Methods and apparatuses are provided for communicating by a mobility management entity (MME) in a mobile communication system. A method includes receiving, from a target base station, a first message including a first network identification of a target node, in a connected state of a terminal; determining whether the first network identification differs from a second network identification of a source node, in an idle state of the terminal; and transmitting to the source node a second message requesting disconnection, if the first network identification differs from the second network identification of the source node.