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Development of GNS3

Using the GNS3 API

Get the Source Code

At first you need to clone both project:

git clone
git clone

If you want to access to the code of next big release in both project:

git checkout NEXT_RELEASE

For example:

git checkout 2.0



If you are on Linux the best is to install GNS3 via the ppa. This will setup all the dependencies required for the development.

Go to both folder (gns3-gui & gns3-server)

sudo pip3 install -r dev-requirements.txt


On Windows you need to install Python 3.5 and PyQT. Go to both folder (gns3-gui & gns3-server)

python.exe -m pip install -r dev-requirements.txt

Mac OS X

With homebrew:

brew install python3
brew install PyQt5

Go to both folder (gns3-gui & gns3-server)

pip3 install -r dev-requirements.txt

Run Tests

For Linux & Mac OS X

After that the tests should work go to both projects. And run:


For Windows

After that the tests should work go to both projects. And run:

python.exe -m py.test

Start the Server

For Linux & Mac OS X

Go to the gns3-server folder and run:

python3 -m gns3server --debug --local

For Windows

python.exe -m gns3server --debug --local

Start the GUI

For starting the gui go to the gns3-gui folder.

For Linux & Mac OS X

python3 -m gns3

For Windows

python3.exe -m gns3

Modify the GUI

We will start by a simple modification by adding your name to the thanks to in the about dialog.

In the gns3-gui folder open with the Qt Designer the file gns3/ui/about_dialog.ui click on Thanks to and add your name to the list:


Click on About (otherwise the dialog will open the Thanks to tab) and save. Now you need to export the dialog to python code. Just run:

python scripts/

This will regenerate all the changed Qt interface. You can now start the GUI and see your change.

Contribute Code

You can create a pull request on Gui or Server via Github. Even for work in progress code. We will help you.