Understanding the 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 will always assume mastership if the acting master Routing Engine is rebooted.

To see how the default Routing Engine redundancy setting works, follow these steps:

WARNING: Do not try this procedure on a production network.

1. Make sure the router is running on RE0 as the master Routing Engine (see Displaying Redundant Routing Engine Mastership and Backup).
2. To manually switch the state of the Routing Engine mastership, use the request chassis routing-engine master command. RE0 is now the backup Routing Engine and RE1 is the master Routing Engine. If you use this command to change the master Routing Engine, and then restart the chassis software for any reason, the master reverts to the default setting. For information about switching Routing Engine mastership, see the request chassis routing-engine master command in the JUNOS Protocols, Class of Service, and System Basics Command Reference.
   

   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. When you do this, the Routing Engine boots up and reads the configuration. If 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 with RE0 assuming mastership.