Various applications used by mobile users today need seamless connectivity for providing a good quality user experience. Enterprise Wireless Local Area Network (WLAN) is one of the technologies used by mobile devices to connect to the Internet in several environments. For providing seamless connectivity and communication, mobility management becomes an important aspect of such deployments. In this paper, we propose a client-unaware handover process for NAT (Network Address Translation) operation mode of the access points in a Software Defined Networking (SDN) based enterprise WLAN framework. The proposed mechanism has been implemented in simulation and the results show that the proposed mobility management mechanism is able to achieve seamless handover and provide uninterrupted connectivity and communication to the mobile devices.