Given the urgency of standardizing the 5th generation mobile systems (5G) to meet the ever more stringent demands of new applications, the importance of field trials and experimentation cannot be overstated. Practical experimentation with cellular networks has been historically reserved exclusively to operators, primarily due to equipment costs and licensing constraints. The state of play is changing with the advent of open-source cellular stacks based on increasingly more affordable software defined radio (SDR) systems. Comprehensive understanding of the performance, limitations, and interoperability of these tools however lacks. In this article we fill this gap, by assessing by means of controlled experiments the performance of today’s most popular open software Evolved Node B (eNB) solutions in combination with different commodity User Equipment (UE) and an SDR alternative, over a range of practical settings. Although these cannot underpin complete 5G systems yet, their development is progressing rapidly and researchers have employed them for 5G specific applications including LTE unlicensed and network slicing. We further shed light onto the perils of open tools and give configuration guidelines that can be used to deploy these solutions effectively. Our results quantify the throughput attainable with each stack, their resource consumption footprint, and their reliability and bootstrap times in view of automating experimentation. Lastly, we evaluate qualitatively the extensibility of the solutions considered.