A packet type corresponding to a packet received by a network device is determined. Based on the packet type, one or more header fields to be extracted from a header of the packet are identified. Identifying the one or more header fields includes extracting, from a memory based on the packet type, respective indicators of locations of the one or more header fields and respective indicators of sizes of the one or more header fields. The one or more identified header fields from the header of the packet, based on the respective indicators of locations of the one or more header fields and respective indicators of sizes of the one or more header fields. The packet is then processed based on the one or more header fields extracted from the header. The processing includes deter mining at least one port to which to forward the packet.