Implementing Cisco Enterprise Advanced Routing and Services (ENARSI) — Question 228

What must be configured by the network engineer to circumvent AS_PATH loop prevention mechanism in IP/VPN Hub and Spoke deployment scenarios?

Answer options

• A. Use allowas-in at the PE_Hub.
• B. Use allowas-in and as-override at all PEs.
• C. Use allowas-in and as-override at the PE_Hub.
• D. Use as-override at the PE_Hub.

Correct answer: D

Explanation

The correct answer is D because using as-override at the PE_Hub allows the hub to accept routes containing its own autonomous system number in the AS_PATH, effectively circumventing the loop prevention mechanism. Options A and B are incorrect as they involve configurations that don't specifically address the hub's need, and option C adds unnecessary complexity by including allowas-in, which is not required in this scenario.