GINI (GINI Is Not Internet) is an open-source toolkit for creating virtual micro Internets for teaching and learning computer networking. It provides lightweight virtual elements for machines, routers, switches, and wireless devices that can be interconnected to create virtual networks. The virtual elements run as unprivileged user-level processes. All processes implementing a virtual network can run within a single machine or can be distributed across a set of machines. The GINI provides a user-friendly GUI-based tool for designing, starting, inspecting, and stopping virtual network topologies. This paper describes the different components of GINI, briefly discusses ways of using the toolkit in a computer networking course, and reports on user feedback on an early (incomplete) version of the toolkit. Categories and Subject Descriptors K.3.1 [Computers and Education]: Computer Uses In Education; D.2.0 [Software Engineering]: General General Terms Design, Experimentation, Human Factors...