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3850 stack reboots with different code

We have three 3850 switches. They came with code 3.2.2 and work fine when stacked. We upgraded two of them to 3.3 and stacked them. That also worked fine. We added the third switch running 3.2.2 to the stack. It would not stack. The show ver command showed that the third switch model was model_unset. It would not stack. After a few minutes the active switch 1 reloaded. So the stack was missing switch 1 and 3. The only way to fix the issue was to unstuck all three switches, upgrade the third switch to 3.3 to match the other two, and then stack all three again. Has anyone experienced this?

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Cisco Employee

Re: 3850 stack reboots with different code

Hi Eric,

I have yet to see "model_unset" - were you logging the session when this happened? If so, please paste.  The switches will not stack if running different versions, you should see "V-Mismatch" in the "show switch" output.  It sounds like you most likely hit a Stack Merge that caused the reload, but its going to be tough to say for sure without logs.