Explains MPLS LDP-IGP synchronization compatibility with IGP NSF, including requirements for LDP graceful restart, effects on LDP synchronization state during IS-IS NSF, and considerations for maintaining state across restarts and failovers.
MPLS LDP-IGP synchronization compatibility is a protocol feature that
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enables LDP synchronization to operate together with IS-IS nonstop forwarding (NSF)
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requires LDP graceful restart to be enabled over the interface for full compatibility, and
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does not retain LDP synchronization state across restarts and failovers unless IS-IS NSF is enabled.
IS-IS nonstop forwarding (NSF) protects traffic during IS-IS process restarts and route processor (RP) failovers. LDP IS-IS synchronization is supported with IS-IS NSF only if LDP graceful restart is also enabled over the interface. Without IS-IS NSF, LDP synchronization state is not preserved across restarts and failovers.
If IS-IS NSF is enabled on the device and LDP graceful restart is active on the interface, LDP synchronization maintains state during RP failover and IS-IS process restarts. If IS-IS NSF is not enabled, synchronization will not persist across processes.