The application provides a method for routing updating in a network, network devices, and a system. A first network device establishes a correspondence relationship between an IP network segment and a first IP address, wherein the first IP address is an IP address of the first network device; the first network device sends a first LSA message to a third network device, so that the third network device generates a first route with a second IP address as a destination address, wherein an IP address of a next hop of the first route is an IP address of the first network device and the second IP address belongs to the IP network segment; and when the first network device determines to carry out switching of a next hop of the route whose destination address belongs to the IP network segment and the IP address of the next hop is the first IP address in the third network device, a second LSA is transmitted to the third network device. Therefore, the third network device can switch the next hop of the route belong to the IP network segment from the first network device to the second network device, so that the route updating speed can be increased.