Moderate nat problem?!

I have just recently started playing Halo Reach with my new 360 slim and though I can get on matchmaking I keep getting pop-ups saying that I may have problems with my connection and every time my friend tries to invite me to play I get a pop-up saying that I am unable to play do to having a moderate NAT. It says to go to halo.xbox.com to fix this but I have found nothing. I tried going through my router gateway and changing the setting but nothing. Can anyone help please?

http://www.bungie.net/Forums/posts.aspx?postID=45148977

This explains it pretty clearly as long as you are familiar with computers.

http://support.xbox.com/en-US/xbox-live/connecting/nat-type-strict

This also should help.

But I know for me, I used to have moderate NAT but never had any issues connecting to people, and my Network status was always Good, but after I opened my NAT my network status has been at Warning, fwiw.