Spanning-tree changes

[venturas05]

This is appearing all over my network and I cannot fingure why. There are PC's plugged into the ports that are giving these events. When this first started happening my whole network was shutting down so I have went through the last two days adding "spanning-tree bpduguard enable" on all my switch ports at the access layer. If anyone can provide me with any insight or any advice on figuring this out i would appreciate it. Some of the events are up to 30,000+ changes. Below is an example of one.

VLAN0006 is executing the ieee compatible Spanning Tree protocol

  Number of topology changes 3988 last change occurred 00:39:09 ago

          from FastEthernet0/1

Thank you,

Anthony

[glen.grant]

Make sure all user ports have portfast turned on. 

[venturas05]

All of my acess layer ports are configured with portfast.

[Sandeep Choudhary]

Hi Venturas,

"show spanning-tree active detail"

See how much more concise this command is. You can quickly see which VLAN has experienced changes and from which port.

"show spanning-tree active detail | inc executing|y changes | from"

and show us the output.

follow this document:

http://www.pingjeffgreene.com/networkers-corner-2/troubleshooting-tools/spanning-tree-loop-troubleshooting-and-safeguards/

Regards

[venturas05]

#show spanning-tree active detail | inc executing|y changes | from
***** output omitted *********

VLAN0015 is executing the ieee compatible Spanning Tree protocol

  Number of topology changes 5969 last change occurred 00:39:45 ago

          from FastEthernet0/35

***** output omitted *********

#show run int fa0/35

Building configuration...

Current configuration : 399 bytes

!

interface FastEthernet0/35

switchport access vlan 15

switchport trunk native vlan 15

switchport trunk allowed vlan 15,115

switchport mode trunk

switchport voice vlan 115

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape  10  0  0  0

mls qos trust device cisco-phone

mls qos trust cos

auto qos voip cisco-phone

spanning-tree portfast

spanning-tree bpduguard enable

end

#show run | include span*

spanning-tree mode pvst

spanning-tree extend system-id

[Aninda Chatterjee · Accepted solution]

Hello,

From the running-configuration of the port, it is not an access port. You can verify that using show interface fa0/35 switchport and look at what the 'operational mode' is. Considering that, a spanning-tree portfast command does nothing here. To have portfast enabled on a trunk port, you would have to use spanning-tree portfast trunk.

I hope this helps.

Regards,

Aninda

[venturas05]

Just an update. The issue was the previous netowrk administrator set all voice ports to trunk voice and data. I have changed it after learning this was incorrect. Also, the TCN's where from faulty nic drivers which was fun because we had 1000 machines with this issue. The driver on our HP systems failed when WoL was enabled sending out millions of fragmented packets.

[Aninda Chatterjee]

Apart from making that small change, you might also want to explore why you have TCNs from this port. Is it flapping?