Although there are quite a few open sources monitoring tools, choosing a tool can be challenging due to the variety of available options and their different levels of complexity. Many administrators must deal with the issue of finding and deploying a monitoring tool that is suited for their infrastructures needs. In this thesis, I compare two important open-source monitoring tools by analyzing and evaluating their main strengths and limitations. The tools are compared using the same resources as to demonstrate their user-friendliness, metrics performances like CPU and memory usage, cost and their ability of data visualization.  The work was structured into literature studies and practical phase whereby the relevant literature and work were reviewed and documented which helped in conducting and building the experimental environment. The performance metrics focused on in this thesis were system availability and uptime, CPU usage, memory and response time. The results obtained from these performance metrics helped in revealing the best tool depending on the organization's needs and requirements. The evaluation of results revealed that Icinga offers more functionalities making it more suitable for larger IT infrastructures with complex environment while Cacti demonstrated the ability to be more user friendly and easily deployed making it a safer choice for smaller enterprises that may lack specialized experts.