A car integrated management system has a plurality of communication apparatuses, each including: an extraction unit to extract entries from a table; an address unit to generate a destination address of a packet, using information to identify a subnet connected to each of the communication apparatuses, and to generate a next hop address that indicates an address of a transfer destination to which the packet is to be transferred, using information to identify each of the communication apparatuses, the subnet identification information and the communication apparatus identification information being included in entry extracted by the extraction unit; an acquisition unit to acquire information about an IP port to be used for sending the packet to a communication apparatus at the next hop address; and an entry addition unit to add information about the destination address, the next hop address, and the IP port to a routing table.