GNS3: A Graphical User Interface for Simulating Complex Networks

1. What is GNS3?

GNS3 is a software that simulates complex networks while being as close as possible to the way real networks perform. It can be used to practice for Cisco exams, to build CCNA and CCNP labs or to learn networking concepts in general.

GNS3 is based on Dynamips, Qemu and Dynagen. It is released under the GNU General Public License version 2 (GPLv2).

Dynamips: This is the heart of GNS3. It allows you to run Cisco IOS images in a virtual environment.

Qemu: This is required for running other types of images such as Juniper or MikroTik.

Dynagen: This is a text-based front-end for Dynamips. It makes the configuration of virtual networks much easier.

GNS3dev: GNS3dev is the development branch of GNS3. It contains new features and bug fixes that will be included in the next stable release of GNS3.

IOS: IOS stands for Internetwork Operating System. It is the software that runs on Cisco devices such as routers and switches.

VPN: VPN stands for Virtual Private Network. A VPN allows you to connect to a private network over the internet.

Certifications: Certifications are a way of proving your skills in a particular technology or product. Cisco offer many different certifications, such as the CCNA and CCNP.
Routers: A router is a device that forwards data packets between computer networks. Routers use protocols such as IP to determine where to send each packet.
Complexity: The complexity of GNS3 can be seen in its wide range of features and capabilities. However, it is also easy to use once you get familiar with it.
Installation: Installing GNS3 is simple and only requires a few minutes. All you need is a computer with an internet connection and enough storage space for the images you want to use.
Images (ISO): Images are files that contain all the data needed to run an operating system or application. In GNS3, you can use ISO files to install images of routers and switches.
There are two main ways of using GNS3, either through a Graphical User Interface (GUI) or Command Line Interface (CLI). In this paper we will focus on the GUI since it is more user-friendly for beginners.
1) lab1_topologydiagram ( Picture should go here)
2) Choose your image file: In this case we will be using the c3745-adventerprisek9-mz.124-25d.image
3) Click on the “wrench” icon next to the Router in order to open theConfigure window.

4. In the General settings Tab, check the “ Idle-PC value” box and click Ok

5) Your router should now be up and running


GNS3 is a network simulator that allows you to create and configure virtual networks.

GNS3 works by emulating the behavior of real networking devices, such as routers and switches. This allows you to test out configurations and experiment with different scenarios without having to physically purchase or set up equipment.

The benefits of using GNS3 include being able to save money on hardware costs, being able to test out complex configurations before implementing them in a production environment, and being able to learn about networking concepts in a safe and controlled environment.

To get started with using GNS3, you will need to download and install the software from the website ( Once installed, you can begin creating your first virtual network by adding devices and configuring their settings.

Some tips for working with GNS3 effectively include starting with a simple setup and gradually adding complexity as you become more familiar with the software, taking advantage of online resources such as tutorials and user forums, and backing up your work frequently in case of unexpected software crashes or corruptions