Troubleshooting Spanning-tree #show spanning-tree vlan detail

[D@1984]

Hi,

when I do show spanning-tree vlan detail on my core switch, I see the TCNs on an interfaces that is connected to an access switch. So next I connect to the access switch and do the same command, but it shows the same thing that the last change was from the interface that its connected to my core switch. is that normal to have regular TCNs between core(as root) and the access switch root port ? if not, what I need to do next to find out whats going on.

Thanks

[balaji.bandi]

TCN not regularly change until you have network changes done, can you post some example what you see.

is the root port VLAN also changed ?

[D@1984]

this is outcome from the root bridge :

#show spanning-tree vlan 10 detail

VLAN10 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority :
Configured hello time 2, max age 20, forward delay 15
We are the root of the spanning tree
Topology change flag not set, detected flag not set
Number of topology changes 6034 last change occurred 10:41:05 ago
from GigabitEthernet1/0/25
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300

GigabitEthernet1/0/25 is connected to an access switch port gi1/0/20:

#show spanning-tree vlan 10 detail

VLAN10 is executing the rstp compatible Spanning Tree protocol
Bridge Identifier .....
Configured hello time 2, max age 20, forward delay 15, transmit hold-count 6
Current root has priority (thats my core switch)
Root port is 20 (GigabitEthernet1/0/20), cost of root path is 4
Topology change flag not set, detected flag not set
Number of topology changes 803459 last change occurred 00:02:03 ago
from GigabitEthernet1/0/20
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300

# show int gi1/0/20 | i rate
Queueing strategy: fifo
5 minute input rate 32000 bits/sec, 42 packets/sec
5 minute output rate 21000 bits/sec, 14 packets/sec

# show int gigabitEthernet 1/0/25 | i rate
Queueing strategy: fifo
5 minute input rate 25000 bits/sec, 16 packets/sec
5 minute output rate 34000 bits/sec, 42 packets/sec

[paul driver]

Hello
Access-ports can produce tcns so make sure to disable them from being initiated on any access-ports, (spanning-tree portfast).

Also check for interface drops/reset on the switch(s) trunk interconnects.

[Georg Pauwen]

Hello,

run

debug spanning-tree events

on both switches and post the output.

[D@1984]

I can see that I've got a flapping interface (for some reason), but I configured that port with portfast and also bpdguard. so dont understand why stp still send topology changes to other switches. 

 %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/3, changed state to down
%LINK-3-UPDOWN: Interface GigabitEthernet1/0/3, changed state to down
set portid: VLAN10 Gi1/0/3: new port id
STP: VLAN10 Gi1/0/3 ->jump to forwarding from blocking

#show run int 1/0/3

spanning-tree portfast
spanning-tree bpduguard enable
end