ldp-sync enable

Function

The ldp-sync enable command enables synchronization between LDP and IS-IS on all interfaces in an IS-IS process.

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

By default, synchronization between LDP and IS-IS 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

Synchronization between LDP and IGP reduces LSP traffic loss on a network with both primary and backup LSPs. Traffic loss occurs in either of the following situations:

The primary LSP works properly and an LDP session between two nodes on the primary LSP fails. IGP guides traffic still through the primary LSP even though a primary/backup LSP switchover is performed.
If a link on the primary LSP or the primary LSP recovers, IGP routes converge. IGP routes associated with the primary LSP become reachable earlier than the primary LSP because IGP routes converge faster than LDP routes. IGP routes guide traffic through the primary LSP before the primary LSP recovers.

Synchronization between LDP and IGP 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 synchronization between LDP and IS-IS on all interfaces within a specified IS-IS process.

Follow-up Procedure

Run the isis ldp-sync block command to disable synchronization between LDP and IGP on desired IS-IS interfaces.

Precautions

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

Example

# Enable synchronization between LDP and IS-IS on all interfaces in an IS-IS instance.

<HUAWEI> system-view
[HUAWEI] isis 100
[HUAWEI-isis-100] ldp-sync enable