Public IP(s) or range for ELB

The Public IPs assigned to an NLB are static and do not change during the life of the load balancer.

When you create an internet-facing load balancer, you can optionally specify one Elastic IP address per subnet. If you do not choose one of your own Elastic IP addresses, Elastic Load Balancing provides one Elastic IP address per subnet for you. These Elastic IP addresses provide your load balancer with static IP addresses that will not change during the life of the load balancer. You can't change these Elastic IP addresses after you create the load balancer.

Reference: https://docs.aws.amazon.com/elasticloadbalancing/latest/network/network-load-balancers.html

As for ALB, see this Knowledge center article: https://repost.aws/knowledge-center/alb-static-ip