Internet Tips: Double Up With Internet Connection Sharing

So you have two PCs? They'll be more useful if they're networked, letting you share printers, hard disks, and Internet connections. There are multiple ways to double up your Internet link. (For the scoop on wireless home networking, see " Wireless Comes Home.")

All computers connected to the Internet are identified by a unique IP address, a four-part number such as 209.1.23.30 (the address of PC World's Web server). Static IP addresses are often assigned to servers and to cable and DSL connections. They must be entered into your computer's network settings by hand, and they remain unchanged every time you go onto the Internet.

Dynamic IP addresses are used by most dial-up ISPs and are dispensed by a DHCP (Dynamic Host Control Protocol) server that assigns a different address to your computer every time you connect. To see your Windows 9 x or Me system's current IP address, choose Start, Run and enter winipcfg. For Windows NT or 2000, enter the command ipconfig.

A router forwards, or routes, TCP/IP data packets between your network and the Internet. One great new feature of Windows 98 SE was its Internet Connection Sharing option. ICS is essentially a simple router and DHCP server that dispenses the TCP/IP address a PC may require to connect to the Internet (see FIGURE 1).

Another ICS component, NAT (Network Address Translation), works with the DHCP server to assign local machines nonunique addresses from a reserved address range (the most common is 198.168.0. x) and routes incoming and outgoing packets between the networks appropriately. Outside your shared connection, all packets appear to be heading toward a single computer that uses the ISP-assigned IP address. But on your side of the NAT server, the individual computers have distinct addresses, such as 192.168.0.1 or 192.168.0.2.

Skating on Thin ICS

ICS works fine for many but not all home networks. In Windows 98 SE, ICS has virtually no interface, so if something goes wrong, the simplest fix may be to uninstall and then reinstall ICS. To uninstall, launch Control Panel's Add/Remove Programs applet, choose Windows Setup, double-click Internet Tools in the Components window, uncheck Internet Connection Sharing, and then click OK twice.

An alternative to Windows 98 SE's minimal ICS interface is Alan McCombs's free, 22KB ICSConfig 2.03 utility. Get it at PCWorld.com's Downloads or from the author's Web site.

ICS has other drawbacks as well. If the ICS host system crashes, every machine on the network loses its connection. Sharing a cable or DSL connection may require two ethernet adapters in the host system, and figuring out which one connects to what can be confusing. One alternative is to switch to a separate hardware router or home gateway.