Abstract: A method for operating a communication network bridge is disclosed. The bridge receives a message frame from a first network connected thereto and reads the source and destination addresses of the received frame. The bridge determines if the addresses are contained in a source address table maintained thereby and if both addresses are present, discards the frame. The bridge transmits the frame to a second network connected thereto if the source address is not in the table or if the source address but not the destination address is in the table.

Abstract: Apparatus for bridging between two local area networks is disclosed. The apparatus has two bridge sides each including means for receiving or transmitting a message frame, controller means for directing an incoming message frame into a memory means shared between the bridge sides or directing a frame out of the memory means for transmission, address reading means for reading an address portion of the incoming frame and processor means for determining frame transmissibility from the address portion as provided by the address reading means. The apparatus is configured such that the processor means determines incoming frame transmissibility substantially concurrent with the controller means directing the incoming frame into the memory means.