Transparent bridge

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A transparent bridge is a computer network device: i.e. a device that is used to interconnect several computers in a network enabling the exchange of data among them.

Physically it looks like a box with two or more holes (ports) where network cables are plugged. The other extreme of each cable is usually connected to the network port of a computer, or to another network device, which is further connected to one or more computers. This builds a computer network.

[edit] Advanced description

A transparent bridge is a particular case of network bridge, i.e. a (computer) network device that interconnects mutilple networks of computers (a layer 2 device in OSI terms).

While a network bridge simply enables local networks (or segments) to communicate with each other, but forwards the traffic to all ports, a transparent bridge is capable of redirecting the packets to the proper port, hence it can isolate the networks from broadcast traffic.

A transparent bridge directs the outgoing data traffic using a forwarding table that assocites addresses to ports. The table can be static or built by learning the network topology from the analysis of the incoming traffic. e.g. learning happens by the device inspecting the source Media Access Control (MAC) address of all incoming data frames. The device will send frames out off all its ports (except the one it received the frame from) unless it has an entry in the forwarding table.

The bridge is called transparent because its activity is transparent to the network hosts.

The behavior closely resembles that of a network switch.

The technology was originally developed by the Digital Equipment Corp. in the 1980s

[edit] Advantages of network bridge

  • Easy configuration
  • Network segments isolation

[edit] Disadvantages of a network bridge

It does not enable complex topologies. E.g. can suffer in specific configurations (like transparent bridge loops). The spanning-tree algorithm can help reduce this problems.