Although adjacency will be formed between routers of the same level on the same network segment of IS-IS in the broadcast network, that is, adjacency will be formed between all non-DIS routers, but…

Although adjacency will be formed between routers of the same level on the same network segment of IS-IS in the broadcast network, that is, adjacency will be formed between all non-DIS routers, but in the implementation of IS-IS and BFD linkage, BFD sessions are only established between DIS and DIS, and BFD sessions are not started between non-DIS.