Users Guide

Stack Management Roles
The stack elects the management units for the stack management.
• Stack master — primary management unit, also called the master unit.
• Standby — secondary management unit.
The master holds the control plane and the other units maintain a local copy of the forwarding databases. From the stack master you
can congure:
• System-level features that apply to all stack members.
• Interface-level features for each stack member.
The master synchronizes the following information with the standby unit:
• Stack unit topology
• Stack running conguration (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 o line, the standby replaces it as the new master and the switch with the next highest priority or MAC
address becomes standby.
NOTE: An S5000 switch stack has only one management IP address.
Stack Master Election
By default, the stack determines a master and standby unit at bootup time by electing the units with the highest MAC addresses.
You can precongure the units which are elected master and standby by assigning higher priorities to these units. (By default, all
stack units have priority 0. Valid priority values are from 0 to 14. A higher value means a higher priority. To remove the stack-unit
priority and set the priority back to the default value of zero, use the no stack-unit priority command.)
If you add a standalone unit, which has the same priority as the master stack unit, the standalone unit joins the stack as a member
unit.
NOTE: The units with the highest MAC addresses become master and standby only if you do not congure priorities. The
MAC address of the master unit is refreshed only when the stack is reloaded and a dierent unit becomes the stack
manager.
To view which switch is the stack master, enter the show system command. The following example shows sample output from an
established stack.
A change in the stack master occurs when:
• You power down the stack master or bring the master switch oine.
• A failover of the master switch occurs.
• You disconnect the master switch from the stack.
When a stack reloads, the stack master is determined as follows:
Stacking
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