GNS3 Legacy Setup

This page details how to install GNS3 to run the labs downloaded from netquirks, based on an older version of GNS3. For the most recent installation instruction, it is recommended to look at the GNS3 site itself.

The example uses GNS3 version 2.0.0 and the screenshots are from a Macbook Pro, however installations on other systems will be analogous.

The labs available from netquirks run IOS and on the local machines server. However, these instruction detail how to install the both the local and GNS3 VM servers for the following reasons:

  • Through the GNS3 VM you can can run more modern systems (like IOS XRv or ASA) as well non-Cisco appliances
  • The GNS3 VM gives better performance than running routers on the local machine
  • There will be labs available on netquirks in the near future that need the GNS3 VM…

VirtualBox is used to run the GNS3 VM.

VirtualBox is free but doesn’t support nested virtualizaiton, meaning GNS3 systems like Qemu will experience degraded performance. This doesn’t affect the labs available on netquirks but VMWare Workstation and Fusion do supported nested virtualisation. Full and comprehensive documentation around installation and setup see the GNS3 site:

These instructions are divided into six stages…

Stage One – Downloads

  1. Download and install GNS3. Downloads and guides can be found here (you will need to create a free GNS3 account).
  2. Download and install VirtualBox from here.
  3. Download the file from GNS3 here.

Stage Two – Import GNS3 VM into VirtualBox

  1. Unzip


  1. Open VirtualBox and select New.
  2. In the that pops up, enter the following and click Continue:
    • Name: GNS3 VM
    • Type: Other
    • Version: Other/Unknown (64-bit)


  1. On the next screen, select the amount of memory appropriate for this VM given the system you are working on, then click Continue.


  1. Virtual Box will ask for the appliance to import. Browse to the GNS3 folder within the newly unzipped folders and select GNS3 VM.ovf. Then select Continue.GNS3_Instructions_Appliance_Import
  1. Set the appliance settings as needed, here I have just left all of the defaults in place. Then select Import. Virtual Box will begin the import process.GNS3_Instructions_Import_Appliance_Settings
  2. Once the import is done, go to the Virtual Box Preferences and select the Network menu. Once there select the Host-only Networks tab:GNS3_Instructions_Network_tab
  3. Select the plus symbol on the right-hand-side and enter an IP and subnet mask for this adapter. In this instance my system automaitcally assigned so I left it as it. Once done Click OK.


  1. Now right click on the GNS VM  and select Settings….
  2. Go to the Network menu and set Adapter 1 to be Attached toHost Only Adapter. Select vboxnet0 from the dropdown and click OK.


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Stage Three – Source the Images

Images are not included in the lab downloads. The images used are as follows:

  • Image for Cisco 3725: c3725-advipservicesk9-mz.124-17.image
  • Image for Cisco 7200: c7200-spservicesk9-mz.150-1.M.image

Store these in the IOS directory for GNS3.

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Stage Four – Configure GNS3

  1. Open GNS3
  2. The Setup Wizard should begin automatically or you can select it from the Help menu as follows:


  1. Whilst the labs downloaded from netquirks run on the local machine, it is worth configuring GNS3 to run using the GMS3 VM. As such, on the next menu, select the Run Modern IOS option and click Next.GNS3_Instructions_Server_Type
  1. You will first be prompted for the local server configuration. Select from the drop down. Click Next.


  1. You should then see a screen stating the local server is validated. Click Next.


  1. If you get a warning stating that VirtualBox doesn’t support Nested virtualisation just click OK.


  1. Next the GNS3 VM will be configured. Select the VirtualBox radio button. Under VM Name use the dropdown to select the name of GNS3 VM that configured in VirtualBox (it should automatically be detected – make sure the VM is running at this point). Assign appropriate vCPU cores and RAM, then click Next.


  1. Finally you will see a summary page showing the last setup of the VM. Click Finish.


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Stage Five – Configuring the IOS Routers

  1. After finishing the above section a New Appliance Template window will appear. Select the Add an IOS router using a real IOS Image Option. If coming from the main GNS3 screen, go to the Preferences menu, select the Dynamips > IOS routers menu, followed by the New button.
  2. On the window that pops up, select the radio button called Run the IOS on my local computer. Select Next.
  3. Select the New Image radio button.
  4. Browse to and select the image you wish to use. Select Next.
  5. Give the router a name. Select Next.
  6. Select the RAM as follows and click Next
    • 128MB for the 3725 image
    • 512 for the 7200 image
  7. Select a sufficient number of Fast Ethernet adapters. Select Next.gns3_instructions_image1
  8. If applicable, select a sufficient number of WIC modules. Once done select Next.
  9. Select Idle-PC finder and let GNS3 find the correct value.
  10. Select Finish and then OK to go back to the main topology window of GNS3.

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Stage Six – Downloading and Importing the Labs

  1. On the Lab page, download the lab that you want to run.
  2. Extract the .zip and make sure the extension is .gns3project
  3. Open GNS3 and select File > Import Portable Project
  4. Browse to the .gns3project file and select it. The project will import itself and the topology will appear.
  5. Press Play and the lab will start
  6. To access a device, double-click on it and a console will open.

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