Implementing Cisco Enterprise Advanced Routing and Services (ENARSI) — Question 589

How is the LDP router ID used in an MPLS network?

Answer options

• A. The force keyword changes the router ID to the specified address without causing any impact.
• B. The loopback with the highest IP address is selected as the router ID.
• C. The MPLS LDP router ID must match the IGP router ID.
• D. If not configured, the operational physical interface is chosen as the router ID even if a loopback is configured.

Correct answer: B

Explanation

The correct answer is B because the LDP router ID is determined by the loopback interface with the highest IP address in an MPLS network. Option A is incorrect as it misrepresents the force keyword's functionality, while C is wrong because the MPLS LDP router ID does not need to match the IGP router ID. Option D is also inaccurate since the presence of a loopback will take precedence over the operational physical interface if configured.