AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 158

AnyCompany has acquired Example Corp. AnyCompany's infrastructure is all on premises, and Example Corp's infrastructure is completely in the AWS Cloud. The companies are using AWS Direct Connect with AWS Transit Gateway to establish connectivity between each other.

Example Corp has deployed a new application across two Availability Zones in a VPC with no internet gateway. The CIDR range for the VPC is 10.0.0.0/16. Example Corp needs to access an application that is deployed on premises by AnyCompany. Because of compliance requirements, Example Corp must access the application through a limited contiguous block of approved IP addresses (10.1.0.0/24).

A network engineer needs to implement a highly available solution to achieve this goal. The network engineer starts by updating the VPC to add a new CIDR range of 10.1.0.0/24.

What should the network engineer do next to meet the requirements?

Answer options

• A. In each Availability Zone in the VPC, create a subnet that uses part of the allowed IP address range. Create a public NAT gateway in each of the new subnets. Update the route tables that are associated with other subnets to route application traffic to the public NAT gateway in the corresponding Availability Zone. Add a route to the route table that is associated with the subnets of the public NAT gateways to send traffic destined for the application to the transit gateway.
• B. In each Availability Zone in the VPC, create a subnet that uses part of the allowed IP address range. Create a private NAT gateway in each of the new subnets. Update the route tables that are associated with other subnets to route application traffic to the private NAT gateway in the corresponding Availability Zone. Add a route to the route table that is associated with the subnets of the private NAT gateways to send traffic destined for the application to the transit gateway.
• C. In the VPC, create a subnet that uses the allowed IP address range. Create a private NAT gateway in the new subnet. Update the route tables that are associated with other subnets to route application traffic to the private NAT gateway. Add a route to the route table that is associated with the subnet of the private NAT gateway to send traffic destined for the application to the transit gateway.
• D. In the VPC, create a subnet that uses the allowed IP address range. Create a public NAT gateway in the new subnet. Update the route tables that are associated with other subnets to route application traffic to the public NAT gateway. Add a route to the route table that is associated with the subnet of the public NAT gateway to send traffic destined for the application to the transit gateway.

Correct answer: B

Explanation

The correct answer is B because a private NAT gateway is necessary for routing traffic to an on-premises application without exposing the VPC to the internet. Option A is incorrect as it suggests using a public NAT gateway, which is not suitable due to the need for compliance and security. Option C does not provide high availability since it only creates one subnet, and option D is also incorrect for the same reason as A, as it uses a public NAT gateway.