AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 250

A company uses transit gateways to route traffic between the company's VPCs. Each transit gateway has a single route table. Each route table contains attachments and routes for the VPCs that are in the same AWS Region as the transit gateway. The route tables in each VPC also contain routes to all the other VPC CIDR ranges that are available through the transit gateways. Some VPCs route to local NAT gateways.

The company plans to add many new VPCs soon. A network engineer needs a solution to add new VPC CIDR ranges to the route tables in each VPC.

Which solution will meet these requirements in the MOST operationally efficient way?

Answer options

• A. Create a new customer-managed prefix list. Add all VPC CIDR ranges to the new prefix list. Update the route tables in each VPC to use the new prefix list ID as the destination and the appropriate transit gateway ID as the target.
• B. Turn on default route table propagation for the transit gateway route tables. Turn on route propagation for each route table in each VPC.
• C. Update the route tables in each VPC to use 0.0.0.010 as the destination and the appropriate transit gateway ID as the target.
• D. Turn on default route table association for the transit gateway route tables. Turn on route propagation for each route table in each VPC.

Correct answer: A

Explanation

The correct answer is A because creating a customer-managed prefix list allows for efficient management of multiple CIDR ranges without needing to manually update each route table individually. Option B does not provide a direct way to add new CIDR ranges efficiently, while Option C incorrectly uses an invalid CIDR notation, and Option D does not address the need to handle multiple CIDR ranges effectively.