R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide

Configuring OSPF FRR

When a link fails, the packets on the link are discarded, and a routing loop might occur until OSPF

completes routing convergence based on the new network topology.

You can enable OSPF fast reroute (FRR) to resolve this issue.

Figure 21 Network diagram for OSPF FRR

In Figure 21, 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 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 might fail to take effect.

• Do not use the fast-reroute auto command together with any of these commands: vlink-peer,

sham-link, enable traffic-adjustment, and enable traffic-adjustment advertise (in MPLS Command

Reference).

Configuring OSPF FRR to automatically calculate a backup next hop

To configure automatic OSPF FRR:

Ste

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.