When calculating a forwarding path for a packet, a control apparatus determines a second node on the exit side of the packet forwarding path and an output port thereof. Next, the control apparatus sets in a second node located upstream of the first node on the packet forwarding path a packet handling operation for writing flow identification information associated with the output port in a packet header field not to be referred to when the first node forwards the packet and rewriting address information in the packet header such that the packet arrives at the second node on the exit side, and then causing the packet to be forwarded. A packet handling operation for causing the packet with the flow identification information given thereto to be transmitted from the port associated with the flow identification information is set in the second node on the exit side.