ip-address— Neighbor's IP address.
peer-group-name— Name of the peer group. See section 8-19.
interface-name— Any physical or logical router interface. Usually, a loopback interface is used.
Purpose: An IBGP connection can occur as long as there is a TCP/IP path between the routers. If multiple paths exist between the IBGP routers, using a loopback interface as the neighbor's address can add stability to the network. Using loopback interfaces with EBGP speakers is not necessary, because EBGP neighbors are usually directly connected.
Cisco IOS Software Release: 10.0. Peer group support was added in Release 11.0.