XBox 360: Getting NAT status to OPEN

Like many others I've had some trouble getting my XBox 360 to have an 'Open' NAT status so XBox Live chat (and potentially other functionality) would work correctly. I was having a hard time getting this right, even when I did what seems to be the most common solution to the problem: adding the XBox 360 to my router's DMZ.

Here's one additional step I had to do to get things to work, that I haven't seen mentioned elsewhere: In order to get your 360 into your DMZ you have to have a constant IP address for it. (Which plenty of sites did mention) HOWEVER, at first I was enforcing a consistent IP address for the 360 by setting the *360* to manually demand that IP address each time, rather than use DHCP. Doing that, my NAT kept staying at 'Strict'.

But, when I set my 360 back to using DHCP to get its IP address, and told my router to RESERVE the IP address I wanted for the MAC address of my 360, then POOF, my NAT setting went to Open! So, at least in my case, I had to not only add my 360 to my router's DMZ, but I also had to make sure that I enforced a consistent IP for it at the router instead of in my 360s network settings.