Aller au contenu

Quick Start Guide


This quick start guide describes how to install GNS-3 on your machine, add a Cisco 7200 Router, a simple and a complete L2 Switch. It will allow you to emulate different topologies



Available on the GNS3 Website and works on Windows, OSX or Linux. The direct links to the repository:


If you use the GNS-3 VM, it is important to have the same version of the VM and GNS-3 for everything to work perfectly.

Cisco IOS

Available on main courses pages (require login).


Start the installation package on your machine.

Step 1: Choose components

Step 2: Where to run the emulation

We will run the emulation locally on our computer.

Step 3: Local Server configuration

Step 4: Adding an IOS router

Step 5: Adding a “simple” L2 Switch

If needed, you can add a very simple L2 Switch, based on a Cisco 3725 router with an Ethernet Switch module.

Step 6: Adding a “complete” L2 Switch

If needed, you can add a more complete L2 Switch, based on a Cisco IOU (IOS on Unix). This will run only on the machine where QEMU is installed (mainly Linux).

Project Structure

GNS-3 Directories

Project Management

Some Remarks

  • Changes to the network structure (routers, connections between interfaces, labels, etc.) are automatically saved in the project configuration file
  • The configuration changes on the routers are not! You have to save them before stopping the simulation.
    • Save the «running-config» into the «startup-config» using «copy running-config startup-config» or «write»
    • Use the command «show archive config diff» to see the differences between the («running-config») and the «startup-config»
  • Start each configuration phase with a new copy of the project (the name of this copy should describe the state at the end of this configuration phase)
  • Do the configuration / manipulations
  • Save the modified configurations on the routers at the end before stopping the simulation

Dernière mise à jour: 9 March 2023