Ethernet bridge is a fast computer with two Ethernet interfaces and a fixed program that improve upon the functions of repeaters by replicating the packets, instead of amplifying them. Bridges, thus do not amplify the noise, errors or malformed frames like the repeaters, but only reproduces a completely valid frame. Ethernet bridges supports CSMA/CD mode of data transmission. Ethernet bridges are also adaptive by employing artificial intelligence by learning laws. An adaptive ethernet bridge has an intelligent software that keeps a list of source addresses of machines on various ethernets. It updates the source addresses of the machines of any ethernet connected to it when request is made to tit by any of those host machines. By subsequent updates of the list, the bridge learns which lies on which ethernet. When the bridge receives a frame, it notes the source address and the destination and if the destination address lies on the same ethernet.
Adaptive Ethernet bridges thus eliminate forwarding when un-necessary bridged ethernet forms a single physical network system. Ethernet bridges are auto configurable i.e. they learn the network topology once powered up and they use distributed spanning-tree algorithm to decide how to forward frames.