ldp-sync enable

Function

The ldp-sync enable command enables LDP-Interior Gateway Protocol (IGP) synchronization on all interfaces in an IS-IS process.

The undo ldp-sync enable command disables LDP-IGP synchronization on all interfaces in an IS-IS process.

By default, LDP-IGP synchronization is disabled on all interfaces in an IS-IS process.

Format

ldp-sync enable [ mpls-binding-only ]

undo ldp-sync enable

Parameters

Parameter	Description	Value
mpls-binding-only	Synchronization between LDP and IS-IS can only be enabled on MPLS LDP-enabled interfaces.	-

Views

IS-IS view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

On a network with both the primary and backup label switched paths (LSPs), to minimize traffic loss if the primary LSP fails, run the ldp-sync enable command to enable LDP-IGP synchronization. LDP-IGP synchronization minimizes traffic loss in the following situations:

When the primary LSP is working properly but an LDP session on the primary LSP goes Down, LSP traffic is switched to the backup LSP. IGP traffic is still forwarded along the primary LSP. As a result, LSP traffic is lost.
After the primary LSP recovers, IGP traffic is switched back to the primary LSP earlier than LDP traffic because IGP routes converge more rapidly than LDP routes. As a result, LSP traffic is lost.

LDP-IGP synchronization delays IGP route advertisement so that the LDP session and IGP route can converge simultaneously.

The ldp-sync enable command run in the IS-IS view can enable LDP-IGP synchronization on all interfaces within a specified IS-IS process.

Follow-up Procedure

To disable an interface from supporting LDP-IGP synchronization, run the isis ldp-sync block command.

Precautions

Although the undo ldp-sync enable command has been run, LDP-IGP synchronization configured using the isis ldp-sync command still takes effect on an IS-IS interface.

Example

# Enable LDP-IGP synchronization on all interfaces within an IS-IS process.

<sysname> system-view

[sysname] isis 100

[sysname-isis-100] ldp-sync enable