In the case of a system where a communication device is remote-controlled from a control server, depending on timing when an entry is written into a forwarding table of the communication device from the control server, there is a possibility that a loop and discard of the traffic occur. Therefore, for registration, rewriting and deletion of the entry of the forwarding table which are performed on the communication device 102 by the control server 101; the communication device 102 verifies contents of control instructions from the control server 101; the communication device 102 holds the result of this verification; the control server 101 acquires the result of the verification; the control server 101 judges whether or not a series of controls can be executed based on the results of the verification from the plurality of communication devices 102; and then the control server 101 invokes the execution at the plurality of communication devices 102.