Configuring Ospf Frr; Prerequisites····································································································································9 - H3C S5800 Series Configuration Manual

To do...
Configure the LSU
transmit rate

Configuring OSPF FRR

Do not use OSPF FRR and BFD (for OSPF) at the same time; otherwise, OSPF FRR may fail to
take effect.
Do not use the fast-reroute auto command together with the commands vlink-peer.
Introduction
When the link in the OSPF network below fails, the packets on the path may be discarded, or a routing
loop may occur. Then, the traffic will be interrupted until OSPF completes routing convergence based
on the new network topology.
In this case, you can enable OSPF fast reroute (FRR) to reduce traffic recovery time.
Figure 4-21 Network diagram for OSPF FRR
In Figure 3-4, after you enable FRR on Router B, OSPF automatically calculates or designates a
backup next hop when a network failure is detected. Packets are directed to the backup next hop, thus
to reduce traffic recovery time greatly. At the same time, OSPF calculates the shortest path based on
the new network topology, and forwards packets over the path after network convergence.
You can either configure OSPF FRR to calculate a backup next hop automatically, or to designate a
backup next hop by using a route policy for routes matching the specified filtering conditions.
Configuration prerequisites
Before configuring OSPF FRR, you need to:
Configure network layer addresses for interfaces to make the neighboring nodes reachable at the
network layer
Enable OSPF
Use the command...
transmit-pacing interval interval count count
4-45
Remarks
Optional
By default, an OSPF interface
sends up to three LSU
packets every 20 milliseconds.