Load Balancer Issues when AWS Windows EC2 is in private subnet but website in IIS needs to be accessible from a public IP

The first thing that catches my eye here is that the target health is "unhealthy". You need to fix that first. If you create another EC2 instance and put it in the same subnet as the ALB, can you connect to the IIS server on ports 80 and 443? If not, you need to fix that. As Gary has mentioned - Security Groups and NACLs are usually the thing here but I would also check the host firewall on the IIS instance.

Second: Why are you connecting to load-balancer-dns-name:82 - shouldn't you connect to http://load-balancer-dns-name (which is port 80) or https://load-balancer-dns-name (which is port 443)?

• Ensure no ACLs are blocking access between public and private subnets

• Ensure Security group allows the ALB IP Addresses

• Check your Target Group configuration is set to Health Check Protocol HTTP(s) and Traffic port.

• Check the sucess codes are set to the correct value

When creating the Target Group you can configure the Protocol : Port. Select HTTP or HTTPS