Have DHCP use different scopes based on MAC address using Server 2012
Solution 1:
I believe this is possible according to this article. You can set allow/deny filters for the scopes within DHCP. The article is for 2008R2, but I don't see why it wouldn't also be available in 2012.
Solution 2:
There is a second way if your network supports vlans. It can get a bit complicated, but basically the phone asks for an address, notes the vlanid tag & re-asks DHCP for an ip address but this time using the specified vlan. This request then gets an IP address in the new range. It remembers the config, so all future requests (until the phone thinks it has to start again) will be using the new vlan. Here's the full article from ShoreTel https://www.shoretel.com/sites/default/files/ShoreTel%20Premises%20Services%20Data%20Network%20Best%20Practices.pdf