Connecting Two Dissimilar Networks, Intentionally

Microsoft Windows operating systems in general, and Windows NT (2000, XP, 2003) in particular, use Internet Protocol for connectivity. In most cases, when I'm providing advice about connecting two dissimilar networks, I'll advise using a router.

  • With two different networks, using a different medium, the differing nature of the network traffic justifies use of a router, for efficiencies sake.
  • With two dissimilar networks, with differing security levels, the security differences justifies use of a router.

But what about those cases where you own and control both networks, and you intentionally want to keep the traffic on both networks equal? If you have a LAN, you want all computers on the LAN to be able to access each other, seamlessly. But Windows Networking in general, and NetBIOS Over TCP in particular, doesn't pass thru a router transparently.

What you need is a simple switch, but for two different network mediums. And that is called a bridge.

Now if you do WiFi, you may have already read about making a WiFi bridge from a NAT router. That's a standard solution. But what if you only have a computer, but with 2 different network connectors? Pick 2 of any:

If you have 2 computers, and a network, and only one of the 2 computers has the proper equipment to connect to the network, but both computer can connect to each other, what do you do? If the one computer (with 2 connections) is connecting to a public network, and the second computer needs access to that public network, you can run Internet Connection Sharing on the first computer.

But ICS provides a routed connection. When the first computer is connecting to a public network, connecting the second computer thru a router makes sense - a router is the outer layer in a layered security strategy.

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