The Internet, undoubtedly, is the most influentialtechnical invention of the 20th centurythat affects and constantly changes all aspectsof our day-to-day lives nowadays. Although itis hard to predict its long-term consequences,the potential future of the Internet definitelyrelies on future Internet research. Prior toevery development and deployment project, anextensive and comprehensive research studymust be performed in order to design, model,analyze, and evaluate all impacts of the newinitiative on the existing environment. Takingthe ever-growing size of the Internet and theincreasing complexity of novel Internet-basedapplications and services into account, theevaluation and validation of new ideas cannotbe effectively carried out over local test bedsand small experimental networks. The gapwhich exists between the small-scale pilots inacademic and research test beds and the realsizevalidations and actual deployments in productionnetworks can be bridged by usingvirtual infrastructures. FEDERICA is one ofthe facilities, based on virtualization capabilitiesin both network and computing resources,which creates custom-made virtual environmentsand makes them available for FutureInternet Researchers. This article provides acomprehensive overview of the state-of-the-artresearch projects that have been using the virtualinfrastructure slices of FEDERICA inorder to validate their research concepts, evenwhen they are disruptive to the test bed’s infrastructure,to obtain results in realistic networkenvironments.