A network management system includes a plurality of server units. A first management server included in a first server unit transmits a disconnection setting request for disconnecting an abnormal flow to each of a communication node connected to a self-region covered by the first management server, and one or more second server units covering one or more primary adjacent regions adjacent to the self-region. Disconnection setting is executed in response to the disconnection setting request. Each of a plurality of regions includes two or more areas each of which is covered by corresponding one of two or more base stations connected to an identical communication node.