Definitions
Network Uplink: This is the broadband port that connects to the Internet. Typically this will be on your cable modem or ADSL router.
Network Card: This is a 10 or 100BaseT network connection (either a PCI card or a USB box).
Hub: A hub allows multiple machines to be on the same network as each other.
Switch: A switch is similar to a hub, but is smarter about routing traffic between machines on the network.
NAT Router: Also known as "broadband gateways" or "Cable/DSL routers" these devices allow you to share a single broadband IP address with multiple machines. You may already have one of these if you have multiple computers at home on your broadband connection.
Firewall: This device blocks most network traffic to your machine. Some NAT Switches have a built-in firewall, and software firewalls such as "Zone Alarm" are also popular. You may need to disable your firewall to use the GameSpy Tunnel.
Network Cable: This is a regular RJ45 network cable
Configuration
Hub/Switch Direct to Internet
This is a common configuration if you have a single machine and want to put your Xbox on the same network. If your current Internet connection goes directly from the Network uplink into your network card, this will be the easiest configuration to set up. Just plug the Network Uplink into the Uplink port on the hub, and plug your computer and console into the hub. No networking changes are needed. 4 or 5 port hubs can be purchased for $30-$50.
NAT (DSL/Cable Router)
If you are already sharing your network connection with multiple computers, or plan to in the future, you may need a NAT if you do not have enough IP addresses from your ISP for each computer. You can simply plug your Xbox into the NAT router and it will be on the same network as your computer. No additional configuration is needed. Note that you may need to open (forward) ports on your NAT as outlined above.
Two PC Network Cards
If you do not want to use a hub, you can choose to use two network cards in the same machine. One network card will connect to your Internet connection. The second (console-connected) network card will need to be configured with TCP/IP enabled. You can use an IP address of "192.168.0.1" on it, a Subnet Mask of "255.255.255.0" and leave the gateway and other settings blank. Make sure you configure the GameSpy Tunnel application with the network card that is connected to the Xbox when asked to select one.
NAT + Hub/Switch
If your NAT (Cable/DSL Router) does not have enough ports on it, you may need to plug a hub or switch into it, and then plug your computer and Xbox into the hub. When connecting the NAT to the Hub, you should use the uplink port on one of the devices (but not both).
USB Cable Modem
If you have a cable modem that connects directly to your machine via USB, then you will need a second network card to connect to the game console. See the section above on Two PC Network Cards for more info. Note that if you have a USB Ethernet adapter for use with your Cable/DSL Uplink you can use any of the other configurations since a USB Ethernet adapter is basically just a type network card. An additional card is ONLY needed if your Cable Modem connects directly to your machine via USB (no network cable).
Source: gamespy.com
