How It's Done
You can share your Internet connection with more than one computer by using a device called a "router." The router forwards traffic from the Internet to the computers "behind" it on your private home network or Intranet.
How does this work? The router accepts requests from your personal computers, and then "pretends" to be one very busy computer, forwarding all of the requests to the modem as if they came from a single computer. This is why you don't need to tell your DSL or cable provider that you have more than one computer - although you might find that the legal fine print of your broadband contract requires you to do so.
Wireless Versus Wired Routers
Buying a router is a good opportunity to go wireless. For those with laptops, this is usually a no-brainer, because laptops typically have wireless capability built in. And that means you can use the computer from any room you wish. Just be sure to secure your wireless network correctly. Don't use WEP "security," which has long since been cracked. Use WPA instead - and use a truly random password, never a password containing one or more dictionary words. See the manual of your wireless router for more information about WEP and WPA.
Wireless routers are very cheap now ($50 or less), and almost all wireless routers also include a few wired jacks. So you don't have to invest in a wireless adapter for each of your desktop PCs - although USB wireless adapters are available for less than $30 each. And even though you don't move your desktop PCs every day, it's still nice to avoid rewiring your house when you do.
Try a Froogle search for wireless router to get an idea of what's currently available. I have personally had good results with both Linksys and Belkin routers. My Belkin router cost under $50. Nearly all currently available units support Wireless-G, which is the fastest widely supported wireless network technology. Even if some of your PCs have older wireless network interfaces, they should still work with a newer router. So I recommend purchasing a Wireless-G router.
Setting Up Your Router Correctly
Until now you hooked up your computer directly to your cable or DSL modem. From now on you'll hook up your router to the modem. Just disconnect the Ethernet cable from your computer and plug it into the "WAN" jack of the router. Then connect your computer to one of the wired jacks of your router with another Ethernet cable - or use wireless, if your computer has wireless capability. If not, as I've mentioned, you can buy a separate USB wireless ("WiFi") adapter for under $30.
When you plug in your router and you connect your computers to it for the first time (whether wired or wireless), you may find that the only web site you can access is a built-in site that allows you to configure the router. This is actually a good thing - you should set up your router's wireless security features first, choosing a WPA password and configuring each of your wireless PCs to connect with that password. Otherwise the rest of the world can borrow your connection and, more worrisome, snoop on what you're doing. They can't see you shop on secure sites, but they can see you browsing and sending email, and you probably don't want to broadcast everything you do to the world.
So even if you are able to access the Internet immediately, stop and configure your router first via its built-in website. Set up WPA security and make sure it is required for any use of your wireless connection. Usually this is done by accessing http://192.168.1.1/ or http://192.168.2.1/. But see the manual of your router for the details. There are hundreds of routers on the market and I cannot document every single one.
PPPOE SetupDid you have to do any special setup when you first plugged your computer into your cable or DSL modem... such as installing and configuring PPPOE (PPP Over Ethernet) software that logs your computer in to the network? If so, don't worry. Your router can do exactly the same thing. In your router's setup screens, you'll need to select the same type of connection (usually PPPOE) and enter the same login and password information that you configured in your PC's PPPOE software.
Fortunately, most ISPs no longer require this step. Usually, if PPPOE is used at all, it is taken care of automatically via the modem. Your router will automatically receive an Internet address from the modem, and you'll get online right away.
A major fringe benefit of using a router is that, since only the router appears directly on the Internet, other computers can't reach out and try to connect to your personal computers. This definitely doesn't protect you from all threats. But it does protect against quite a few potential security holes that can result in the loss of control over your computer.
Sharing Dialup Modems: The Cheap Fix
What if you only have a dialup modem... presumably for cost reasons?
It's still possible to share your connection, by using Internet Connection Sharing, a feature of Windows XP that enables one Internet-connected computer to serve as a router for the rest. (A similar feature exists in MacOS X, and I'll address that briefly as well.)
With Windows XP Internet Connection Sharing, you'll still need an Ethernet hub and some sort of Ethernet connection on each computer. So you may find yourself buying a router anyway. In theory, you only need an Ethernet "hub" or "switch" without all of the features of a router. But with connection-sharing routers available for roughly the same price, you may be better off purchasing a router and configuring it to operate as a switch. Most routers support this feature. This way, you already have a nice router in your home when you're ready to upgrade to broadband. In this scenario, the computer that runs Internet Connection Sharing looks just like a cable or DSL modem to the router. So just connect the computer with the modem to the router's WAN jack, and connect the other computers to the router normally.
For complete information on how to configure Internet Connection Sharing, see Microsoft's Knowledge Base article on Internet Connection Sharing.
MacOS X users actually have it easier in this department. If you have MacOS X 10.2 or better on a Mac with a wireless card, you can share your connection wirelessly without the need for a separate router. And if you don't have wireless, you can still share it over a wired network exactly as I've described above for Windows users.
To configure MacOS X Internet Sharing, just follow these steps:
1. Pull down the "Apple" menu.
2. Pick "System Preferences."
3. CLick on the "Sharing" icon.
4. Click on the "Internet" tab.
5. You should see the message "Internet Sharing off," with a "Start" button and a "Share this connection with other computers on Built-in Ethernet" checkbox. You may also see other sharing options. Check those boxes to begin sharing your connection. That's all there is to it!
Risks Of MacOS X Internet Sharing
MacOS X Internet Sharing should be used to share a connection that comes into your computer via a dialup modem or another interface that is not already shared with the other computers. If your computer is plugged into a campus or business network, please don't enable MacOS X Internet Sharing - you will create problems on the network, interfere with other users, expose your data to privacy risks, and possibly get fired or expelled. Yes, really! You may also have problems sharing a cable or DSL connection in this way (so just use a real router instead as described above).
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