A network device receives data packets and derives a key from headers in the packets. A search engine in the device searches, or performs a table lookup, for information based on the key and multiple programmable masks. The search engine includes a hash based search engine that comprises multiple mask modules each to mask an input key with a respective programmable mask, to produce multiple masked keys. The search engine also includes an array of hash modules each corresponding to a respective one of the masked keys and including a hash table. Each of the hash modules searches its hash table for a data value based on a hash of the corresponding masked key, and outputs a found data value, if any, resulting from the search. A selector selects among the found data values and output the selected data value.