Dell POWEREDGE M1000E - Manual (Page 140)

140 Managing a Switch Stack
• 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.
You can manually set the unit number for the switch. 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 that
you add to the stack changes its configured unit number to the lowest
unassigned unit number.
• If the switch you add 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 maximum number of units already exist in
the stack making it unable to assign a unit number, then the switch sets its
unit number to unassigned and does not participate in the stack.
Adding a Switch to the Stack
When adding a new member to a stack, make sure that only the stack cables,
and no network cables, are connected before powering up the new unit. Make
sure the links are not already connected to any ports of that unit. This is
important because if STP is enabled and any links are UP, the STP re-
convergence will take place as soon as the link is detected.
After the stack cables on the new member are connected to the stack, you can
connect the power. Do not connect a new member to the stack after it is
powered up. Also, do not connect two functional, powered-up stacks together.
Hot insertion of units into the stack is not supported.
If there are any unassigned units already configured on the stack, remove
them prior to adding a new unit to stack. This is important because when
there is any preconfigured unit and the Master holds some configuration of
that unit, as soon as the unit is detected, the configuration is applied, which