9.4 Peer Groups
9.4.2 Peer group configuration example
In the figure, RTC has IBGP peering sessions with RTD, RTE, and RTH, and has similar policies toward each. Instead of formulating and applying similar policies for each neighbor individually, you can define a peer group that contains the policies and then place RTC's IBGP peers in the peer group (see the first running configuration in the figure).

The configuration shown in the figure defines a peer group called INTERNALMAP that contains several policies. These policies are applied to all internal neighbors: RTD, RTE, and RTH. Note that an additional policy, filter-list 3, has been applied to incoming updates from 172.16.12.1 (RTH). Filter list 3 will override any incoming policies set by the peer group INTERNALMAP for neighbor RTH. Remember that outbound update policies cannot be overridden, although additional policies can be defined to specific peers.

As a final example, look at the peer group configuration used by RTC for EBGP peers (see the second running configuration in the figure).

A major difference between IBGP and EBGP peer groups is that the neighbor remote-as statement is typically placed outside the EBGP peer group configuration. This is usually necessary because external peers do not often reside in the same AS (although they certainly can). Also note that the configuration shown defines filter list 3, which can be used to override configuration options for incoming updates from the neighbor at IP address 172.16.20.3 (RTF).