Method of performing image forming operation using user information and image forming apparatus for performing the method

An image forming apparatus comprising:

• a local panel unit to receive domain information used for user authentication and a request for an image forming operation;
• a Web user interface (UI) unit to set an external authentication server used for the user authentication and an external lightweight directory access protocol (LDAP) server for acquiring user information;
• a communication unit to perform the user authentication by communicating with the authentication server and acquiring the user information by querying the external LDAP server;
• a control unit to allow the communication unit to query the external LDAP server by using the domain information used for user authentication;
• and
• an image processing unit to perform the image forming operation by using the acquired user information.