How to configure IOU in GNS3 for real Cisco Switching Labs

Use .ova for GNS3-IOU instead of pre configured VM.

We all may have heard the saying GNS3 is great for practicing routing labs but switching Nah Nah!! Don’t underestimate the power of GNS3. It has a special IOU feature which will let you emulate real Cisco Switch both L2 & L3 in GNS3 without any trouble.

If you want to know what is an IOU? Refer to this excellent article here else follow along…

To configure IOU in GNS3 you will need the following files:

  • GNS3 (I used v1.2.3)
  • Virtual Box
  • GNS3 IOU VM (or .ova file available on GNS3 Official Site)
  • L2 IOU image
  • L3 IOU image
  • License file

For you to access them easily I am making all the “rare files” available for you here :

Let us now go through the step by step process to configure IOU in GNS3:

  1. Install the GNS3-IOU .ova file in Virtual Box. Make Sure you don’t have any older version of IOU installed in it.
  2. Start the VM. It may take a few moments to run at the first time.
  3. After it has started, you will note an IP address shown above the console screen. In my case it was: where was the IP of the VM which was the Host-Only adapter of the Virtual Box instance.
  4. Next open your web browser and go to
  5. Select the L2 and L3 IOU image one by one and click on the upload button. The full path will be shown after uploading is completed.
  6. Now open GNS3.  Goto edit->preferences.
  7. Click IOS on Unix. Under path to IOURC put D:\GNS3 IOU\IOURC.txt (the location of IOURC.txt file).
  8. Next, goto GNS3 server->Remote server. Under host type – and port 8000. Click Add. Then click Apply->Ok.
  9. Change host binding. (Very important)
  10. Now under IOU devices, Click New->Next->Ok->Give a name(like Switch IOU). Under IOU image paste the location which you have copied from the image upload screen.. Select L2 or L3 depending on the type.
  11. Repeat step 9* for the Router IOU image.
  12. Now simply drag your IOUs to your working area and create your switching lab.

Now let us test inter-vlan routing in this simple topology.


Sample R1 Config:


Sample SW1 Config:


Final Testing:


Cheers ! Happy Switching 😉


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