Abstract: A method and apparatus for generating a data structure for classifying an Internet Protocol packet. The data structure generation method may include creating a level-2 table with a plurality of bins for storing therein classification rules and using a first hashing data to derive a hash key1 from a classification rule to point at, or to designate, an entry of a level-1 table, and populating the entry with a pointer to the level-2 table. The method may further comprise populating a bin in the level-2 table with the classification rule, which bin is pointed at, or designated, by a hash key2 that is derived from the rule by using a second hashing data contained in the entry.