A control unit included in an information processing system determines, on the basis of information indicative of interface units and path information indicative of communication paths through a plurality of relay apparatus, whether or not the number of communication paths for access from the interface units to a node is greater than the number of the interface units. When the number of the communication paths is greater than the number of the interface units, the control unit controls the plurality of relay apparatus so as to block a part of the communication paths.