How to get VOIP and Data DHCP Address

I work in an environment where we have several VLAN for both data and VOIP traffic. Unfortunately I don't have access to the switch to quickly determine which VLANs are assigned to each port.

I was hoping to use an arduino with an Ethernet shield and LCD as a DHCP probe to quickly determine which VLANs are assigned. Getting the data VLAN seems pretty straight forward as there is a sketch provided in the the Ethernet library that demonstrates this.

We use an Avaya switch and Avaya phones. Is there a way that I can program the arduino to mimic an Avaya phone when requesting an IP?

Does the Avaya phone speak Ethernet like a regular client (so it will be on whatever VLAN the switch port defaults to), or does it speak VTP (so it can negotiate which VLAN it will use)?

For the former, you can probably just use plain old DHCP with at most hardcoding a MAC address similar to a phone.

For the latter, I don't know of any Arduino libraries that can use the VLAN trunk protocol so you might have to roll your own. One thing you could do is sniff the packets between a real phone and the switch, then mimic them with your Arduino.

Good luck!