Showing results for 
Search instead for 
Did you mean: 
Join Customer Connection to register!
Michael Fox

Spanning-Tree Topology Change Once per Day

Hi Folks,


For the past while we have been getting daily topology changes on our Cisco 2960-X Switches. They are all configured with standard PVST settings, but still do topology change frequently. This is causing our access points to drop sessions whilst the recornvergence is occuring. "last change occurred 00:25:19 ago"


Our debug logs do not appear to be showing anything and our settings are relatively simple:


spanning-tree mode pvst
spanning-tree logging
spanning-tree extend system-id
no spanning-tree vlan 1
spanning-tree vlan 2-45,69,75 priority 20480


show spanning-tree detail

VLAN0009 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 20480, sysid 9, address 00b6.70aa.0680
Configured hello time 2, max age 20, forward delay 15
Current root has priority 12297, address 00b6.7054.ed80
Root port is 46 (GigabitEthernet1/0/46), cost of root path is 4
Topology change flag not set, detected flag not set
Number of topology changes 100 last change occurred 00:25:19 ago
from GigabitEthernet1/0/46
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


Any suggestions?

Martin L
VIP Advocate

why use standard STP ? use Rapid STP , RSTP to limit number of ports that would force TCN (only non-edge ports will do TCN). Add to that portfast for all edge ports and BPDU guard

what is vlan 9 used for? and who connects to GigabitEthernet1/0/46 ?
why no spanning-tree vlan 1 ?