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Figure 1 Network diagram for LDP FRR
In Figure 1, configure IP FRR on LSR A by using IGP to calculate or specify a backup next hop. LDP
creates a primary LSP and a backup LSP according to the primary route and the backup route
calculated by IGP. When the primary LSP operates correctly, it forwards the MPLS packets. When
the primary LSP fails, LDP directs packets to the backup LSP.
When packets are forwarded through the backup LSP, IGP calculates the optimal path based on the
new network topology. When IGP route convergence occurs, LDP establishes a new LSP according
to the optimal path. If a new LSP is not established after IGP route convergence, traffic forwarding
might be interrupted. Therefore, HPE recommends that you enable LDP IGP synchronization to work
with LDP FRR to reduce the traffic interruption time.
Command reference
igp sync delay
Use igp sync delay to configure the delay for LDP to notify IGP of the LDP convergence completion.
Use undo igp sync delay to restore the default.
Syntax
igp sync delay time
undo igp sync delay
Default
LDP immediately notifies IGP of the LDP convergence completion.
Views
LDP view
Predefined user roles
network-admin
Parameters
time: Specifies the notification delay in the range of 5 to 300 seconds.
LSR A
LSR
C
LSR B
Primary LSP
Backup LSP
Backup LSP
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