How can I put my nat to strict?

[zsniprx]

So pretty straight forward, I don't want to be able to host any games in mw3 because my internet is bad with 3 people using it. How can I make sure I don't host games?

My router doesn't have an option to block ports

[Nachos]

You should be able to disable UnPnP in your router settings, that should make it at least moderate.

[zsniprx]

I contacted my service provider. I just need the exact port to block. 27000 or 27014 to 27050 blocks the entire game from starting up. 3074 didn't work either. What is the exact ports I need to block in order to set my nat to strict?

Edit: UPnP set my nat to moderate which should be good enough. Thanks nacho