The purpose of the present application is to provide a technique for the exchange of path information between different routing domains, which, while reducing the exchange of useless path information in the stage for constructing a hierarchical structure, can maintain robustness of path recognition that tolerates network partition. Of the management communication node identifiers which are described in hierarchical information included in a path control message received from a neighboring communication node and in hierarchical information held by the local communication node and which indicate a communication node that manages each level of the hierarchicalized network structure, the identifier indicating the highest level communication node and the identifier indicating the transmission source communication node are used to identify whether the routing domain to which the aforementioned neighboring communication node belongs is the same as the routing domain of the local communication node, and if the routing domain to which the aforementioned neighboring communication node belongs is different from the routing domain of the local communication node, the path information held by the local communication node is made known.