Spanning Tree always noticed on event log

[AYEN]

Hi,

   I have noticed that spanning tree always see in event log in some of my switchport eventhough the connected device is Meraki MR. Is this normal? or I have to check on my config.

[ww]

It is a event of the port going down and up. I assume this is not good when there is a AP connected to that port.  

This should only happen at firmware upgrades or port/power schedules.

Check if the cable is good.

and the switch has enough poe power (in case you have many PoE devices)

[cmr]

It looks like bad cabling to me, is it a CAT6a run all the way from the switch to the AP?  Anything less and you'd be better to limit the AP to auto negotiate only up to 1Gb/s.

[AYEN]

@cmr Yes, it's CAT6 run all the from AP to switch. what do you mean to limit the AP to auto negotiate?

[cmr]

CAT6 is only rated for 1GbE.  Only CAT6a is rated for faster speeds.  Faster speeds may work on CAT6, but the longer the cable, the less reliable it will be.

[cmr]

You will find a number of sites stating that CAT6 is good enough for 2.5 and 5 GbE, but my experience when using PoE APs is that anything less than CAT6a isn't reliable above 1GbE.  Endpoint devices can run higher speeds over CAT6, generally reliably.

[AnthonyN]

Hey @AYEN 

+1 to the other responses here, the spanning tree events are just a response to the physical port flaps. ie when a port goes down, spanning tree state moves to disabled, when port comes up it moves to designated/root state

https://documentation.meraki.com/MS/Port_and_VLAN_Configuration/Spanning_Tree_Protocol_(STP)_Overvie...

I agree, run some cable tests to ensure the cable is good, remove the AP and plug it directly into the switchport with a known working cable to see if you get the same issues. The port flapping events is purely based on Layer 1 (whether the interface is up or down), nothing to do with software. 

[AYEN]

Hi @AnthonyN ,

     To be able us to understand me on my concerns here is the current topology
MX ---- Core(Aruba)----- Aruba(Distri)----- MS130-24X , no aggregated port, only single connection on the MS130 side only 4 APs use PoE and the other APs used power injector because of the current setup.

  I don't understand why always have port election on the port 25. Hoping someone can't give me some idea. Thank you in advance

[cmr]

• What spanning tree mode are the Arubas set to?  Meraki switches only support a single instance of spanning tree.
• What priority are they set to?  The core should be the smallest number (say 4096), the distribution bigger (16384, 20480 etc.) and the edge the biggest (40960+).  If they are all left at the default 32768 then you will get regular stp elections.

[RaphaelL]

The logs that you have shared only mentions port 12 and port 24. Which are not currently up ,so probably from another switch. Are you troubleshooting multiple issues ?

[AYEN]

Hi @RaphaelL sorry for the confusion, the first image on my chat was questioning why STP always show even the connection is MR and MS only and no other switches connected that can cause STP. Then the next image was shown how the network topology was made. Only flat network and how come STP was form.

[cmr]

Any port going up and down will trigger an STP event, not an election that could be disruptive, but a notification.