The latest and greatest installment in the Call of Duty franchise just went live yesterday on XBOX 360, PlayStation 3, and PC. One issue that comes up every time a new CoD game is released is the NAT type issues. The game lists three different NAT types when you’re in the multiplayer section, they are Strict, Moderate, or Open.
Strict is a pretty severe issue for most, and that means your traffic really isn’t getting through to the game and you’ll likely have issues joining and hosting games if you can even play at all.
Moderate isn’t something to be hugely worried about unless you notice issues getting into the games. Most likely moderate would keep you from hosting games yourself though and should be fixed.
Open is where you want to be, all traffic between the game and the host/server is free flowing.
On XBOX 360 and PlayStation 3, you should just set a static IP address to your console and put it in the DMZ (De-Militarized Zone) on your router. The DMZ is a big security risk for a PC, but it’s nothing to be worried about the consoles.
If you’re like me, and on a PC and have a NAT type of Moderate it will drive you insane until it is fixed…
The quickest way to solve this, is to be sure UPnP and NAT-PMP are ENABLED on your router. Look around in the settings as each router is different, but be sure to enable them, or check the boxes next to those options. If you were at Strict before this should get you to Moderate, but there’s one more step to get from Moderate to Open, and that is actually a simple solution.
Open up Windows Firewall with Advanced Security and create new Inbound and Outbound rules for “iw5mp.exe” (Located in Steam\steamapps\common\call of duty modern warfare 3\) and be sure to explicitly allow all connection both inbound and outbound.
The default location for iw5mp.exe is as follows…
C:\Program Files\Steam\steamapps\common\call of duty modern warfare 3\iw5mp.exe
If you’re on a x64 system, it will be similar, just inside the Program Files (x86) folder instead.
Restart your PC for good measure and fire up the game one more time and verify your NAT type is now Open.