I was hoping not to get long-winded about this.

1. The XBox cannot host a USB modem directly, so the XBox must be placed on either a host PC (where the modem can be connected) using ICS(NAT) or a LAN (router - NAT). Once it's here, it has a private address and cannot be addressed from outside - although it can connect out. It cannot act as a server.

2. Some broadband ISPs use private addressing to prevent users from setting up servers. If the modem assigns a private address to the PC, no games can be hosted.

3. Some USB modems do not install a TCP/IP stack in the usual place - Network Properties. A proprietary USB modem will not be game server-friendly.

There are only three ways that an XBox can host a game:

a. An Ethernet modem is connected directly to the XBox.
b. The XBox is connected to a router where the XBox's IP is set as the DMZ Host.
c. The XBox is connected to a router where port forwarding is used for the game port in question - i.e. 27960 for Quake3.

The USB modem adds an extra translation layer assuring the use of private addressing, which rules out connecting to a server behind one.

Bill

: : It may be because the user is on the ISP's LAN with a private address (192.168.x.x) or that the modem uses NAT and is acting as a hardware firewall.

: : Bill

: I don't think that those are the reasons for the problems. We've already exhausted virtually all the possibilities with "average" networking issues such as those. It is something about USB in particular that causes the problems. What about USB networking is so different from ethernet that it can cause problems? That's what I'm asking.