Configure DHCP to Exclude MAC range

if you are using different DHCP server. Could you not seperate the VOIP completely have it physically on a different network? that way it will improve your network as well as working on DHCP.

If you cant do that you could probably set vendor classes on your DHCP server for your PC's and exclude the IP range the other DHCP server is leasing.

Both DHCP servers need to be aware of the ranges and exclude the range you dont want them to lease.

ie
server 1 scope 192.168.0.1 - 192.168.1.254 - Exclude 192.168.1.0 - 192.168.1.254
server 2 scope 192.168.0.1 - 192.168.1.254 - Exclude 192.168.0.1 - 192.168.0.254

Our PBX has 2 nics, one for the voice lan 192.168.1.1 and one the binds to the data lan, 10.1.15.1, for inbound/outbound access via the internet. These lans are physically separated (separate switches) with the exception of that 2nd nic that binds to the 10. network. This server is managed by an outside vendor.

At some point the lans were bridged, or some other configuration changed, and all devices on the network would communicate with the data DHCP on the 10. network 1st. While I continue to sniff that out, I'd like to exclude these voice devices (with MAC's that start with '004') from receiving assignments form the 10. DHCP server and just communicate with the 192. DHCP server. Right now I have to down the data DHCP server every time a phone has to be restarted (so the 192. DHCP server hands out the ip/etc.).