Reserved IP addresses (via DHCP)

I want to be able to setup reserved IP addresses for all of my network devices via DHCP/MAC address. The Arris modem that I currently have (TG2472) only allows me to enable/disable devices by MAC address, not assign an address. Is there a Cox modem that has this feature? If not, can someone point me to one that does? I'm running a Cox land-line and 300 MPS.