluster-ID in redundant route reflector designs. Cisco Systems.1. Lab 6-1 Answer Key: Introducing Route Reflectors When you complete this activity.1 remote-as x WGxR3(config-router)#neighbor 197.2 remote-as 20 WGxR2(config-router)#no neighbor 197.1.x.x.x.6. 98 Configuring BGP on Cisco Routers (BGP) v3.1 next-hop-self WGxR2(config-router)#neighbor 197.x. and may not be distributed for purposes other than individual self-study.168.4.1 remote-as x WGxR4(config-router)#end Answers to Review Questions Q1) Did this design require you to configure a cluster-ID? This design did not require specified cluster-IDs.x.1 next-hop-self WGxR2(config-router)#no neighbor 197.x.1 remote-as x WGxR1(config-router)#no neighbor 197. .3x.1.x.168. your router configuration will be similar to the following.x.2 © 2005.4. because there are no redundant route reflectors in the network.x. The PDF files and any printed representation for this material are the property of Cisco Systems. for the sole use by Cisco employees for personal study. Use the following command sequence on your router WGxR1: WGxR1(config)#router bgp x WGxR1(config-router)#no neighbor 197.x. The files or printed representations may not be used in commercial training.1 next-hop-self WGxR2(config-router)#no neighbor 197.1 remote-as x WGxR1(config-router)#no neighbor 192..20 shutdown WGxR1(config-router)#end WGxR1# Use the following command sequence on your router WGxR2: WGxR2(config)#router bgp x WGxR2(config-router)#bgp cluster-id 102 WGxR2(config-router)#no neighbor 192.1 remote-as x WGxR2(config-router)#no neighbor 197.6. Inc.2. with differences that are specific to your device or workgroup.x. Q2) What is the default cluster-ID? The default cluster-ID is the BGP router-ID. Inc.1 route-reflector-client WGxR3(config-router)#end Use the following command sequence on your router WGxR4: WGxR4(config)#router bgp x WGxR4(config-router)#no neighbor 197.6.2.

x.168.0 WGxR3(config-router)#bgp confederation identifier x WGxR3(config-router)#bgp confederation peers 65003 WGxR3(config-router)#neighbor 197.1 update-source loopback0 WGxR3(config-router)#neighbor 197.4. The files or printed representations may not be used in commercial training.1.22 remote-as 22 WGxR1(config-router)#neighbor 197.6.x.4.x.x.4. with differences that are specific to your device or workgroup.x. and may not be distributed for purposes other than individual self-study.0 WGxR3(config-router)#network 197.1 update-source loopback0 WGxR3(config-router)#neighbor 197.6.2.20.1.x.20.1.6.168.8.2.1 update-source loopback0 WGxR2(config-router)#neighbor 197.0 © 2005.0 WGxR4(config-router)#network 197.0 WGxR1(config-router)#network 197.6.0 WGxR2(config-router)#bgp confederation identifier x WGxR2(config-router)#bgp confederation peers 65001 WGxR2(config-router)#neighbor 197.20 remote-as 20 WGxR1(config-router)#neighbor 192.x.1 remote-as 65001 WGxR2(config-router)#neighbor 197.x.0 WGxR1(config-router)#ip route 192.168. Lab 6-2 Answer Key: Configuring and Monitoring Confederations When you complete this activity.x.0 255.3.1 ebgp-multihop WGxR1#neighbor 197.x.x.0 WGxR3(config-router)#network 197.1 remote-as 65002 WGxR3(config-router)#neighbor 197.1 ebgp-multihop WGxR2(config-router)#neighbor 197.x.1.0 null 0 WGxR1(config-router)#bgp confederation identifier x WGxR1(config-router)#bgp confederation peers 65002 WGxR1(config-router)#neighbor 192. Inc.2.5.x.x. Inc.2.1 remote-as 65002 WGxR1(config-router)#neighbor 197.255.1 remote-as 65002 WGxR2(config-router)#neighbor 197.255.x.1 next-hop-self WGxR1(config-router)#end Use the following command sequence on your router WGxR2: WGxR2(config)#no router bgp x WGxR2(config)#router bgp 65002 WGxR2(config-router)#no synchronization WGxR2(config-router)#network 197.1 ebgp-multihop WGxR3(config-router)#end Use the following command sequence on your router WGxR4: WGxR4(config)#no router bgp x WGxR4(config)#ip as-path access-list 10 permit ^99$ WGxR4(config)#ip as-path access-list 11 permit ^$|\)$|_37$ WGxR4(config)#router bgp 65003 WGxR4(config-router)#network 192..x. Cisco Systems.x.x.168.1 update-source loopback0 WGxR2(config-router)#end Use the following command sequence on your router WGxR3: WGxR3(config)#no router bgp x WGxR3(config)#router bgp 65002 WGxR3(config-router)#no synchronization WGxR3(config-router)#network 197. .x.x.0 WGxR1(config-router)#network 197.x.1 update-source loopback0 WGxR1(config-router)#neighbor 197.x. for the sole use by Cisco employees for personal study.x.2. your router configuration will be similar to the following.2.x.168. Use the following command sequence on your router WGxR1: WGxR1(config)#no router bgp x WGxR1(config)#router bgp 65001 WGxR1(config-router)#network 192.2. Lab Guide 99 The PDF files and any printed representation for this material are the property of Cisco Systems.1 remote-as 65003 WGxR3(config-router)#neighbor 197.

