Cisco IOU L2 L3 lab with GNS3 | Switching in GNS3

Cisco IOS on Unix, also known as Cisco IOU,  is released for internal Cisco use only. IOU permits to run IOS natively on x86 platform while GNS3 must emulate the whole hardware. The big difference is that IOU can run more IOS instance than GNS3, but GNS3 can run real IOS version. The purpose of this article is to let you know how IOU can be integrated with GNS3 emulator software to practice switching concepts.

**Pay Attention:** Cisco IOU binaries are not for public use. If you are a Cisco guy you must ask your company how you can get IOU binary files and license. Other do not have rights to use IOU images.

Make sure you have...

Before we start I want to make sure that you all have the required tools and softwares. I have listed down them with download links below,

Virtual Box 4.3.12 (I had some bad experience with version 5.0, Check my article to know more VirtualBox EFAIL error) -
IOU Images - As already mentioned, strictly for Cisco guys! But still you might get these images by Googling!  
GNS3 IOU VM - Available from sourceforge, I downloaded and used a older version in this post. But you can use any version from this link. -
IOURC - Cisco license file for IOU Images. It is not available for public use, but while surfing I found this link which could help you!

Setting Up GNS3 IOU VM in Virtual Box

Download the IOU Virtual Machine from the given Sourceforge link.

In the above image I have marked the file which I downloaded, However you can use any of the available versions. Once downloaded extract the tar file using 7zip or Winzip. You would see below files inside the zip file,

Open Virtual Box 4.3.12 application from the start menu. Make sure that you have already downloaded and installed it. I downloaded it from the below URL,

In Virtual Box, Click on File -> Import Appliance. It will prompt below window, 

Select the path of your ovf file (you can find it in extracted folder) and click Import as depicted in the above snapshot. And ensure that Network settings looks like below,

As shown, Make sure that VM is attached to Host-only Adapter before we start the VM. Now start the VM and check for the IP configuration using ifconfig command. Use username root and password cisco to login into the appliance. Refer the below image for example,

Now it's time to upload the IOU images. Well! I happened to find some IOU Images from this link. Type on your browser address bar. Click on 'Choose file', a file browser window will open. Select the downloaded IOU image and click 'Upload', this might take few minutes.

Make a note of displayed path, /home/gns3/GNS3/images/IOU/xxxxxxxx. Later you will have to enter this path in GNS3.

With this step, we have completed IOU end configuration. Let's start with GNS3...

GNS3 IOU Server Configuration

By default, GNS3 is binded with server address We have to change this value with our new IOU server address. Follow the below instructions to bind the new server.

Go to Edit -> Preferences -> GNS3 Server. Click on Local server tab. From the Host Binding drop down window select ''. Make sure that port is also set to 8000. Then click Apply and OK.

Again go to Edit -> Preferences -> GNS3 Server. This time click on Remote access tab. Add a host by entering UNIX GNS3 IOU VM IP address that we found using ifconfig (mine and 8000 as port.

Integrating GNS3 and Cisco IOU

Final step of this tutorial would be to add IOU templates to GNS3. Go to Edit -> Preferences -> IOS on UNIX. And click 'General Settings' tab, click browse to set the path to IOURC.txt file. IOURC license file would like below,

Once you have given license file details, click Apply. And now go to IOU Devices, click New button and select server type as Remote. Your remote server will be listed there → Next

Here you will receive a message “You have chosen to use a remote server, please provide the path to IOU image located on the server!”, just click OK.

Now type a Name for the IOU image and set IOU image path to be the one that you noted already while uploading the image through through browser. Refer the snapshot below to understand what I am trying to say,

Click Finish! Yes, we are done with all the configurations. By repeating the above steps, you can upload as many as images you want and you can add them to your GNS3 emulator window. For example I have uploaded 2 images (L3 and L2) as shown below.

Now go to GNS3 main window, pull the configured IOU devices. Power them on, start building your labs! Since you can configure all the devices inside your GNS3 itself, I guess this method is much better than IOU Web.

That's all folks! I believe I have covered all the required steps to get IOU running with GNS3, In case of any clarifications, do let me know through comment section below. 

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Hey there! I'm Senthil Kumar Murugesan, An Infrastructure engineer with a focus on Cisco Unified Communications and Hacking. Also I’m happy to mention that I’m a Linux junkie, a Cisco proponent, a Tools fanatic and Script lover. This is a blog, a rambling of thoughts, and a result of technical experiments


  1. Replies
    1. bro i was looking for gns3 iou image, i hv tried 100 of times but after doing all steps. I am getting error message in the end as of server cannot access this image o r denied. please send me gns3 iou images of l2 & l3. its request you to privide version of gns3 and gns3 vm server version, so i can do steps properly.

  2. Thank you man!!! This post helped me a lot on my CCNP studies.


  3. thak you very much, and we can now connect l3 and l2 but we faces problem when connecting gns ios to iou

    "server cannot communicate with server, most likely because your local server host binding is set to a local address"

  4. Thanks a ton !!!

    It's really helpful.... Much appreciative you work... !!! :)

    1. bro i was looking for gns3 iou image, i hv tried 100 of times but after doing all steps. I am getting error message in the end as of server cannot access this image o r denied. please send me gns3 iou images of l2 & l3. its request you to privide version of gns3 and gns3 vm server version, so i can do steps properly.

