Voice VLAN Question

Answered Question

I have a user port configured for voice and data as follows:


interface FastEthernet0/10

switchport access vlan 100

switchport voice vlan 101

spanning-tree portfast

end


However, the users phone doesn't seem to come up on vlan 101. The user's data vlan works fine but the phone doesn't. When I look at the mac address table for the interface I also only see a mac associated with the data vlan but not the voice vlan. Any ideas??

Correct Answer by Edison Ortiz about 9 years 4 months ago

What type of phones ? Some phones do not recognize the concept of the voice vlan.


They come up on the data vlan, arp for an address from DHCP. DHCP supplies the address along with an option with some additional information such as TFTP server and QoS settings.


Once they obtain that information, they reboot again and run on the Vlan provided in the DHCP packet.


On this case, you would have to configure the switchport as trunk with native Vlan being the data Vlan.


interface f0/0

sw en trunk dot1q

sw mo tr

sw tr native vlan 100

sw tr allo vla 100, 101


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Correct Answer
Edison Ortiz Tue, 12/11/2007 - 11:13
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What type of phones ? Some phones do not recognize the concept of the voice vlan.


They come up on the data vlan, arp for an address from DHCP. DHCP supplies the address along with an option with some additional information such as TFTP server and QoS settings.


Once they obtain that information, they reboot again and run on the Vlan provided in the DHCP packet.


On this case, you would have to configure the switchport as trunk with native Vlan being the data Vlan.


interface f0/0

sw en trunk dot1q

sw mo tr

sw tr native vlan 100

sw tr allo vla 100, 101


Edison Ortiz Wed, 12/12/2007 - 16:12
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Those VoIP phones understand the concept of voice vlans at the switchport. You may need to configure your DHCP properties. Best to ask in the Unified Communications forum.

juan-ruiz Tue, 12/11/2007 - 11:17
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I'm going to assume you are running 802.1q as the trunking protocol. configure this port as a trunk port and pass vlans 100, and 101 if you are passing selective vlans or leave the defaults which pass all the vlans.


Are you using DHCP for voice and data vlans?

Make sure to issue the ip helper for your dhcp server on each vlan interface 100, 101


allan.thomas Wed, 12/12/2007 - 16:18
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A few aspects which you could initially verify via the phone:-


1. Within the network settings has the phone negotiated the correct Voice VLAN ID?


2. Has the Phone obtained a DHCP address, and default gateway? Are you able to ping this address?


If the phone has obtained the above, then the next step would be for the phone to obtain it's configuration through the TFTP option 150 specified in your DHCP scope.


Again you can verify whether the phone has TFTP server through the network settings on the phone.


Incidentally, what is the status of the phone? Does the display mention 'Configuring IP' or 'Registration Failed'?


If the message is referring to the first then this IP connectivity, and you would need to verify reachability, dhcp scope, dhcp forwarding on the gateway(s) etc.


The other refers to the CallManager IP Phone device configuration.


Regards

Allan.

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