A method of allowing a packet in a network image forming apparatus includes setting user account information corresponding to the plurality of network interfaces, determining allowability of a received packet by using information included in the received packet and the set user account information, and when the received packet is allowable, performing an operation corresponding to the received packet. Accordingly, in an image forming apparatus installing a plurality of network interfaces, not only allowability of each interface to each user but also a type of protocol provided to each user can be setup. Consequently, an environment that can use an interface in various forms according to each user can be provided.