Concept 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.
• Stack units — the remaining units in the stack, also called stack members. The system supports up to twelve stack units.
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.
Stack Master Election
The stack elects a master and standby unit at bootup time based on two criteria.
• Unit priority — User-congurable. 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.
DellEMC#show system
Stack MAC : 34:17:17:18:19:1e
Reload-Type : normal-reload [Next boot : normal-reload]
-- Unit 1 --
Unit Type : Member Unit
Status : online
Next Boot : online
Required Type : S3124F - 28-port GE/TE (S3100)
Current Type : S3124F - 28-port GE/TE (S3100)
Master priority : 0
Hardware Rev : 5.0
Num Ports : 30
906
Stacking