Bridge Configuration

DSL-500G ADSL Router User’s Guide

The Router can be configured to act as a bridging device between your LAN and your ISP. Bridges are devices that enable two or more networks to communicate as if they are two segments of the same physical LAN. This section describes how to configure the Router to operate as a bridge.

IMPORTANT

Before changing the bridge configuration, check with your ISP to determine the type of connection used to exchange data with their client’s DSL Routers (such as Ethernet bridging).

A bridge is a device used to connect two or more networks. A bridge device is able to learn the unique manufacturer-assigned hardware identifier (MAC Address) of each computer or device on either or both networks to which it is connected. It learns that some of the MAC addresses represent computers attached via one of the device's interfaces and other MACs represent computers connected via other interfaces. For example, the MAC addresses of your home computers are learned through (or associated with) the Ethernet port, and the MACs of your ISP's computers are attached via the WAN (DSL) port. It stores the MAC addresses and the interface associated with each MAC in its bridge forwarding table.

When the bridge receives a data packet, it compares its destination MAC to the entries in the bridge forwarding table. When the packet's destination MAC address matches one of the entries, it forwards the packet through the interface that connects to the corresponding network. The bridge does not send the data directly to the receiving computer, but broadcasts it to the receiving network, making it available to any node on that network. On the receiving network, the packet is delivered in a form recognized by the network protocol (Ethernet for the LAN side of the Router) and delivered to its destination.

When the bridge does not recognize a packet’s destination MAC address, it broadcasts the packet through all of its interfaces – to both networks.

You may need to use the device as a bridge if:

Your ISP uses 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® and AppleTalk®. In this case, the device can be configured to act as a bridge for packets that use these protocols while continuing to serve as a router for IP data.