BGP Peer Groups on Quagga

Objective: To set up a "peer-group" on our Quagga router to limit advertisements within an Autonomous System.

Setup: Refer to previous post "Headless BSD Quagga Router" to get you started.

Under the running config on the quagga router I have formed the peer group 'localAS' for AS3 with the following command:

neighbor localAS remote-as 3

next I include the neighbors I wish to be in the peer-group:

neighbor 172.16.1.2 peer-group localAS
neighbor 192.68.1.1 peer-group localAS

It is the same as declaring a normal neighbor however I use the 'peer-group' option. The 'remote-as' option is not needed, as in the preceding command 'neighbor localAS remote-as 3' confirms which remote the peer-group is in.

Excerpt on BGP Technology from Cisco Systems:

The major benefit you achieve when you specify a BGP peer group is that a BGP peer group reduces the amount of system resources (CPU and memory) necessary in an update generation. A BGP peer group reduces the load on system resources by allowing the routing table to be checked only once, and updates to be replicated to all peer group members instead of being done individually for each peer in the peer group. Based on the number of peer group members, the number of prefixes in the table, and the number of prefixes advertised, this can significantly reduce the load.

BGP peer groups also simplifies the BGP configuration. Instead of configuring each neighbor with the same policy individually, a peer group allows you to group the policies which can be applied to individual peers thus making efficient update calculation along with simplified configuration.

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