GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.
NetSim - NetSim software was created to simulate various Cisco systems. Cisco software is known around the world as being one of the best network, routing and switch systems for businesses and private use. Read more about NetSim.
ns-3 - a discrete-event network simulator for internet systems
Paessler Multi Server Simulator - Paessler Multi Server Simulator is inexpensive and robust software that helps you power massive-scale testing.
FlexSim - Simulation software to model, simulate, predict, and visualize systems in manufacturing, material handling, healthcare, warehousing, mining, etc.
Ranplan Wireless - Ranplan Wireless is a leading platform that has revolutionized itself with innovative wireless tools and software based on extensive technology.