Provided is a method of defining an interface identifier (IID) of an Internet Protocol version 6 (IPv6) address and devices operating the same, wherein the method includes defining a first IID and a second IID in an IID based on a predetermined value at a predetermined location in the IID of an IPv6 address, assigning, based on an node identification (ID), a first node ID to the first IID and a second node ID to the second IID; and assigning information on a network connecting condition of a communication device to at least one of a first sub-IID corresponding to an area excluding the first node ID in the first IID and a second sub-IID corresponding to an area excluding the second node ID in the second IID.