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Strange STP Blocking

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Strange STP Blocking


Just wondering if anyone has any ideas with the below problem. 

Our enviroment is all RDS about 50 Thin clients (hard wired) and 2 laptops (hard wired) it all sits on VMware and our main switch is a Aruba 5406zl2 and handles all my VMWare and this conects to 2 x HP2530's that all my users are connected to.  

The issue is that when one of my laptop users catches her cat5 cable (its a lenovo laptop with one of them ports that expands for the cable to fit)  it not only discoects her RDP session as the connection is lost but it casues a STP error on the port that conects to my 2 2530's and disconects everyones RDS session for about 2 to 30 seconds. Looking at the events on the 5406 i can see the STP blocking on the port and then coming back on line seconds later.

Last night i upgraded the firmware on the 5406 to 16.10.0001 but that has not done anything. 

Any help would be much appriciated 





Re: Strange STP Blocking


All the ports of the switch are auto-edge by default. After an auto-edge-port goes online it will wait for 3 second in order to determine if BPDUs are received, before going to forwarding state.  For this 3 seconds the port will be blocked and you will see in the log "port x is blocked by STP."

In order to avoid this delay of 3 seconds you can configure all ports connecting to end nodes as admin-edge-ports. An admin-edge-port will go immediately in forwarding state and will not wait for 3 seconds.

This document provides more details about auto-edge and admin-edge ports.

The fact that losing the connection on one port causes disconnection on other ports could mean that the port to the laptop is not properly recognized as STP edge port. A disconnection of an non-edge port could cause STP topology change which causes recalculation of the spanning tree and flushing of MAC address tables. In this case it is also recommended to configuration the port as admin-edge. Here is a document that describes how you can troubleshoot STP topology changes

Disconnections for 30 second could mean that this switch or other switches are using the old original STP standard 802.1D. It had convergance time of about 30 seconds. You have to make sure that the switches are using RSTP or MSTP.

I am an HPE employee

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