Different from dynamic routing protocols, static routes do not have a detection mechanism. As a result, when a fault occurs on the network, the administrator needs to handle it. A static route can be bound to a bidirectional forwarding detection (BFD) session or IP-link. When a network link fails, the device can detect the fault, adjust routes in a timely manner, and forward service traffic through the backup link.
BFD and IP-link are two link reliability technologies. Compared with IP-link unidirectional detection, BFD has higher reliability. It is recommended that static routes be associated with BFD. In this mode, the devices at both ends of a BFD session must support and be configured with BFD.
IPv6 static routes cannot be associated with IP-Link.
Single-hop detection
The two communication parties are directly connected or connected through a Layer 2 switch. In this case, the peer IP address bound to the BFD session is the next hop of the static route, and the outbound interface is the outbound interface of the static route. That is, the connectivity of a fixed channel with this interface as the outbound interface and the peer IP address as the next hop is checked.
Multi-hop detection
The two communication parties are not directly connected. Instead, multi-hop routing channels exist. In this case, the peer IP address bound to the BFD session is the destination address of the static route, and the outbound interface is not bound. That is, the connectivity of any channel between the two devices is checked.
After static routes are associated with IP-link and IP-link detects a link fault, the FW adjusts its static routes accordingly to ensure that the link used every time has the highest priority and is reachable, which keeps service continuity.