We already have a VOIP VLAN for Cisco phones on Cisco switches. A phone can be plugged into any building switch port and it just magically gets diverted onto its own private VOIP VLAN, away from the general VLAN that is also available on the same port.

I also need prioritization for videoconferencing, and I would like it to work the same as the VOIP VLAN so that the codec (Polycom HDX) which sits on a mobile cart, can plug into any network jack and it just magically gets assigned a high priority VLAN.

It doesn't need higher prioritization of the phones, and the same priority as the phones is fine. Is there a way to have the codec use the phone VOIP VLAN, to make the Cisco building switch think it is a phone?

Would I need to put a mini Cisco switch or router on the cart with the codec, to have the building Cisco switch think it is a phone?

  • How many VoIP vlans do you have? If only one, you can configure your Polycom to use the voice vlan.
    – Ron Trunk
    Commented Dec 2, 2017 at 2:02
  • There is only the one VLAN. I will look through the Polycom docs to see if I can find this. Commented Dec 2, 2017 at 2:37
  • 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 can provide and accept your own answer.
    – Ron Maupin
    Commented Feb 19, 2018 at 20:20

1 Answer 1


A Cisco switch uses the Cisco-proprietary CDP to identify a Cisco phone connected to a switch interface. You will have both the access and VoIP VLANs configured on a switch interface, and the Cisco switch and Cisco phone will use CDP to negotiate a trunk on an access interface.

Non-Cisco phones may use LLDP for this. You will need to see if your non-Cisco equipment can do this, and if it can, you will need to enable LLDP globally on the switch and on each switch interface.

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