Default Routing Engine Redundancy Behavior

By default, the JUNOS software uses re0 as the master Routing Engine and re1 as the backup Routing Engine. Unless otherwise specified in the configuration, re0 always becomes master when the acting master Routing Engine is rebooted.

Note: A single Routing Engine in the chassis always becomes the master Routing Engine even if it was previously the backup Routing Engine.

Perform the following steps to see how the default Routing Engine redundancy setting works:

1. Ensure that re0 is the master Routing Engine.
2. Manually switch the state of Routing Engine mastership by issuing the request chassis routing-engine master switch command from the master Routing Engine. re0 is now the backup Routing Engine and re1 is the master Routing Engine.

   Note: On the next reboot of the master Routing Engine, the JUNOS software returns the router to the default state because you have not configured the Routing Engines to maintain this state after a reboot.

3. Reboot the master Routing Engine re1.

   The Routing Engine boots up and reads the configuration. Because you have not specified in the configuration which Routing Engine is the master, re1 uses the default configuration as the backup. Now both re0 and re1 are in a backup state. The JUNOS software detects this conflict and, to prevent a no-master state, reverts to the default configuration to direct re0 to become master.

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