How to configure Avaya IP Phones to use DHCP and VLAN

by ScanSource Catalyst Tech Support on February 21, 2011 · 6 comments

in ScanSource Catalyst,VOIP


Scenario: DHCP is needed to assign IP phones an IP address. The ports the phones will be plugged into will connect the IP phone and the PC, which will be plugged in to the back of the IP phone.

The switch will need to have 2 VLANs on it, one for voice and one for data. The port the phone is plugged into will need to be assigned to the data VLAN as untagged and the voice VLAN as tagged

The call server (IP phone system) will be plugged into a port assigned only to the voice VLAN. There will also need to be a DHCP server on the data VLAN and the voice VLAN.

For Avaya IP phones, there is a need to create a custom option in the DHCP server named SSON, the option number will be 176. The string value of this option is:


The VLAN is set by the L2QVLAN parameter. L2Q=1 enables VLAN tagging.

The option 176 will have to reside in the data VLAN DHCP server as well as the voice VLAN DHCP server. The reason is as follows: When a phone is plugged into the port that is untagged for data and tagged for voice it will speak on the untagged network. This is because the IP phone does not know what VLAN the voice resides on. If there is a DHCP server on the data VLAN that tells the phone (with option 176) to use the voice VLAN tag, the phone will accept this reboot and come up on the voice VLAN. At that time the IP phone will accept the DHCP offer from the voice VLAN DHCP server.

If there is not a DHCP server on the data VLAN, the IP phones will have to have the VLAN ID manually assigned. This can be done by pressing * when the phone is waiting for a DHCP offer; this is identified on the IP phone screen with DHCP # of seconds and * to program. Make certain the 802.1Q = Auto or on. Next set the VLAN ID= to the voice VLAN ID. VLANTEST can be left at default. When asked to save the new values say yes (#) and reboot.

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{ 6 comments… read them below or add one }

Mik Poussa August 4, 2011 at 4:24 pm

Hello, a good article!

How do you get round running the same IP500 as a DHCP server on both voice and data VLANs, albeit different IP address ranges?

We are migrating from a a flat LAN structure to a data and voice VLAN setup.

Kind Regards

Mik Poussa


Robert Brown October 10, 2011 at 8:05 am


The DHCP server will be put into the data switch as an IP-Helper address. You will need to add this to tell everything on the network where the DHCP server is. If you want to use 2 separate DHCP servers then you will have the IP Helper pointing to the DHCP server in the Data VLAN, and then in the Voice VLAN you will add the IP Helper to point to the phone system.

In some switches IP helper is also known as the DHCP-Relay Forwarding address.




Omar Fahnbulleh October 31, 2011 at 7:25 pm

I would even take the route of creating a third Vlan on my network and sperating my Voice Vlan, Data and the network the Call Server will be situated into. I will take this precaution in case there are any kind of networking issues on the Voice or Data Vlans.


Quan Nguyen July 23, 2012 at 2:58 am

“For Avaya IP phones, there is a need to create a custom option in the DHCP server named SSON, the option number will be 176. The string value of this option is:


The VLAN is set by the L2QVLAN parameter. L2Q=1 enables VLAN tagging.”

I wonder that: does this option must be configure when using Cisco switches.
Cause of, there is a command in Cisco that untag VLAN ID for voice VLAN: switchport voice vlan VLAN_voice_id

When I use the layer 3 Switch/Router as a DHCP server, I usually leave the configuration on switch port as below:

switchport mode access
switchport access vlan data_vlan_id
swtichport voice vlan voice_vlan_id

And after that, I can use Avaya phone with PC attached in this port.


Darrell January 21, 2013 at 12:08 pm

the IP phone will bootp on the untagged vlan and get a data DHCP address. From there he is provided the Voip vlan and releases the data IP address. So, the first IP is subject to the lease period of the Data dhcp? We are planning to deploy 500 phones over 2 days – will 500 data ip be locked up according to the lease of that scope?


Renat January 25, 2013 at 6:42 am

IP phone releases address gotten from DHCP


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