sample configuration for ib

Table of ContentsSample Configuration for iBGP and eBGP With or Without a Loopback Address....................................1

Introduction.............................................................................................................................................1 Prerequisites............................................................................................................................................1

Requirements....................................................................................................................................1 Components Used.............................................................................................................................1 Conventions......................................................................................................................................1

Configure................................................................................................................................................1 Network Diagram.............................................................................................................................2 iBGP Configurations........................................................................................................................2 eBGP Configurations.......................................................................................................................2 BGP Configurations Using a Loopback Address.............................................................................3

Verify......................................................................................................................................................3 Troubleshoot...........................................................................................................................................4 Related Information................................................................................................................................4

Cisco − Sample Configuration for iBGP and eBGP With or Without a Loopback Address

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Sample Configuration for iBGP and eBGP With orWithout a Loopback AddressAuthor: Syed Faraz Shamim

IntroductionPrerequisites Requirements Components Used ConventionsConfigure Network Diagram iBGP Configurations eBGP Configurations BGP Configurations Using a Loopback AddressVerifyTroubleshootRelated Information

Introduction

You can configure Border Gateway Protocol (BGP) either within an autonomous system or between differentautonomous systems. When run within an autonomous system, it's called internal BGP (iBGP). When runbetween different autonomous systems, it's called external BGP (eBGP). The sample configurations in thisdocument are for iBGP and eBGP, both with and without a loopback addresses.

Note: You can use these configurations for establishing neighbor relationship. Refer to Using the BorderGateway Protocol for Interdomain Routing for more complex configurations.

Prerequisites

Requirements

Before attempting this configuration, please ensure that you meet the following prerequisites:

Knowledge of BGP protocols•

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

For more information on document conventions, see the Cisco Technical Tips Conventions.

Configure

This section contains the following configuration examples:


iBGP• eBGP• BGP using a loopback address•

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command LookupTool ( registered customers only) .

Network Diagram

This document uses the network setup shown in the diagram below.

iBGP Configurations

R1−AGSR6−2500

Current configuration:

interface Serial1 ip address 10.10.10.1 255.255.255.0!router bgp 400 neighbor 10.10.10.2 remote−as 400

end


interface Serial0ip address 10.10.10.2 255.255.255.0!router bgp 400 neighbor 10.10.10.1 remote−as 400

end

The iBGP show command:

R1−AGS(9)# show ip bgp summaryBGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd10.10.10.2 4 400 3 3 1 0 0 00:00:26 0

eBGP Configurations

R1−AGSR6−2500


interface Serial1 ip address 10.10.10.1 255.255.255.0!router bgp 300


interface Serial0ip address 10.10.10.2 255.255.255.0!router bgp 400


neighbor 10.10.10.2 remote−as 400

end

neighbor 10.10.10.1 remote−as 300

end

The eBGP show command:



Peers must be directly connected when using eBGP. If they are not directly connected, an iBGP route mustexist in order for the peer address to establish neighbors.

BGP Configurations Using a Loopback Address

You can also configure iBGP and eBGP using a loopback address. We recommend you use a loopbackinterface to guarantee reachability in networks with multiple paths.

Note: To configure iBGP with a loopback address, you can use the configurations below, omitting theebgp−multihop command.

R1−AGSR6−2500


interface Loopback0 ip address 1.1.1.1 255.255.255.255 ! interface Serial1 ip address 10.10.10.1 255.255.255.0 ! router bgp 300 neighbor 2.2.2.2 remote−as 400 neighbor 2.2.2.2 ebgp−multihop 2 neighbor 2.2.2.2 update−source Loopback0 ! ip route 2.2.2.2 255.255.255.255 10.10.10.2

end


interfacee Loopback0 ip address 2.2.2.2 255.255.255.255!interface Serial0 ip address 10.10.10.2 255.255.255.0!router bgp 400 neighbor 1.1.1.1 remote−as 300 neighbor 1.1.1.1 ebgp−multihop 2 neighbor 1.1.1.1 update−source Loopback0!ip route 1.1.1.1 255.255.255.255 10.10.10.1

end

The BGP show command:



Verify

There is currently no verification procedure available for this configuration.


Troubleshoot

There is currently no specific troubleshooting information available for this configuration.

Related Information

BGP Support Page• Technical Support − Cisco Systems•

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sample configuration for ib

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