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Synchronizing Routing Engines

If your router has two Routing Engines, you can manually direct one Routing Engine to synchronize its configuration with the other by issuing the commit synchronize command. The Routing Engine on which you execute this command (requesting Routing Engine) copies and loads its candidate configuration to the other (responding Routing Engine). Both Routing Engines then perform a syntax check on the candidate configuration file being committed. If no errors are found, the configuration is activated and becomes the current operational configuration on both Routing Engines.

The commit synchronize command does not work if the responding Routing Engine has uncommitted configuration changes. However, you can enforce commit synchronization on the Routing Engines by using the force option. When you issue the commit synchronize command with the force option from one Routing Engine, the configuration sessions on the other Routing Engine will be terminated and its configuration synchronized with that on the Routing Engine from which you issued the command.

Note: We recommend that you use the force option only if you are unable to resolve the issues that caused the commit synchronize command to fail.

For example, if you are logged in to re1 (requesting Routing Engine) and you want re0 (responding Routing Engine) to have the same configuration as re1, issue the commit synchronize command on re1. re1 copies and loads its candidate configuration to re0. Both Routing Engines then perform a syntax check on the candidate configuration file being committed. If no errors are found, re1's candidate configuration is activated and becomes the current operational configuration on both Routing Engines.

Note: When you issue the commit synchronize command, you must use the groups re0 and re1. For information about how to use the apply-groups statement, see Applying a Junos Configuration Group. The responding Routing Engine must be running Junos OS Release 5.0 or later. For information about issuing the commit synchronize command on a routing matrix, see the Junos OS System Basics Configuration Guide.

To synchronize a Routing Engine's current operational configuration file with the other, log in to the Routing Engine from which you want to synchronize and issue the commit synchronize command:

Note: You can also add the commit synchronize statement at the [edit system] hierarchy level so that a commit command automatically invokes a commit synchronize command by default. For more information, see the Junos OS System Basics Configuration Guide.

To enforce a commit synchronize on the Routing Engines, log in to the Routing Engine from which you want to synchronize and issue the commit synchronize command with the force option:

If you have nonstop routing enabled on your router, you must enter the commit synchronize command from the master Routing Engine after you make any changes to the configuration. If you enter this command on the backup Routing Engine, the Junos OS displays a warning and commits the configuration. Starting with Junos OS Release 9.3, accounting of backup Routing Engine events or operations is not supported on accounting servers such as TACACS+ or RADIUS. Accounting is only supported for events or operations on a master Routing Engine.

For the commit synchronization process, the master Routing Engine commits the configuration and sends a copy of the configuration to the backup Routing Engine. Then the backup Routing Engine loads and commits the configuration. So, the commit synchronization between the master and backup Routing Engines takes place one Routing Engine at a time. If the configuration has a large text size or many apply-groups, commit times can be longer than desired.

You can use the commit fast-synchronize statement to have the synchronization between the master and backup Routing Engines occur simultaneously instead of sequentially. This can reduce the time needed for synchronization because the commits on the master and backup Routing Engines occur in parallel.

Include the fast-synchronize statement at the [edit system] hierarchy level to have synchronize occur simultaneously between the master and the backup Routing Engines:

If commit fails on either Routing Engine, the commit process is rolled back on the other Routing Engine as well. This ensures that both Routing Engines have the same configuration. 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.