A network switch includes a plurality of ports, a parser coupled to the plurality of ports, and a processor coupled to the ports and configured to process a received packet via one of the ports. The received packet includes a first header field, a second header field, and a destination header field, each of the first, second, and destination header fields including a TTL field. The parser is configured to decide a valid bit for each of the first header field, the second header field and the destination header field, based on an availability for each of the first header field, the second header field and the destination header field. The processor is configured to execute an instruction to cause content of a select one of the first or second header field's TTL field to be copied to the destination header field.