Method of allocating IP address of image forming apparatus using DHCP, image forming apparatus and system of allocating IP address using DHCP

An image forming apparatus comprising:

• a storage unit to store an IP address previously allocated by a Dynamic Host Configuration Protocol (DHCP) server;
• a network interface to transmit/receive packets to/from the DHCP server used in IP address allocation through a network;
• and
• a controller to request the DHCP server to allocate an IP address through the network interface in response to the image forming apparatus being re-connected to the network, receive a packet to confirm whether the image forming apparatus is connected to the network from the DHCP server through the network interface, check an IP allocation mode set for the image forming apparatus, determine whether to respond to the response of the DHCP server according to the checked IP allocation mode, and receive the previously allocated IP address or a new IP address according to the checked IP allocation mode.

An IP allocation system using Dynamic Host Configuration Protocol (DHCP), comprising:

• an image forming apparatus to operate as a DHCP client;
• and
• a network managed by at least one DHCP server;
• wherein the at least one DHCP server allocates an IP address to at least one DHCP client comprising the image forming apparatus through the network using DHCP,
• the image forming apparatus comprises:
• a storage unit to store an IP address previously allocated by the at least one DHCP server,
• a network interface to transmit/receive packets to/from the at least one DHCP server used in IP allocation through the network, and
• a controller to request the at least one DHCP server to allocate the IP address through the network interface in response to the image forming apparatus being re-connected to the network, receive a packet to confirm whether the image forming apparatus is connected to the network from the at least one DHCP server through the network interface, check an IP allocation mode set for the image forming apparatus, determine whether to respond to the response of the DHCP server according to the checked IP allocation mode, and receive the previously allocated IP address or a new IP address according to the checked IP allocation mode;
• and
• the at least one DHCP server comprises:
• a server storage unit to store a range of IP addresses to be allocated to DHCP clients and a lease list including IP addresses that have been allocated to the DHCP clients and MAC addresses of the DHCP clients, which correspond to the IP addresses,
• a server network interface to transmit/receive packets to/from the DHCP clients used in IP allocation through the network, and
• a controller to receive the IP address allocation request from the image forming apparatus through the server network interface, transmit the packet to confirm whether the image forming apparatus is connected to the network to the image forming apparatus, read the previously allocated IP address of the image forming apparatus from the server storage unit and transmit the read previously allocated IP address to the image forming apparatus when a response is not received from the image forming apparatus, or transmit a new IP address to the image forming apparatus when a response is received from the image forming apparatus.