A network device may forward fragments of an IPv4 network packet to an IPv6 network without reassembling the IPv4 network packet. The network device may receive and buffer one or more fragments of a fragment flow associated with the IPv4 network packet until it receives a fragment of the fragment flow that includes an indication of the destination port of the IPv4 network packet. When the network device receives the fragment that includes the indication of the destination port of the IPv4 network packet, the network device may encapsulate each fragment of the fragment flow that it has received into respective IPv6 network packets to the IPv6 network.