Reference Guide
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Stacking
Stacking is supported on the S4820T platform.
Stacking is supported on the S4820T platform with the Dell operating system (FTOS) version 8.3.19.0 and newer.
NOTE: The S4820T commands accept Unit ID numbers 0-11, though the S4820T supports stacking up to three units
only with FTOS version 8.3.19.0 and version 8.3.10.2. The S4820T supports stacking up to six units with FTOS version
8.3.19.0.
Using the FTOS stacking feature, you can interconnect multiple S-Series switch units with dedicated stacking ports or
front end user ports. (The S50, S55, and S60 use dedicated stacking ports; the S4820T uses front end user ports for
stacking.) The stack becomes manageable as a single switch through the stack management unit.
S-Series Stacking Overview
An S-Series stack has redundant RPMs and multiple line cards. FTOS elects a management (master) unit, a standby unit,
and all other units are member units.
FTOS presents all of the units like line cards; for example, to access GigabitEthernet Port 1 on Stack Unit 0, enter
interface gigabitethernet 0/1 from CONFIGURATION mode.
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 six stack
units.
• Stack group — Each set of four 10G ports or each individual 40G port correspond to a stack-group. To configure
the front ports on the S4820T to be stacking-ports, use the CLI.
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, and so on.)
• Logs
The master switch maintains stack operation with minimal impact in the event of:
• Switch failure
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