How should a solutions architect ensure that the web application can continue to call the third-parly API after the migration?

An AWS customer has a web application that runs on premises. The web application fetches data from a third-party API that is behind a firewall. The third party accepts only one public CIDR block in each client’s allow list.

The customer wants to migrate their web application to the AWS Cloud. The application will be hosted on a set of Amazon EC2 instances behind an Application Load Balancer (ALB) in a VPC. The ALB is located in public subnets. The EC2 instances are located in private subnets. NAT gateways provide internet access to the private subnets.

How should a solutions architect ensure that the web application can continue to call the third-parly API after the migration?
A . Associate a block of customer-owned public IP addresses to the VPC. Enable public IP addressing for public subnets in the VPC.
B. Register a block of customer-owned public IP addresses in the AWS account. Create Elastic IP addresses from the address block and assign them lo the NAT gateways in the VPC.
C. Create Elastic IP addresses from the block of customer-owned IP addresses. Assign the static Elastic IP addresses to the ALB.
D. Register a block of customer-owned public IP addresses in the AWS account. Set up AWS Global Accelerator to use Elastic IP addresses from the address block. Set the ALB as the accelerator endpoint.

View Answer

Answer: B

Explanation:

When EC2 instances reach third-party API through internet, their privates IP addresses will be masked by NAT Gateway public IP address. https://aws.amazon.com/blogs/networking-and-content-delivery/introducing-bring-your-own-ip-byoip-for-amazon-vpc/