The Software-Defined Network (SDN) paradigm suggests separating the control and data planes and using a centralized software-oriented management approach based on a central controller to facilitate network management and services, as well as the creation of new programs. This design concept paves the way for a more adaptable, quick, and dynamic software-controlled network. However, in terms of security, the SDN architecture presents several vulnerabilities that attackers can use to carry out malicious activities thus compromising the network and its services. Man-in-the-Middle (MITM) attacks, which exploit SDN vulnerabilities such as centralized intelligence and a lack of encryption in some communications, are among the most dangerous attacks that can be carried out on SDN networks. These attacks can cause disruptions in SDN operations by intercepting or altering control messages, subsequently degrading network performance. This paper demonstrates how an SDN network can be targeted by MITM attacks, namely Address Resolution Protocol (ARP) poisoning. The analysis revealed how the attack degrades the network’s performance, taking into account important performance metrics like round-trip time, throughput, packet loss, and jitter.