GNS3 – Graphical Network Simulator

Keep on Guard!


GGNS3 is a graphical network simulator that allows simulation of complex networks. It’s an excellent complementary tool to real labs for network engineers, administrators and people wanting to pass certifications such as CCNA, CCNP, CCIP, CCIE, JNCIA, JNCIS, JNCIE. It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers.

To allow complete simulations, GNS3 is strongly linked with:

  • Dynamips, the core program that allows Cisco IOS emulation.
  • Dynagen, a text-based front-end for Dynamips.
  • Qemu, a generic and open source machine emulator and virtualizer.

Features Overview

  • Design of high quality and complex network topologies.
  • Emulation of many Cisco IOS router platforms, IPS, PIX and ASA firewalls, JunOS.
  • Simulation of simple Ethernet, ATM and Frame Relay switches.
  • Connection of the simulated network to the real world!
  • Packet capture using Wireshark.

This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X.

You can download GNS3 v0.7.2 here:

Windows All-in-one – GNS3-0.7.2-win32-all-in-one.exe
Windows Binary – GNS3-0.7.2-bin-win32.zip
Mac DMG Package – GNS3-0.7.2-intel-x86_64.dmg
Linux/Source – GNS3-0.7.2-src.tar.gz

Or read more here.


Posted in: Hardware Hacking, Network Hacking

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8 Responses to GNS3 – Graphical Network Simulator

  1. Chad November 3, 2010 at 11:18 am #

    To use GNS3 for Cisco IOS emulation, you will need an IOS image. You can only get one of these legally from Cisco. I went to use GNS3 to study for a CCNA but it was useless unless I illegally downloaded an IOS image and/or bought some Cisco gear. In my case, this prevented me from using GNS3 at all.

  2. stretch November 3, 2010 at 7:14 pm #

    @Chad: Aye, it’s a very gray area with Cisco, and while they’ve avoided making any substantial statements on the matter, they have casually acknowledged the value of Dynamips as both a training aid and a lab utility. Many of us have been pushing Cisco for an educational/lab-type license for IOS for a while now, but we’re not holding our collective breath. =\

  3. Sebbe November 3, 2010 at 8:34 pm #

    Anyone know any good switching simulator? One that handles STP and stuff…

  4. Mamat November 4, 2010 at 1:21 am #

    @Sebbe, I recommend you to use Boson Simulator. However, it’s not free

  5. Mayank Jain November 4, 2010 at 11:32 am #

    @sebbe LISA is a good linux based switching simulator

  6. prabhu November 5, 2010 at 8:08 pm #

    Thanks for the information, actually i was bored up with packet tracer now iam going to taste GNS3…

  7. Anon November 5, 2010 at 9:32 pm #

    GNS3 is a network emulator (You need real copy of Cisco IOS so it emulates it).
    PacketTracer is a network simulator. It just simulates some devices fonctions.

    Of course emulation is better and more realistic but it’s more ressource hungry.

  8. regedit November 9, 2010 at 10:57 pm #

    packet tracer! hello