Anyone help with a problem i am having with trying to configure my AWS Application Load Balancer to use an HTTPS upstream on a IIS server.
Everything works fine when I set the target group to hit the IIS server on http/80 with no issues. Due to some config in the site I need it to stay on https on the upstream and having some issues getting it to work. The application works over https from the server, using local host entries, and also from a machine in the same subnet. No SSL certificate warnings or similar. Site works fine from a machine on the same subnet.
As soon as I switch the target group/upstream from 80 to port 443 the site starts getting a 502 error.
Enabled logging on the ALB and nothing flagged up in the logs that would point to anything.
Only thing I can see is a few Target TLS Negotiation Errors around the time of the errors when running with https upstream.
Absolutely drawn a blank with it and struggling. Everything when hitting the site directly in IIS works on port 443 as normal. Just not through the ALB catching the traffic on 443 and using the upstream on 443.