  5. Thank you ! this has been informative

  6. Hi Senthil,

    I'm trying to integrate IOU with GNS3 1.3.11. I've following components with me;

    1. GNS3 1.3.11 (downloaded from GNS portal)
    2. GNS3.IOU.VM-1.3.11 (downloaded from GNS portal).
    3. L2 and L3 images:

    I followed the same procedure mentioned by you above, but L2 and L3 IOU devices are not coming up. i.e I can't start the devices. Please help me to fix it.

  7. Hi,

    I'm trying to integrate IOU with latest version of gns3 (1.3.11). Tried with below components;

    1. gns3 1.3.11
    2. GNS3.IOU.VM-1.3.11
    3. L3 and L2 images:

    The above listed L3 and L2 images worked fine with gns3 1.2.3 and corresponding IOU.VM, but with new version of gns3 1.3.11, the IOU devices(router and switch) are not coming up. i.e, not able to start the devices. Please help me to fix it....


    1. check the message in the console box in gns3. i think it is IOURC mismatch

  8. Hi Senthil,

    I have followed all the necessary steps to setup GNS3 IOU on VM.

    But I keep getting error on gns3 (The node is intialized unknown error)
    Kindly help.


    1. it works with GNS3 1.2 version

  9. I am getting error in gns3. After all setting successful when i tried to run the router or switch then I am getting error that "This nod doesn't initialized unknown error". Please help on this.

  10. Where can we download the IOU image L2, L3, seems can't find it online? can you send me a link to download this Cisco ious ?

  11. Thanks a lot for detailing the integration of GNS3 with IOU.

  12. Hi senthil... I tried your tutorial and worked. But I have problem while I save my project and then I open again next time. The notification is "Server error from DLS1: Could not find a iourc file (IOU license)
    ". I use GNS3 version 1.3.0. Do you know the reason? Thanks

  13. thank you dude. it is very helpful for ccie workers :).

  14. Can we configure HSRP by using IOU?

  15. Hy bro. where i must located the iourc file ? in server or in local drive like drive D or C in Windows OS ?

    and what file type the license ? IOURC.txt or .iourc ?

    thanks before..

  16. your license file is less semicolon in end line..

    gns3-iouvm = cd11acbc599f2364;

    thank you bro.. :)

  17. Could anyone send me i86bi_linux-l3-adventerprisek9 file?
    I have tried searching on google but just shady sites and ads everywhere. Just downloaded a file and got WAJAM browser extension was installed instead :(

  18. Thank you!! This info has helped me immensely.

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  20. Great howto, made setting the whole thing up very easy!

  21. how to connect asa with L2 and L3 switches do we need to import in VM if yes please share procedure for same

  22. I cant find any l2 IOUs on your link. Can you advise? Thanks

  23. I recived the following message:

    "The virtual machine 'GNS3 IOU VM_1' has terminated unexpectedly during the start with the exit code 1 (0x1). More details may be avaliable in etc etc"

    What would be the problem?

  24. I started running oracle IOU VM and before Type login and password it appears "use your browser with http://:8000/upload" i really dont know what to do? I become crazy

  25. thanks lot... done successful installation!!!

  26. thank you, works awesomely

  27. Hi
    Please suggest how to overcome the problem such as...
    IOU SW imges opend but does not accept some command like. int vlan 1 and IP address to the same SW.Error massage is...invalid command.Request you to help me out in this regard.

  28. Please help me to resolve this:
    => Server error from IOU1: IOU image '/home/gns3/GNS3/images/IOU/i86bi-linux-l3-adventerprisek9-15.4.1T.bin is not accessible in gns3 1.3.13 and same iouvm on vmware in win7

  29. => Server error from IOU1: IOU image '/home/gns3/GNS3/images/IOU/i86bi-linux-l3-adventerprisek9-15.4.1T.bin is not accessible in gns3 1.3.13 and same iouvm on vmware in win7

  30. Hi Senthil, Thanks for this Step by Step procedure. It helped me in setup.

    I faced the problem of getting the IP of Local server in the drop down list in GNS3 instead of 101. remote server is .101.

    Please guide me to rectify this error. rest everything is going good. This is creating problem when I am trying to start router and it checks for Idle PC

  31. working fine, but when i reopen a saved project the following error occur "Server error from IOU1: Could not find a iourc file (IOU license)" please suggest its resolution.

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  33. Hello,
    Instead of port number 8000, I always have 3080 on GNS 3. Can I work with it?

  34. hi,
    I have followed the steps, but am getting this message bellow, please help
    Error while creating project: Client version 1.5.2 differs with server version 1.3.3

    1. I guess this would fix your problem.

  35. Thanks a lot. Your efforts are truly appreciated.

  36. These ways are very simple and very much useful, as a beginner level these helped me a lot thanks fore sharing these kinds of useful and knowledgeable information.
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