1. A method for an intermediate network node to efficiently lookup routing information associated with a network address, the method comprising: (a) selecting a lookup table from a set of one or more lookup tables in the intermediate network node, each lookup table being associated with a different range of subnet mask lengths, wherein the selected lookup table is associated with the largest subnet mask lengths not yet searched; (b) searching the selected lookup table based on the value of the network address to locate a memory location of the network address's routing information; (c) if the network address is not found in the selected lookup table, then repeating steps (a) and (b) until the memory location of the network address's routing information is found or until all the lookup tables have been searched; and (d) searching an MTRIE for the memory location of the network address's routing information if the network address is not found in any of the lookup tables.