BGP and MPLS peerings

[yuchenglai]

Hey All,

I was wondering if someone could help remind me whether or not BGP and / or MPLS LDP peerings have to occur using a / 32 address.  If so, why?

Thanks in advance!

David

[Konstantin Dunaev]

do you mean IP addresses on loopback interfaces? It's not really necessary, you can use just a normal "link-net" address, but BGP and MPLS needs an uniqe router-id, and a loopback IP is normaly used for this.

[Craig_Baum_2]

And of course any /32 would require some form of routing (static or other for reachability) as opposed to say using a /30 address on a pt-pt Ethernet link for peering which would be picked up by the local network..

Sent from Cisco Technical Support iPad App

[Marwan ALshawi]

hi David,

you right you need a host route /32 for MP-BGP with MPLS

You need to use a /32 loopback as the router id for LDP. Without this the PHP is happening one hop too early. This causes to recieve an untagged frame instead of a MPLS frame

however for normal eBGP or iBGP you can use any interface with any subnet as long as it is reachable via IGP or directly connected

hope this help

if helpful Rate