A method and system for managing addresses of network host interfaces in a data-over-cable system such as Internet Protocol interfaces. The method allows network host interfaces addresses to be removed from routing tables on network devices such as cable modems or customer premise equipment when their lease expires. This helps prevent the data-over-cable system from exhausting available network host interface addresses of the data-over-cable system. In addition, the method helps ensure that transactions are not conducted on a network host interface address in the data-over-cable system unless it has a valid lease in the one or more routing tables on network devices.