Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.0P1 - Page 866

• Switch failure • Inter-switch stacking link failure • Switch insertion • Switch removal If the master switch goes off line, the standby replaces it as the new master and the switch with the next highest priority or MAC address becomes standby. Stack Master Election The stack elects a master and standby unit at bootup time based on two criteria. • Unit priority - User-configurable. The range is from 1 to 14. A higher value (14) means a higher priority. The default is 0. By removing the stack-unit priority using the no stack-unit priority command, you can set the priority back to the default value of zero. The unit with the highest priority is elected the master management unit; the unit with the second highest priority is elected the standby unit. • MAC address (in case of priority tie) - The unit with the higher MAC value becomes the master unit. The stack takes the MAC address of the master unit and retains it unless it is reloaded. To view which switch is the stack master, enter the show system command. A change in the stack master occurs when: • You power down the stack master or bring the master switch offline. • A failover of the master switch occurs. • You disconnect the master switch from the stack. When a stack reloads and all the units come up at the same time; for example, when all units boot up from flash, all units participate in the election and the master and standby are chosen based on the priority or MAC address. When the units do not boot up at the same time, such as when some units are powered down just after reloading and powered up later to join the stack, they do not participate in the election process even though the units that boot up late may have a higher priority configured. This happens because the master and standby have already been elected, hence the unit that boots up late joins only as a member. When an up and running standalone unit or stack is merged with another stack, based on election, the losing stack reloads and the master unit of the winning stack becomes the master of the merged stack. For more details, see sectionsAdd Units to an Existing Stack and Remove a Unit from a Stack. It is possible to reset individual units to force them to give up the management role or reload the whole stack from the CLI to ensure a fully synchronized bootup. Example of Viewing Stack Members Dell#show system brief Stack MAC : 00:01:e8:8c:53:32 Reload Type : normal-reload [Next boot : normal-reload] -- Stack Info -- Unit UnitType Status ReqTyp CurTyp Version Ports 0 Member not present 1 Management online S4810 S4810 4810-8-3-12-1447 64 2 Standby online S4810 S4810 4810-8-3-12-1447 64 3 Member online S4810 S4810 4810-8-3-12-1447 64 4 Member online S4810 S4810 4810-8-3-12-1447 64 5 Member not present 6 Member not present 7 Member not present 8 Member not present 9 Member not present 10 Member not present 866 Stacking