A communication apparatus for a car integrated management system that includes a plurality of communication apparatuses which are connected to each other, the communication apparatus comprising: an entry extraction unit configured to extract information of each entry from a train network directory table; an address generation unit configured to generate, with reference to a network address translation unit of the communication apparatus: a destination address as a delivery destination of a packet, by use of subnet identification information for identifying a subnet connected to each of the communication apparatuses among information of entry extracted by the entry extraction unit; and a next hop address that indicates an address of a transfer destination communication apparatus to which the packet is to be transferred from its own apparatus, by use of communication apparatus identification information for identifying each of the communication apparatuses, wherein the subnet identification information and the communication apparatus identification information are included in entry information extracted by the entry extraction unit; an internet protocol port information acquisition unit configured to acquire information about an internet protocol port to be used for sending the packet to a communication apparatus at the next hop address; and an entry addition unit configured to add information about the destination address, the next hop address, and the internet protocol port to a routing table. an entry extraction unit configured to extract information of each entry from a train network directory table; an address generation unit configured to generate, with reference to a network address translation unit of the communication apparatus: a destination address as a delivery destination of a packet, by use of subnet identification information for identifying a subnet connected to each of the communication apparatuses among information of entry extracted by the entry extraction unit; and a next hop address that indicates an address of a transfer destination communication apparatus to which the packet is to be transferred from its own apparatus, by use of communication apparatus identification information for identifying each of the communication apparatuses, wherein the subnet identification information and the communication apparatus identification information are included in entry information extracted by the entry extraction unit; a destination address as a delivery destination of a packet, by use of subnet identification information for identifying a subnet connected to each of the communication apparatuses among information of entry extracted by the entry extraction unit; and a next hop address that indicates an address of a transfer destination communication apparatus to which the packet is to be transferred from its own apparatus, by use of communication apparatus identification information for identifying each of the communication apparatuses, wherein the subnet identification information and the communication apparatus identification information are included in entry information extracted by the entry extraction unit; an internet protocol port information acquisition unit configured to acquire information about an internet protocol port to be used for sending the packet to a communication apparatus at the next hop address; and an entry addition unit configured to add information about the destination address, the next hop address, and the internet protocol port to a routing table.