Next Generation Hotspot (NGH) is being introduced as a new standard that brings higher security and usability to Public Wireless LANs. There has been progress in recent years toward connecting some Roaming Consortia (RCs) by NGH to develop large-scale Wireless LAN roaming systems. However, a communication routing problem has been identified in the identity federation network when an RC consisting of multiple operators is connected. A typical example is eduroam, the roaming system for research and education institutions, which has thousands of different realms. It is hard for wireless Service Providers (SPs) to find which RC the authentication requests should be sent to without having a large realm-RC mapping list. In addition, introducing a new system for realm list exchanges among the operators is not easy as some RCs have difficulties in modifying their existing systems due to operational constraints. To deal with these problems, we developed a Hub Proxy with automatic RC discovery and routing features. In this study, the effectiveness of the system was confirmed through experiments using a virtual inter-federation roaming network.