An information system, comprising: a plurality of physical nodes adapted to hold control information defining an operation corresponding to characteristics of an input/output packet(s) and that perform processing on an input/output packet(s) according to said control information; a control server, comprising: a first storage unit; a second storage unit; and a virtual node emulation unit, wherein said first storage unit is adapted to store configuration information of a virtual network including a virtual node corresponding to at least one of said physical nodes, wherein the virtual network is configured by at least one of a layer 3 switch, L3SW, a firewall, FW, a load balancer, LB, and a layer 2 switch, L2SW; said second storage unit is adapted to stores virtual network identifying information identifying said virtual network from the characteristics of an input packet; said control server is adapted to identify a physical node corresponding to a virtual node included in a virtual network adapted to handle a packet having a characteristic in common with a packet received by said physical node based on a request from said physical node and adapted to update control information for each of said physical nodes; and said virtual node emulation unit is adapted to operate as a virtual node on said virtual network, adapted to receive a packet from said control server, and to output the processing result thereof to said control server, wherein said control server is adapted to identify a physical node for which said control information is updated, based on said processing result; wherein said virtual network configuration information of said first storage unit is configured to include a table that indicates a connection relation between nodes connected on said virtual network, and said virtual network identifying information of said second storage unit is configured to include a table that indicates an association between packet characteristic including an input/output physical node ID and input/output port ID and header information, and a virtual node and a virtual node interface in said virtual network. a plurality of physical nodes adapted to hold control information defining an operation corresponding to characteristics of an input/output packet(s) and that perform processing on an input/output packet(s) according to said control information; a control server, comprising: a first storage unit; a second storage unit; and a virtual node emulation unit, wherein a first storage unit; a second storage unit; and a virtual node emulation unit, wherein said first storage unit is adapted to store configuration information of a virtual network including a virtual node corresponding to at least one of said physical nodes, wherein the virtual network is configured by at least one of a layer 3 switch, L3SW, a firewall, FW, a load balancer, LB, and a layer 2 switch, L2SW; said second storage unit is adapted to stores virtual network identifying information identifying said virtual network from the characteristics of an input packet; said control server is adapted to identify a physical node corresponding to a virtual node included in a virtual network adapted to handle a packet having a characteristic in common with a packet received by said physical node based on a request from said physical node and adapted to update control information for each of said physical nodes; and said virtual node emulation unit is adapted to operate as a virtual node on said virtual network, adapted to receive a packet from said control server, and to output the processing result thereof to said control server, wherein said control server is adapted to identify a physical node for which said control information is updated, based on said processing result; wherein said virtual network configuration information of said first storage unit is configured to include a table that indicates a connection relation between nodes connected on said virtual network, and said virtual network identifying information of said second storage unit is configured to include a table that indicates an association between packet characteristic including an input/output physical node ID and input/output port ID and header information, and a virtual node and a virtual node interface in said virtual network.