mpthrill provisioning server

Hi,

Hope you can help or you can provide me some enlightenment about my project.

Currently we are using mpthrill to provisioned modem and cpe ip however we want to segregate networks for cpe ip based on service class for example

modem ip pool: 172.16.0.0/21
cpe pool 1:192.168.0.0/24
cpe pool 2:192.168.1.0/24
cpe pool 3:192.168.2.0/24
cpe pool 4:192.168.3.0/24

ubr config
interface Cable3/0
ip address 192.168.0.1 255.255.255.0 secondary
ip address 192.168.1.1 255.255.255.0 secondary
ip address 192.168.2.1 255.255.255.0 secondary
ip address 192.168.3.1 255.255.255.0 secondary
ip address 172.16.0.0/21 255.255.248.0
------
-----
cable source-verify
cable dhcp-giaddr primary
cable helper-address 10.10.10.1

Any idea how to achieve the segregation ?
Thanks,
GIman