I checked the forum and did see a pinned topic which could perhaps be referring to the server patch for AVP2. I found that it wasn't very informative and perhaps not best suited for someone peaking in it for the first time. Here's a more detailed thread that serves to give you a description and links to find what you might be looking for. The following has been copy and pasted from the same thread found on Global AVP with minor adjustments.
So after you get the All in One Pack for this game and successfully installed AVP2 with no issues (be sure to check out the All in One Pack thread for troubleshooting info)
, then you have to get the patch in order to go online and play with the rest of the playerbase. The game is still played by a handful of players and some servers grow relatively large enough to get a decent game going. Be sure to check out TBBCBASE Patch Service SiteDownload Patch Installer DirectlyAVP2 Online Server List
For most people trying to play Aliens vs Predator 2 online, this game is still active and has a bit of players playing online on different occasions. Although not as active as it once was, it still has enough people to get a decent sized game going. Below is a server list that shows people still playing this game online.
To play this game online would require a patch which is found on a third party website known as TBBCBASE. This website has its own forum for support and a player stats page. Once you have downloaded the patch and started the launcher up you can direct where to install the needed files. Once that is completed you can hit the Multiplayer menu and you're off and ready!
I have to warn you though that the patch doesn't come with an uninstaller so it might be wise to back your AVP2 folder.
Make sure to use this thread for troubleshooting on the patch.Global AVP troubleshooting threads in case some of you might want to ask questions or find solutions there.AVP2 All in One Pack Troubleshoot @ Global AVPAVP2 Master Service Patch Troubleshoot @ Global AVP
Hope this helps you guys out!