Concept Guide

● the management unit is powered down or a failover occurs.
● you disconnect the management unit from the stack.
When the management unit fails, the unit disappears from the stack topology. At that time, the standby unit detects the
communication loss and switches from the standby unit role to the management unit role in the stack. From the remaining units
in the stack, the system selects a new standby unit based on the unit priority using the same algorithm used when the stack was
initially created. When the failed unit recovers, it takes the next available role, usually that of a stack member.
● Influence the selection of the stack management units.
CONFIGURATION mode
stack-unit unit-number priority priority-value
The unit with the numerically highest priority is elected the master management unit, and the unit with the second highest
priority is the standby unit.
The range is from 1 to 14.
The default is 0.
Managing Redundancy on a Stack
Use the following commands to manage the redundancy on a stack.
● Reset the current management unit and make the standby unit the new master unit.
EXEC Privilege mode
redundancy force-failover stack-unit
A new standby is elected. When the former stack master comes back online, it becomes a member unit.
● Prevent the stack master from rebooting after a failover.
CONFIGURATION mode
redundancy disable-auto-reboot stack-unit
This command does not affect a forced failover, manual reset, or a stack-link disconnect.
● Display redundancy information.
EXEC Privilege mode
show redundancy
Resetting a Unit on a Stack
You may reset any stack unit except for the master management unit, as shown in the following message.
% Error: Reset of master unit is not allowed.
To rest a unit on a stack, use the following commands.
● Reload a stack-unit.
EXEC Privilege mode
reset stack-unit unit-number
● Reload a member unit, from the unit itself.
EXEC Privilege mode
reset-self
● Reset a stack-unit when the unit is in a problem state.
EXEC Privilege mode
reset stack-unit unit-number {hard}
Verify a Stack Configuration
The light of the LED status indicator on the front panel of the stack identifies the unit’s role in the stack.
● Off indicates the unit is a stack member.
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Stacking