An inspection device includes a memory and a processor. The processor is coupled to the memory and configured to transmit, to a network, an inspection packet that includes a first address for which a plurality of transfer devices in a network does not learn correspondences between the first address and transfer destination devices. The first address is a transmission destination address. The inspection device receives a first packet from the network and determines whether the first packet matches the inspection packet. The inspection devices transmits, to the network, a setting packet of which a transmission source address is set to the first address.