Things You'll Need
Instructions
Set Up Internet Sharing
Connect your MacBook to your wireless Internet connection.
Connect the Xbox 360 to the MacBook via Ethernet cable.
Type "Internet Sharing" into the "Finder" application, located at the top-right corner of your MacBook's screen. Click the top result, "Sharing." A new window loads.
Select "AirPort." This means you will share your wireless connection.
Choose "Ethernet" in the "To computers using" section. This means you will share your AirPort connection with whatever device is connected via Ethernet cable. In this case, it is your Xbox.
Place a check next to "Internet Sharing" on the left-hand side of the window. A prompt appears asking you to enable the option. Choose "Start." This enables Internet sharing.
Configure Mac Settings
Open "System Preferences."
Click "AirPort." Make sure you are connected to your wireless network.
Record your computer's IP address, listed in the "Status" section.
Click "Ethernet" on the right-hand side. Make sure your Mac is connected to your Xbox 360 via Ethernet cable.
Choose "Network."
Click the "Configure" drop-down box. Choose "Manually." This allows you to manually configure your settings.
Enter the IP address as recorded four steps ago, but change the last two digits, preferably to something that your router will likely not assign to another device. Routers assign IP addresses from lowest to highest. So if the last three digits are "101," change it to something much higher, such as "180" or "199." This ensures no other machine will take the IP address. A full IP address assigned by a router reads something similar to "192.168.1.100."
Click "Apply" to save the settings.
Open the "Terminal" by searching for it under "Spotlight." This application is similar to Windows' "Command Prompt."
Type "Dig." Various network settings appears.
Locate the "SEVER" listing near the bottom of the network information that appears. The digits preceding "SERVER" represent your DNS server's, or Internet provider's, address. Record the "DNS" information. You will need to enter the DNS settings into your Xbox 360 to complete the setup.
Configure the Xbox 360
Go to "System Settings," then "Network Settings."
Choose "Configure Network."
Select "Manual."
Change the IP address to the same as recorded in step 7 of section 2, except change the last digit to one higher. For instance, if the last three digits of your IP address in step 7 of section 2 is "180," change your Xbox 360's last three digits of the IP address to "181."
Enter the same IP address as recorded in step 7 of section 2 under the "Router/Gateway" entry. Now your Xbox 360 and MacBook will never use the same IP address. If this occurred, then you would not be able to use the Internet on one of the devices.
Go to the "DNS" settings and change them to "Manual."
Enter the "DNS" address, as recorded in Step 11 of Section 2.
Connect to Xbox LIVE on your console.