Today's wireless access networks consist of several overlapping tiers. Provision of real time undisrupted communication to mobile users, anywhere and anytime through these heterogeneous overlay networks, is a challenging task. This paper presents a handoff technique for mobile devices equipped with dual mode interfaces. The proposed mobile-controlled handoff scheme reduces the service disruption time during both horizontal as well as vertical handoffs. We exploit the IP diversity created by the dual interfaces in the overlapping area by simultaneously connecting to different subnets or networks. Power saving is achieved by activating both interfaces only during the handoff period. The analysis shows that with proper network engineering the service disruption during handoff can be reduced significantly by exploiting the overlapping area between subnets. With more powerful network interfaces our proposal of dual interfaces can be realized.