The present invention is to provide an ADSL modem for providing an IPoA, a PPPoA, or a PPPoE based dial-up networking service over Ethernet, which comprises a DHCP server coupled to at least one computer, each computer is adapted to use a DHCP provided by an OS thereof to obtain an authorized IP address and associated settings from an ISP through the DHCP server, and the DHCP server is adapted to assign the authorized IP address and the associated settings to each computer, enabling at least one computer to access the Internet without installing any driver or application program.