A company is designing a new web service that will run on Amazon EC2 instances behind an Elastic Load Balancing (ELB) load balancer. Many web service clients can only reach IP addresses authorized on their firewalls. What should a solutions architect recommend to meet the clients’ needs?

A Network Load Balancer (NLB) provides static IP addresses, which can be associated with Elastic IP addresses. This allows clients to whitelist a fixed IP address in their firewalls, meeting the requirement for authorized IP addresses. An Application Load Balancer (ALB) does not support static IP addresses directly; its IP addresses can change, making it unsuitable for firewall whitelisting. An A record pointing to an Elastic IP address would bypass the load balancer, losing its benefits like health checks and traffic distribution. An EC2 instance as a proxy adds unnecessary complexity, a single point of failure, and additional management overhead compared to an NLB.