Abstract: An address filter for a transparent bridge interconnecting two local area networks (LANs) is disclosed. The address filter is capable of determining from an address contained in a frame issued on one network if it should be transferred to a second network. The address is verified by determining a most likely address from a search tree. The search tree has a path which is defined by pairs of address bits. At the end of each path within the search tree defined by the address bit pairs is a term node. The term node identifies a location within a compare table which contains the most likely address matching the frame address. The two addresses are compared to make a copy decision. Node addresses which are added to a network can be learned by the filter. The search tree and compare table are reconfigurable by a host processor to accommodate learned addresses.