Graphical Network Simulator-3

Graphical Network Simulator-3 (shortened to GNS3) is a network software emulator first released in 2008.^[2][3][4] It allows the combination of virtual and real devices, used to simulate complex networks. It uses Dynamips emulation software to simulate Cisco IOS.^{[2]: 55 [5]}

Developer(s)	Jeremy Grossmann, Dominik Ziajka, Piotr Pękala
Initial release	2008; 17 years ago (2008)
Stable release	3.0.5[1] / 14 May 2025; 34 days ago (14 May 2025)
Repository	github.com/GNS3/gns3-server
Written in	Python
Type	Network simulator
License	GNU GPL
Website	gns3.com

GNS3 is used by many large companies including Exxon, Walmart, AT&T and NASA, and is also popular for preparation of network professional certification exams. As of 2015, the software has been downloaded 11 million times.^[5]