A web service runs on Amazon EC2 instances behind an Elastic Load Balancing (ELB) load balancer.External clients must whitelist specific public IP addresses in their firewalls to access the service.
What load balancer or ELB feature should be used for this application?
Network Load Balancer
Application Load Balancer
Classic Load Balancer
Load balancer target groups
Explanations:
A Network Load Balancer (NLB) provides a static IP address, which can be whitelisted by clients in their firewalls, allowing consistent access to the service.
An Application Load Balancer (ALB) uses dynamic IP addresses, making it challenging for clients to whitelist specific IPs due to frequent changes.
Classic Load Balancers do not support static IP addresses, resulting in potential issues with whitelisting in external firewalls.
Load balancer target groups are used to route traffic to EC2 instances but do not provide static IPs for whitelisting purposes.
I calculate that the answer is:
Network Load Balancer