Cisco 2960-X Stack Strange STP Log Messages

[kimby200602]

Hello,

I have a few stacks of 2960s operating normally but I see the following sporadic STP messages on some of them:

Root Changed for vlan XXX: New Root Port is StackPort4. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-4)
Root Changed for vlan XXX: New Root Port is StackPort3. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-3)
Root Changed for vlan XXX: New Root Port is StackPort2. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-2)
Root Changed for vlan YYY: New Root Port is StackPort2. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-2)
Root Changed for vlan YYY: New Root Port is StackPort4. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-4)
Root Changed for vlan YYY: New Root Port is StackPort3. New Root Mac Address is aaaa.bbbb.cccc (Stack-Hostname-3)

What makes this a strange message:

1. This stack is directly connected through LACP port-channel to my core switch (MAC aaaa.bbbb.cccc) and there is no other event that could generate this message. None of the port-channel members has gone down/up and there is no STP topology change. Core switch should always be the root bridge since it is configured with lower bridge ID and all user ports have BPDU guard enabled.

2. Why Stack Ports are members of STP topology. My understanding is that they should not take part in STP topology, since the whole stack has a single Bridge ID.

My questions are:

Has anyone seen similar STP messages? Can you explain why these messages are being generated?

If you can share some docs explaining switch stack behavior in STP, so that I could find out what is causing this?

If you need any other info regarding my setup, please let me know.

Thank you!

Regards,

[kimby200602]

I cannot believe there is anyone that has observed the same behavior or has something to say about this?

What is your opinion on this behavior? Is it normal?

[aaah]

Good morning @kimby200602, 

Did you find a solution for this behavior? I'm getting the same logs left and right.

Thanks.

[marce1000]

 - Check for cabling issues , further analyze / troubleshoot with these commands :

sh spanning-tree inconsistentports
show switch

show switch neighbors

show switch stack-port

 Also look for additional messages , use a syslog server as a log-collector, in order to keep an overview of overall stack behavior and or anomalies, if any.

 M.

[paul driver]

Hello

What Software version are you running, Do you have a full stack-ring?
sh version
sh stack-ring speed
sh switch detail