Jul 18

If you have broadband (high-speed) Internet service, like a cable modem or DSL service, you’re a very lucky individual. Not only do you get spectacular speed when surfing the Web or doing email, but you also have a full-time connection. You never have to wait for a modem to dial (screeching all the way), and wait again for it to disconnect.

If your broadband company didn’t supply a piece of equipment (like a wireless or Ethernet router) for sharing that connection with more than one computer, shame on them!

Fortunately, setting up such a system is fairly easy, and practically a requirement if your home or office has more than one PC. There are two ways to go about it.

Get a Broadband Router
As noted earlier, a router (a gateway in Microsoft lingo) is a little box, about $60, that connects directly to the cable modem or DSL box. In most cases, it doubles as a hub, providing multiple Ethernet jacks to accommodate your wired PCs. (Some, on the other hand, offer only a single jack into which you plug a hub, sold separately.) The Internet signal is automatically shared among all the PCs connected to the router.

Use Internet Connection Sharing
Internet Connection Sharing (ICS) is a built-in Vista feature that simulates a router. Like a hardware router, ICS distributes a single Internet connection to every computer on the networkbut unlike a router, it’s free. You just fire it up on the one PC that’s connected directly to your cable modem or DSL boxor, as networking geeks would say, the gateway or host PC.

But there’s a downside: if the gateway PC is turned off or goes into Sleep mode, nobody else in the house can go online.

Also, the gateway PC requires two network connections: one that goes to the cable modem or DSL box, and another that connects it your network.

It might be two Ethernet cards, two WiFi cards, ormost commonly of all, especially for laptopsone Ethernet and one WiFi card. One connects to the Internet (for example, via a cable modem, DSL box, or WiFi), and the other goes to the hub or the router to distribute the signal to the other computers.

Tip: If the “receiving” computers (the ones sharing the connection) are all wireless, you can skip that business about the hub or router. Plug the gateway PC into the cable modem via Ethernet. Then let each of the other wireless computers create ad hoc connections to it wirelessly, as described in the box on page 705.

If you decide to use Internet Connection Sharing, make sure the gateway PC can already get onto the Internet, on its own, before you attempt to enable ICS.

Choose Start > Control Panel. Open Network. At the top, click “Network and Sharing Center.” At left, click “Manage network connections.”

Right-click the icon of the network connection you want to share. From the shortcut menu, choose Properties. Authenticate yourself (page 191), and then click the Sharing tab. Finally, turn on “Allow other network users to connect through this computer’s Internet connection,” and click OK.

Thereafter, other computers on the network can share the gateway PC’s Internet connection, even if they’re running earlier versions of Windows, or even Mac OS X and Linux. In fact, they don’t need to be computers at all: you can use ICS to share your Internet connection with a video game console or palmtop!

Tip: If you’ve created a VPN (virtual private network) on the gateway machine (page 758), all of the PCs sharing the Internet connection can get onto the corporate network!

And now the fine print:

Internet Connection Sharing doesn’t work with domain networks, DNS servers, gateways, or DHCP servers (you know who you are, network geeks).

The “receiving” PCs (the ones that will share the connection) can’t have static (fixed) IP addresses. To check, sit down at each one. Choose Start > Control Panel. In Classic view, open Network Connections.

Right-click the icon of the network connection; from the shortcut menu, choose Properties. Authenticate yourself (page 191). Double-click “Internet Protocol Version 4 (TCP/IPv4); turn on “Obtain an IP address automatically.”

The gateway machine is now the only thing protecting you from all the worms, Trojans, and bad guys on the Internet. If, on the advice of some cable modem technician during a spasm of troubleshooting, you momentarily plug one of the “downstream” PCs directly into the cable modem, you might forget that it has no protection at all.