A communication apparatus includes an acquisition unit, an instruction accepting unit, a generating unit, and a data transmitting unit. The acquisition unit acquires a transmission-source port number which indicates a transmission source of data and which is determined every time transmission of data is to be performed. The instruction accepting unit accepts an instruction which is an instruction to transmit data via a first communication network or an instruction to transmit data via a second communication network. When the accepted instruction is an instruction to transmit data via the second communication network, the generating unit generates data including the acquired transmission-source port number. The data transmitting unit transmits the generated data via a communication control apparatus connected to the first and second communication networks. The communication control apparatus performs routing so that a route via the first or second communication network is selected for the transmitted data.