What should the solutions architect recommend to meet these requirements?
Create a AWS Lambda function to keep track of the IPs for all the ALBs in different Regions. Keep refreshing this list.
Set up a Network Load Balancer (NLB) with Elastic IPs. Register the private IPs of all the ALBs as targets to this NLB.
Launch AWS Global Accelerator and create endpoints for all the Regions. Register all the ALBs in different Regions to the corresponding endpoints.
Set up an Amazon EC2 instance, assign an Elastic IP to this EC2 instance, and configure the instance as a proxy to forward traffic to all the ALBs.
Explanations:
While a Lambda function could track ALB IPs, it doesn’t inherently reduce the number of IPs to allow on the firewall. Additionally, the list would need to be refreshed regularly, making it less ideal for a one-time solution.
Using an NLB with Elastic IPs could work but wouldn’t reduce the number of IPs required for the firewall. Each ALB would still have its own IP, and you’d be managing an additional layer that doesn’t solve the core issue.
AWS Global Accelerator provides a static IP address and routes traffic to the ALBs across multiple Regions. This significantly reduces the number of IPs to allow on the firewall to just the Global Accelerator IPs, making it a highly available one-time solution.
While an EC2 instance with an Elastic IP could act as a proxy, it introduces complexity, single points of failure, and does not inherently reduce the number of allowed IPs for the firewall since each ALB would still be reachable directly unless explicitly routed through the EC2 instance.
I suspect that the answer is:
Launch AWS Global Accelerator and create endpoints for all the Regions. Register all the ALBs in different Regions to the corresponding endpoints.