What is GNS3 ?

GNS3 is an open source software (under GPL) that simulate complex networks while being as close as possible to the way real networks perform. All of this without having dedicated network hardware such as routers and switches.

Our software provides an intuitive graphical user interface to design and configure virtual networks, it runs on traditional PC hardware and may be used on multiple operating systems, including Windows, Linux, and MacOS X.

In order to provide complete and accurate simulations, GNS3 actually uses the following emulators to run the very same operating systems as in real networks:

  • Dynamips, the well known Cisco IOS emulator.
  • VirtualBox, runs desktop and server operating systems as well as Juniper JunOS.
  • Qemu, a generic open source machine emulator, it runs Cisco ASA, PIX and IPS.

Who can use it?

GNS3 is an excellent alternative or complementary tool to real labs for network engineers, administrators and people studying for certifications such as Cisco CCNA, CCNP and CCIE as well as Juniper JNCIA, JNCIS and JNCIE. Open source networking is supported too!

It can also be used to experiment with features or to check configurations that need to be deployed later on real devices.

Our program includes exciting features, for instance connection of your virtual network to real ones or packet captures using Wireshark.

Finally, thanks to the VirtualBox support, even system administrators and engineers can take advantage of GNS3 to make labs, test network features and study for Redhat (RHCE, RHCT) and Microsoft (MSCE, MSCA) certifications to name a few.

Where do I start?

In most situations, to use GNS3 you first need to provide your own copy of a network operating system, like Cisco IOS, PIX, ASA, IPS or Juniper JunOS. Here is a complete list of what hardware is emulated by GNS3. We also suggest ready to use non-copyrighted appliances.

Once you have your operating system, you can start reading our documentation and learn how to use GNS3. Watching video tutorials is also a good way to better understand the program. Please note that to GNS3 might be daunting for beginners, you will need patience and practice. Our community is ready to help you on our forum and social media sites.