4A0-102 · Question #77
Which of the following is NOT a BGP message type?
The correct answer is B. OpenSent. OpenSent is a state in the BGP Finite State Machine (FSM), not a message type - this is a classic trick question that tests whether you know the difference between BGP states and BGP messages. The four core BGP message types defined in RFC 4271 are OPEN, UPDATE, NOTIFICATION…
Question
Options
- ARoute-Refresh
- BOpenSent
- CNotification
- DUpdate
- EKeepalive
How the community answered
(44 responses)- A5% (2)
- B93% (41)
- E2% (1)
Explanation
OpenSent is a state in the BGP Finite State Machine (FSM), not a message type - this is a classic trick question that tests whether you know the difference between BGP states and BGP messages. The four core BGP message types defined in RFC 4271 are OPEN, UPDATE, NOTIFICATION, and KEEPALIVE (options C, D, and E), making them all valid message types and therefore wrong answers here. Route-Refresh (option A) is a fifth, optional message type added by RFC 2918, used to request a peer to re-advertise their routes without tearing down the session. The BGP FSM states (Idle, Connect, Active, OpenSent, OpenConfirm, Established) are a separate concept entirely - they describe the status of the peering session, not packets exchanged.
Memory tip: Remember "NOUN-K" for BGP messages - Notification, Open, Update, Not-applicable (filler), Keepalive - then add Route-Refresh as a bonus. If you see a word ending in "-Sent" or "-Confirm," that's a FSM state, not a message.
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