1. A filtering setting support device, comprising: an electronic computer device, which includes a processing unit and data storage having stored therein programming code readable by the processing unit, said processing unit, upon executing the programming code, causing the computer device to function as: a logical/physical mapping unit which generates mapping information expressing a path on a configuration of a network from a transmission source node to a destination node for each flow identifier by using a combination of a start node and an end node, based on access policy information which manages flow information composed of a combination of the transmission source node and the destination node included in the network with attaching the flow identifiers and based on physical configuration information of the node included in the network, a filtering point analysis unit which specifies the node in which a plurality of flows are intermingled as a filtering point based on a number of arcs, which is extracted from the mapping information, a common format rule generation unit which generates a common format rule to be set to the filtering point from the flow information including the filtering point, and a common format rule output unit which presents the common format rule to an administrator of the network.