Build a BGP session and apply routing policy

Two Cisco routers share a transit link and use different autonomous system numbers.

Configure each neighbor with the address and autonomous system number of its peer.

Router two advertises two loopbacks, and the summary shows both prefixes received.

The curved line shows the established BGP session over TCP.

Shut down the BGP neighbor and check that the transit link still responds.

Bring the neighbor back up and verify that both routes return.

Before filtering, ping each remote loopback to confirm both are reachable.

Create a prefix list that denies one loopback and permits the remaining prefixes.

Apply that list to an inbound route map for the BGP neighbor.

The session stays established, but the denied route disappears from the routing table.

Ping both loopbacks again to see how the policy changes reachability.

Remove the deny entry and confirm that the route and ping return.