Why the cisco 3850 was restarted by SSO switchover?

[Herman2018]

Hi, we have one c3850 switch stack (c3850-12s +c3850-24t). recently switch c3850-24t rebooted, check the log , it shows "System was restarted by SSO switchover". What does it mean? Is it related to stack port or cable issue? can anyone pls advise? thanks in advance. 

[Leo Laohoo]

It means the stack master crashed.

[Herman2018]

Thanks @Leo Laohoo for your kind advice. Is it possible caused by defective stack cable or software? 

[johnd2310]

Hi,

Most probable the issue is software bug. How long has the stack been running and what software version is on the switches?

Thanks

[Herman2018]

Thanks @johnd2310 for your kind advice. we powered cycle switch01 on 1 month ago, then power cycled switch02 on the following day because of power system maintenance, there is no stack power cables between the switches. Then one later later, switch02 auto- rebooted. Stack switch ver is XE 16.9.6. , pls advise, thx. 

[Herman2018]

sorry, typo, should be * one week later, switch02 auto-rebooted" 

[Leo Laohoo]

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@Herman2018 wrote:
Stack switch ver is XE 16.9.6.

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[Leo Laohoo · Accepted solution]

Prior to the crash, are there any log entries about the stack flapping? 

If there is none, this crash is most like caused by a software bug.