Microsoft Internet Connection Sharing

By Joshua Erdman
Digital Foundation, inc.

Windows Me/2K/XP comes with a feature called Internet Connection Sharing. It allows the Internet connection used by one machine to be shared to all other local computers. This includes DSL, Cable modem, wireless, and dial-up connections.

Internet Connection Sharing Requirements

The computer that is doing the sharing must have an internet connection and also a spare network card to be used to communicate to the other computers that it is sharing to. For sharing to work, this computer must be left on while all other computers are conected to the Internet. If you plan on sharing to more than one computer, you will need to by a network hub or switch. If you are sharing to just one computer you can save some cash and just use a crossover cable.

Clue: All computers that are connected to the sharing computer can be of any operating system and do not need the ICS feature to work. This includes Macintosh, Windows 95, and Linux machines.

When to use

Internet Connection Sharing can used for sharing DSL or Cable but then a reliance is created on the sharing computer. Instead, I recommend using a Router to share your Internet Connection.

Typically when a user gets DSL or Cable Internet they get the choice of connecting to their provider by a USB or Ethernet device. By all means, choose ETHERNET. This is the networking standard and gives you more flexibility.

Ethernet Router instead of ICS

With Ethernet you can then use a router and avoid all kinds of complexities and requirements that are incurred by Internet Connection Sharing. You will have this little router box that shares the connection, so there will be no computer that you must leave on. Also, you will not have to deal with the complications that come with having a multi-homed computer (A computer with 2 network cards).

ICS with a modem/USB connection

ICS is your only option when using a dial-up connection or a device that requires being directly connected to a computer via USB or by a proprietary card installed in the computer. I do not recommend even attempting to share a software based Internet program (like AOL or MSN).

Setting up ICS

Choose your computer

Choose the computer that is to do the sharing, we will call this the Primary PC. This computer will need to stay on all time and should already be connected to the Internet over the connection you intend to share. This computer should also have a network card installed that is not being used. We will call the other computers Secondary PCs.

Creating your network

First, read the network wiring article to learn about running wire throughout your home or office.

Now that you are up to speed on that, you must make sure each computer has a network card. If you have more than two computers total, you must also get a hub or switch so all the computers can talk to each other.

Starting the Sharing

On the Primary PC, view your network connections (you can find this in Control Panel). There should be displayed the Internet Connection and the network card that you will use to share to the rest of the computers. Right click the Internet Connection and click 'Properties'. Click the 'Advanced' tab and you will see halfway down the option to 'Allow other network users to connect through this computer's Internet connection'. Check this box and then in the drop-down box labeled: 'Home networking connection' choose the network card that is connected to the rest of the computers in your home/office.

That is it! The connection is now shared to the Secondary PCs. The rest of the job is configuring the Secondary PCs. To do this, go into the properties of the network card on each Secondary PC and set the TCP/IP settings to 'Obtain IP address automatically' and 'Obtain DNS server address automatically'. Now the Secondary PCs are configured to ask the Primary PC for a network address when they turn on.

CLUE: For everything to work properly, the Primary PC must be up and running before any of the Secondary PCs are turned on. The Primary PC must be available to assign the Secondary PCs their network address.

Troubleshooting

To test that everything is working properly, use the IPConfig tool to find out the IP address of the Primary PC on its network card that is doing the sharing. Then use it again on the secondary PCs to verify that the Primary PC's Address is listed as the DHCP server.

References:
Using a Router to Share your Internet Connection
Switches vs. Hubs
Network Wiring

Article last reviewed: 12/30/2005

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Created by: Digital Foundation, inc.

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