Can't host listen server no matter what I do. (Forwarded ports already)

I’m having issues with hosting a listen server for me and my friend. I have forwarded all kinds of ports that relates to steam in any sort of way (or Half-Life 2) and nothing works! I assume that Gmod has the same ports as HL2 since I can’t find anything specific for Gmod.

I tried using the ip command in the console and put my own ip in there and then use net_Start but whenever I do that gmod closes and I get the message “Couldn’t allocate any server IP port” so it’s something with the ports. Please help me out here, I’d really like to host a server!

[editline]05:12PM[/editline]

Which ports I forwarded and whatnot can be specified if needed.

Did you setup an internal static IP? This is often overlooked.

I do have a static ip me thinks. Even though I resart my modem it doesn’t change. So yes.