A method for obtaining and utilizing internet protocol (IP) subnet information, the method may include obtaining by a layer two cable modem termination system (L2 CMTS) information about IP subnets that comprise DHCP leased IP addresses assigned to devices serviced by the L2 CMTS; and maintaining, by the L2 CMTS and based on the information about the IP subnets, a data structure that reflects the IP subnets that comprise the IP addresses that are allocated to the devices serviced by the L2 CMTS.