First of all devices:

  • HP ProCurve Switch 2610-24-PWR

  • Cisco IP Phone 8811

  • PC

I'm receiving loads of logs like these:

I 01/16/17 23:58:39 ports: port 20 is Blocked by STP
I 01/16/17 23:58:39 ports: port 20 is now on-line
I 01/16/17 23:58:54 ports: port 20 is now off-line

These logs are occurring every minute of every hour.

Is this a problem with cable or IP Phone considered as a switch? Or maybe something else?

Thanks in advance.

  • 1
    Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 15, 2017 at 15:32

3 Answers 3


Make sure you've got your spanning tree set up, so that a central switch is the root. If you don't configure spanning tree priority, a random switch becomes root (the one with the lowest MAC address) - if that's a phone switch or any other 'peripheral' switch you're bound to have unexpected reconvergences.

We've set our core switch to priority 4 (16384) and the other central switches to 6 (24576). The priority of the edge switches stays at 8 (32768), so they won't ever become root.

Additionally, you might want to protect the root ports on the edge switches so that no rogue switch can grab the root.


Have you verified that the IP Phone isnt faulty and rebooting due to an issue with that device?

You seeing that it is Blocked by STP could merely be the port being blocked by STP due to that being the initial state of the port before it goes into forwarding.


An IP phone through which you connect a PC is a switch. Depending on how you have things configured, you will either trunk VoIP and data VLANs to the phone (recommended), or you will have a single VLAN for both VoIP and data (not recommended). In either case, the phone has an integrated switch to allow the PC to communicate with the rest of the network.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.