Cybersecurity testing in military contexts demands highly adaptable, scalable, and realistic testing environments capable of simulating both offensive and defensive cyber operations. Traditional testing methods often face limitations such as resource constraints, risks of disruption in live systems, and difficulty maintaining test fidelity. To overcome these challenges, this paper investigates the use of Docker containerization as a foundational technology for cybersecurity testing, emphasizing practical implementation and reproducibility. We present a flexible virtual network environment built using Docker, Python scripts, Open vSwitch, and the ONOS software-defined networking (SDN) controller. Our approach facilitates rapid deployment and dynamic reconfiguration of complex network topologies, enabling comprehensive simulation of cyberattacks and defensive measures. The results demonstrate significant advantages in terms of scalability, portability, reproducibility, and resource efficiency compared to traditional virtualized environments. Despite identified limitations related to shared kernel vulnerabilities and reduced realism for hardware-specific scenarios, these issues can be effectively mitigated through complementary security practices and integration with real-time simulation platforms. The study contributes to the ongoing discussion about advanced cybersecurity testing methodologies, reinforcing Docker’s potential as a key enabler of agile, safe, and realistic cyber experimentation, particularly within critical military applications.