Adding switch to stack - Downgrade new switch version

[DHGmem]

I'm adding a new 9300 to an existing 9300 x 4 switch stack that are running a different version of IOS.

After i boot the new switch and perform the software auto-upgrade enable command - is it certain that the new switch will downgrade its IOS to the running IOS of the existing stack? And NOT the existing stack "upgrading" to the new switches IOS?

Priorities have been set higher on the existing stack.

I'm asking because i don't want the existing stack to reboot. All examples of adding a switch to a stack show the new switch "upgrading" its software to a newer version.

I believe the new switch will downgrade - i don't think the stack will know which version of IOS is newer, just that they are v-mismatch - is that correct?

Thanks.

[balaji.bandi]

If you do not like any interuption or reboot of exiting stack, i would go offline downgrade the IOS to match the existing on the new switch , change the swithc number and  adding to stack is advised (i do the same personally)

Note : Make sure some mode of Cat 9300 come with version you can downgrade, make sure you check before you break things.

[Leo Laohoo]

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@DHGmem wrote:

software auto-upgrade enable

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This command will only work if all switches in the stack (including the new ones to be added) are in Install Mode.  

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@DHGmem wrote:

I'm asking because i don't want the existing stack to reboot.

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DO NOT POWER ON new stack member before connecting the stacking cable.  Only when the stacking cable(s) is/are secure is power applied to the new switch.  

[duskokovic]

pay attention at the full stack ring not to partition your stack if the unit that needs the downgrade is in the middle of the stack

v-mismatch should be observed when you check the switch stack mode and the new unit must be in the install mode (traditional)

move the desired IOS onto the new unit from any other unit in the stack or load it via a usb and remove the stacking cables  

remote onto that unit and change the boot system to the "new" or desired IOS, save and reload that unit (with stacking cables removed)

after the unit is reloaded, check the version of the IOS and if the version matches the desired one, insert the stacking cables

the stack will converge and after some 10 minutes it should all be ok

you said that the priorities are already set to the other units so you are good to go