First... sorry if im bad at english.

So as the Title Said, the Server did not listed on the Modded Server List.
Recently i have got 6 static ip from my provider and also got a firewall called "FortiNet 81E" To Setup my server.
After all things setup, my firewall took 1 ip for outside ip, and 1 for inside ip. Ex: 103(FireWall tooked) 108(inside IP)
And now in my pc im using 108 and outside is 103, so i opend Rust server, it showed 103.
When the server have been fully opend, the Modded list will showed up my server about 1-5 minute, after all it just dissapear, donno why but me and my friend could still use F1 to connect into it with 103.
This has bothered me for a long time, and I don’t know how to solve it. I really need someone to help me solve this.
I'd tried to tell the problem easly :( Sorry if it still messy...

If you still dont know how this firewall work. here's a  Sketch
Internet -> FireWall (*.*.*. 103) -> inside ip (*.*.*. 108) -> fake ip to pc (192.168.1.*)  #When Player joined the server.
pc (192.168.1.*) -> inside ip (*.*.*. 108) -> FireWal (*.*.*. 103) -> Internet #When i opend a server.