CME phone fails to reg when voice and data vlan are same

Unanswered Question
Nov 6th, 2009


I have a phone that is trying to register to CME.

On the switch that connects the CME router and the phone, I had

switchport voice vlan 30

switchport mode access

switchport access vlan 30

The router could not ping the phone (statically assigned IP and VLAN set to 30)

The moment I changed the access vlan to 1, the phone registered..

The router could also ping the phone.

I cant seem to understand why having the voice and data vlans to be the same should cause an issue..

The phone had static IP address and network config along with static voice vlan 30.

My only guess is that when the voice and data vlans are the same on a switchport, it reverts from Trunk back to access, and does not send the dot1q header to the phone.

However, a

show int fa x/x switchport

either with both voice and data vlans being same or different does not show ay difference in the dot1q mode.

Any ideas ?

I have this problem too.
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Paolo Bevilacqua Fri, 11/06/2009 - 07:10

A vlan cannot be tagged and untagged at the same time. You configuration is confliticing.

So if you want the phone into access vlan, do not configure voice vlan altogether.

shahedvoicerite Fri, 11/06/2009 - 08:11

I tried various combinations, but I cannot get the phone and the pc plugged into the back of the phone to be on the same VLAN !!!

If I set it to trunk, and manually set the phone admin vlan to 30, the phone registers, but the pc does not.

shahedvoicerite Fri, 11/06/2009 - 08:25

Ok, I finally got it to work, by setting all the VLANs on the phone settings to 0.

Now my switchport is in simple access mode, with vlan 30.

The phone and the pc are in access mode too (I guess)



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