—There are increasing interest and big challenge in designing a scalable and robust multicast routing protocol in a mobile ad hoc network (MANET) due to the difficulty in group membership management, multicast packet forwarding and the maintenance of multicast structure over the dynamic network topology for a large group size or network size. In this paper, we propose a novel Robust and Scalable Geographic Multicast Protocol (RSGM). Several virtual architectures are used in the protocol without need of maintaining state information for more robust and scalable membership management and packet forwarding in the presence of high network dynamics due to unstable wireless channels and node movements. Specifically, scalable and efficient group membership management is performed through a virtual-zone-based structure, and the location service for group members is integrated with the membership management. Both the control messages and data packets are forwarded along efficient tree-lik...