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Topology change occurring several times every minute

  • 13 April 2015
  • 4 replies


I have the following problem: topology change is occurring all the time on my Core Switch (B5G124-48). I believe this is realcionado to some "network loop" that is going on in my network. Am I right?
I wonder if there is some command (I'm new to Enterasys platform) that allows me to see where (What port) these network changes are coming?

For a better understanding, my network topology consists of Core with B5G124-48 (Stack with 3 Switches). My distribution layer and access is all based on switches 3COM / HP. I have about 11 LAGs distributed to my access layer (LACP 2Gbps).

I need to understand where you coming from so many topology changes and why is happening for me solve the problem. Can anyone help me?

Bridge Hello Time - 2
Bridge Forward Delay - 15
Topology Change Count - 136 187
Since Time Top Change - 0 days 00:04:42
Max Hops - 20

4 replies

Userlevel 2

Whats your Spanningtree version? You should use MSTP to interwork with HP devices. Do you have different instances on the HP devices of Spanningtree?

Typically such a TCC rising is coming from a faulty or misconfigured Uplink port (i.E. half duplex, Policy on Uplink Port or even an enabled authentication on that interface)
Userlevel 3
show spantree debug port ge.*.*;lag.*.*
Userlevel 5

You can ensure that your STP configuration is correct by confirming the following:

1. Ensure that you Core (B5's) is configured as the STP root bridge (If using MSTP ensure it is root for all instances)
2. On the HP edge you can enable STP, configure edge ports for "STP edge" and enable "BPDU Protection"

On your Core run "Show spantree stats active" and ensure that the Core is indeed the STP Root brdige.
Do the same on the HP edge, show spanning-tree and ensure that the Core is the root bridge.

Also on the HP edge you should notice one or two ports in discarding state, this will be your port that is causing the loop.

Hope this helps
Userlevel 4
Here are some articles you can read that may shed some light on this issue:
How to troubleshoot spanning tree topology changes on SecureStack, N-Series and S-Series

SpanningTree Topology Changes Seen From Downstream Device

S-Series showing a lot of topology changes in the Netsight