User's Manual

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16 Configuring Bridging
The NEOBIT 1014VA 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 chapter describes how to configure
the NEOBIT 1014VA to operate as a bridge.
Note
Before changing your bridge configuration, check with your ISP to
determine the type of connection they use to exchange data with
their customer’s DSL modems (such as Ethernet bridging or IP
routing).
Overview of Bridges
A bridge is a device used to connect two or more networks so they
can exchange data. A bridge learns the unique manufacturer-
assigned hardware IDs of each computer or device on both (or all)
networks it is attached to. It learns that some of the IDs represent
computers attached via one of the device's interfaces and others
represent computers connected via other interfaces. For example,
the hardware IDs of your home computers are attached via the
Ethernet port, and the hardware IDs of your ISP's computers are
attached via the WAN (DSL) port. It stores the ID list and the
interface associated with each ID in its bridge forwarding table.
When the bridge receives a data packet, it compares its destination
hardware ID to the entries in the bridge-forwarding table. When the
packet's ID matches one of the entries, it forwards the packet
through the interface that connects to the corresponding network.
Note that 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, a
LAN protocol such as Ethernet takes over, helping the packet
reaches its destination.
When the bridge does not recognize a packet’s destination
hardware ID, it broadcasts the packet through all of its interfaces –
to each network it is attached to.