It combines the best features of the existing emulation software (such as Dynamips and Qemu) into a GUI interface and allows you to create an unlimited number of Cisco routing-and-switching lab scenarios. GNS3, short for Graphical Network Simulator-3, is an open-source network software emulator initially released in 2008. With this VM, you can do experiments with different configurations there rather than on actual hardware. This post from MiniTool shows you how to install and run GNS3 VM.
It can allow you to create a virtual network right on a PC.