Transparent Bridge Internals

Now it is time to look inside bridges and find out what makes them tick.

The main function of a bridge is to forward any frame whose source and destination are on different sides of the bridge.

  • If the frame's destination is reached through the frame's arrival port, the bridge discards the frame.

  • If the frame's destination is not reached through the arrival port, the bridge forwards the frame.


How does a bridge know where a station with a particular MAC address is located? The method, which is called learning, is straightforward:

  • The bridge watches all the traffic at each of its ports.

  • The bridge notes the source MAC address of each frame and the port at which the frame was observed.

  • The bridge adds ...

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