Mac OS X 10.6: Sharing your Internet connection
If your computer is connected to the Internet, you can share its Internet connection with other computers on your local network.
For example, if your computer is connected to the Internet using a DSL modem and has an AirPort Card installed, you can share the DSL connection with other AirPort-equipped computers.
On Windows computers, sharing your Internet connection is sometimes referred to as a “network bridge” or “bridging your network.”
To set up Internet sharing:
Choose Apple menu > System Preferences and click Sharing.
Select Internet Sharing.
Choose the Internet connection you want to share from the “Share your connection from” pop-up menu. For example, if you’re connected to the Internet over Ethernet, choose Ethernet.
Select how you want to share your Internet connection in the “To computers using” list. For example, if you want to share your Internet connection over AirPort, select AirPort.
If you share your Internet connection using AirPort, click AirPort Options and give your network a name and password.
If your Internet connection and your local network use the same port (Ethernet, for example), investigate possible side effects before you turn on Internet sharing. In some cases (if you use a cable modem, for example) you might unintentionally affect the network settings of other ISP customers, and your ISP might terminate your service to prevent you from disrupting its network.