Look-up table for a bridge in a data communications system

In a bridge for interconnecting first and second networks in a data communications system, each network including a plurality of nodes having respective source addresses, said bridge being responsive to a destination address associated with a data transmission reaching the bridge from one of the nodes in the first network for forwarding the data transmission to the second network unless the destination address corresponds to an address in the first network, said source and destination addresses each having a total of (m+n) binary data bits;

• a look-up table for storing the destination addresses therein, comprising:
• an encoding means responsive to an (m+n) bit address for producing first and second codes having respectively m and n bits of data which together allow the (m+n) bit address to be decoded unambiguously,
• a random access memory (RAM) coupled to the encoding means and having m addressable locations each for storing at least n bits of data, and
• a contents addressable memory (CAM) coupled to the encoding means and having a plurality of addressable locations each for storing at least (m+n) bits of data;
• wherein:
• if the location in RAM whose address is equal to the first code is available, then the second code is stored in said location,
• if the location in RAM whose address is equal to the first code is not available and the second code is not stored therein already, then all (m+n) bits of said (m+n) bit address are stored in an available location in the CAM unless they are stored therein already, and
• a destination address is looked up by reading the contents of the CAM as well as the contents of the location in the RAM whose address is equal to the first code.