We propose a simple and practical solution, called the Virtual Interface-based aPproach (VIP), for seamless vertical handover in single-subnet networks. VIP combines a virtual interface and ARP update messages to achieve vertical handovers, and can run stand-alone without modification of existing network protocols or installation of additional servers. Therefore, it is ready for immediate realworld deployment. Using testbed experiments, we evaluate VIP by observing TCP (FTP downloading) behavior in various vertical handover scenarios. The results show that the proposed approach can successfully maintain an application's connectivity in all test cases. Furthermore, the results show that handover from a low capacity link to a high capacity link does not cause service latency; however, during handover from a high capacity link to a lower capacity link, non-negligible latency can not be alleviated unless early handover notification is provided.