Security in Mobile Ad hoc NETworks (MANETs) is a critical issue. MANETs are vulnerable to different types of attacks. Many of the routing attacks have been identified at network layer such as black hole, worm hole, gray hole and byzantine attacks. Out of all these attacks, black hole is the most important attack which disrupts the network performance severely. Most of the researchers have analyzed the impact of black hole attacks using throughput, packet delivery ratio and delay however, they have not considered number of packets dropped, jitter and many other performance metrics.