How to use GNS3, GNS3 Terminology, and Overview

This tutorial provides a basic overview or introduction to the GNS3 graphic user interface (GUI). Learn how to use or create and test your first GNS3 topology.

GNS3 allows you to create and test network topologies in a virtual environment. To use GNS3, you need to create a project. A project is your network. When you create a new project or network, GNS3 does not add any device to the network. It creates a blank project or network.

After creating a blank project, you can add any available device to it. To create a new blank project, click File, and click New blank project.

create new blank project

Set the name and location for the project and click OK.

name and location

Overview / Introduction to GNS3 GUI

overview of GNS3

GNS3 workspace The area where you create the network by adding devices and links.
GNS3 Toolbar Contain the group of icons that allow you to perform common tasks.
Device Toolbar Contain devices that you can add to your network.
Topology Summary pane List all devices that you are using in the current network topology.
Server Summary pane Show the status of the local server and GNS3-VM (if in use).
Console pane Show errors and logs GNS3 encounters while executing tasks.

Adding devices to the network

Currently, our network has no devices. To use it, we need to add devices to it. GNS3 supports two types of devices: emulated devices and simulated devices. The default installation of GNS3 includes simulated devices. We have already discussed the emulation and simulation process in the previous parts of this tutorial.

Let’s build and test a simple network that contains two PCs and an Ethernet switch. To build this network, first, we need to add the PCs and Ethernet switch to the workspace.

To add a device to the network, select the device from the device toolbar, and drag the device to the workspace. To unselect a selected option on the device toolbar, click the selected option or close the opened sub pane.

The following image shows the process of adding two virtual computers to the network.

adding virtual pc

The following image shows the process of adding an ethernet switch to the network.

adding ehternet switch to workspace

Connecting devices

To connect devices, click Add a Link. The mouse pointer will change into a plus sign. Click the first device (PC1). The device will display all available interfaces. Select the interface you want to use to connect this device to another device.

Now, click the second device (Switch1) and select the interface you want to use to connect to the first device (PC1).

The following image shows how to connect the PCs to the Ethernet switch.

connecting devices

GNS3 adds PCs in the powered-off state while it adds switches in the powered-on state. To show the state of a device, it uses three different colors.

Color State
Red Powered off
Green Powered on
Yellow Suspended

device state

GNS3 does not use a color indicator for the interface state. To check an interface state, you have to check the running configuration of the interface's device. If you are a Packet Tracer user, this indication may confuse you. Packet Tracer uses colors to show the state of an interface.

To change the state of the device, select the device and right-click, From the right-click context menu, you can change the state of the device. To change the state of all devices on the workspace, you can use the options available on the GNS3 toolbar.

changing state

Labeling/showing interface names

By default, GNS3 does not display interface names. To show interface names, click Show/hide interface labels. It toggles the current state. For example, if interface names are visible, clicking it will hide them. Or if interface names are hidden, clicking it will show them.

You can also add notes. To add a note click Add a note. The following image shows, how to show and hide interface names and add a note.

labeling devices

Configuring a device

GNS3 does not provide a graphical utility to configure devices. To configure a device, you have to use the console prompt. To open the console prompt of a device, right-click the device and click Console.

To open the console prompt of all devices, click Console on the GNS3 toolbar.

opening console prompt

Assigning an IP address

To assign an IP address to the PC, use the following command.

ip  [IP address] [Subnet mask]

GNS3 checks the supplied IP address on the network. If the supplied IP is not in use, it assigns the supplied IP address to the PC.

The following image shows the process of assigning an IP address to PC1 and PC2.

assigning IP to PC

Verifying connectivity

To test connectivity between devices, you can use the ping command. The ping command sends small test data packets to the destination device in a sequence. If the destination device is connected to the source device, the destination device replies. If you see reply messages in the output of this command, it verifies that the source device and the destination device have proper connectivity.

verifying connectivity

Saving configuration

By default, GNS3 does not save the configuration running on the device. It means if you reload the project or device, the running configuration on the device will be lost. To save the running configuration on the device, you need to use the device’s save function. To save running configuration on a PC, use the save command.

saving configuration

Use the save command to save the running configuration on all PCs. If you save the project after saving the running configuration on all PCs, on reload, all PCs will start from where you left them.

Video version

This tutorial is also available in video format on our YouTube channel.

Watch This video on YouTube

That’s all for this tutorial. In this tutorial, we discussed the GNS3 GUI terminology and learned how to use GNS3.

ComputerNetworkingNotes CCNA Study Guide How to use GNS3, GNS3 Terminology, and Overview