Cisco Tips & Tricks

March 5, 2008

Cisco Graphical Simulator or GNS3

Filed under: cisco, Router, Switching, Technology and Software — ciscotips @ 6:38 pm

What is GNS3 ?

GNS3 is a graphical network simulator that allows you to design complex network topologies and to launch simulations on them.

To allow complete simulations, GNS3 is strongly linked with :

  • Dynamips, an IOS emulator which allows users to run IOS binary images from Cisco Systems.
  • Dynagen, a text-based front-end for Dynamips.

GNS3 is a excellent complementary tool to real labs for administrators of Cisco networks or people wanting to pass their CCNA, CCNP, CCIP or CCIE certifications.

It can also be used to experiment features of Cisco IOS or to check configurations that need to be deployed later on real routers. This project is an open source product that may be used on multiple platforms, including Windows, Linux, and MacOS X.

Features overview

  • Designing high quality complex network topologies.
  • Emulating Cisco routers.
  • Simulating simple Ethernet, ATM and Frame Relay switches.
  • Load and save in Dynagen’s INI-like format.
  • Image export (JPEG, PNG, BMP and XPM).

Important notice: users must provide their own Cisco IOS to use GNS3.



  1. Great program. Though it claims it’s in beta, it feels more like alpha stage software to me. It crashes a lot.

    Can’t wait for them to get something more stable though. Will make Dynamips so much easier to use.

    Comment by James — March 5, 2008 @ 7:25 pm

  2. yup – agreed , its good software.

    Comment by binary-zero — March 5, 2008 @ 7:35 pm

  3. Great post ! GNS3 help a lot for making dynamips/dynagen template and make life easyer when it come to build from a vision or from mind 🙂

    GNS3 beta version is the 0.4 and will be released in a couple of weeks,
    the stable version seem to work great on my computer 🙂
    What version and what platform do you use ?

    Comment by lessaid — March 6, 2008 @ 9:27 am

  4. GNS3 0.4 beta has been released ! 🙂

    Comment by jgrossmann — March 22, 2008 @ 12:50 am

  5. Hello Raman,

    I’m looking for a (free) way to measure QoS at layer 2 for now, later on L3.
    Over your years of cisco mangling, did you find anything that could be used ?
    This GSN3 doesn’t cut it 😐 and i’ve searched all over but only comercial software for this…

    Comment by Marco — March 27, 2008 @ 9:01 am

  6. wow keren

    Comment by Alfin — June 5, 2008 @ 1:34 am

  7. This is really a good software and help us to acheive the goals easily.


    Comment by shivlu — July 14, 2008 @ 9:04 am

  8. i want this to learn ruoter configuration

    Comment by santosh — July 24, 2008 @ 4:38 pm

  9. how i can install cisco ios image in gns3?

    Comment by yasir — September 27, 2008 @ 2:31 am

    • press ctrl+shift+i
      or insart images with browse..

      Comment by cpsingh — May 20, 2011 @ 12:38 pm


    Comment by ASHWINI — November 3, 2008 @ 9:03 am

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