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Dell EMC Configuration Guide for the S4048T–ON System 9.14.2.4

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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.

DellEMC#show system 

Stack MAC                  : 34:17:eb:f2:94:c4
Reload-Type                         : normal-reload [Next boot : normal-reload]

--  Unit 1 --
Unit Type                  : Management Unit
Status                     : online 
Next Boot                  : online 
Required Type              : S4048-ON - 54-port TE/FG (SK-ON)
Current Type               : S4048-ON - 54-port TE/FG (SK-ON)
Master priority            : 14 
Hardware Rev               : 2.0 
Num Ports                  : 72 
Up Time                    : 33 min, 51 sec
Dell Networking OS Version : 1-0(0-5005) 
Jumbo Capable              : yes 
POE Capable                : no 
FIPS Mode                  : disabled 
Burned In MAC              : 34:17:eb:f2:94:c4 
No Of MACs                 : 3

--  Power Supplies  --
Unit   Bay   Status       Type    FanStatus   FanSpeed(rpm)
---------------------------------------------------------------------------
  1     1    up           UNKNOWN up          10704
  1     2    absent               absent      0

--  Fan  Status  --
Unit Bay   TrayStatus  Fan1    Speed   Fan2    Speed   
------------------------------------------------------------------------------------
1    1     up          up      10134   up      10031   
 1    2     up          up      10031   up      10031   
 1    3     up          up      10031   up      10031   

Speed in RPM

--  Unit 2 --
Unit Type                  : Standby Unit
Status                     : online 
Next Boot                  : online 
Required Type              : S4048-ON - 54-port TE/FG (SK-ON)
Current Type               : S4048-ON - 54-port TE/FG (SK-ON)
Master priority            : 10 
Hardware Rev               : 2.0 
Num Ports                  : 72 
Up Time                    : 33 min, 52 sec
Dell Networking OS Version : 1-0(0-5005) 
Jumbo Capable              : yes 
POE Capable                : no 
FIPS Mode                  : disabled 
Burned In MAC              : 34:17:eb:f2:83:c4 
No Of MACs                 : 3

--  Power Supplies  --
Unit   Bay   Status       Type    FanStatus   FanSpeed(rpm)
---------------------------------------------------------------------------
  2     1    up           UNKNOWN up          10768
  2     2    down         UNKNOWN down        0

--  Fan  Status  --
Unit Bay   TrayStatus  Fan1    Speed   Fan2    Speed   
------------------------------------------------------------------------------------
2    1     up          up      10031   up      10031   
 2    2     up          up      10031   up      10031   
 2    3     up          up      10134   up      10031   

Speed in RPM

--  Unit 3 --
Unit Type                  : Member Unit
Status                     : online 
Next Boot                  : online 
Required Type              : S4048-ON - 54-port TE/FG (SK-ON)
Current Type               : S4048-ON - 54-port TE/FG (SK-ON)
Master priority            : 5 
Hardware Rev               : 2.0 
Num Ports                  : 72 
Up Time                    : 33 min, 45 sec
Dell Networking OS Version : 1-0(0-5005) 
Jumbo Capable              : yes 
POE Capable                : no 
FIPS Mode                  : disabled 
Burned In MAC              : 34:17:eb:f2:99:c4 
No Of MACs                 : 3

--  Power Supplies  --
Unit   Bay   Status       Type    FanStatus   FanSpeed(rpm)
---------------------------------------------------------------------------
  3     1    up           UNKNOWN up          10704
  3     2    absent               absent      0

--  Fan  Status  --
Unit Bay   TrayStatus  Fan1    Speed   Fan2    Speed   
------------------------------------------------------------------------------------
 3    1     up          up      10031   up      10031   
 3    2     up          up      9929    up      10031   
 3    3     up          up      10031   up      10134   

Speed in RPM

DellEMC#
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

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