52 Dell PowerConnect 55xx Systems User GuideFILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Maintenance Projects\DellContax\sources\CxUGStacking.fmD E L L C O N F I D E N T I A L – P R E L I M I N A R Y 1 0 / 3 0 / 1 3 - F O R P R O O F O N LY– When a master-enabled unit is inserted to a running stack, (or whenMaster and Backup master both start at the same time), theyexchange each other’s UP TIME (the time since they powered up). Ifthe time difference is smaller than 10 minutes, the unit with thelowest unit ID is elected; otherwise, the unit with the longest UP timeis elected.– If a Master-enabled unit (with ID 1 or 2) is inserted into anoperational stack, it will be elected as a backup master.– If a Master unit and/or a backup Master unit is removed from thestack and the user wishes to configure one of the slave units(numbered 3-8) to be a Master backup, the user must reset the unit’sID. This can be done as follows:• If there is a Master-enabled unit in the stack: Do -switch nrenumber 2 (through CLI or GUI). This makes the nth unit amaster-enabled unit.• If there is no Master-enabled unit in the stack: Press the resetbutton on the unit to be master-enabled, and assign it a unit ID=1 using the boot menu.• The user can force a master-enabled unit to be the master unit of thestack, even if the master election process did not select it. This is done byswitching over to the backup unit.NOTE: Two stacking member are considered the same age if they wereinserted within a ten minute interval, for example, if Unit 2 is inserted in thefirst minute of a ten-minute cycle, and Unit 1 is inserted in fifth minute of thesame cycle, the units are considered to be the same age.NOTE: If two stack members are discovered to have the same Unit ID, onlythe older unit is included in the stack. The stack continues to function and amessage is sent notifying that a unit failed to join the stack.The Stack Master and the Master Backup maintain a Warm Standby. TheWarm Standby ensures that the Master Backup takes over for the StackMaster if a failover occurs, so that the stack continues to operate normally.During the Warm Standby, the Master and the Master Backup aresynchronized with the static configuration. When the Stacking Master isconfigured, it must synchronize the Master Backup . The dynamic
