Reference Guide

898 | Stacking
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Stack Management Roles
The stack elects the management units for the stack management:
• Stack master: The primary management unit, also called the master unit.
• Standby: The secondary management unit.
• Stack units: Also called stack members, these are the remaining units in the stack. The system
supports up to four S4810 stack units.
• Stack group: On the S4810, each set of 4 10G ports or each individual 40G port correspond to a
stack-group. The CLI is used to configure the front ports on the S4810 to be stacking-ports.
The master holds the control plane and the other units maintain a local copy of the forwarding databases.
From the stack master you can configure:
• 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 configuration (which includes ACL, LACP, STP, SPAN, etc.)
• 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. Range is from 1 to 14. A higher value (14) means a higher priority.
Default: 1. 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. Figure 46-322 shows sample
output from an established stack.