setting multiple scope DHCP Server on redhat.

hi, im trying to setup a small lab.. to learn about networking and, i have a voip call manager (cisco) im trying to set up a DHCP Server to serve three subnets. one for Voice, and other for DATA, the third is for future usage.

i want to enable tftp option 66 on the voice Vlan so that the phone can auto provision and get firmware and configuration file from my Call manager..

i tried searching but most results explain about doing it with dual LAN interfaces which.. i dont have..

can someone guide me with this..

Thanks