Users Guide

• Stack unit topology
• Stack running configuration (which includes ACL, LACP, STP, SPAN, and so on.)
• Logs.
The master switch maintains stack operation with minimal impact in the event of:
• 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 : 90:b1:1c:f4:a7:c7
Stacking 942