Voice VLAN

Unanswered Question
May 17th, 2008
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I wanna clarify few things on the voice vlan;

1) I am going to use 1000+ phones on my new work and my current configuration is;

interface GigabitEthernet0/1

description PHONE D104

switchport trunk encapsulation dot1q

switchport trunk native vlan 4

switchport mode trunk

speed 100

duplex full.

The native VLAN is for the PC. But is it a good configuration. Now i am planning to put voice vlan.

Which configuration will be good, trunk or voice.

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Overall Rating: 5 (1 ratings)
mahmoodmkl Sat, 05/17/2008 - 22:01
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i think it will be good to define seprate vlans for both data and voice.And in u r above config u havent defined the voice vlan.

intergace gig/0/1

switchport mode access

switchport access vlan 4

switchport voice vlan 10

spanning-tree portfast



drnteam Sat, 05/17/2008 - 22:14
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Thanks mahmood,

My current setup is not having a voice VLAN as it is configuring on the phone. (specifying the vlan on phone).

But now i am planning to put the voice vlan, does a mls qos is necessary for IP phones.

Justin Brenton Sun, 05/18/2008 - 14:08
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Hi Drnteam,

You should definately use Voice vlan's. If you don't you will most likely have voice quality issue's.


Just add this to your config on your interfaces if you are using Cisco IP Phones.

Make note of the prompt #.

Config#mls qos

interface FastEthernet1/0/4

description IP Phone/Data Port

switchport access vlan xx

switchport mode access

switchport voice vlan xx

mls qos trust device cisco-phone

mls qos trust cos

auto qos voip cisco-phone

spanning-tree portfast

spanning-tree bpduguard enable

HTH, Please rate


Justin Brenton


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