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DSL-500G ADSL Router User’s Guide
Bridge Configuration
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.
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