and may not be distributed for purposes other than individual self-study.21.0 255.255.99 filter-list 11 out WGxR4(config-router)#neighbor 197.255. The files or printed representations may not be used in commercial training.x.4. WGxR4(config-router)#network 197.168.21.0 null 0 WGxR4(config-router)#bgp confederation identifier x WGxR4(config-router)#bgp confederation peers 65002 WGxR4(config-router)#neighbor 192.x.4.7.4. 100 Configuring BGP on Cisco Routers (BGP) v3.x.99 filter-list 10 in WGxR4(config-router)#neighbor 192. Cisco Systems.x.1 next-hop-self WGxR4(config-router)#end Answers to Review Questions Q1) What additional command did you have to use to establish intra-confederation EBGP sessions between loopback interfaces? To establish intra-confederation EBGP sessions between loopback interfaces.4. for the sole use by Cisco employees for personal study.2 © 2005.99 remote-as 99 WGxR4(config-router)#neighbor 192. .168.21.168. Inc. Q2) Why was it necessary to change the AS-path filters? The AS path of the local network has changed.x.0 WGxR4(config-router)#ip route 192.. because it includes the member-AS numbers. Inc.1 ebgp-multihop WGxR4#neighbor 197.1 update-source loopback0 WGxR4(config-router)#neighbor 197. The PDF files and any printed representation for this material are the property of Cisco Systems.1 remote-as 65002 WGxR4(config-router)#neighbor 197. you must specify ebgp-multihop on the intra-confederation EBGP neighbor.x.168.

with differences that are specific to your device or workgroup.20.20. and may not be distributed for purposes other than individual self-study.22 Answer to Review Question Q1) What can you configure on your router to allow the BGP session to restart automatically if the received number of prefixes exceeds the configured maximum? restart parameter of the maximum-prefix command: neighbor ip-address maximum-prefix maximum restart © 2005.22 WG1R1(config)#router bgp 65001 WG1R1(config-router)#no neighbor 192.20. Lab Guide 101 The PDF files and any printed representation for this material are the property of Cisco Systems.22 maximum-prefix 15 WG1R1#clear ip bgp 192. .22 maximum-prefix 15 warning-only WG1R1(config-router)#neighbor 192.168. for the sole use by Cisco employees for personal study. The files or printed representations may not be used in commercial training.20. Inc. your router configuration will be similar to the following.168..20.168.168. Inc. Cisco Systems. Use the following command sequence on your router WGxR1: WGxR1(config)#router bgp 65001 WG1R1(config-router)#neighbor 192.22 maximum-prefix 15 warning-only WG1R1#clear ip bgp 192. Lab 7-1 Answer Key: Limiting the Number of Prefixes Received from a BGP Neighbor When you complete this activity.168.

.20.. Inc. The files or printed representations may not be used in commercial training. and may not be distributed for purposes other than individual self-study.20. The PDF files and any printed representation for this material are the property of Cisco Systems.168. for the sole use by Cisco employees for personal study. Lab 7-2 Answer Key: Implementing BGP Peer Groups When you complete this activity. what single command can you use to reset the BGP sessions on both routers? clear ip bgp peer-group peer-group-name soft in In this example it would be the following: clear ip bgp peer-group SvcPro soft in 102 Configuring BGP on Cisco Routers (BGP) v3. Inc. your router configuration will be similar to the following.22 peer-group SvcPro WG1R1(config-router)#neighbor SvcPro maximum-prefix 50 WG1R1(config-router)#neighbor SvcPro soft-reconfiguration in WG1R1(config-router)#end Answer to Review Question Q1) If the number of prefixes that are received from both providers exceeds 50.20 peer-group SvcPro WG1R1(config-router)#neighbor 192. with differences that are specific to your device or workgroup.168. Use the following command sequence on your router WGxR1: WG1R1(config)#router bgp 65001 WG1R1(config-router)#neighbor SvcPro peer-group WG1R1(config-router)#neighbor 192. Cisco Systems.2 © 2005.

Use the following command sequence on your router WGxR4: WGxR4(config)#ip bgp-community new-format WGxR4(config)#ip community-list 10 permit x:300 WGxR4(config)#ip prefix-list RFD24 permit 0.0. The files or printed representations may not be used in commercial training..0.0.0/0 ge 9 WGxR4(config)#route-map RFD permit 10 WGxR4(config-route-map)#match community 10 WGxR4(config-route-map)#route-map RFD permit 20 WGxR4(config-route-map)#match ip address prefix-list RFD24 WGxR4(config-route-map)#set dampening 20 750 2000 80 WGxR4(config-route-map)#route-map RFD permit 30 WGxR4(config-route-map)#match ip address prefix-list RFD8 WGxR4(config-route-map)#set dampening 15 750 2000 60 WGxR4(config-route-map)#route-map RFD permit 40 WGxR4(config-route-map)#set dampening 10 750 2000 40 WGxR4(config-route-map)#exit WGxR4(config)#router bgp 65003 WGxR4(config-router)#bgp dampening route-map RFD WGxR4(config-router)#end Answers to Review Questions Q1) What is the purpose of route dampening? Route dampening minimizes the impact of route flaps in downstream autonomous systems upon local and upstream autonomous systems. Inc. Cisco Systems. . for the sole use by Cisco employees for personal study. © 2005. Lab Guide 103 The PDF files and any printed representation for this material are the property of Cisco Systems.0/0 ge 24 WGxR4(config)#ip prefix-list RFD8 permit 0. Q2) Which routes are affected by route dampening? Route dampening affects only EBGP routes. Lab 7-3 Answer Key: Using BGP Route Dampening When you complete this activity. your router configuration will be similar to the following. Inc. with differences that are specific to your device or workgroup.0. and may not be distributed for purposes other than individual self-study.

Inc. The files or printed representations may not be used in commercial training. for the sole use by Cisco employees for personal study. and may not be distributed for purposes other than individual self-study. Inc..2 © 2005. 104 Configuring BGP on Cisco Routers (BGP) v3. Cisco Systems. . The PDF files and any printed representation for this material are the property of Cisco Systems.