title: AWS Load Balancer to EC2 instance firewall rules
body: <p>I have an AWS EC2 load balancer that is in two availability zones. I am using the load balancer to front an apache server on an ec2 instance and I am using Cognito for authentication to the application.</p>
  <p>For now, I have identified the private IP addresses of the load balancer network interfaces and created firewall rules on my backend ec2 instance to only allow traffic from the load balancer's private IP addresses. However those private IP addresses are constantly changing.</p>
  <p>What is the best practice for setting up firewall rules on my backend ec2 instance to only allowed HTTP requests which are essentially proxied by the load balancer and then authenticated by Cognito?</p>