I can actually help everyone with this, if they're still interested that is.
As of now, the only way you can ever play LAN is if you owned the original 1999 or Gold Edition of AvP
as AvP Classic 2000 had the other multiplayer methods codes completely removed other than the Steam Client and GOG Galaxy Client.
But even if you own the original 1999 or Gold Edition of AvP, you would need to use a special program called dgvoodoo2
) that allows compatibility with current modern Windows Operating Systems (Windows 7, 8 ,10). Meaning you would need some of the original files such as the original .exe executable launchers of AvP 1999 or AvP Gold in order for LAN play to work correctly. There will be some visual problems as widescreen was not implemented at the time. So if you use a really high resolution such as full HD 1920x1080 there will be some visual issues as the HUD will be awkward, the display for ammo, health, armor and even the motion tracker will all be too big and disproportional, simply because you'll be running an older DirectX emulated version of the game, DirectX 6, thus you will not get any of the current better DirectX 9 features of AvP Classic 2000, but this is the only way as of now that LAN play will work for AvP
This guide explains clearly how to get AvP Gold or 1999 edition to work on current Windows operating systems/computers with Windows Vista, 7, 8, 10, etc. https://steamcommunity.com/sharedfiles/filedetails/?id=528034575
Basically after getting AvP gold or 1999 to load again, you can play LAN games simply by selecting TCP/IP
in the Multiplayer menu.
Hopefully sirlemonhead the author of the unofficial update patch for AvP Gold will get around to implementing and support LAN gameplay eventually for his patch: [url=http://homepage.eircom.net/~duncandsl/avp/
http://homepage.eircom.net/~duncandsl/avp/[/u[/url]] Because as of now, even his patch had all of the multiplayer coding removed and unsupported, or maybe some of you can try and contact him and see if he still has the interest or time to create and implement a new update that will allow LAN gameplay again but still have Full DirectX9 Support