World at War modded zombie maps connecting to online

I've recently bought World at War on Steam so that I could play custom modded zombie maps. Though I can play them in single player mode I can not connect to these maps in online multi player mode.
I was wondering what I could do to solve this problem. I've tried watching videos and I tried looking for other methods like attempting to make LAN parties but it doesn't seem to work.
Best Answer
I played this with a friend a few years back. I believe the way we did it was by inviting to a lobby from the friends list in-game. If that does not work, you may have to port-forward your router in order to get your friend to join.
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How do you play custom zombies with friends?
You just start a match (doesn't matter if its solo or not) and when you're in-game, your friend can connect to you.How do you play with friends on World at War?
you need to go to friends in the main menu, and add your friend. then go into cooperative and click invite friends and bam!How do I connect to LAN World at War?
How to set up Call Of Duty server for coopWorld at War Online Profile/No CD Key Workaround (basically a fix) With Plutonium
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