Configure BGP Using Loopback Address
Configuring BGP using loopback addresses is a very good practise, especially with iBGP. Loopback interface is virtual; only implemented in software without any association to the hardware.
Loopback interface is always up and will be reachable through an IP address configured on it.
To configure iBGP using a loopback address, use the following command:
neighbor ip-address update-source interface
RouterHQ Configuration Command:
BranchOffice Configuration Command :
Looking at the above configuration base on the sample topology, , RouterHQ and BranchOffice belongs to the same AS 556 (iBGP).
RouterHQ is configured to use the loopback IP address as the source in the TCP neighbor connection. For BranchOffice to speak to RouterHQ, it uses the loopback interface of RouterHQ.