176 Managing a Switch Stack• If the switch you add does not have an assigned unit number, then theswitch sets its configured unit number to the lowest unassigned unitnumber.• If the unit number is configured and there are no other devices using theunit number, then the switch starts using the configured unit number.• If the switch detects that the maximum number of units already exist inthe stack making it unable to assign a unit number, then the switch sets itsunit number tounassigned and does not participate in the stack.Adding a Switch to the StackWhen 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. Stackport configuration is stored on the member units. If stacking over Ethernetports (N4000 only), configure the ports on the unit to be added to the stack asstacking ports and power the unit off prior to connecting the stacking cables.Make sure the links are not already connected to any ports of that unit. This isimportant because if STP is enabled and any links are UP, the STPreconvergence will take place as soon as the link is detected.After the stack cables on the new member are connected to the stack, you canpower up the new units, beginning with the unit directly attached to thecurrently powered-up unit. Always power up new stack units closest to anexisting powered unit first. Do not connect a new member to the stack after itis powered up. Also, do not connect two functional, powered-up stackstogether. Hot insertion of units into a stack is not supported.If a new switch is added to a stack of switches that are powered and runningand already have an elected stack master, the newly added switch becomes astack member rather than the stack master. Use the boot auto-copy-swcommand on the stack master to enable automatic firmware upgrade of newlyadded switches. If a firmware mismatch is detected, the newly added switchdoes not fully join the stack and holds until it is upgraded to the samefirmware version as the master switch. After firmware synchronizationfinishes, the running configuration of the newly added unit is overwrittenwith the stack master configuration. Stack port configuration is always storedon the local unit and may be updated with preconfiguration information fromthe stack master when the unit joins the stack.
