Communication networks and the systems they interconnect are going through a phase of tremendous change. The former agnostic delivery of content between endpoints has given way to networks increasingly adding functionality beyond moving data. Softwarization technologies including network function virtualization (NFV) and soft-ware-defined networking (SDN) are key enablers that introduce computing into the network. This revolution, especially for mobile communication networks, represents a major paradigm shift away from agnostic data delivery. Subsequently, there is a significant need to provide well-defined environments offering replicability to effectively test and evaluate protocols and mechanisms that integrate computing into networks. This article presents the Communication Networks Emulator (ComNetsEmu), which provides an SDN and NFV network emulation environment based on community-embraced open source packages and enables replicable research and development on limited resource commodity hardware. In this article, we describe the underlying ComNetsEmu architecture and provide a hands-on description of its use for researchers, practitioners, and educators alike.