I've been trying to solve this for ages and it's driving me mad so I'm hoping you clever people can help me.
I have an ADSL Plusnet broadband connection running at 0.75mbps (due to my rural location) this connection is dedicated to my 360 and nothing else in the house uses it. I have a Belkin Enhanced Wireless Modem Router (F6D4630-4 v2), which is badged as "Vista Compatable", connected via ethernet to my 360.
With the Xbox Network settings all set to Automatic and the UPnP enabled on the Router the Xbox Live Connection Test reports that my NAT is Open. However, I am unable to connect to some members on my Friends list who have Moderate or Strict NATs and it takes ages to find a game in public matchmaking.
If I switch off the UPnP, set the Xbox with a Static IP address and manually forward the ports my NAT goes Strict. Basically any combination of manual settings that use a Static IP for the xbox (Firewall On or Off, Deny Ping to WAN Interface On or Off, DMZ On or Off) NAT is strict.
I have used the www.portforward.com tutorial to set up my router manually and I have tested all the Xbox Live ports through that router using my laptop and the PFPortChecker tool and all report as open, provided they are forwarded.
I have one Friend who I can connect to, no matter what, who uses a Static IP address, no UPnP and has no Firewall on his router. His Broadband connection is through Virgin. I have to use him as a go-between to play with any other Friends on my list.
I have another Friend who up until yesturday had his NAT reporting as Moderate and I could not connect to him at all, Party or Games. He has forwarded the relevant ports on his router, his Xbox now reports his NAT as Open and we can connect & play.
Also, when I first turn on my Xbox and it connects to Xbox live, if I load a game (I have tested GoW 2, GoW 3 & Bulletstorm) and go to the Multiplayer lobby the game says my NAT is Strict. If I come out of the game run an Xbox Live Connection Test, which reports my NAT as Open, and then go back to the game. The game lobby now says my NAT is Open.
Can someone please help me?