Managing Device Information
Managing Stacking
Cisco Small Business SFE/SGE Managed Switches Administration Guide 19
2
Master Election
The Master and Backup unit selection is known as Master Election. Master Election
takes place if there are one or more eligible candidates contending to be the
Master unit.
Master Election Candidate Eligibility
In general, not all stack member units are eligible to be candidates for Master
Election. Eligibility for Master Election is determined in the following order.
STEP 1 All Master-enabled switching units present in a stack are candidates for Master
Election. All units that are not Master-enabled are not eligible for Master Election.
STEP 2 If there are no Master-enabled units present in a stack, then all units in factory
default mode (Unit ID=0, Switch Operation Mode=Stack) are candidates for Master
Election. No other units are eligible for Master Election.
If neither Master-enabled nor factory default units are present, Master election
does not take place and all units in the stack are effectively shut down. The stack
remains in this inoperable state until either a new Master-enabled unit is
connected to the stack or a current stack unit is manually reset to factory default
mode (by pressing the reset switch on the front panel of the switch and holding it
down for at least ten seconds).
Master Election Selection Rules
If there are two or more candidates for Master Election, the Stack Master is
determined by comparing attributes of the contending units in a specific order.
The order in which the attribute comparisons are made is:
• 1 - Unit assigned by the system administrator as Force Master
• 2 - Unit with the longest running time (measured in 10 minute increments)
• 3 - Unit having Unit ID=1
• 4 - Unit having the lowest MAC address
The Master Election proceeds by making the attribute comparisons in the above
specified order. If there is a tie at any step, the election proceeds to the next step.
However, units that fail to tie at any step are eliminated from the competition. Units
that succeed in the tie in a given step, go on to compete in the next step. The
election is decided at the first step for which there is a clear winner. The winner of
that step is the winner of the Master Election and becomes the Master unit.
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