
150
Figure 39
Network diagram for IS-IS FRR
, 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 designate a backup next
hop with a routing policy for routes matching specific criteria.
Configuration prerequisites
Before you configure IS-IS FRR, complete the following tasks:
•
Configure IP addresses for interfaces to ensure IP connectivity between neighboring nodes.
•
Enable IS-IS.
Configuration guidelines
•
Do not use FRR and BFD at the same time. Otherwise, FRR might fail to take effect.
•
The automatic backup next hop calculation of FRR and that of TE are mutually exclusive.
Configuring IS-IS 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
By default, the source address of
echo packets is not configured.
3.
Enter IS-IS view.
isis
[
process-id
] [
vpn-instance
vpn-instance-name
]
N/A
4.
Enable IS-IS FRR to
automatically calculate a
backup next hop.
fast-reroute
auto
By default, IS-IS FRR is disabled.
Configuring IS-IS FRR using 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, and perform this task to reference the routing policy for IS-IS