Nov 26

How to Configure VirtualBox Network Adapters for the GNS3 VM (with GNS3 GUI)

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How to Configure VirtualBox Network Adapters for the GNS3 VM (with GNS3 GUI)

Setting up the GNS3 VM correctly inside VirtualBox is essential if you want the GNS3 GUI on your computer to communicate smoothly with the backend VM. This guide walks through the recommended adapter configuration and explains why each setting matters.

Step 1: Open the Network Settings for the GNS3 VM

  1. Launch VirtualBox.
  2. Select GNS3 VM from the list.
  3. Click Settings, then open the Network section.

All adapter configuration will happen here.

Step 2: Configure Adapter 1 (Host-Only Network)

Purpose: Creates a direct link between your host computer and the GNS3 VM.
This connection allows the GNS3 GUI to manage devices inside the VM.

  1. Enable Adapter 1.
  2. Set Attached to → Host-Only Adapter.
  3. Choose your default VirtualBox host-only network (commonly vboxnet0).
  4. Leave Promiscuous Mode at Deny.
  5. Keep the default adapter type (Intel PRO/1000 MT Desktop is fine).

This first adapter is the most important one — without it, the GNS3 GUI cannot reach the server process running inside the VM.

Step 3: Configure Adapter 2 (NAT for Internet Access)

Purpose: Allows the GNS3 VM to reach the internet for updates, image downloads, or cloud-related labs.

  1. Enable Adapter 2.
  2. Set Attached to → NAT.
  3. Keep all other settings at their defaults.

This adapter is optional, but recommended if your labs need online access.

Step 4: Start the GNS3 VM

  1. Power on the GNS3 VM.
  2. When it finishes booting, the console will display something like:

GNS3 VM is running

IP: 192.168.56.x

This IP address is assigned from your Host-Only network and is used by the GNS3 GUI to communicate with the VM.

Step 5: Connect the GNS3 GUI to the VM

  1. Open the GNS3 GUI.
  2. Go to Edit → Preferences → GNS3 VM.
  3. Check Enable the GNS3 VM.
  4. Set the virtualization platform to VirtualBox.
  5. Select your GNS3 VM from the list.
  6. Click Test Settings.

You should see a message confirming that the GUI has successfully connected to the VM.

Step 6: Confirm Everything in GNS3

You can verify the setup by:

  • Adding a device (router, switch, or appliance) to a new project
  • Starting the device
  • Watching VirtualBox to see CPU activity inside the GNS3 VM

If the VM is doing the work, you’ve configured everything correctly.

Helpful Tips

  • Start the GNS3 VM first, then open the GNS3 GUI.
  • Use the Host-Only adapter for GUI ↔ VM communication.
  • Add a NAT adapter only if the VM needs internet access.
  • Avoid installing extra software inside the GNS3 VM unless required — it’s already optimized for GNS3.

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