What is the purpose of the BGP keepalive message?

• A. To advertise new routes to neighbors.
• B. To cause a neighbor to reset.
• C. To propagate metrics across the network.
• D. To maintain an active TCP session with a neighbor.

Answer: (D)

Keepalive messages are there to keep the BGP control connection alive. Once two routers have formed a BGP session over TCP, they exchange keepalive messages at a configured interval to show that the neighbor is still reachable. This helps refresh the hold timer and prevents the session from aging out when there are long periods without updates. Keepalives themselves do not carry routing information or metrics; their sole purpose is to ensure the TCP session remains active and that either side can detect a failure if keepalives (or other messages) stop arriving within the hold time.