BGP Peer Group


Peer groups create a more manageable method of creating new bgp sessions and improving the performance of BGP Update message generation.

Peer Groups

  • There are two aspects of Peer Groups: group configuration and BGP Update optimization.
  • Peer-group simplify BGP configuration, (neighbors remote-as 300 vs neighbor PEER remote-as 300), don't have to keep on typing the IP address of the peer for each session command.
  • Peer-groups also reduces the Update generation process. The BGP table is scanned only once per each peer-group. The scan produces update messages. Update messages are then replicated to other peer-group members without scanning the BGP table again. Update messages are originally scanned for the peer-group leader. The leader is a peer with the lowest IP address.
  • Formatted routes are created by scanning the BGP table and generating Update messages specifically for a neighbor. Replicated are Update messages that were generated for the peer leader and copied for other peer members.
  • Replication Ratio is the replicated messages / formatted messages. Ideal replication ratio is 1 less than the number of peers in a peer group.
  • Limitation of peer-groups is that all of the peers have to have the same outbound policy and be in the same address-family. BGP-Peer-Templates over come this limitation.

Relevant Commands


Peer groups name has to be created first, then peer IP addresses associated with the group.

R1(config-router)#                 neighbor (group name)  peer-group
R1(config-router)#                 neighbor (group name)  remote-as 100
R1(config-router)#                 neighbor (a.b.c.d) peer-group (group name)

show ip bgp peer-group

show ip bgp peer-group

Show an example of an IBGP=PEERS group name.


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