Identify MAC from BPDU TCs

[jchaumeton]

Hi,

we actually have a Fabric core with 4xVSP7400 we activate STP mstp because of an interconnection any to any with a provider.

We have 2 core by room and each room as an attach to the provider because of the STP one link is in Forwading and the other in blocking.

We actually have regulary TC become from the forwading port : 

GlobalRouter BRIDGE WARNING Spanning Tree: Port 1/10/1 - Received 2 TCs in 1 minute(s) 

Each TCs receive there is recalculation of topology in our network and it generate IP Phone reboot.

I try to find a way to find the Mac source of TCs without port mirroring. Maybe in activate a particular debug on STP.

Sorry for my english.

Regards,

Jonathan

[Roger_Lapuh]

Jonathan

did you enable Fabric-STP Multi-homing functionality, or did you want to loop the externally coming BPDUs back to the providers so that the provider bridges will block the redundant ports? There are options for both available. What is your design goal?

Roger

[jchaumeton]

I Roger,

thanks for the feedback, STP Multi-Homing is in fact enable. Actually the operators infrasctructure is "transparent" and act like a wire.

Currently it is the switches Fabric that blocks the redundant ports that works correctly. The problem is that i have several topology change by day and i would know which equipement send the TCs.

Regards,

Jonathan

[Ludovico_Steven]

Who is the root bridge ? Your switch ? If you are receiving Topology Change Notification packets (TCNs) the root is on your side. But the way it works is that any non-root bridge who has a port moving into Forwarding state, sends a TCN towards the root bridge. The root bridge then sets the TCN bit in the BPDUs it emits on all its ports and all other cascaded spanning tree bridges in the domain do the same for about a minute I think. During that time all STP bridges in the domain replace the MAC aging timer of all the applicable VLANs (all VLANs if you are not using MSTI instances) with a 15sec timer. The result is fast aging of all MAC entries. MSTP and RSTP are a bit more clever and try to only fast age those MACs in the direction of the TCN. But so the net effect is just to refresh your MAC tables in case the forwarding topology might have changed. There is no recalculation but as MACs get re-learnt some traffic will get flooded in the VLANs.

[jchaumeton]

The root bridge is the VSP74 Core 1 so logically I should only receive TCNs and not TCs. Yet if I look at the statistics of the ports of my switch being the root bridge STP. I can see that : 

Port Number : 1/10/1
Cist Port Fwd Transitions : 1
Cist Port Rx MST BPDUs Count : 306
Cist Port Rx RST BPDUs Count : 98
Cist Port Rx Config BPDUs Count : 0
Cist Port Rx TCN BPDUs Count : 0
Cist Port Rx TC BPDUs Count : 170
Cist Port Tx MST BPDUs Count : 1585595

Port Number : 1/17/1
Cist Port Fwd Transitions : 5
Cist Port Rx MST BPDUs Count : 55
Cist Port Rx RST BPDUs Count : 0
Cist Port Rx Config BPDUs Count : 0

Cist Port Rx TCN BPDUs Count : 0
Cist Port Rx TC BPDUs Count : 39
Cist Port Tx MST BPDUs Count : 913109

MSTP Bridge Statistics
====================================================================================================
Mstp UP Count : 1
Mstp Down Count : 0
Region Config Change Count : 186
Time since topology change : 0 day(s), 01H:33M:59S
Topology change count : 109
New Root Bridge Count : 0