Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Cisco Packet Tracer - Download Cisco Packet Tracer, an innovative network simulation and visualization tool used by Cisco Networking Academy students and instructors.
FreeCAD - An open-source parametric 3D modeler
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.
Inventor - Inventor is a 3D CAD software that lets you quickly create 3D models with embedded intelligence, intuitive workflows, and optimized performance.