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Topology Change, Loop-back detect and Storm Control

Hello everyone,

 

We have some strange things going on in the network, I hope your suggestions will help to find the right path for me

 

Yesterday 3 edge switches in the network started throwing Loop-detected messages and the uplink ports went into err-disabled state

I issued the no keepalive command, and it did the trick, everything is ok

 

However, when I run sh storm control broadcast on the uplink ports of these 3 switches, I can see 0,56%-0,89% broadcasts. I have checked other switches in the network, they never detected a loop and broadcast level is 0%

One of these 3 switches is connected to our Root Bridge, I checked storm control on the port of the Root Bridge going to this switch - it is 0%. However, as I told before, the other end the link is showing some broadcasts

We have a ring topology in the network, running MST, no loops are detected.

When I issue sh spanning-tree detail on the affected switch (Which is connected to the Root Bridge), I can see this:

 MST1 is executing the mstp compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, sysid 1, address 0019.aacb.b200
  Configured hello time 2, max age 20, forward delay 15, transmit hold-count 6
  Current root has priority 24577, address 0019.554a.b380
  Root port is 26 (FastEthernet1/0/24), cost of root path is 200000
  Topology change flag not set, detected flag not set
  Number of topology changes 39 last change occurred 00:05:11 ago
          from FastEthernet1/0/24
 

Fast Ethernet 1/0/24 is a root port

On the Root Bridge, when I issue the same comand, I get this:

 MST1 is executing the mstp compatible Spanning Tree protocol
  Bridge Identifier has priority 24576, sysid 1, address 0019.554a.b380
  Configured hello time 2, max age 20, forward delay 15, transmit hold-count 6
  We are the root of the spanning tree
  Topology change flag not set, detected flag not set
  Number of topology changes 466 last change occurred 00:06:44 ago
          from StackPort1

Dont really understand, why is it showing StackPort1.

Is there any way I can track down which port cause Topology Change?

Can the small broadcasts on the switch and loop-detect have any relation to each other?

How is it possible that Loop-detection happened only on 3 switches in the network, and these switches are Edge switches?

Thank you!

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