The essential difference between a bridge and a router is that a router uses a higher-level protocol (such as the IP) to determine how to pass data. IP data packets contain IP addresses that specifically identify the destination computer. Routers can read this information and pass the data to the destination computer, or determine which next router to send the data to if the destination is not on a connected network.

Bridges cannot read IP information, but instead refer to the hardware ID of the destination computer, which is also included in data packets. Hardware IDs are unique numbers that manufacturers assign to each piece of hardware they sell. A bridge learns to recognize the hardware IDs accessible through each of its ports. When it receives a packet, the bridge simply forwards the packet through the port it associates with the given hardware ID, or through all its ports if it does not recognize the ID. The hardware ID is often referred to as the Media Access Control (MAC) address.

Routers are considered more intelligent and flexible devices than bridges, and often provide a variety of security and network administration services.

Using the Bridging Feature

Although the device is preconfigured to serve as a router for providing Internet connectivity to you LAN, there are several instances in which you may also want to configure bridging:

Your ISP may use protocols that require bridging with your LAN. The device can be configured to appear as a bridge when communicating with your ISP, while continuing to provide router functionality for your LAN. Your LAN may include computers that communicate using "layer-3" protocols other than the Internet Protocol. These include IPX

Updated On: 15.10.06