ADTRAN AOS Version R10.1.0 Troubleshooting Guide

61200860L1-29.4EMarch 2012Configuration GuideConfiguring Border Gateway Protocol in AOS for Releases Prior to 18.03.00/R10.1.0This configuration and t

Basic BGP Configuration Using the CLI 10 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EIf the routing table does not include a route that has been spe

Basic BGP Configuration Using the CLI61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 11The following example configures a remote AS number of 200 for

Additional BGP Configuration 12 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EAdditional BGP ConfigurationDepending on the network, additional BGP con

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 13BGP CommunitiesWithin BGP, the community is an optional attribute that c

Additional BGP Configuration 14 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Elocal-as Specifies routes that contain the reserved community number for

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 15<value> Specifies a privately defined community for routes service

Additional BGP Configuration 16 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EDeleting communities from a route can be accomplished by first creating

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 17Distribute ListUse the distribute-list command to add route filtering fu

Additional BGP Configuration 18 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EHold TimerUse the hold-timer command to set the default hold time for BG

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 19Log Neighbor ChangesUse the bgp log-neighbor-changes command to control

BGP Overview 2 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EBGP OverviewBGP is an Exterior Gateway Protocol (EGP) that is used within the Internet an

Additional BGP Configuration 20 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Ethe external AS, packets destined for those networks will be dropped. A

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 21PasswordUse the password command to enable message digest 5 (MD5) passwo

Additional BGP Configuration 22 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Edeny <network ipv4 address/length> Denies access to entries matchi

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 23(config-bgp-neighbor)#prefix-list <name> [in | out]<name> As

Additional BGP Configuration 24 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EDefining Routes and Attributes to Advertise Outbound or Filter InboundTh

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 25If an attribute is to be applied to the route, then a set command must b

Additional BGP Configuration 26 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EFiltering Routes According to AS PathRoutes can also be filtered accordi

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 27(config-as-path-list)#permit \b400\bAfter configuring the AS path list,

Additional BGP Configuration 28 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EPrepending Private AS Numbers for Load BalancingA router sends identical

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 29This metric is sometimes called the multi-exit discriminator or MED beca

BGP Overview61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 3By defining autonomous systems, a demarcation point is created between organizations and

Additional BGP Configuration 30 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4E(config-route-map)#set local-preference <value><value> Sets

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 31Router IDThe BGP interface identifies itself to neighbors with its route

Additional BGP Configuration 32 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EUpdate SourceUse the update-source command to specify which interface’s

Additional BGP Configuration61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 33The peering router would also use a loopback interface in this scenario.

Additional BGP Configuration 34 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Eset local preference 110!router bgp <AS number>redistribute <so

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 35Example ConfigurationsThe example scenarios contained within this section are

Example Configurations 36 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EThe following configuration applies to Example 1:!interface eth 0/1ip address

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 37Example 2: Exchanging Routes between Peers with the Same AS NumberSome MPLS p

MPLSSite B(LAN)AS 65003AS 65002192.168.1.1 /24172.16.1.2 /30172.16.1.1 /30T1(PPP)(ETH 0/1)PEPE(LAN)AOS Device(CE)AOS Device(CE)CE - Customer Edge Rout

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 39Example 3: Filtering Routes with Prefix ListsBGP routes advertised and receiv

BGP Overview 4 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EBGP Neighbors and MessagesUnlike other routing protocols, BGP does not automatically disc

Example Configurations 40 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Einterface ppp 1 ip address 208.61.209.254 255.255.255.252 no shutdown cross-c

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 41Example 4: Multihoming and Influencing Traffic over a Preferred PathMultihomi

Example Configurations 42 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EThe following configuration applies to Example 4:!interface eth 0/1 descript

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 43Example 5: Load Sharing When Multihomed to Multiple ISPsAOS allows multiple e

Example Configurations 44 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Eoutbound to both ISPs. This prefix will prevent any routes learned by the AOS

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 45interface ppp 2ip address 65.162.109.201 255.255.255.252no shutdowncross-con

Example Configurations 46 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EExample 6: Configuring Local Preference, MED, and Next-Hop-Self on an AOS Rou

192.168.2.2 /30G2G3G4NetVanta 12347123456789101112131415161718192021222324G1G2G3G413591113152468101214161719212318202224STATG1172.16.5.0 /24Remote Rou

Example Configurations 48 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Eroute-map SETMULTIEXIT2 permit 10 match ip address prefix-list NETWORK set met

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 49Example 7: Using Local Preference to Promote a BGP Route as the Primary Inter

BGP Overview61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 5Multi-Exit DiscriminatorThe multi-exit discriminator (MULTI_EXIT_DISC or MED) attribute i

Default RouteDefault RouteG2G3G4NetVanta 12347123456789101112131415161718192021222324G1G2G3G413591113152468101214161719212318202224STATG1InternetAS 50

