An access network system connected to an ISP network including a subscriber authentication server comprised of a plurality of packet forwarding apparatuses each for connecting user terminals to an Internet network via the ISP network and an address pool management server having an address pool management table for holding, as a sub-address pool, a plurality of IP addresses usable over the ISP network. Each of the packet forwarding apparatuses acquires from the address pool management server an IP address to be allocated to the user terminal having requested connection to the Internet when the subscriber authentication server has succeeded in authentication of the user terminal.