Sharing Internet through a home network

Zatni Arbi, Columnist, Jakarta, zatni@cbn.net.id

Sharing Internet access among two or more PCs, requires you to make one of them the gateway. Microsoft calls it the Internet Connection Sharing (ICS) computer. This computer can be connected to the second computer using another Ethernet network interface card (NIC). This also means that you have to install two NICs on your system, which on its own is enough to give you a migraine.

If you want to share the connection among more than two computers, you need a hub or a router. Some routers can accommodate four to eight computers, or can be stacked to increase the number of ports to support more computers. Your ICS computer is connected to the router with a UTP cable -- the standard network cable -- attached to its NIC, just like the other computers.

At home, I set up my own small local area network. My work PC, which is a Pentium III 733 MHz machine, serves as the ICS computer. I run Windows XP Professional on it, and it has been a good choice because good Internet sharing capability was already built-in. You can also choose to run popular software such as WinGate (www.deerfield.com).

I subscribe to CBNNet Cable Internet service, and my PC is connected to the ASUS cable modem through an Ethernet (NIC). Another NIC connects it to a Compex NetPassage, which is the router for my home network.

My wife's PC, a Pentium 4-based HP Pavilion, is connected to the router through its own Ethernet NIC. Connecting the two PCs required me to set up a home network from my PC. It was not difficult to accomplish. All I had to do was go to my control panel, and click on task. However, because my wife's Pavilion runs Windows Me, I had to run the setup utility for it from a floppy disk, which had been created by my Windows XP. I could have also used the Windows XP setup CD.

After rebooting, the two PCs were connected. I had a third UTP cable connected to the router, which I usually use if I want to use another PC to access the Internet. Sometimes vendors let me play around with their notebooks for a week or so, so this third UTP cable would come in handy. * IP Addresses

As my modem is a DOCSYS device, I have a dynamic IP address. It means that the address is assigned by the cable operator. However, when my PC is connected to the Internet, it does not necessarily mean that other PCs on my home network can have access.

First, I had to tell my gateway NIC -- the NIC that was connected to the cable modem -- to allow Internet access sharing. To do this with Windows XP, I had to go to its control panel, and click on the network connections icon. I had to find the exact NIC that was connected to the cable modem, and click with my right mouse button to access its properties. I had to go to the advanced tab in the properties dialog box, and activate the allow other network users to connect with this computer's Internet connection option. If this option had not been activated, Internet sharing would not have been possible.

Second, since my PC has an IP address assigned by the cable network, all the other PCs or notebooks should not have an IP address. All you have to do is clear all the IP addresses in each PC or notebook. If any of them has an IP address, it will not be able to access the Internet through the gateway.

With Windows Me or Windows 98, you have to go to control panel, click on the network icon and then look for the TCP/IP of your NIC on the list of installed components. On my wife's Pavilion, for example, it is TCP/IP -

When you find yours, double click on it or click on the properties button. In the IP address, automatically select obtain an IP address. This will also erase all the existing IP addresses, if there were any. You will need to reboot the computer afterwards, but you should be able to access the Internet through the ICS computer. * Dial-up as Backup

Sometimes the cable network is down and we have to rely on a dial-up connection. Since my wife and I have to use the Internet for much of our work, I still retain a dial-up account with the ISP just in case the cable network has a glitch.

As with using the cable modem, I have to move the Internet sharing capability to the modem if I want to enable other PCs or notebooks on my network to share the access through the dial-up modem. With Windows XP, this is done by clicking on the network connections button. I have to locate dial-up connection, click on it with the right mouse button and then on properties. I have to click on the advanced tab in the properties dialog box, and then activate the same option I did with the NIC component.

The gateway can only support one shared connection to the Internet, and this will automatically disable sharing it through the NIC. When the cable network is up again and I no longer have to use the backup dial-up connection, I have to repeat the process and assign Internet sharing to NIC.

This may seem really complicated, but it will become second nature the more times you do it. Remember that a different configuration may require a slightly different setting. In general, though, this should work.