Egress packet processing using a modified packet header separate from a stored payload

A network device includes a packet processor that: determines at least one egress port via which a received packet is to be transmitted by the network device; modifies one or more fields in a header of the packet to generate a modified header; determines, based at least in part on the modified header, whether the packet a) is to be transmitted or b) is to be discarded; and stores the modified header in a packet memory. In response to the determination that the packet is to be transmitted, a transmit processor of the network device: retrieves a payload of the packet from the packet memory; retrieves the modified header from the packet memory; generates a transmit packet at least by combining the payload of the packet with the modified header; and transmits the transmit packet via the determined at least one egress port of the network device.