Three NE40s are connected. NE40s at both ends wants to implement multi-hop BFD. After the configuration of BFD is complete, BFD session cannot be Up.
1. Check the routing table. The route is existent and the router can ping the interface address of remote NE40.
2. Check BFD configuration. Remote IP is specified and local outbound interface is also specified. If the remote IP and local interface are specified simultaneously, indicating that single hop link is detected. That is, a fixed route whose outbound interface is the interface and next-hop address is peer-ip is detected. Multi-hop BFD is taken as single BFD incorrectly. BFD session cannot be Up. Delete bundled outobund interface of BFD, and then BFD session is Up.
1. The route is unreachable.
2. BFD configuration error.