update source lo0 and ebgp

[petercinvest]

R1 and R2 is ibgp, R1 and R3 is ebgp.

so in R1, I configure nei 2.2.2.2 update-source lo0

do I need to configure nei 3.3.3.3 update-souce lo0? thanks

[chrihussey]

It all depends on how the peering is set up.

If R1 will be using its L0 interface as the source, then R3 should peer with that IP. In addition R3 would need a route to R1's L0 interface and EBGP multihop would need to be enabled.

Don't know your situation, but it wouldn't be necessary for R3 to use it's L0 for it's source, but there is something to be said for consistency.

Regardless, it's always easier to EBGP peer through connected interfaces.

[andnagy122]

Hello,

yeah that's right that it's easier to configure peerings with connected interfaces as the source.

The problem is that connected interfaces can sometimes go down and then the peering fails.

Loopback interfaces are logical ones, therefore, until the router itself doesn't fail, the BGP peering can remain up.

[Mark Malone]

There's 2 ways to do it , with or without loopback

heres the doc with examples

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13751-23.html