How A Master (Management Unit) Is Selected - Dell PowerConnect M8024-k User Manual

Stacking PowerConnect 10G Switches: M8024-k, 8024, 8024F
Management Standby
SW Status
--- ---------- --------- ------------- ------------- -------
1 Mgmt Sw
2 Stack Mbr
3 Stack Mbr
Note that in this example Unit 1 is the Master (Mgmt Sw) and Unit 3 is the Standby (Oper Stby) ready to
take over as Master in the event the Master fails.
Note: If the stack consists of M8024-k modular switches in an M1000e chassis, the CMC also shows each
Master in the chassis and the fabric (A1, A2, B1, B2, C1, or C2) where it is located. See Figure 8.

How a Master (Management Unit) is Selected

A Master is elected or re-elected based on the following considerations, in order:
1. The switch is currently the Master.
2. The switch has the higher MAC address.
3. A unit is selected as standby by the administrator, and a fail over action is manually initiated
or occurs due to a Master unit failure.
Note: The terms "Master" and "Manager/Management Unit" are often used interchangeably in regards to
Stacking.
In most cases, a switch that is added to an existing stack will become a stack member, and not the
Management Unit. When a switch is added to the stack, one of the following scenarios takes place
regarding the management status of the new switch:

If the switch has the Management Unit function enabled but another Master unit is already
active, then the switch changes its configured Management Unit value to disabled.

If the Management Unit function is unassigned and there is another Management Unit in the
system, then the switch changes its configured Management Unit value to disabled.

If the Management Unit function is enabled or unassigned and there is no other Management
Unit in the system, then the switch becomes Management Unit.

If the Management Unit function is disabled, the unit remains a non-Management Unit.
If the entire stack is powered OFF and ON again, the unit that was the Management Unit before the
reboot will remain the Management Unit after the stack resumes operation.
A Unit number for the switch can be manually set. To avoid unit-number conflicts, one of the following
scenarios takes place when you add a new member to the stack:

If the switch has a unit number that is already in use, then the unit added to the stack changes
its configured unit number to the lowest unassigned unit number.

If the switch added does not have an assigned unit number, then the switch sets its configured
unit number to the lowest unassigned unit number.
Preconfig
Status Model ID
PC8024
PC8024F
Oper Stby PC8024
Plugged-in Switch
Model ID Status
PC8024 OK
PC8024F OK
PC8024 OK
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