Voice VLAN and Native VLAN Tagging

[Craddockc]

Hello,

I needed some guidance/information on configuring Voice VLANs as well as their operation. I am currently implementing VLANs on the network at my job. From what I read you can configure both an access VLAN and a voice VLAN on the same switchport of a Cisco switch. However, all the literature I read on this subject always uses the terminology "native vlan" for the data traffic and "voice vlan" for the voice traffic. This has me a bit confused. Is this to say that if I have a PC and an IP phone hooked up to the same switchport that only the voice traffic will be tagged with the voice VLAN and the PC traffic must ride on the untagged native vlan? If so, this does not work for me. I would like to assign the PC traffic to a tagged VLAN so it gets the IP address range of the rest of the other PC's on that same segment that are not hooked up to IP phones. Or are all the PC's that are hooked up to IP phones acrossed the campus forced to ride on the same untagged native vlan? Below is a hypothetical config I would like to use, please let me know if this is possible:

Switch#(config-if) Switchport access VLAN 80 <-- (not the native vlan)

Switch#(config-if) switchport voice vlan 100

Also, I am using Toshiba IP phones, not Cisco. Does anyone know if these phones will behave the same way as a Cisco phone when I go to set up the Voice Vlans?

Thanks alot for any help you can provide!

Chris.

[paolo bevilacqua]

On a given port:

native vlan = access vlan = untagged.vlan

Other brand phones will likely not behave like cisco. You have to check with their maker how do they select voice vlan.

[Craddockc]

Paolo,

Thank you for your response. So in this instance the "native vlan" is the Access Vlan assigned to that switchport? From my understanding, when you assign a vlan to a specific switchport the traffic traversing that port gets tagged with a PVID indicating which vlan that traffic belongs to. Is this still true even when you assign a Voice vlan to the same port? Thanks.

Chris.

[paolo bevilacqua]

No. As above: 'assign vlan to a port' = access vlan = native vlan = untagged vlan.

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[Craddockc]

Paolo,

So if I understand you correctly. Access VLAN = Native VLAN = UNtagged VLAN only in the instance of assigning a voice vlan to the same switchport? Thanks.

[paolo bevilacqua · Accepted solution]

Not really. Voice VLAN (that I did not mentioned so far) is tagged, unless set same as access VLAN.

[Craddockc]

Paolo,

Please forgive my confusion, but I always understood that if you assign a switchport to a vlan (an access vlan), then that traffic traversing that switchport is considered "tagged." Only the "native vlan" (vlan 1 by default) is considered "untagged."

In the instance of using an access vlan and a voice vlan on the same port, does this behavior change? Is the "access vlan" now considered "native" and "untagged" because now the voice traffic is being tagged on the voice vlan? Thanks again!

Chris. 

[Ayodeji Okanlawon · Accepted solution]

Yes the answer is just as you described it. The native vlan is untagged. This is used for data vlan. The voice vlan is tagged.

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[Craddockc]

Thank you both for your responses. I was getting the term "tagged traffic" confused. I was thinking of the PVID and VVID assignments as "tagging" when you were referring to 802.1q tags. Thanks again!

[Ayodeji Okanlawon]

Yes I was going to add that its tagged with 802.1q. I assumed you knew that..Thanks for the nice rating and feel free to comeback if you need any more help.

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"'Nature is too thin a screen, the glory of the omnipresent God bursts through it everywhere"-Ralph Waldo Emerson