Ad-hoc network has opened a new dimension in wireless networks. It allows wireless nodes to communicate with each other in the absence of centralised support. It does not follow any fixed infrastructure because of the mobility of nodes and multi-path propagations. Link instability and node mobility make routing a core issue in MANETs. A suitable and effective routing mechanism helps to extend the successful deployment of MANETs. In this thesis, we have studied details of TORA, LDR and ZRP routing protocols which are routing protocols on use in MANET. The effects on the routing efficiencies with a special focus on the pause time, scalability and node density using throughput, network load, end-to-end delay and packet delivery ratio as indices of performance evaluation for FTP traffic were observed by using OPNET 14.0 modular as simulation tool. Based on our observations from literature and empirical study conducted using OPNET, we have found that among the three protocols, no single protocol can successfully provide optimum efficiency in different MANET scenarios.