Voice Vlan

[mskaelita]

Gents, could you please explain, what does mean voice vlan?

My the existing configuraton: all pc and voip phones are located in vlan 2 in the same subnet.

Questions:

1. Should it be the separated vlan (vlan 7)?

2. Or it can be the same vlan (vlan 2), but voip ports will have better QoS (TOS and COS =5) ?

Is there need the config commands switchport voice vlan bla-bla-bla for that?

Please provide example how do it.

3. How should be configured switch port, if I decide to use the separated vlan (vlan 7) for voice traffic (pc located in vlan 2) ?

Example of port's config:

interface GigabitEthernet2/0/22

switchport mode access

switchport access vlan 2

switchport voice vlan 7

i.e. pc traffic is untagged, voice traffic is tagged with vid=7.

Is it correct?

Can it be vice versa?

ps. I understand, if I will use the separated vlan for voice traffic (vid=7), it will be another subnet for voip phones.

pps. Sorry for silly questions.

Thanks.

[ankbhasi]

Hi Friend,

When you connect ip phone to a switch and a pc to your ip phone the recommended configuration is always to use voice vlan and its exactly what you mentioned.

switchport mode access

switchport access vlan 2

switchport voice vlan 7

In this scenario an internal trunk link is formed which will carry vlan 7 as tagged traffic with cos value of 5 and because we have configured switchport mode access so all pc traffic in vlan 2 will be untagged.

So answering yoru quesitons now

1) It should always be seperated by some other vlan that normal data vlan.

2) It should never be same vlan and once voice vlan is configured it will set the cos value to 5

3) The config you mentioned it perfectly fine.

You should never go for vice versa as it is very less desirable to give higher priority to data vlan compared to voice vlan.

Have a look at this link which will guide you more about the same

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12220se/3560scg/swvoip.htm

HTH

Ankur

*Pls rate all helpfull post

[mskaelita]

Thanks, Ankur, your answer is brilliant.

I've read this chapter, but this is not explain the main idea or design :)

There are some additional questions about global idea:

Can I define the voice vlan on all access ports/interfaces on the switch?

But it will works only with Cisco VoIP phones through CDP. If PC will be connected to this port, it will be in the data vlan 2, but voice vlan/qos will not work.

Is it possible to use in this way?

mls qos

mls qos trust device cisco-phone # on each access interface

Another question (theoretical): can I configure different QoS levels for different ports on the switch?

I.e. Gi1/1 has COS value 5, Gi1/2 has COS value 3. Both these ports are located in the same vlan 2.

Thanks.

[amit-singh]

Hi friend,

Please see the answers below:

** Can I define the voice vlan on all access ports/interfaces on the switch?

Yes, you can define it. For example

conf t

interface range fa 0/1-24

switchport voice vlan 10

**Is it possible to use in this way?

I really didnt understood your question but by default voice traffic will be given the high priority as compared to data.You have trust the device i.e IP phone when you connect it to the switchport.

**can I configure different QoS levels for different ports on the switch?

Yes, you can do that, but why do you want that? It will never be a good design to implement it which can bring some inconsistency over the network.Its better to have the same policy across your whole network.

HTH,Please rate if it does.

-amit singh