How can you add resiliency to a BGP session?

• A. Use the loopback address interface on each router for peering, as loopbacks are always available as long as the router remains up.
• B. Use physical interface addresses for peering.
• C. Disable loopback peering.
• D. Use only internal BGP neighbors.

Answer: (D)

Loopback-based BGP peering is a robust way to add resiliency. When the BGP session uses a loopback address, the session is no longer tied to a single physical interface that can flap during link failures or reconfigurations. As long as the loopbacks are reachable through IGP or static routes, your BGP session can remain up even if a particular physical link goes down. In practice, you’d enable EBGP multihop and source the session from the loopback (neighbor update-source loopback) so the TCP connection can be established across multiple paths, and you’d keep the session secured with authentication. This approach increases path stability and availability compared with peering directly on a physical interface.

Using only internal BGP neighbors does not inherently improve resiliency. It constrains reachability to within the same AS and reduces external path diversity, so it doesn’t address failures affecting external links or paths. Peering over loopbacks with proper reachability and multihop is the standard way to harden BGP sessions against such issues.