Mobile IP represents a simple and scalable global mobility solution but lacks support for fast handoff control and real-time location tracking found in cellular networks today. In contrast, third generation cellular systems offer seamless mobility support but are built on complex and costly connection-oriented networking infrastructure that lacks the inherent flexibility, robustness and scalability found in IP networks. Future wireless networks should be capable of combining the strengths of both approaches without inheriting their weaknesses. In this talk I will outline a new protocol called Cellular IP that we have implemented at Columbia University in collaboration with Ericsson Research, IBM and Intel. A demonstration of the Cellular IP testbed will be shown.