A MANET (Mobile Ad hoc NETwork) is a network with the features of infrastructure-less, multi-hop, self-configuring, and distributed-routing, which are quite different from a traditional wired network. Since nodes in a MANET are free to move, causing the topology of the MANET to change frequently, a routing protocol able to accommodate the rapidly changed topology is required. The MANET routing protocols can be classified into three categories based on routing information update mechanism: (1) proactive/table-driven protocol (2) reactive/on-demand protocol (3) hybrid protocol. Every category has its own advantages and disadvantages. Among these, the hybrid protocol tries to combine the advantages of proactive and reactive ones. This work presents a novel hybrid routing protocol - CG2R (Core Gateway Relay Protocol). The CG2R partitions a network into several regions called zones. The proactive mechanism is used within the zone, while the reactive one is applied outside the zone. Each zone contains one core gateway; the core gateway constitutes the backbone of the routing path. Unlike conventional cluster-based routing protocols which require the algorithm of electing cluster head to get some value such as ID number or Weight to elect cluster heads, the node in CG2R can decide itself a core gateway or not by using the algorithm that we present. The core gateway covers more cells and manages more nodes than the others to reduce the cases of a node moving out the zone. Based on this feature, the backbone of the network can be formed by the gateway nodes. The simulation results reveal that CG2R is more scalable and efficient than CGSR and AODV protocols.