MW2 NAT type

[#1]

anyone lknow how to get my NAT from strict to open. It was open all the time recently but it is now strict and will not change. Any help very much appreciated.

[#2]

i have the same issue

[#3]

depending what router you have just forward these

Required Ports for Modern Warfare 2
In addition to the required ports for Steam, Modern Warfare 2 requires the following ports for multiplayer:
   * UDP 1500 (outbound only, no forward needed)
   * UDP 3005 (outbound only, no forward needed)
   * UDP 3101 (outbound only, no forward needed)
   * UDP 28960 (inbound/outbound, must forward to act as a multi-player host, but no forward or inbound traffic needed to find and join games)

For more information please see this page.
Configuring Your Router
If you do not have the original instruction manual for working with your router, please check your router for the manufacturer or brand name and the router's model number. You will need to run a search for your router manufacturer's website to find instructions for configuring your router to work with Steam and Modern Warfare 2.
PortForward.com is also a useful resource for router-specific instructions (please note that the information provided at PortForward.com may not reflect recent additions to the required ports for Steam).
source..http://forums.steampowered.com/forums/showthread.php?t=1019454
you will have to enable UPnP aswell if you want to be hosting..
hope this helps.

[#4]

I carnt be sure. but changing the setting extended security to off may fix this