Vehicle-mounted control device, ethernet switch and device setting method

A vehicle-mounted control device to be mounted in a vehicle, includes: an acquisition unit configured to acquire calculation information to be used to calculate a setting change timing of a vehicle-mounted network from an electronic device in the vehicle-mounted network; a calculation unit configured to calculate the setting change timing based on the calculation information acquired by the acquisition unit; and a control unit configured to perform processing for executing a setting change of the vehicle-mounted network at the setting change timing calculated by the calculation unit, wherein the calculation information includes at least one of a topology of the vehicle-mounted network, a service of a system to which the electronic device belongs, a travel state of the vehicle, and a power supply state of the vehicle.