Method for setting up fast initialization of cable modem

A method for setting up the fast initialization of a cable modem is provided to reduce the loss of resources by allowing a cable modem termination system to allocate only a predetermined length of request band to the cable modem. A method for setting up the fast initialization of a cable modem includes the steps of: transmitting a synchronization message to the cable modem(601), and receiving a ranging message from the cable modem(602); transmitting a ranging response message according as a bit requesting periodical band allocation is set in the received ranging message(603); allocating a first band for receiving a band allocation request message from the cable modem, and receiving the band allocation request message(606); allocating a second band requested by the received band allocation request message; and receiving a registration request message from the cable modem through the allocated second band, and transmitting a registration response message(612).