The underlying element that supports the device communication in the MANET is the wireless connection capability. Each node has the ability to communicate with other nodes via the creation of routing path. However, due to the fact that nodes in MANET are autonomous and the routing paths created are only based on current condition of the network, some of the paths are extremely instable. In light of these shortcomings, many research works emphasizes on the improvement of routing path algorithm. Regardless of the application the MANET can support, the MANET possesses unique characteristics, which enables mobile nodes to form dynamic communication irrespective the availability of a fixed network. However the inherent nature of MANET has led to nodes in MANET to be vulnerable to denied services. A typical Denial of Service (DoS) in MANET is the Black Hole attack, caused by a malicious node, or a set of nodes advertising false routing updates. Typically, the malicious nodes are difficult to be detected. Each node is equipped with a particular type of routing protocol and voluntarily participates in relaying the packets. However, some nodes may not be genuine and has been tampered to behave maliciously, which causes the Black Hole attack. Several on demand routing protocol e.g. Ad hoc On Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) are susceptible to such attack. In principle, the attack exploits the Route Request (RREQ) discovery operation and falsifies the sequence number and the shortest path information. The malicious nodes are able to utilize the loophole in the RREQ discovery process due to the absence of validation process. As a result, genuine RREQ packets are exploited and erroneously relayed to a false node(s). This paper highlights the effect Black Hole nodes to the network performance and therefore substantiates the previous work done . In this paper, several simulation experiments are iterated using NS-2, which employed various scenarios and traffic loads. The simulation results show the presence of Black Hole nodes in a network can substantially affects the packet delivery ratio and throughput by as much as 100%.