Sharing an Internet Connection

You have a connection to the Internet—either through a dial-up modem or a broadband solution such as cable modem, DSL, or satellite—and a home network using wired or wireless solutions. The next step is to connect the two and share your external connection so that people using any PC on your home network can access the Internet. Thanks to today's modern OSs, some simple networking hardware, and a little know-how, sharing your Internet connection is easier than ever.

You can share a connection using one of two basic methods—a hardware solution such as a home gateway or router, or your PC. Let's take a look at both options.

Internet Sharing with a Home Gateway or Router

If you spend time in stores such as Best Buy or CompUSA (and let's face it, Connected Home EXPRESS readers probably do hang out in these stores), you're probably familiar with the proliferation of devices from companies such as Linksys, D-Link, Netgear, and others that let you share broadband access among two or more PCs. Dubbed home gateways, broadband routers, or similar names, these devices essentially act as splitters between your cable modem or other broadband connection (and, in some cases, a dial-up connection, although this is less common) and your home network. Most home gateways offer five to eight Ethernet ports for wired-network access, and some recent models also incorporate wireless antennas so you can connect wirelessly. (One-port models are designed to work with a second hardware switch, which will generally include five to eight Ethernet ports).

On the technical side, these devices offer a range of services, including DHCP support, Network Address Translation (NAT), Internet-connection-sharing functionality, and basic firewall support. DHCP is a network service that provides IP addresses to machines that boot up on the network. In the case of a home network, these IP addresses are typically in a range of private addresses that the TCP/IP specifications set aside for internal networks. NAT is the networking technology behind Internet connection sharing; it lets you split your single IP address among several internal PCs so that the gateway also serves as a simple hardware "block" to the outside world. This gateway provides only one externally available IP address (the one your ISP provides) and not the IP addresses of the multiple machines sitting on your home network. Firewall capabilities are important for protecting your internal network against intruder attacks.

The firewall capabilities in hardware gateways are, perhaps, these devices' greatest weakness because hardware gateways are generally set-it-and-forget-it products, and most people don't think about looking for and downloading crucial upgrades to the products' firewall functionality. For this reason, I still recommend software firewall products, such as Zone Alarm, if you're using a hardware-based solution. And newer gateways will integrate with software firewalls, such as Zone Alarm, that overcome this complaint.

Internet Sharing with a PC

For many people, especially those who access the Internet with a dial-up connection, a PC is the so-called edge device on the home network (i.e., the device that bridges the outside network called the Internet with the internal home network). In this case, you'll need two networking devices, a modem, and a NIC for sharing a dial-up connection, or two NICs for sharing a broadband account. In the case of broadband sharing, the first NIC connects to the cable modem or other broadband account and the second connects to the internal network.

To share your Internet account, your OS must support NAT. Most recent Windows versions enable NAT through a feature logically called Internet Connection Sharing (ICS). ICS is a no-configuration option, which is nice. Simply locate the network or dial-up connection you want to share in Network Connections, right-click, choose Properties, then navigate to the Advanced tab and check the correct option. In Windows XP, you also have the option of turning on the Internet Connection Firewall (ICF) feature, a simple inbound-only firewall that also doesn't require configuration. However, even if you enable IFC, I still recommend a third-party firewall because these products tend to be more full featured. And you can't beat the price of Zone Alarm: it's free.

No matter how you share your account, configuration is generally fool-proof. You can leave all your network cards on the default automatic configuration, and the system will automatically populate them with IP addresses, either through the DHCP server in the gateway or through Windows' internal automatic-addressing feature.

Limitations and Restrictions

Internet-connection sharing has some shortfalls that you need to be aware of. First of all, because your home network accesses the Internet through one IP address in most cases (some DSL accounts do provide multiple IP addresses to customers; check with your ISP), each machine on your home network isn't technically a unique Internet host. So two users sitting at different machines on the same home network won't be able to play the same online game at the same time because the game server will see only one machine and, thus, one player.

Also, most of today's hardware gateways aren't compatible with the file sharing and audio- and video-conferencing features in Windows XP. XP requires Universal Plug and Play (UPnP) compatibility for these features to work; if you use an XP or Windows Me box as your edge device, you're all set, but if you prefer to use a hardware device, look specifically for UPnP compatibility.

But for the most common online activities (e.g., Web browsing, email, instant messaging—IM), these shortfalls aren't a concern. And because setting up Internet-connection sharing is so simple and readily available, you need to add only a second NIC or a hardware gateway, both of which are generally available for under $100—a low-cost way of extending the benefits of your home network. Have fun!

TAGS: Security
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