Numerous studies have shown the difficulty for a routing protocol to scale to large mobile ad hoc networks. A scheme called a cluster-based multipath dynamic source routing (CMDSR) in MANET is proposed, which is designed to be adaptive according to network dynamics. It uses the hierarchy to perform route discovery and distributes traffic among diverse multiple paths. The CMDSR is based on a 2-level hierarchical scheme: the 1-cell cluster and 2-server cluster. The main idea of the proposition is to transfer the route discovery procedure to the 1-server level to prevent the network flooding due to the DSR route discovery. Thus, route discovery does not require flooding mechanism and the overhead is minimized, thus improving the network scalability. Furthermore, the CMDSR solves reliability problem by selectively choosing more reliable paths and by providing end-to-end QoS soft guarantees. By implementing the algorithm in the OPNET environment, the results show that the CMDSR can balance the load of the network and deals with the frequent change of the network topology effectively, thus improving the reliability and robustness of the network efficiently.