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TACK
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PERATIONS
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• If the Master unit fails and another unit takes over control of the stack,
the unit numbering will not change.
• If a unit in the stack fails or is removed from the stack, the unit
numbers will not change. This means that when you replace a unit in
the stack, the original configuration for the failed unit will be restored
to the replacement unit.
• If a unit is removed from the stack and later reattached to the stack, it
will retain the original unit number obtained during stacking.
• If a unit is removed from the stack, and powered up as a stand-alone
unit, it will also retain the original unit number obtained during
stacking.
Selecting the Backup Unit
Once the Master unit finishes booting up, the Slave unit with the lowest
MAC address will be selected from the stack as the primary backup unit.
The stack Master immediately downloads all configuration information to
the backup unit, and continues to update the backup unit with information
about any subsequent configuration changes made to any unit in the stack.
If the Master unit fails or is powered off, the backup unit will take control
of the stack without any loss of configuration settings.
The Slave unit with the lowest MAC address is selected as the Backup unit.
If you want to ensure a logical fail over to next unit down in the stack,
place the Slave unit with the lowest MAC address directly beneath the
Master unit in the stack.
Recovering from Stack Failure or Topology Change
When a link or unit in the stack fails, a trap message is sent and a failure
event is logged. The stack will be rebooted after any system failure or
topology change. It takes two to three minutes to for the stack to reboot. If
the Master unit fails, the backup unit will take over operations as the new
Master unit, reboot the stack, and then select another backup unit after the
stack finishes rebooting. Also note that powering down a unit or inserting