DSL FAQ - Local Area Networks

Network Security

Many people and businesses have an network of some type, This could just be two Windows 95/98 computers connected to share a printer. It could also be a large network with several computers and one or more servers running Windows NT/2000 or Unix/Linux.

Often, it is possible to connect all the computers on the network into the DSL line just by adding the Cisco 675 into the mix. Often this results in TCP/IP being used for both the local network and Internet access. In other words, you would be using the same protocol for two different networks.

You could compare that situation to trying to have two different conversations on a three-way call. You might have a friend on one line and have an important business client on the other. You may be talking to your friend about the most embarrassing moment of your life--not something you'd probably want to share with a client.

Thus you can see one possible downside to this is the possible security risks.

Let's take an example of a DSL user at home. He has three computers hooked up via ethernet and is using Windows' "File and printer sharing" so that the printer on one computer can be used by the other two.

In order to set it up, he just installs the "File and printer sharing" service. The only protocol for the network card is TCP/IP for his DSL connection. Windows will automatically use TCP/IP for the sharing.

Since TCP/IP is also being used for the DSL connection, it is possible for someone on the Internet to access his computer using the "File and printer sharing" protocols. If he has set his hard drive to be shared, then someone on the Internet could possibly get complete access to every file he has on the computer.

Another possible problem is the confusion. Let's say your friend asks when you want to get together in person. Just after, you say the two of you should meet tonight at 8pm. That was actually intended for the potential client, but now your friend thinks he'll be meeting you at 8pm.

The way networked DSL works, each computer is assigned an IP address, either by a DHCP server (for bridging mode) or via the Cisco 675 (for PPP mode). TCP/IP uses those addresses to figure out what computer is what on the network.

If you were to disconnect the Cisco, you could lose all those IP addresses. If you are also using TCP/IP for the local network, some or all the computers might not work on the network anymore.

For the above reasons, it is advisable to use the TCP/IP protocol for the DSL/Internet connection and then use another protocol (such as NetBEUI or IPX) for the local network. In some cases, this option may not be available, but usually it is.

For people using Windows' "File and printer sharing" on a home network, StarNet has instuctions available for switching it to use NetBEUI only. Those instructions can be found under the security section of the StarNet DSL pages.

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