Configuring OSPF FRR
A link or router failure on a path can cause packet loss and even routing loop until OSPF completes routing convergence based on the new network topology. FRR uses BFD to detect failures and enables fast rerouting to minimize the impact of link or node failures.
Figure 21: Network diagram for OSPF FRR
As shown in Figure 21, configure FRR on Router B by using a routing policy to specify a backup next hop. When the primary link fails, OSPF directs packets to the backup next hop. At the same time, OSPF calculates the shortest path based on the new network topology. It forwards packets over the path after network convergence.
You can configure OSPF FRR to calculate a backup next hop by using the loop free alternate (LFA) algorithm, or specify a backup next hop by using a routing policy.