Configuring Is-Is Frr - H3C S5800 Series Configuration Manual

Configuring IS-IS FRR

Do not use IS-IS FRR and BFD (for IS-IS) at the same time; otherwise, IS-IS FRR may fail to take
effect.
Introduction
When the link in the IS-IS network below fails, the packets on the path may be discarded, or a routing
loop may occur. Then, the traffic will be interrupted until IS-IS completes the routing convergence
based on the new network topology.
In this case, you can enable IS-IS fast reroute (FRR) to reduce traffic recovery time.
Figure 5-15 Network diagram for IS-IS FRR
In Figure 5-15, after you enable FRR on Router B, IS-IS automatically calculates or designates a
backup next hop when a link failure is detected. In this way, packets are directed to the backup next
hop for forwarding, thus to reduce traffic recovery time greatly. Meanwhile, IS-IS calculates the
shortest path based on the new network topology, and forwards packets over the path after network
convergence.
You can either enable IS-IS FRR to calculate a backup next hop automatically, or to designate a
backup next hop with a routing policy for routes matching specific criteria.
Configuration prerequisites
Before configuring IS-IS FRR, you need to:
Configure network layer addresses for interfaces to make the neighboring nodes reachable at the
network layer
Enable IS-IS
Configure IS-IS FRR to automatically calculate the backup next hop
Follow these steps to configure IS-IS FRR:
To do...
Enter system view
Use the command...
system-view
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Remarks
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