How to Change Strict Nat to Open Nat

I've got the same problem from time to time. The problem is the router. You can reboot it on your pc at Networklocations/Boardname NAT. After you reboot your NAT should be open.einstein666

It's Network settings/boardname Nat I've got a dutch pc so i just translated it.
double click on boardname Nat (if you haven't changed the password it's admin / admin)

In the Address bar, enter the default router IP address: http://speedstream and press Enter. This displays the "Gateway Administrator Setup" window.

Select Setup>NAT/NAPT from the left navigation pane of the Web interface. This displays the "NAT/NAPT Configuration" window showing the WAN Interface connections.

You need to set port forwarding on the following ports to your PC's ip address:

-UDP 88
-UDP 3074
-TCP 3074
-TCP 2074

A lot of people forget about the 2074 port which actually works as a backup to 3074. Get your router to forward those ports to your xbox IP and your ready to rock.

I just ran into the Strict NAT issue with CoD4. After hours of fighting this I finally figured out what the cause was.

A few months ago for a unrelated test my buddy gave me his old Speedstream modem. Well out of the blue while on hold with Xbox Live support I swapped my modem out with his and BAM, my NAT was OPEN. I flipped over the modem and it was a Siemens SpeedStream 4100. The modem that I received from AT&T was a Siemens SpeedStream Rev B.

So something in the latest Rev B SpeedStream modem keeps your NAT set to strict. I would recommend calling AT&T and see what they can do.

Also you will still need to have UPnP and Gaming Mode enabled or the proper ports forwarded on your router.