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Abstract — Adhoc Networks (MANETs) are an emerging area of mobile computing. There are various challenges that are faced in adhoc environment. These are mostly due to the resource poorness of these networks. They are usually set up in situations of emergency, for temporary operations or simply if there are no resources to set up elaborate networks. Adhoc networks therefore throw up new requirements and problems in all areas of networking. The solutions for conventional networks are usually not sufficient to provide efficient adhoc operations. The wireless nature of communication and lack of any security infrastructure raise several security problems. With little protection against tampering, nodes are susceptible to compromise. Thus the networks are vulnerable to DOS attacks through compromised nodes or intruders. Many denial of service type of attacks are possible in the MANET and one of these type attacks is flooding attack in which malicious node sends the useless packets to consume the valuable network resources. Flooding attack is possible in all most all on demand routing protocol. Thus the paper introduces an opportunistic routing technique to forgo this instant attack. The opportunistic routing takes into account the relative velocity rather than the distance between nodes