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 51router bgp 500no auto-summaryno synchronizationnetwork 0.0.0.0 mask 0.0.0.0nei

Example Configurations 52 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EExample 8: Using BGP Communities in an MPLS Network to Change Local Preferenc

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 53Figure 10. Three Internet-Provisioned Sites on an MPLS Network Provide Intern

Example Configurations 54 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4Einterface t1 1/1clock source linetdm-group 1 timeslots 1-24 speed 64no shutdow

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 55router bgp 65002redistribute rip route-map REDISTRIBUTEnetwork 192.168.2.0 mas

Example Configurations 56 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4E!interface eth 0/1ip address 192.168.X.1 255.255.255.0no shutdown!interface t1

Example Configurations61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 57!router bgp 65000neighbor 172.16.1.1route-map BGP-IN insend-community standard

Configuration Command Summary 58 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EConfiguration Command SummaryIt is important to note that BGP sessions

Table 5. Additional BGP Configuration Options(config-bgp)#distance bgp <external> <internal> <local>Specifies the administrative di

BGP Overview 6 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EBGP Path SelectionWhen BGP receives advertisements for the same route from multiple sourc

Table 6. Additional BGP Neighbor Configuration Options(config-bgp-neighbor)#advertisement-interval <value>Specifies the minimum interval betwee

Table 7. Filtering Routes and Applying Attributes with Route MapsStep 1 (config)#route-map <name> [deny | permit] <number>Creates a route

Configuration Command Summary 62 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ELists referenced in Step 2 (prefix, IPv4 ACL, AS path, and community) f

Configuration Command Summary61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 63Step 8 (config-bgp)#neighbor <ipv4 address> Enters BGP Neighbor C

Table 9. Advertising a BGP Community(config)#ip prefix-list <name> seq <number> [deny | permit] <network ipv4 address/length> [ge |

Table 10. Deleting a Community(config)#ip prefix-list <name> seq <number> [deny | permit] <network ipv4 address/length> [ge | le] &

Troubleshooting 66 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ETroubleshootingAfter configuring BGP, several different commands can be issued from E

Troubleshooting61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 67#show ip bgp neighbors <ipv4 address> received-routesDisplays all IPv4 routes (

Troubleshooting 68 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EShow CommandsShow IP AS-Path ListUse the show ip as-path-list command to display any

Troubleshooting61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 69Use the show ip bgp summary command to display a summary of the BGP route table.#show

BGP Overview61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 7For example, in Figure 1 on page 7 the provider’s edge routers connect to two independent

Troubleshooting 70 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EIn the following example, all BGP routes are displayed whose community attributes mat

Troubleshooting61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 71Show IP BGP NeighborsUse the show ip bgp neighbors command to display information for

Troubleshooting 72 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4E#show ip bgp neighbors 10.15.43.34 advertised-routesBGP local router ID is 10.0.0.1,

Troubleshooting61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 73* 10.22.132.8/29 10.22.132.9 0 303 i* i10.22.132.240/28 10.22.132.1 0 100 303 i*>

Troubleshooting 74 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EDebug CommandsDebug IP BGPUse the debug ip bgp command to activate debug messages ass

Troubleshooting61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 75Strategies for Troubleshooting Specific BGP ProblemsAn AOS device running BGP might n

Troubleshooting 76 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ERemove an IPv4 ACL:(config-bgp-neighbor)#no distribute-list <ipv4 acl name> [in

Router# show ip bgp neighbors 192.168.0.25 routes BGP local router ID is 192.168.88.1, local AS is 501. Status codes: * valid, > best, i - internal

Troubleshooting 78 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ENext, record the current settings in the AOS device and verify that they match those

Router#show ip bgp neighborsBGP neighbor is 192.168.0.25, remote AS 500, external link Configured hold time is 180, keepalive interval is 60 seconds D

Hardware and Software Requirements and Limitations 8 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EThe Internet connections for a multihomed router ca

Troubleshooting 80 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ECheck all of the statements for hits. Statements that have been misconfigured often h

NetVanta_4305#show route-map route-map DEFAULT-ROUTE-IN, permit, sequence 10 Match clauses: ip address (prefix-lists): DEFAULT Set clauses:

Troubleshooting 82 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4ENetwork Flooded with External TrafficOne of the most common uses for BGP is BGP multi

Appendix61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 83AppendixAS Regular ExpressionsRegular expressions, also known as regexp, are used in BGP to

Appendix 84 Copyright © 2012 ADTRAN, Inc. 61200860L1-29.4EExamples of Regular Expressions.* Matches any character or sequence of characters.3+ Matches

Basic BGP Configuration Using the CLI61200860L1-29.4E Copyright © 2012 ADTRAN, Inc. 9Basic BGP Configuration Using the CLIThere are several commands