MACFLAP

[Buka Jorbenadze]

Hello,

I have two WS-C3850-24XS switches in a stack. Yesterday, we had to power down one of the switches, and when it came back online, it caused MAC flapping across various port-channel links as well as physical links. This switch is connected to floor switches and other core switches primarily through port-channel links, but there are also single-link connections established with two switches. RSTP is enabled on this switch. For some reason, when it powered back on, this issue occurred. Please see the attached log file.

And how should I proceed to avoid this issue in the future?

Thanks 

[MHM Cisco World]

Check if this SW is root' and do you have core SW? If yes make Core SW is root of stp and use root guard.

With this if this SW is reboot it not effect all your network.

MHM

[Buka Jorbenadze]

This switch is not the root switch at the moment; it should be the core switch in this segment, and I made this switch the root.

[MHM Cisco World]

please share topolgy to make me sure what can we do to eliminate the flapping issue 

MHM 

[paul driver]

Hello

@Buka Jorbenadze wrote:
we had to power down one of the switches, and when it came .

This switch is connected to floor switches and other core switches primarily through port-channel links, but there are also single-link connections established with two switches. RSTP is enabled on this switch.

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So this is a distribution switch , so you would expect some stp re-convergence towards the root switches so your mac-flaps  could just be due the re-convergence.

How you have your stp applied, are you manually load balancing the switching traffic ?
Do your have PCs to all the other switches and are you running RSTP throughout the estate.
Do you have portsfast on all edge ports and do you have your stp link types manually set (especially on your PCs)

As for the logging your have shared that shows the switch stack and its stacking ports disconnecting between the active/rebooted switch and obviously your stp convergence