http://windows.microsoft.com/en-us/windows-vista/what-is-a-network-bridge

What is a network bridge?

A network bridge is software or hardware that connects two or more networks so that they can communicate.

People with home or small office networks generally use a bridge when they have different types of networks but they want to exchange information or share files among all of the computers on those networks.

Here's an example. Let's say you have two networks: in one, the computers are connected with cables; and in the other, the computers are connected using wireless technology. The wired computers can only communicate with other wired computers, and the wireless computers can only communicate with other wireless computers. With a network bridge, all of the computers can communicate with each other.

If you use the network bridge software built into Windows, you don't need to buy additional hardware.

Create a network bridge

A network bridge is software or hardware that connects two or more networks so that they can communicate. You can create only one network bridge on a computer, but one bridge can handle any number of network connections.

1. Open Network Connections by clicking the Start button , clicking Control Panel, clicking Network and Internet, clicking Network and Sharing Center, and then clicking Manage network connections.

2. Hold down CTRL and select each network connection that you want to add to the bridge.

3. Right-click one of the selected network connections, and then click Bridge Connections.  If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

   

   Warning

   • You shouldn't create a bridge between an Internet connection and a network connection because it creates an unprotected link between your network and the Internet, which makes your network accessible to anyone on the Internet.

Add a connection to a network bridge

If your computer is connected to a network, network policy settings might prevent you from completing these steps.

If you have two or more networks connected by a network bridge, you can add another network to the bridge by adding a new connection.

1. Open Network Connections by clicking the Start button , clicking Control Panel, clicking Network and Internet, clicking Network and Sharing Center, and then clicking Manage network connections.

2. Right-click the network bridge, and then click Properties.  If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

3. On the Networking tab, under Adapters, select the check box next to each connection that you want to add to the bridge, and then click OK.