Okay, so my NAT type used to be Moderate, but when I tried changing it to Open, it changed to Closed. Now, I have a wireless Xbox 360 Slim and I have my connections set to Manual and I use Linkseys. In my Single Port Forwarding I have:
Port 88 (UDP)
Port 3074 (Both)
Port 53 (Both)
Port 80 (TCP)
All of them are enabled, so I don't know what the problem could be. In Security I have Filter Multicast and Filter Internet NAT Redirection unchecked I also have Upnp enabled, but after all that, it's still closed! My computer is a Windows XP, I don't know if that has anything to do with it.