H3C Technologies H3C S10500 Series Switches - Manual (Page 180)

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Figure 63 Network diagram for IS-IS FRR
In Figure 63 , 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 to reduce
traffic recovery time. 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, complete the following tasks:
• 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 a backup next hop
Follow these steps to configure IS-IS FRR:
To do… Use the command… Remarks
Enter system view system-view —
Configure the source address of
echo packets
bfd echo-source-ip ip-address
Required
Not configured by default.
Enter IS-IS view
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
—
Enable IS-IS FRR to automatically
calculate a backup next hop
fast-reroute auto
Required
Not configured by default.
Configure IS-IS FRR to designate a backup next hop with a routing policy
You can use the apply fast-reroute backup-interface command to specify a backup next hop in a routing
policy for routes matching specific criteria. For more information about the apply fast-reroute
backup-interface command and routing policy configurations, see the chapter “Routing policy
configuration.”
Follow these steps to configure IS-IS FRR:
To do… Use the command… Remarks
Enter system view system-view —
Configure the source address of
echo packets
bfd echo-source-ip ip-address
Required
Not configured by default.
Enter IS-IS view
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
—