Sample configuration for eBGP and iBGP

BGP is the Exterior Gateway Protocol used over Internet. Infact BGP is such a wonderful and flexible routing protocol that Service Provider private networks widely use BGP protocol to exchange networks. BGP can accommodate more than 600,000 IPv4 routes and can scale further. BGP does not advertise incremental updates or refresh network advertisements like IGPs. BGP has been designed to function differently within own and between different AS. To support this behavior, BGP Neighborship can be formed in two types

  1. iBGP (Internal Gateway Protocol) and
  2. eBGP (External Gateway Protocol).
  • iBGP Neighbors are those who form neighborship within Same Autonomous System Number. Like in below example, R1 and R2 are 2 routers forming iBGP neighborship within same AS.

  • eBGP Neighbors are those who form neighborship between different Autonomous System Number. Like in below example, R1 and R2 are 2 routers forming eBGP neighborship within different AS.

 

iBGP Neighborship Example

Below is example scenario of iBGP configuration between R1 and R2 –


R1

R1(config)#Router BGP 65001

R1(config-router)#Neighbor 192.168.10.2 remote-as 65001

R1(config-router)#exit

R2

R1(config)#Router BGP 65001

R1(config-router)#Neighbor 192.168.10.1 remote-as 65001

R1(config-router)#exit

Helpful iBGP verification commands –

 To check neighbor status

Rx#show ip bgp summary

Rx#show ip bgp neighbor <Neighbor-IP>

To verify TCP socket detail

Rx#show tcp brief

To verify BGP running process

Rx#show process cpu | include BGP

 

eBGP Neighborship Example

Below is example scenario of eBGP configuration between R1 and R2 –

R1

R1(config)#Router BGP 65001

R1(config-router)#Neighbor 192.168.10.2 remote-as 65002

R1(config-router)#exit

R2

R1(config)#Router BGP 65002

R1(config-router)#Neighbor 192.168.10.1 remote-as 65001

R1(config-router)#exit

 

Helpful eBGP verification commands

To check neighbor status

Rx#show ip bgp summary

To verify Neighbor Detail information

Rx#show ip bgp neighbor <Neighbor-IP>

To verify TCP socket detail

Rx#show tcp brief

To verify BGP running process

Rx#show process cpu | include BGP
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