Mobile Ad-hoc Networks (MANETs) are decentralized, multi-hop networks where the intermediate nodes acts like routers to pass data packets to destination. Routing protocols play an important role in the efficiency of MANETs due to mobility and dynamically changing of topology. Most of the routing protocols are vulnerable to attacks due to broadcast nature of wireless medium and lack of central control. AODV is a very popular routing protocol which is vulnerable to Black Hole attacks. In Black Hole attack a mobile node falsely advertises the route and sinks the data packets instead of forwarding to destination. There is a discussion in this Book on Black Hole attack and its step wise procedure and sequence of AODV routing messages. In last we have proposed an enhancement in AODV to identify and mitigate the black hole attacks. Results show that our proposed solution brings not only reliability but also achieve performance gain in term of network capacity.