Embodiments of this application disclose a route configuration method. The method in embodiments of this application is applied to a communications network. The communications network includes a first network slice and a second network slice. The first network slice includes a first path from a first network device to a target network device, and the second network slice includes a second path from the first network device to the target network device. The method includes: The first network device receives an association relationship sent by a second network device, where the association relationship includes an association relationship between the first path and the second path. The first network device generates first routing information between the first network device and the target network device based on the association relationship, where the first routing information is used by the first network device to send a packet to the target network device through the first path, and when a cross-slice condition is met, the first routing information is used by the first network device to send a packet to the target network device through the second path.