Hello networking community! I need a setup where I can forward my server from my private network to another network which has a public ip to forward the server itself to the internet. When a client connects to the server, traffic should get forwarded to my private network somehow. I know that's possible, but don't know how I can achive that.
Came back after a year, got some knowledge. I achieved this setup using WireGuard (+ PersistentKeepAlive) and custom iptables rules on an old laptop with barebones arch install. By masquerading, we loose the source ip when forwarding, and to preserve it we need a L2 tunnel (L2GRE).
I agree with the double nat on the adsl side. If you have a private IP and still have internet it's behind a NAT. You need a public IP on the top right. When you say forward traffic what type of traffic is being sent? Do you want it relayed or are you ingesting it and manipulating it in some way? I guess what is the server in top left doing with it before it goes to game server at top right? A simple route would pass this traffic from server to game server at the routing level.
I cannot acquire a public ip on the top right, it is nearly impossible. Forwarded traffic will mostly be straight TCP and UDP traffic. The server at the top left must only forward all traffics to top right network somehow. It should not modify anything. I just need to make use of that public ip from my private network.