Selecting The Master Unit; Selecting The Standby Unit - Dell PowerConnect PC7024 Technical White Paper

Stacking Dell PowerConnect 7000 Series Switches

Selecting the Master Unit

A stack manager is elected or re-elected based on the following considerations, in order:
•
Whether the switch that was previously the stack manager.
•
Whether the switch has the higher MAC address.
When a switch is added to the stack, one of the following scenarios takes place:
•
If the switch was previously designated as the stack master but another master unit is
already active, then the switch changes its configuration to be a slave unit.
•
If the switch was not designated as the stack master and there is another stack master
in the system, then the switch changes its configuration to be a slave unit.
•
If the switch is enabled as the stack master or there is no other stack master, then the
switch becomes stack master.
•
If the switch is not enabled as the stack master, the unit remains a slave unit.
The administrator can manually set the unit number for the switch using the Stack Management > Unit
Configuration page in the web interface, or the switch renumber command in the CLI. To avoid
unit-number conflicts, one of the following scenarios takes place when a new member is added to the
stack:
•
If the switch has a unit number that is already in use, then the unit that is added to the
stack changes its configured unit number to the lowest unassigned unit number.
•
If the added switch does not have an assigned unit number, then the switch sets its
configured unit number to the lowest unassigned unit number.
•
If the unit number is configured and there are no other devices using the unit number,
then the switch starts using the configured unit number.
•
If the switch detects that the stack already has the maximum number of units, making
it unable to assign a unit number, then the switch sets its unit number to "unassigned"
and does not participate in the stack.
If a new switch is added to a stack of switches that are already powered and running and already have
an elected master unit, the newly added switch becomes a stack member rather than the master. On
the master unit, if there is no saved configuration for the newly added unit, it applies the default
configuration. If there is a saved configuration on the master for the newly added unit, it would apply
the saved configuration to the new unit. If the entire stack is powered OFF and ON again, the unit that
was the master before the reboot will remain the master unit after the stack resumes operation.

Selecting the Standby Unit

When the stack is formed, one of the units is automatically selected as the standby unit for the stack.
The standby unit takes over as manager if the current manager fails. Alternatively, the administrator
can specify the standby unit.
To configure the standby unit using the CLI, use the standby command in Stack Configuration Mode.
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