What is contained in a BGP notification message?

• A. The list of learned routes
• B. A session establishment timestamp
• C. An error code, an error subcode and data related to the error
• D. A checksum of the BGP message

Answer: (C)

BGP notification messages are used to signal that something went wrong and to carry details about the error. They contain three parts: an error code that identifies the general category of the problem, an error subcode that pinpoints the exact condition within that category, and a data field with additional information related to the error to aid troubleshooting. This structure is why this option is the best choice: it directly communicates what went wrong and offers context to diagnose the issue.

In contrast, learned routes are conveyed in Update messages, not in Notifications. There isn’t a session establishment timestamp in BGP messages. And while TCP provides the transport reliability for BGP, BGP messages themselves do not include a checksum field.