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Initial Configuration
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• If more than one stack Master is selected using the Master/Slave push button on
the switch’s front panel, the system will select the unit with the lowest MAC address
as the Master.
• 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 a new unit in the stack will cause the stack to
reboot. If a unit is removed from the stack (due to a power down or failure) or a new
unit added to the stack, the original unit IDs are not affected after rebooting, and a
new unit is assigned the lowest available unit ID.
Broken Link for Line and Wrap-around Topologies
All units in the stack must be connected via stacking cable. You can connect the
units in a simple cascade configuration from the top to the bottom unit. Using this
kind of line topology, if any link or unit in the stack fails, the stack will be broken in
two. The Stack Link LED on the unit that is no longer receiving traffic from the next
unit up or down in the stack will begin flashing to indicate that the stack link is broken.
When the stack fails, a Master unit is selected from the two stack segments, either
the unit with the Master button depressed, or the unit with the lowest MAC address if