A bridge that is able to build its own address table, rather than having to be programmed. Such a bridge typically broadcasts a query to all attached devices. When the devices respond, the bridge associates the originating address of each response frame with the port over which it entered. In this fashion, the bridge builds medium access control (MAC) address tables on a port-by-port and, by implication, segment-by-segment basis. Subsequently, the bridges view the destination MAC addresses of transmitted frames, consult the address table, and forward the frames only over the link connected to the proper port. Most bridges are self-learning, filtering bridges. Self-learning bridges are standardized in IEEE 802.1D, which describes the spanning tree protocol (STP). See also bridge, broadcast, filtering bridge, frame, MAC, port, and STP.