In this paper we explain the deployment of a testbed that emulates a network by means of virtualization, allowing us to implement a set of virtual nodes in one physical machine or a small LAN. Nodes participating in the communication are virtual machines adequately connected. The system is a hybrid testbed, as it includes simulation and emulation. But simulations are done in a previous offline stage, in order to avoid computer load caused by the need of real-time simulations, which could limit the maximum number of hosts to be included into the scenario. Finally, two uses of the testbed are presented.