Techniques relate to the regeneration of a cyclical redundancy check (CRC) value of a data packet in a manner that avoids a complete CRC recomputation based on the entire packet after only a portion of a packet has been modified. When modifying and forwarding a packet, a network device identifies only the changed portions of a packet and computes an updated CRC for the packet based on the original CRC, the modified portions, and the length from the modified field to end of packet.