How to Force BGP Session Tear-Down for Excessive Learned Routes

B.

The correct answer is option B - "neighbor 10.0.0.1 maximum-prefix 10 80".

BGP (Border Gateway Protocol) is a routing protocol used to exchange routing information between different autonomous systems (AS). The "maximum-prefix" command is used to limit the number of prefixes that can be learned from a BGP neighbor.

The syntax of the "maximum-prefix" command is as follows: neighbor {ip-address} maximum-prefix {value} [{threshold}] [{action}]

Where:

• ip-address: The IP address of the BGP neighbor.
• value: The maximum number of prefixes that can be learned from the neighbor.
• threshold: The percentage of prefixes learned from the neighbor that triggers the configured action (default is 75%).
• action: The action to take when the threshold is exceeded. This can be "warning-only" or "shutdown" (default is warning-only).

Option A - "neighbor 10.0.0.1 maximum-prefix 10 80 warning-only": This command sets the maximum number of prefixes that can be learned from the neighbor to 10. If the number of learned prefixes exceeds 10, a warning message will be generated, but the session will not be torn down.

Option B - "neighbor 10.0.0.1 maximum-prefix 10 80": This command sets the maximum number of prefixes that can be learned from the neighbor to 10. If the number of learned prefixes exceeds 10, the session will be torn down.

Option C - "neighbor 10.0.0.1 maximum-prefix 80 10 warning-only": This command sets the threshold for the percentage of prefixes learned from the neighbor that triggers a warning to 80%. It also sets the maximum number of prefixes that can be learned from the neighbor to 10. If the number of learned prefixes exceeds 10, a warning message will be generated, but the session will not be torn down.

Option D - "neighbor 10.0.0.1 maximum-prefix 80 10": This command sets the threshold for the percentage of prefixes learned from the neighbor that triggers a warning to 80%. It also sets the maximum number of prefixes that can be learned from the neighbor to 10. If the number of learned prefixes exceeds 10, the session will be torn down.

Therefore, option B is the correct answer as it sets the maximum number of prefixes that can be learned from the neighbor to 10, and if the number of learned prefixes exceeds 10, the session will be torn down.