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Hierarchy Level

Release Information

Statement introduced in Junos OS Release 12.2.


Configure commits to run in parallel (simultaneously) on both the master and backup Routing Engines to reduce the time required for commit synchronization. The fast-synchronize configuration is valid only on systems with two Routing Engines.


Starting in Junos OS Release 18.2R1, Junos OS does not support the configuration option commit fast-synchronize at the [edit system] hierarchy level for all the products with single Routing Engine for which chassis redundancy graceful-switchover is not supported. This option is disabled from the CLI.

  • When the fast-synchronize statement is configured, the commits on the master Routing Engine and the backup Routing Engine run in parallel. In this process, the configuration is validated only on the Routing Engine where you execute the commit command. Therefore, it is recommended not to include too many configuration details in groups like re0 and re1, because the configuration specified in group re0 is applied only if the current Routing Engine is in slot 0. Likewise, the configuration specified in group re1 is applied only if the current Routing Engine is in slot 1.

  • Ensure that the Junos OS software version running on both the Routing Engines is same.

Note the following prerequisites before configuring the fast-synchronize statement:

  • Enable graceful Routing Engine switchover (GRES) by configuring the chassis redundancy graceful-switchover command.

  • Configure the system commit synchronize command to automatically result in a commit synchronize action between dual Routing Engines within the same chassis.

Required Privilege Level

system—To view this statement in the configuration.

system-control—To add this statement to the configuration.