A private network device such as a security device is inserted in a private network using ARP spoofing, which includes sending periodic ARP packets from the private network device to a router and to client devices to ensure the private network device spoofing remains intact. The private network device determines when at least one of the one or more private network devices is inactive, such as by monitoring the network for activity between the devices and a router, and suspends sending the periodic ARP packets to the client devices when they are inactive.