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STP topology changes

STP topology changes

New Contributor II
I've been trying to track down an issue with STP in one of our branch offices, for some reason STP has an immense amount of STP changes logged;

Topology Change Detected: FALSE Topology Change: FALSE

Number of Topology Changes: 4974700

Time Since Last Topology Change: 42s

It's worth to note that we have a mixed environment with HP's and EXTREME's, does this config look correct ?
Stpd: s1 Stp: ENABLED Number of Ports: 46

Rapid Root Failover: Disabled

Operational Mode: 802.1W Default Binding Mode: EMISTP

802.1Q Tag: (none)

Ports: 1:1*,1:3,1:4,1:5,1:6,1:7,1:8,1:9,1:10,1:11,





Participating Vlans: Default

Auto-bind Vlans: Default

Bridge Priority: 28672

BridgeID: 70:00:02:04:96:51:b9:fd

Designated root: 70:00:02:04:96:51:b9:fd

RootPathCost: 0 Root Port: ----

MaxAge: 20s HelloTime: 2s ForwardDelay: 15s

CfgBrMaxAge: 20s CfgBrHelloTime: 2s CfgBrForwardDelay: 15s

Topology Change Time: 35s Hold time: 1s

Topology Change Detected: FALSE Topology Change: FALSE

Number of Topology Changes: 4974700

Time Since Last Topology Change: 192s

HP-2848-LA-CAR-R8-1# show spanning-tree

Rapid Spanning Tree (RSTP) Information

STP Enabled : Yes

Force Version : RSTP-operation

Switch Priority : 32768 Hello Time : 2

Max Age : 20 Forward Delay : 15

Topology Change Count : 405,614

Time Since Last Change : 4 mins

Root MAC Address : 020496-51b9fd

Root Path Cost : 22000

Root Port : 43

Root Priority : 28672

Any ideas?


Extreme Employee
Hi Tom,

Yes. You are correct. You will only need to configure the ports with hosts connected (Servers/PCs etc..) as edge ports and not the trunk links between switches.
Please let us know if you have any other questions.
Thank you.

Best regards,

You should always specify a root bridge, otherwise the system will determine a root bridge based off of MAC address and that can be unpredictable. all your nodes will block or forward based upon path to that root bridge, so usually it is place pretty centrally in the environment.

Thanks Andrew, also any reason to specify a designated root bridge?

Extreme Employee
Hi Tom,

Please bear in mind that if the user ports of HP switch are not configured for edge port (or PortFast in Cisco terms) then each time a PC disconnects/connects you will get a Topology change. So you should configure edge ports on both switches' user ports.

Also, you can prevent the ARP entries from being cleared when a TC occurs by enabling iparp fast-convergence. Please see below article.

Emre Kurtman Technical Marketing Engineer / Extreme Networks