Data units that are fragments of a larger data unit are received at a network device. A first received fragment of the larger data unit is processed to determine a port of the network device via which the larger data unit is to be transmitted based on a first received fragment of the larger data unit and prior to receiving all of the fragments of the larger data unit. After processing the first received fragment, processing of second received fragments for the purpose of determining the port of the network device via which the larger data unit is to be transmitted is skipped. The larger data unit is reassembled from all of the fragments of the larger data unit after determination of the port of the network device via which the larger data unit is to be transmitted. The larger data unit is forwarded to the port for transmission.