14.6. Sharing an Internet Connection
Psssst. You don't have to buy a router (Section 14.1.3) to share your Internet connection with other PCs. Windows XP's built-in "Internet Connection Sharing" (ICS) feature lets one PC share its Internet connection with any other networked PC.
Since it doesn't require any extra equipment, this freebie comes in handy on several occasions. For instance, when you set down your laptop on the same desk as your broadband-connected PC, Internet Connection Sharing lets your laptop piggyback on your PC's Internet connection: both computers can go online simultaneously .
Or perhaps you've got one PC plugged into a broadband modem and you want to share its Internet connection with another PC in a different room. By connecting each PC to a Powerline adapter (Section 18.104.22.168) and turning on Internet Connection Sharing, you've solved your problems.
Internet Connection Sharing even lets your laptop share the wireless connection of any other Windows-laptop in your favorite WiFi-enabled coffee shopprovided you find a laptop with a friendly owner, that is.
Whatever your situation, ICS takes any Internet-connected PCknown as the host and transforms it into a makeshift router, letting it shuffle Internet information to and from any connected PC (or PCs), known as the clients .
ICS comes with a few shortcomings, though. Since your host PC works double-time dishing out the Internet information, it may run more slowly than usual. And the host PC must be left turned on, or the poor client PCs won't have Internet access. Likewise, should the host PC crash, it cuts off Internet access to all the other PCs. (A router, by contrast, provides an "always on" connection to any PC that wants it.)
One more problem surfaces when you share a PC's broadband Internet connection. Since the broadband modem must plug into the PC's Ethernet port, that speedy port is no longer available to connect to another PC. The easiest fix for that problem is to install a second Ethernet adapter into the host PC, a job detailed on Section 14.2.2. That gives you a host PC with two ports: one for the broadband modem, and the other to connect with another PC.
Windows XP's Network Setup Wizard (Section 14.4) offers to set up Internet Connection Sharing for you when you let the wizard connect your PCs. The following describes how to take it up on its offer.
If you have any problems browsing the Web or sending email from a client PC, first double-check that your host PC's Internet connection is working (visit http://www.microsoft.com; that's always a reliable test). If your host PC's Internet connection is down, it takes down the connection of all your client PCs.