What message will be identified as incorrect during negotiation in the Error Code of the Notification message when BGP peer settings are inconsistent?

In BGP (Border Gateway Protocol), the error codes associated with the Notification message are critical for diagnosing issues in the connection between peers. When there are inconsistent peer settings or parameters during the establishment of a BGP session, the Open message is crucial. This message is the first type of communication that occurs after a TCP connection between peers is established.

If there is an inconsistency, such as a mismatch in AS numbers or capabilities, the BGP peer will generate a Notification message, and the specific reason for the shutdown of the session will be indicated as an error in the Open message. This is because the Open message is responsible for initial communication, including the advertisement of the peer's AS number and the allowed capabilities. Therefore, if these settings do not match, it will be identified through an error in the Open message, leading to the negotiation failing and the session not being established.

The other types of messages, such as Route-refresh, Keepalive, and Update, occur after a BGP session is already established and are designed for different purposes. The Route-refresh message is used to request a full re-advertisement of routes, the Keepalive message is sent to maintain the connection, and the Update message carries route information. Since these messages are part