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Transparent bridge

(also learning bridge, transparent bridging)

Transparent bridge definition

A transparent bridge serves as a networking apparatus that links a minimum of two network segments, facilitating the transfer of data between them without changing or modifying the data packets. Functioning at the data link layer (Layer 2) within the OSI model, its main responsibility is to learn and transmit ethernet frames according to their media access control (MAC) addresses. By utilizing transparent bridges, network collisions can be minimized and overall network efficiency is enhanced.

See also: OSI layer, data link layer

Transparent bridge examples

  • Hardware transparent bridge: A physical device, such as a switch, that connects multiple network segments and forwards Ethernet frames based on their MAC addresses.
  • Software transparent bridge: A software-based solution that can be used to bridge network connections on virtual machines or other software-defined networking environments.

Transparent bridge vs. other bridging techniques

Transparent bridging differs from other bridging techniques like source route bridging (SRB) and translational bridging. While transparent bridging relies on MAC addresses to forward data, SRB uses source routing information within the frame to determine the path, and translational bridging converts between different network protocols.

Advantages and disadvantages of transparent bridges


  • Reduces network collisions and improves performance.
  • Self-learning capability — it builds and updates its MAC address table dynamically.
  • Compatible with most Ethernet network environments.


  • Not suitable for networks with complex topologies or multiple routing paths.
  • Not as efficient as routing in larger networks with many subnets.

Tips for using transparent bridges

  • Ensure that you have a stable network topology before implementing transparent bridges.
  • Use managed switches with advanced features like the Spanning Tree Protocol (STP) to prevent loops and maintain network stability.