A control apparatus includes: at least one memory configured to store instructions; and at least one processor configured to execute the instructions to: control communication in a vehicle by setting a control entry to a plurality of switches relaying, by referring to the control entry, a packet input to and output from an ECU installed in the vehicle, and perform an authentication processing for a device attempting communication with the ECU via any one of the plurality of switches. The control sets, to the switch, a temporary control entry realizing the communication between the device and ECU when authentication of the device is successful.