Is it possible to create 2 unique Cisco voice vlans on the same switch ports ?

[blaine.pullin]

Hi

I have a client who currently has a Cisco UCM in-house.  One Voice and one data VLAN are applied to each port on the switch stack.  There is a dhcp server in the 3750 supplying config data for the phones.

They are planning to migrate to a cloud-based Cisco UCM setup.  This will require my connecting a preconfigured ASA device to the switch stack.  The ASA will be supplying config data for the phones on their voice network.

The client wants to test this first with a couple of phones on the production network.  My problem is:  Is it possible to create a second voice vlan and assign it to all of the switch ports that the existing voice vlan is on ?  Will the creation of a second  voice vlan corrupt or change my existing voice vlan configs ?  I understand this would not be an issue if the two voice providers were different, such as Cisco and Avaya.  But this is going to be two unique Cisco voice networks on the same switch stack.

If I were to do a standard trunk, how would I differentiate between two Cisco networks?

Thank you in advance for your help.

Blaine Pullin

Atlanta, GA.

[Deven Gandhi]

If I am not mistaken, Switchport voice vlan xxx on switchport will replace your existing voice vlan on switchport.  You can create second voice vlan and apply it only to switchport you are testing with.  You will have to create SVI on switch hosting second voice vlan.  As long as your routing is correct, those test phones should reach appropriate destination.

-Deven Gandhi
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[Carlo Poggiarelli]

Hi Blaine,

Deven is correct (+5) you can define just one voice vlan per port.

Alternatively you can:

Configure a "classic " trunk on switch ports allowing different vlans but you have to manually define the desired voice vlan on each ip phone.

The other way ( depends on which ip phone model your customer owns)  you can disable through cucm LLDP support on all ip phones , configure LLDP on switch ports advertising the newly created Voice Vlan .

One you are ready  to migrate , disable cdp and enable lldp support on every ip phones, reset them so that they would be able to join the new vlan.

In this case you have a fast way back to the previous situation.

HTH

Regards

Carlo

[Ryan Huff]

You'll also want to consider, and be cautious of SBD (Security By Default). Its very likely that you'll need to manually remove the CTL/ITL trust list on the phone, in order to join the cloud-based solution. Additionally, to bring the phone back to the original cluster, you would need to perform the same process.

While not usually a significant concern to do manually with a few test phones that you have physical access to; performing a staged migration or a '1 and done cutover', I would advise becoming familiar with the "Cluster Rollback" or "Bulk Certificate" methods before executing any phone migrations lest you be in for some midnight pains ;).

Thanks,

Ryan

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