Designing Cisco Enterprise Networks (ENSLD) — Question 69
An engineer is tasked with designing a dual BGP peering solution with a service provider. The design must meet these conditions:
* The routers will not learn any prefix with a subnet mask greater than /24.
* The routers will determine the routes to include in the routing table based on the length of the mask alone.
* The routers will make this selection regardless of the service provider configuration.
Which solution should the engineer include in the design?
Answer options
- A. Use a route map and access list to block the desired networks, and apply the route map to BGP neighbors inbound.
- B. Use a route map and prefix list to block the desired networks, and apply the route map to BGP neighbors outbound.
- C. Use an IP prefix list to block the desired networks and apply the IP prefix list to BGP neighbors outbound.
- D. Use an IP prefix list to block the desired networks and apply the IP prefix list to BGP neighbors inbound.
Correct answer: D
Explanation
The correct answer is D because applying an IP prefix list inbound allows the routers to filter out any prefixes longer than /24 before they are added to the routing table. Options A and B incorrectly suggest the use of a route map, which is not necessary for this specific requirement. Option C applies the prefix list outbound, which does not meet the requirement of filtering incoming routes.