Voice VLAN


Say I have 4 router switchports, I configure three to be switchport access vlan 100 and one to be switchport voice vlan 100.

I plug in to the access port, not the voice one.

My phone are picking up IPs, the correct IPs I might add for vlan100, but voice traffic is not working.

Does the voice vlan command over-ride the access vlan command? There is no need for this to be configured as it is only voice on this set up, but nevertheless it is there.


  • ReibeReibe Member Posts: 56 ■■□□□□□□□□
    The access vlan and voice vlan just help certain devices like Cisco VoIP phones decide what vlan to go into. Access vlan 100 and voice vlan 100 are the same vlan. Phones typically (depending on vendor) pick up whatever the voice vlan is and the access vlan is passed through the phone (if it has a built-in switchport).

    An example would be if I have:
    Fa0/1 - Access VLAN 100
    Fa0/2 - Access VLAN 101, Voice VLAN 100.

    If PC-A was connected to Fa0/1, and Phone-A & PC-B are connected to Fa0/2 (PC-B connects through Phone-A). Then Phone-A and PC-A would be on the same vlan (100) and PC-B would be on vlan 101.
  • KelkinKelkin Member Posts: 261 ■■■□□□□□□□
    The Voice Vlan command doesnt over ride the access vlan command.. The switch uses it so if it detects a phone either by CDP or LLDP to use that vlan for voice not the data vlan.
  • Magic JohnsonMagic Johnson Member Posts: 414
    It was a misconfig in the office, I think.

    What happened was I had a netgear switch plugged in to Fa2 (switchport access vlan 100) and the phones were a dream. I plugged the cisco switch in to Fa3 (switchport access vlan 100) and none of them worked apart from the Polycom (which doesn't use CDP).

    The switch had CDP enabled, but the router had it disabled.

    I still can't work this out, but I enabled CDP and plugged the switch in to Fa0 (switchport voice vlan 100) and they started working. Was it enabling CDP that did it?
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