A BGP session is in OpenConfirm state. Which of the following messages must be received to transition to Established state?

Question

Options

• AUpdate
• BOpen
• CNotification
• DKeepalive

• A
  3% (1)
• B
  3% (1)
• C
  9% (3)
• D
  85% (29)

Explanation

In the BGP Finite State Machine (FSM), OpenConfirm means the local router has already sent and received OPEN messages - it is now waiting for confirmation that the peer accepts the session. Receiving a Keepalive (D) serves as that acknowledgment and triggers the final transition to Established, where routing information can be exchanged.

Why the distractors are wrong:

• A (Update): Update messages carry routing prefixes and are only valid after Established state is reached - sending one before that is a protocol error.
• B (Open): OPEN messages were already exchanged in the preceding OpenSent state; receiving another one in OpenConfirm would be unexpected and treated as an error.
• C (Notification): Receiving a Notification in OpenConfirm is the opposite of success - it signals an error and forces the session back to Idle.

Memory tip: Think of OpenConfirm as "I sent my handshake, now I'm waiting for a thumbs-up." The Keepalive is that thumbs-up - a lightweight "I accept you" with no routing data attached. If you see Notification in any answer choice for a question about successfully advancing through BGP states, eliminate it immediately, since Notification always means something went wrong.

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