What is GNS3? | What Does it Do?

GNS3 (Graphical Network Simulator-3) software allows you to emulate complex network designs such as Cisco Router/Switch.

This program is Open Source, and you can download and use it for free.

What is GNS3? | What Does it Do?

What is GNS3?

It enables you to run real Cisco IOS images using Dynamips in the GNS3 infrastructure, and with this software, you can create complex network designs on your computer and study in more detail for exams such as Cisco Certified Network Associate (CCNA) and Cisco Certified Network Professional (CCNP).

You can easily install this network simulator on Windows, Mac OS X, Linux, Unix, FreeBSD.

Christophe Fillot is the founder of Dynamips (MIPS Processor Emulation Program), which enables network devices such as Cisco Routers to work in a virtual environment. The founder of Dynamips is Grossman.

This software not only supports Cisco devices but also supports the JuniperMikroTikArista , and Vyatta network devices.

As an alternative to this program, you can also use the Cisco Packet Tracer program developed by Cisco Networking Academy.

What Does GNS3 Do?

Compared to other network simulator programs (RouterSim, Boson NetSim), you can use Cisco IOS images more specifically with the back-end Hypervisor software through this network simulator program.

Other software includes network devices such as Routers or Switches. As a result, you can run and use a real Cisco Router on your computer with GNS3.

A Network Topology with Two Routers

This simulator software uses IDLE-PC Value to show better performance of Cisco Routers or Switch IOS and shows you the optimal value with * character.

You can set the Idle-PC value when adding a device to the program.

Network Simulator Program Term

GNS3 → GUI (Graphical User Interface)
Dynamips → Emulator for IOS
Dynagen → Beginning Front End for Dynamips
Pemu → Cisco PIX Firewall Emulator Based on Qemu
(Win)Pcap → Packet Capture Library (Driver for Sniffer)
Wireshark (Old Name: Ethereal) → Network Monitoring / Listening to Network
VPCS → Virtual PCs (Virtual Computer) → Adding a virtual computer.
VMware VMS → VMware Virtual Machines → Including virtual machines in topology with VMware Workstation.
VirtualBox VMS → VirtualBox Virtual Machines → Including virtual machines in topology with VirtualBox.
IOU Devices → A real Layer2 and Layer3 Switch lets you use all the features of your network device by adding an IOS image.


After making the GNS3 definition, let’s examine what the advantages are.

  1. Free software.
  2. Open Source software.
  3. No monthly or annual license fees.
  4. There is no limit to the number of supported devices (only the limitation is your hardware: CPU and memory).
  5. Supports multiple switching options (ESW16 Etherswitch, IOU / IOL Layer 2 images, VIRL IOSvL2):
  6. Supports all VIRL IOS images (IOSv, IOSvL2, IOS-XRv, CSR1000v, NX-OSv, ASAv).
  7. Supports devices of many brands.
  8. It can be run without hypervisor.
  9. Supports both free and paid hypervisors. (VirtualboxVMware Workstation, VMware Player, ESXiFusion).
  10. No need for additional virtualization software.
  11. Large and active community (more than 800,000 members).


  1. IOS images are downloaded by the user. (You can download it from Cisco.com and purchase a VIRL license).
  2. You need to manually add the Router/Switch images you download.
  3. The program runs based on the hardware performance of your computer.

How to Install it on Windows ⇒ Video

You can watch the video below to install GNS3 on your Windows computer and also subscribe to our YouTube channel to support us!

How to Install it on Linux Systems

As mentioned above, you can install GNS3 network simulator on Linux systems (Ubuntu, Debian, Linux Mint).

For example, to install GNS3 on Ubuntu, click on the image below to browse our article.

Ubuntu Cisco Simülatör Kurma

How to Install it on Mac PC

To install GNS3 on macOS operating system on a Mac computer, you can access our related article from the image below.

macOS Cisco Simülatör Kurma

   Final Word

Instead of buying network devices such as Routers, you can use the GNS3 network simulator to prepare for Cisco exams or to develop yourself in the network.

In addition, you can access all configuration commands that are not supported in the Cisco Packet Tracer using the image files of the actual Routers on GNS3. Thanks for following us!

   Related Articles

♦ Cisco IOS Images
Adding Cisco Router
♦ Router IP Address
♦ Router Basic Settings
♦ Switch Basic Settings

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