Thursday, January 28, 2010
BGP Peer Groups
I spent the better part of my morning learning how to configure BGP Peer Groups. Peer Groups provide a way to save router processing time by not having to send an individual update for each IBGP neighbor. If your Autonomous System has a rather large amount of routers (neighbors) running BGP, the processing time each router would have to run could be pretty intensive. Remember that when running IBGP within a transitive AS, all neighbors should be fully-meshed with one another due to the way BGP sends updates (unicast). I was also introduced to distribution lists and how they could be used to tune BGP updates. In the lab I created I used a distribution list to permit internal IP networks from being addressed outside the AS to other AS's.
As you see in the Router A BGP example, the commands to create a peer-group, distribution list, and creating updates for specific networks can be quite extensive compared to other routing protocols.