To provide a public radio Internet service system provided with an authentication system capable of connecting to the respective networks in a public radio Internet service in the different networks.

The networks 30,40 are provided with DHCP servers 33,43 to register an MAC address of a user terminal 11 necessary for the establishment of a communication between the network and the user terminal 11, and at the same time, to issue an IP address to the user terminal 11. An MAC address database server 51 for registering and sharing the MAC address of the user terminal 11 is provided between the mutual systems. When the user terminal 11 uses the public radio Internet service of the network, if the data stored in the DHCP server 33 or 34 and the data stored in the MAC address database server 51 are matched regarding the user terminal 11, the IP address can be acquired from the respective systems, and the public radio Internet service can be received even in the different networks.

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