A company hosts an application on Amazon EC2 instances behind an Application Load Balancer (ALB).

Objective:

Provide a static IP address that the vendor can whitelist for accessing the application.

Using Network Load Balancer (NLB):

Unlike Application Load Balancers, NLBs support static IP addresses through Elastic IPs.

NLBs operate at the transport layer (Layer 4) and are ideal for use cases requiring a static IP.

Steps to Implement:

Step 1: Create an NLB in the same VPC as the application.

Step 2: Associate Elastic IP addresses with the NLB subnets.

Step 3: Update the target group to point to the existing EC2 instances.

Step 4: Update DNS records to map the application domain (www.example.com) to the NLB 's static IP or DNS name.

AWS References:

Elastic IPs with NLB:Static IPs for NLB

NLB vs. ALB:Comparison of Load Balancers

Why Other Options Are Incorrect:

Option A: ALBs do not support Elastic IPs.

Option B: AWS WAF is for web access control, not providing static IPs.

Option C: VPC endpoints do not replace load balancers and are unrelated to static IP requirements.