ebgp-multihop 1

[Morini]

When BGP peering to a loopback address, is it neccessary to use the ebgp-multihop command? What are the consequences if you don't - unstable peerings, or will the peerings simply not come up?

If you use the loopback address as the update source, is it neccessary to also use ebgp-multihop in this situation?

Thanks!

 

[KiscoKid]

The rules of EBGP is that both neighbors must be directly-connected and therefore on the same IP subnet.

As the loopback is not on the same directly-connected IP subnet, you have to configure ebgp multihop to allow you to peer with that address. This is still the case even of update source is configured.

If you don't configure multihop, you will never be able to establish a session with the remote peer.