AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 173

A company has an AWS Site-to-Site VPN connection between AWS and its branch office. A network engineer is troubleshooting connectivity issues that the connection is experiencing. The VPN connection terminates at a transit gateway and is statically routed. In the transit gateway route table, there are several static route entries that target specific subnets at the branch office.

The network engineer determines that the root cause of the issues was the expansion of underlying subnet ranges in the branch office during routine maintenance.

Which solution will solve this problem with the LEAST administrative overhead for future expansion efforts?

Answer options

• A. Determine a supernet for the branch office. In the transit gateway route table, add an aggregate route that targets the VPN attachment. Replace the specific subnet routes in the transit gateway route table with the new supernet route.
• B. Create an AWS Direct Connect gateway and a transit VIF. Associate the Direct Connect gateway with the transit gateway. Create a propagation for the Direct Connect attachment to the transit gateway route table.
• C. Create a dynamically routed VPN connection on the transit gateway. Connect the dynamically routed VPN connection to the branch office. Create a propagation for the VPN attachment to the transit gateway route table. Remove the existing static VPN connection.
• D. Create a prefix list that contains the new subnets and the old subnets for the branch office. Remove the specific subnet routes in the transit gateway route table. Create a prefix list reference in the transit gateway route table.

Correct answer: C

Explanation

The correct answer, C, allows for a dynamically routed VPN connection which can automatically adapt to changes in the branch office's subnet ranges, thus reducing administrative overhead for future expansions. Options A, B, and D involve either maintaining static routes or adding complexity that does not address the need for flexibility in routing as the branch office subnet changes.