What does a BGP Notification Message signify?

A BGP Notification Message is significant because it indicates that an error condition has occurred within the BGP session. When a BGP router detects an issue—such as policy violations, unreachable routes, or configuration problems—it sends a Notification Message to inform the peer router that it can no longer maintain the session or that there was an error with regard to routing information being exchanged.

The key function of a Notification Message is to gracefully inform the other BGP peer of a problem, which leads to proper management of the BGP session by allowing the peer to take appropriate action, like shutting down the session or attempting to recover. Thus, the presence of a Notification Message indicates an error condition rather than successful operations like route advertisements, updates to the routing table, or the establishment of a session.