Private IP availability for Application Load Balancer
We are trying to load balance our web servers behind an ALB. However, we can't find the private ip for the ALB. Right now, our provider NAT's (providers hard requirement) all addresses directly to our web server. We would like to put an ALB in front of it so that we can load balance web servers.
Current Solution: NAT --> Web Server
Targeted Solution NAT --> ALB --> Web Server x3
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Elastic Load Balancers don't have a single predictable private IP address. They will start out using one IP per subnet you've configured, but will scale up using more as needed. The DNS entry for the load balancer actually returns this dynamic pool of addresses, not just one IP. So your NAT should target the load balancer by DNS name not IP. You can use the default DNS name or create a custom one in Route 53 - an A record which is a special "Alias" type that can reference the load balancer.
It is possible to put NLB in front of ALB. ALB cannot have fixed IP addresses, but NLB can.
Targeted Solution NAT --> NLB --> ALB --> Web Server x3
That is a great article, TY. Are there any drawbacks to putting the NLB in front of the ALB? For example, would I lose any functionality or features with the ALB, or would it increase the cost is my solution/application?
I just remembered that another option for static IP on an ALB is Global Accelerator - https://docs.aws.amazon.com/global-accelerator/latest/dg/about-accelerators.alb-accelerator.html
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Got it. If I can't control how the NAT would target the destination (DNS vs IP), could I use a NLB with a static IP to an ALB?