This application provides a method for updating a route in a network. The first network device sends a first LSA packet to a third network device, so that the third network device generates a first route whose destination address is a second IP address, where a next-hop IP address of the first route is the IP address of the first network device, and the second IP address belongs to the IP network segment corresponding to the first IP address which is an IP address of the first network device. The first network device sends a second LSA packet to the third network device when determining that switching needs to be performed on a next hop of a route in the third network device, whose destination address belongs to the IP network segment, and whose next-hop IP address is the first IP address.