This paper has developed a new MAMIP to provide an efficient interoperation mechanism of mobile ad hoc network and mobile IP network. We propose a new clustering mechanism based on the FA. Since the new clustering mechanism uses a periodic agent advertisement message, it can handle a dynamic network topology efficiently. The FA manages mobile nodes in a unit of cluster and provides an access to the internet and the mobility services of Mobile IP to them. For this, we modified existing messages of mobile IP such as an agent advertisement message, registration request message. We can reduce a message overhead in ad hoc network since we use messages of mobile IP to find a path to the destination. Also, because the FA manages a cluster of limited scope, we can reduce a service delay and overhead of FA regardless of the number of visiting nodes significantly. By the simulation, we compared the proposed scheme with an existing scheme under the average service delay and FA overhead. Simulation results demonstrated that our scheme, MAMIP shows the better performance than the existing scheme, MIPMANET.