The IETF MANET working group mandate was to standardise IP routing protocols in MANETs. The RFC 2501 specifies the charter for the working group. The RFCs still has unanswered questions concerning either implementation or deployment of the protocols. Nevertheless, the working group identifies the proposed algorithms as a trial technology. Aggressive research in this area has continued since then, with prominent studies on routing protocols such as AODV, DSR, TORA and OLSR. Several studies have been done on the performance evaluation of routing protocols using different evaluation methods. Different methods and simulation environments give different results and consequently, there is need to broaden the spectrum to account for effects not taken into consideration in a particular environment. In this project, we evaluate the performance of AODV, OLSR, DSR and TORA ad hoc routing protocols in OPNET. We simulate a Mobile ad hoc network with all nodes in the network receiving FTP traffic from a common source (FTP server). In this way, the results of this analysis would also represent a situation where the MANET receives traffic from another network via a common gateway. In addition, the mobile nodes were randomly placed in the network to provide the possibility of multihop routes from a node to the server. The performance of these routing protocols is evaluated with respect to routing overhead, throughput, end-to-end delay and packet delivery ratio. In this study, results show that OLSR floods the network with the highest amount of routing traffic followed by TORA, AODV and DSR. All the protocols exhibit a low packet delivery ratio of maximum 59%. This degradation is expected due to huge retransmissions in the network because of using TCP traffic. OLSR outperforms AODV, DSR and TORA in terms of end-to-end delay and throughput. Varying traffic volumes or speeds in the network, leaves OLSR superior in terms of end-to-end delay and throughput. OLSR build and maintains consistent paths resulting in low delay. The results in this study also confirm TORA’s inability to handle rapid increases in traffic volumes. TORA performs well in networks where the volume of traffic increases gradually.