Ibgp Peer establishment question

[mahesh18]

Hi all,

Here is info

We have two routers R1 and R2 and they are in same  AS  1.

they are in IBGP.

Here is R2 config

router bgp 1

neighbor 1.1.1.1 remote-as 1

neighbor 1.1.1.1 update-source loopback 0

Can someone please explain we why we use the command --neighbor 1.1.1.1 update-source loopback 0 and what does this mean.

Many thanks

mahesh

[dominic.caron]

You will peer with the other router using the logical interface loopback 0. Peering with a logical interface is usualy a good thing. If you peer using a physical interface and it fail, you will lose your peering. If you use a logical interface, your router might still be reachable using another path.

[mahesh18]

Hi dominic,

thanks for reply it means we have to apply IP address of loopback interface ?

or we can say that R1  routers  loopback0 interface has IP  address of 1.1.1.1?

regards

mahesh

[dominic.caron · Accepted solution]

On R1 and R2, you configure loopback IP. The loopback of R1 must be reachable by R2 and R2, by R1. On R1, you peer to R2 Lo0 with a source of R1 Lo0 and on R2, you peer with R1 Lo0 with a source of R2 Lo0

[mahesh18]

Hi Dominic ,

Many thanks for detailed explanation.

regards

mahesh

[cadet alain · Accepted solution]

Hi,

It means the BGP relationship we're having with 1.1.1.1 will be sourced from Lo0 (1.1.1.1 is the Loopback address of the other router).

Regards.

Alain.

[dominic.caron]

--R1--

int lo0

ip add 1.1.1.1 255.255.255.255

router bgp 1

nei 2.2.2.2 remo 1

nei 2.2.2.2 update lo 0

--R2--

int lo0

ip add 2.2.2.2 255.255.255.255

router bgp 1

nei 1.1.1.1 remo 1

nei 1.1.1.1 update lo 0