(adsbygoogle = window.adsbygoogle || []).push({}); Harro, I'm going to teach you hoe to get open nat type on your PS3, follow meh nubz.
1# Type "cmd" in start menu, then type "ipconfig" in cmd.
2# Find the thing that is called "Default gateway" get the IP and put it in your browser.
3# Now try finding "DMZ" Tab, sometimes it may be in "Remote Assistance" and called as "
Assign the public IP address of a connection to a LAN device". THOMSON TG585v7(8,6,5,4,3,2,1): You must login or register to view this content.
4# This is the part where you need to go to your PS3.
5#Find "system" tab in your PS3, And open system settings then System Information.
6#Find your MAC address
7#Go to your laptop, PC. Click "Edit" or "Unassign" if "Unassign" then click "Yes". IN ROUTER!
8#Select your PS3's MAC address in DMZ and done.
9#Go to "Internet" in PS3 and "Internet Settings" now it should say "Nat type : 1" or open.

I did this and it is working, with best connection on MW3.

This tut has been posted so many times.
Also you don't need to do DMZ to open your nat type. You can port forward to a IP or turn on UPnP to a IP.
Don't turn on DMZ and use UPnP at the same time , you get a conflict which on some routers is not very nice when gaming.

UPnP will automatically be disabled by your PS3, The PS3 will not accept having DMZ mode and UPnP at the same time so it disables UPnP.