Route Cache Optimization Mechanism Using Smart Packets for On-demand Routing Procotol in MANET Normally, for an on-demand routing protocol in mobile ad hoc networks, the parameters that ought to be optimized include end-to-end delay and routing overhead. These parameters have a direct relationship with broken links and route discoveries, or in other words the staleness of the cache. In order to minimize the need for such a route discovery, the cache has to be constantly checked from time to time, stale cache entries has to be removed, and proper entries be added. In this paper, a novel approach to reduce this route cache problem is addressed. Hence, a control packet called the smart packet is used to traverse the network and collect the network information. This process is termed as Smart Packet based Dynamic Source Routing (DSR-SP). Once the information is collected, each node updates its route cache with the collected information. Based on the simulations results obtained, it is observed that invalid cache entries have considerably decreased with the advent of this packet, for low and medium density networks, at higher mobility.