Digital Equipment Corporation (DEC) was the first to come to market with a transparent bridge in the early 1980s. IEEE eventually incorporated DEC's work into the 802.1D standard. The term transparent bridge was used because the bridge is completely transparent to the end stations that it is interconnecting. Frames that pass through a transparent bridge are not modified: What comes in on an interface will leave exactly the same way on another interface. Transparent bridges perform three basic functions:
They make forwarding and filtering decisions based on the destination MAC address in a frame.
They learn where end stations reside in the network.
They remove loops.
Remember the three main functions of a transparent bridge ...