Abstract: The routing address lookup problem is one of the major bottlenecks in high performance routers and deals with forwarding of packets. In the Internet domain it is known as “IP address lookup problem.” This invention provides a new and easy way to preprocess routing tables which gives efficient packet/message forwarding and is feasible in the time and the space it consumes. More precisely, the method for m-bit IP addresses gives a balanced trade-off between performing a binary search on T with O(log|T|) accesses, where |T| is the number of entries in T, and executing a single access on a table of 2m entries obtained by fully expanding T. While the prior art starts out from space-efficient data structures and aim at lowering the O(log|T|) access cost, the invention starts out from the expanded table with 2m entries and aim at compressing it without an excessive increase in the number of accesses.