What are the four BGP message types?

• A. Open, Keepalive, Update and Notification
• B. Hello, Update, Withdraw, Tear-Down
• C. Start, Stop, Update and Notify
• D. Connect, Open, Keepalive and Shutdown

Answer: (A)

BGP operates with four message types that drive session setup, maintenance, and routing updates. Open is used to establish a peering session and negotiate parameters between peers. Keepalive exchanges maintain the session and confirm that both sides are still reachable. Update messages carry the actual routing information, including new paths and withdrawals of previously advertised routes. Notification signals errors or issues and can terminate the session when something goes wrong.

This set—Open, Keepalive, Update, and Notification—is specific to BGP. Other terms like Hello belong to other routing protocols (for example, IGPs), and Start, Stop, Tear-Down, Connect, or Shutdown are not BGP message types.