350-401 Question #798: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. R1 and R2 are directly connected, but the BGP session does not establish. Which action must be taken to build an eBGP session?

Options

• AConfigure ip route 1.1.1.1 0.0.0.0 192.168.12.1 on R2.
• BConfigure neighbor 192.168.12.1 activate under R2 BGP process.
• CConfigure neighbor 2.2.2.2 remote-as 65002 under R1 BGP process.
• DConfigure no neighbor 192.168.12.1 shutdown under R2 BGP process.

Explanation

If a BGP neighbor session is not establishing, it is often due to the neighbor being administratively shut down, which can be resolved by issuing the 'no neighbor shutdown' command.

Common mistakes.

• A. Configuring a static route for R1's loopback (1.1.1.1) via a directly connected interface (192.168.12.1) is generally not required for directly connected eBGP neighbors, as reachability is implicitly handled by the connected subnet.
• B. The activate command is usually implicitly enabled for directly connected eBGP neighbors when the neighbor remote-as command is configured and is typically required only when peering over loopback interfaces with an update-source command.
• C. Configuring neighbor 2.2.2.2 remote-as 65002 under R1's BGP process would be a valid configuration step if R2's loopback is 2.2.2.2, but the question implies a specific missing action to build the session, and option D addresses an administrative shutdown state which is a more fundamental impediment.

Concept tested. BGP neighbor session troubleshooting (administrative state)

Reference. https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13768-4.html

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