Problem: Switch Does Not Join the Stack

Your stack might have below three major issues if one of the switches does not join the stack , These issues will further discussed in detail.

  1. Switch Compatibility issues
  2. StackWise connection problem

Switch Compatibility issues

  • Incompatible IOS version and switch-stack versions
  • Software License compatibility issues
  • Incompatible configuration
  • SDM template configuration incompatibilities

Incompatible IOS version and switch-stack versions

Use below command to verify is your switches have Compatibility issue :

INB_Switch# show switch    

Under hardware state, you will see this error: “Version Mismatch”

To further verify that your all switches run the same Verison as Master use below command :

INB_Switch# show version

Switch Ports Model              SW Version            SW Image

—— —– —–              ———-            ———-

*    1 30    WS-C3750E-24PD     12.2(46)SE            C3750E-UNIVERSAL-M

2 28    WS-C3750E-24PS     12.2(46)SE            C3750E-UNIVERSAL-M

3 54    WS-C3750E-48TD     12.2(46)SE            C3750E-UNIVERSAL-M

Software License compatibility issues

All switches in the stack should have same type of license installed verify it with below commands :

INB_Stack# show license all switch 1

License Store: Primary License Storage

StoreIndex: 0   Feature: advipservices

License Type: Permanent        License State: Active, In Use

INB_Stack# show license all switch 2

License Store: Primary License Storage

StoreIndex: 0   Feature: advipservices

License Type: Permanent        License State: Active, In Use

to check further details about the license in particular switch use below command

use below command to check all active license in a stack on all switches :

INB_Stack# show version

Switch 03


License Level                   : advipservices

License Type                    : Permanent

Next reboot licensing Level     : advipservices

Switch 04


License Level                   : advipservices

License Type                    : Permanent

Next reboot licensing Level     : advipservices

Incompatible configuration

Always return the configuration of the switch to default before connecting it to stack if you used that switch somewhere else as standalone.

To prevent incompatible configurations, follow these steps on a previously configured switch that you plan to add to the stack:

  1. Delete the config.text file and vlan.dat files from flash memory.
  2. Set all options such as the SDM template and port numbers to their default values.
  3. Install the same Cisco IOS version that is running in the stack.
  4. Power off the switch.
  5. Connect the StackWise cables.
  6. Power on the switch.

In stack add switch numbering might change from previous instead of starting for F 1/0/1 it might start from F2/0/1, to return switch ports to the default numbering values as shown in this example:

INB_Switch(config)# switch 2 renumber 1

SDM template configuration incompatibilities

The master switch automatically corrects SDM template mismatches in Catalyst 3750 and 3750E switches when you connect one of them to a stack. A configuration mismatch might occur if the switch was a Catalyst 3750G-12S switch configured with a non-default SDM template before you connect it to a stack.

  • To display the configured SDM template on a switch, enter the show sdm prefer privileged EXEC command.
  • To change a Catalyst 3750G-12S switch SDM template to the default setting before you connect it to a stack, enter the sdm prefer default global configuration command.

See the appropriate software configuration guide for additional information on SDM templates.

2. StackWise connection problem

use below command to see if you have cable problems (loose cable).


Current State



The switch is fully operational.


The stack master is communicating with the new switch joining the stack.


Ports are assigned in the stack running-configuration, but no switch with the port numbers Fa3/0/1, G3/0/1, and so on, is detected in the stack. If a switch that previously joined a stack is removed, the port numbers remain in the running-configuration, and the missing switch is shown as Provisioned.

The Provisioned state might be caused by a switch that is no longer connected to the stack or be the result of manually pre-provisioning the related ports. See the Catalyst 3750 or the Catalyst 3750-E switch software configuration guide for more information on pre-provisioning switches in a stack.

Fixing Problems with StackWise Interfaces and Cables

Use below command to verify if all stack cables are working as you can see in Neighbor column switches can see each other on port 1 and 2.

INB_Stack#Show switch details 



if you see output as below , Port 1 of switch 1 shows None and Port 2 on switch shows None . Check stack cable in switch 1 and 3.



Additional Information :

How to manually update the Priority on the switch to select as Master:

Reviewing How the Stack Master is Rebooted or Disconnected

A new stack master is elected when you:

  • Power off, disconnect or reboot the current stack master.
  • Power on all switches in a new stack at the same time.
  • Reboot all switches after you manually change the stack member priorities by using the CLI.
  • Connect a powered-on stack to another powered-on stack merging two separate stacks merge into one.

These rules determine switch priority:

  1. You can manually set the switch priority when stack master election or re-election occurs. You can set a priority of 1 to 15; 15 is the highest priority. This command sets switch 1 to priority 15, and it will be the stack master when you reload the stack if no other switches are also set to priority 15:

INB_Stack(config)# switch 1 priority 15

You can then assign a lower priority to the remaining switches in the stack, or they can remain at default. A priority 15 switch overrides these selection decisions:

  1. The switch with the highest hardware and software priority is the stack master if you do not set the priority. If all switches have the same hardware and software priority, this procedure occurs:
  2. The switch that is not using the default configuration becomes the stack master. The stack manager renumbers and reboots the switches that are using a default configuration (no config.text file in flash memory).
  3. The switch with the lowest MAC address.