A DCN packet processing method, a network device, and a network system are provided. The DCN packet processing method includes: generating, by a network device, a first DCN packet whose destination address is an IP address of an NMS, loading the first DCN packet into a Flex Ethernet (Flex Eth) overhead multiframe, and sending, over a physical link, the Flex Eth overhead multiframe to a network device that has accessed a network, so that the network device that has accessed the network extracts the first DCN packet, and sends the first DCN packet to the NMS based on the destination address, so as to enable the NMS to perceive that a new network device accesses the network.