A method and system for network address maintenance in a data-over-cable system. The method includes determining whether a network device, such as a cable modem, responds to a request in a timely manner. When updating network address tables, such as Address Resolution Protocol tables, an Internet Control Message Protocol (“ICMP”) echo message is generated and sent to the Internet Protocol (“IP”) address of a network device. If an ICMP echo reply message is not detected within a pre-determined time, the network address is deleted from the network address table. The deletion of the network address ensures that the device is isolated from the network. The method and system provide for the rapid removal of stale network addresses, freeing valuable memory space, and increasing security in a data-over-cable system.