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]}

DevelopersJeremy Grossmann, Dominik Ziajka, Piotr Pękala

Initial release2008; 18 years ago (2008)

Stable release

3.0.6^[1] / 28 January 2026; 3 months ago (28 January 2026)

Written inPython

Quick facts Developers, Initial release ...

Graphical Network Simulator-3
Developers	Jeremy Grossmann, Dominik Ziajka, Piotr Pękala
Initial release	2008; 18 years ago (2008)
Stable release	3.0.6[1] / 28 January 2026; 3 months ago (28 January 2026)
Written in	Python
Type	Network simulator
License	GNU GPL
Website	gns3.com
Repository	github.com/GNS3/gns3-server

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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]