First, let's look at the commands used in BGP:
router bgp <asn>
For example:
R1(config)#router bgp 120
This command enables BGP on a router and moves to the router configuration mode. The ASN can be any value between 1 and 65535. Once enabled, the BGP process must choose a router ID. By default, BGP uses the following methods priority-wise, to pick a router ID.
Configured: This is the router ID configured by using the
bgp router-idrouter subcommandHighest loopback: This is the highest numeric IP address configured on any up loopback interface at the time the BGP process is initialized
Highest other interfaces: This is the highest numeric IP address configured on any up non-loopback interface at the time the BGP process is initialized
A router ID can be explicitly configured using the following command:
bgp router-id X.X.X.X
For example, we can use the following command to configure the router ID:
R1(config-router)#bgp router-id 1.1.1.1
For configuring...