Passing Voice VLAN through IP Phone

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Jul 26th, 2010
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Dear Support Community,

We have some users with 2 IP Phone sets cascaded together through one network point like the following:

PC --> 7911 --> 7962 --> network point

While all are working fine, the 7911 does not see the voice vlan and is instead using the data vlan. This has so far resulted in Call Manager not being able to properly manage the 7911 (e.g. timezone not enforced).

Appreciate if anyone could let me know how to let the 7911 subscribe through the voice vlan.


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Ashley Georgeson Mon, 07/26/2010 - 22:47
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This is something I have never tried but don't think is possible.  The phone connected to a switch should negotiate the Voice/Aux Vlan with the switch via CDP.  The host port of the phone should then pickup the native Vlan.

You could try amending the native Vlan of the switch port maybe:


interface fastethernet0/1

     switchport trunk native vlan 1

     switchport voice vlan 1

but I don't know if IOS will allow this combination.

If your requirement for this configuration is cabling constraints, you could try one of these:

Kind regards, Ash.

Phillip Ratliff Tue, 07/27/2010 - 06:56
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  • Cisco Employee,

In CUCM does the 7962 have "PC Voice VLAN Access" enabled?  This is required for the voice vlan to be accessible by devices on the PC port of the phone.  You may also want to enable "Span to PC Port" on the 7962 to try and let it forward CDP from the switch out to the 7911 so that phone can set it's vlan tags appropriately.

That said, the phones may not actually forward switch CDP out the span port and this configuration is not supported.  You may have end up setting the port up as a trunk with the voice vlan as native (no 'switchport voice vlan' so the voice traffic is untagged) and set up the PC's nic to tag it's traffic in the data vlan.   If this doesn't work then you may just need a straight access port in the voice vlan, which of course will put the PC onto the voice vlan.



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