A packet being processed by a network device is parsed by a programmable processing unit executing computer readable instructions stored in a non-transitory computer readable storage medium. Parsing the packet includes identifying one or more protocol layers within a header of the packet, identifying respective locations of protocol headers within the header of the packet, and providing the respective identified locations of protocol headers within the header of the packet to a hardware key generator block. A lookup key corresponding to the packet is generated by the key generator block using the respective identified locations. Generating the lookup key includes extracting, using an identified location of a protocol header, one or more fields from the corresponding protocol header. The lookup key is provided to a lookup engine. A lookup operation with respect to the packet is performed by the lookup engine and based on the lookup key.