In this study, we have proposed a network layer protocol denoted ACRP(Auto-Configurated Routing Protocol) equipped with a function that automatically configures routing addresses and routing tables for a large-scale network system made up of multiple connected physical networks. The goals of the work presented in this paper are to enable adding and deleting physical networks during practical use and designing the protocol in such a way that the auto-configuration is finished within a few minutes. By simulating ACRP, we have succeeded in determining the algorithm structures for routing tables, protocol, that satisfies these requirements in a network with approximately 400,000 nodes. This work will contribute to the improvement of expandability and maintainability of control LANs for intelligent buildings, etc.