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Will Pettit

3650 stack reboots when adding new member


We've started using 3650 switches, and on two occasions when we've added a new member to the stack the stack has rebooted.

Scenario last night:

1 x 3650 powered on and active, running 16.3.6. Connected the stack cables to link in two more switches (not powered up), and the switch rebooted.

When i booted up the two new switches everything was fine. The new switches already had the correct IOS and no config on them. Existing stack had the new switches provisioned. Switches are all WS-C3650-48PD.


Surely just connecting some stack cables shouldn't reboot the stack?


Cheers, Will

Reza Sharifi
Hall of Fame Expert

When you add a new switch to the stack, make sure the new switch is turned off, connect the stacking cable and then turn on the new switch. I have tried this procedure in the past and has worked with no issues.



Yeah the new switches were turned off. 

We've got some more in stock, so we'll give it another try. 

Also, please make sure the switch you are adding to the stack has the same exact software and license as the existing stack installed.


VIP Expert

adding to other post, check the switch priorty also.


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We just had the exact same problem with a WS-C3650-48PQ running 16.3.7. Added stacking modules and as soon as we added the stacking cables the switch restarted. We had not yet connected the stacking cables to second switch which was powered off.

Post the complete logs, and explain more about your environment. how many switches.

A couple of questions along with the below output will give us more information about the issue.


1. have you added the new switch - while new switch on?

2. you have same version of code on new switch before adding to exiting stack and mode of the switch.


post output of show switch.



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I only have logs from the point of the restart.  I think the logs prior to that were gone on boot if I remember correctly.


It was a single switch setup before.  We had only installed the stacking modules, and plugged in the stacking cables.  It was still a single switch stack when it restarted.


Once it had restarted, we connected the second (powered off) switch and turned it on.  It correctly added to the stack without issue.


Both switches were running 16.3.7 install mode when we started, but it doesn't really matter as the second switch wasn't powered on or connected when the original single switch "stack" restarted/crashed.

paul driver
VIP Mentor


Just like to add, when performing the stackwise re-cabling, if you disconnected the cabling and in inadvertently removed the stack master thus made the stack discontinuous this could make the stack reload and another reason could be that the stackwise cabling was lose prior to you touching them thus making the stack reload?

kind regards

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