http://www.mw4online.com/forums/showthread.php?s=703224caff0635497b76deb67f18a15d&threadid=5230
la ya kelkes reponses... enfin si sa veut pas se connecter...
" My computer is DMZ´ed or I´ve opened the right ports, but I still can´t play multiplayer. WTF?
A.) If you´re running ZoneAlarm or some other software firewall, the security settings may be too high. If you´re running Windows XP, you should be sure to disable the built in firewall. Go to the Control Panel and then Network Connections. Find Local Area Connection, right click it, and click Properties. Go to the Advanced tab and uncheck the firewall box. It should be the only checkbox. You might need to update the router´s firmware too.
"