Configuring OSPF FRR
When a link fails, the packets on the link are discarded, and a routing loop may occur until OSPF completes routing convergence based on the new network topology.
You can enable OSPF fast reroute (FRR) to solve this problem.
Figure 37: Network diagram for OSPF FRR
In Figure 37, after you enable FRR on Router B, OSPF automatically calculates or designates a backup next hop when a link failure is detected. Packets are directed to the backup next hop. At the same time, OSPF calculates the shortest path based on the new network topology, and forwards packets over the path after routing convergence.
You can either configure OSPF FRR to calculate a backup next hop automatically, or to designate a backup next hop by using a routing policy.
Configuration prerequisites
Before you configure OSPF FRR, complete the following tasks:
Configure network layer addresses for interfaces.
Enable OSPF.
Configuration guidelines
Do not use FRR and BFD at the same time. Otherwise, FRR may fail to take effect.
Do not use the fast-reroute auto command together with the commands vlink-peer.
Configuring OSPF FRR to automatically calculate a backup next hop
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure the source address of echo packets. | bfd echo-source-ip ip-address | Not configured by default. |
3. Enter OSPF view. | ospf [ process-id | router-id router-id | vpn-instance vpn-instance-name ] * | N/A |
4. Enable OSPF FRR to automatically calculate a backup next hop. | fast-reroute auto [ abr-only ] | Not configured by default. If abr-only is specified, the route to the ABR is selected as the backup path. |
Configuring OSPF FRR to designate a backup next hop with a routing policy
Before configuring this task, you need to use the apply fast-reroute backup-interface command to specify a backup next hop in the routing policy to be referenced. For more information about the apply fast-reroute backup-interface command and routing policy configuration, see "Configuring routing policies."
To configure OSPF FRR:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure the source address of echo packets. | bfd echo-source-ip ip-address | Not configured by default. |
3. Enter OSPF view. | ospf [ process-id | router-id router-id | vpn-instance vpn-instance-name ] * | N/A |
4. Enable OSPF FRR to designate a backup next hop by using a routing policy. | fast-reroute route-policy route-policy-name | Not configured by default. |