Managing a Switch Stack 145• If the stack master function is unassigned and there is another stackmaster in the system then the switch changes its configured stack mastervalue to disabled.• If the stack master function is enabled or unassigned and there is no otherstack master in the system, then the switch becomes stack master.• If the stack master function is disabled, the unit remains a non-stackmaster.If the entire stack is powered OFF and ON again, the unit that was the stackmaster before the reboot will remain the stack master after the stack resumesoperation.You can manually set the unit number for the switch. To avoid unit-numberconflicts, one of the following scenarios takes place when you add a newmember to the stack:• If the switch has a unit number that is already in use, then the unit thatyou add to the stack changes its configured unit number to the lowestunassigned unit number.• 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, configure the ports on the unit to be added to the stack as stackingports and power the unit off prior to connecting the stacking cables. Makesure 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 STP re-convergence will take place as soon as the link is detected.
