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Hierarchy Level


On M20 routers, configure which System and Switch Board (SSB) is the primary and which is the backup.


By default, the SSB in slot 0 is the primary and the SSB in slot 1 is the backup.


slot-number—Specify which slot is the primary and which is the backup.

always—Define this SSB as the sole device.

preferred—Define this SSB as the preferred device of at least two.

Required Privilege Level

interface—To view this statement in the configuration.

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

Release Information

Statement introduced before Junos OS Release 7.4.