I connect the cable to my router and my X-b...

wireless or not I have always had luck assigning a static IP to my 360. So if your network scheme is 192.168.1.1~255 and your router's address is 192.168.1.1. use these settings
IP: 192.168.100.1
Netmask: 255.255.0.0
DNS 192.168.1.1
Secondary DNS: None
(Note if you use the media extender to watch movies on your 360 from your pc you will need to change the Netmask on your pc to 255.255.0.0 otherwise they will not see each other)

Now the important part you will have to log into your router and go to the part that says "Port Forwarding" and use these settings.
UDP Port 88 to 192.168.100.1
TCP/UDP Port 3074 to 192.168.100.1
TCP/UDP Port 53 to 192.168.100.1

You may have to open the manual to your router but once you get this done you should not have any more X-Box Live problems.
Hope this helps

i want my nat to be open can u help me ? Pls