Starting A Modern Warfare 3 PC Dedicated Server
1) Start MW3 Dedi Server from Steam Tools
2) Type in the name of your Dedicated Server Playlist (.DSPL) for dvar "sv_mapRotation"
3) Do a start_map_rotate command to run your server
If you get "Invalid server configuration - strict NAT detected.", you may need to open ports and/or make exceptions for your AntiVirus.
To fix the Master servers not being found, copy Steam.dll from your Steam directory to the dedicated server root directory and restart the server.
More Info: http://sledgehammergames.com/blog/vie...
