follow Valve's guide on setting up a server.
and enable the setting sv_lan 1 and it will not broadcast to the global server list.
https://developer.valvesoftware.com/wiki/SteamCMD
install steam cmd for windows (no linux server currently)
download the server files
https://www.geshl2.com/downloads/
install server with steam cmd install app 218
copy the zip to the /steamcmd/steamapps/common/source base 2007/ folder should end in 2007/gesource
edit the server.cfg file in /gesource/cfg/ folder (make sure to find sv_lan and set it to 1)
create a shortcut to srcds.exe start server with:
srcds.exe -game gesource -console -maxplayers 16 +sv_lan 1 +map ge_archives +exec server.cfg