AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 165

A company has set up a NAT gateway in a single Availability Zone (AZ1) in a VPC (VPC1) to access the internet from Amazon EC2 workloads in the VPC. The EC2 workloads are running in private subnets in three Availability Zones (AZ1, AZ2, AZ3). The route table for each subnet is configured to use the NAT gateway to access the internet.

Recently during an outage, internet access stopped working for the EC2 workloads because of the NAT gateway's unavailability. A network engineer must implement a solution to remove the single point of failure from the architecture and provide built-in redundancy.

Which solution will meet these requirements?

Answer options

• A. Set up two NAT gateways. Place each NAT gateway in a different public subnet in separate Availability Zones (AZ2 and AZ3). Configure a route table for private subnets to route traffic to the virtual IP addresses of the two NAT gateways.
• B. Set up two NAT gateways. Place each NAT gateway in a different public subnet in separate Availability Zones (AZ2 and AZ3). Configure a route table to point the AZ2 private subnets to the NAT gateway in AZ2. Configure the same route table to point the AZ3 private subnets to the NAT gateway in AZ3.
• C. Create a second VPC (VPC2). Set up two NAT gateways. Place each NAT gateway in a different VPC (VPC1 and VPC2) and in the same Availability Zone (AZ2). Configure a route table in VPC1 to point the AZ2 private subnets to one NAT gateway. Configure a route table in VPC2 to point the AZ2 private subnets to the second NAT gateway.
• D. Set up two NAT gateways. Place each NAT gateway in a different public subnet in separate Availability Zones (AZ2 and AZ3). Configure a route table to point the AZ2 private subnets to the NAT gateway in AZ2. Configure a second route table to point the AZ3 private subnets to the NAT gateway in AZ3.

Correct answer: D

Explanation

Option D is the correct choice because it sets up two NAT gateways in different Availability Zones, ensuring that if one becomes unavailable, the other can still provide internet access. Options A and B do not provide the necessary redundancy for both AZs simultaneously, and Option C introduces unnecessary complexity by creating a second VPC, which is not needed for redundancy in this case.