Mac OS X Snow Leopard: Sharing your Internet connection
If your Mac is connected to the Internet and has an AirPort Card installed, you can share your Mac’s Internet connection with your Xbox 360 console. All you need to do is connect your Mac to your console turn on Internet sharing, get your Mac’s DNS server address, and then set the network settings on your Xbox 360 console.
Step 1 – Connect a network cable and turn on Internet sharing
Plug one end of a network cable into the back of your Xbox 360 console.
Plug the other end of the cable into an Ethernet port on your Mac.
On your Mac, choose Apple > System Preferences, and then click Sharing.
Select Internet Sharing.
From the Share your connection from list, select AirPort.
From the To computers using list, select Ethernet Adaptor (en2).
Step 2 – Get the DNS server address for your Mac
The next step is to get your Mac’s DNS server address. Here’s how:
On your Mac, choose Apple > System Preferences > Network.
Click DNS, and then write down the numbers that are listed under "DNS servers."
Click TCP/IP, and then set Configure IPv4 to Off.
Step 3 – Set the network settings on your Xbox 360 console
Change your network settings through your Xbox 360 console.
Press the Guide button on your controller, go to Settings, and select System Settings.
Select Network Settings.
Select Wired Network if you are prompted to do so.
Select Configure Network.
On the Basic Settings tab, select IP Settings.
Select Manual, and then select IP Address.
Enter 192.168.2.2, and then select Done.
Select Subnet Mask, enter 255.255.255.0, and then select Done.
Select Gateway, enter 192.168.2.1, and select Done.
On the Basic Settings tab, select DNS Settings.
Select Primary DNS Server.
Enter the numbers that you wrote down in Step 2: Get the DNS server address, and then select Done.
Select Done again.
Press B on your controller, and then select Test Xbox Live Connection.
Your console should now share the Internet connection that your Mac is using to connect to Xbox Live.
For more help, post a message in the Xbox forums. Our forums have informative topics and knowledgeable gamers who like to help.