How to Run the GNS3 VM Inside Oracle VirtualBox
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How to Run the GNS3 VM Inside Oracle VirtualBox
A Complete Guide
GNS3 becomes far more powerful and efficient when paired with the GNS3 VM. Instead of your host machine running all routers, switches, and appliances, the load shifts into a dedicated virtual machine. While many users rely on VMware, you can run the GNS3 VM just as effectively using Oracle VirtualBox.
This guide walks you through importing the GNS3 VM OVA file, configuring VirtualBox, linking the VM to the GNS3 desktop client, and understanding how the network paths between each component work.
Step 1: Extract the GNS3 VM ZIP File
After downloading the GNS3 VM package for VirtualBox:
- Locate the ZIP file (for example, GNS3.VM.2.x.zip).
- Extract it using your preferred tool.
- Inside the extracted folder, you will find a .ova file — this is the VirtualBox-ready appliance.
What is an OVA file?
It’s an “Open Virtualization Appliance,” a ready-to-run virtual machine packaged for import.
Step 2: Open Oracle VirtualBox
- Launch VirtualBox.
- Go to File → Import Appliance.
This prepares VirtualBox to load the GNS3 VM image.
Step 3: Select the OVA File
- Click Choose.
- Browse to the extracted folder.
- Select the .ova file and click Next.
VirtualBox will show a summary of the machine it is about to import.
Step 4: Adjust the Import Settings
(Highly recommended for performance)
Before completing the import, review the resource allocation:
- CPU: Assign at least 2 cores (more if you run complex topologies).
- RAM: Minimum 4 GB; 8 GB provides much smoother performance.
- Network Adapters: Keep the default NAT + Host-Only configuration.
- NAT helps the VM reach the Internet (for updates).
- Host-Only ensures reliable communication between your GNS3 GUI and the VM.
- MAC Address Policy: Keeping “Generate new MAC addresses for all adapters” can help avoid conflicts.
After reviewing, click Import. VirtualBox will create the VM automatically.
Step 5: Start the GNS3 VM
- Select the imported VM.
- Click Start.
- Allow the VM to boot into the GNS3 VM console (Ubuntu-based).
You should see its IP address and confirmation that the GNS3 backend services are running.
Step 6: Connect GNS3 to the VM
Next, tell your GNS3 desktop application to use the VM instead of running devices locally.
- Open GNS3 on your host computer.
- Go to Edit → Preferences → GNS3 VM.
- Enable “Enable the GNS3 VM”.
- Select VirtualBox as the virtualization provider.
- Choose the GNS3 VM from the dropdown.
- Click Test Settings.
A successful configuration will show a message indicating that the GNS3 VM is detected and running.
How the Host, GNS3 VM, and VirtualBox Communicate
Understanding the communication path helps troubleshoot connectivity and device start-up issues.
+——————-+
| Host OS |
| (Windows/Linux) |
| |
| GNS3 GUI |
+———+———+
|
VirtualBox Host-Only Adapter
|
+———v———+
| GNS3 VM |
| (Ubuntu Core) |
| |
| Dynamips/QEMU |
| Routers/Switches |
+———+———+
|
Internal Networks for Lab Devices
|
+——–v——–+
| Virtual Routers |
| Virtual Switches|
| VPCS / PCs |
+—————–+
How the pieces interact:
1. GNS3 GUI on the Host OS
- You design topologies.
- Commands and device operations are sent to the VM through the Host-Only network.
2. GNS3 VM running inside VirtualBox
- Performs the heavy emulation work.
- Handles IOSv, IOSvL2, QEMU images, VPCS, Docker containers, and more.
- Reduces CPU/RAM load on your host.
3. VirtualBox Network Adapters
- Host-Only Adapter:
Used for stable host ⇄ VM communication. - NAT Adapter:
Allows the VM to access the internet. - Internal GNS3 Networks:
Used by devices inside your topologies to talk to each other.
This architecture ensures that your host machine remains responsive while the VM handles networking workloads.
Final Thoughts
Running the GNS3 VM within Oracle VirtualBox is a powerful solution that avoids the need for VMware products while providing the same performance benefits. Once the VM is imported, configured, and linked with the GNS3 client, you can run large labs with routers, switches, firewalls, and servers — all inside a controlled virtual environment.
If you want, I can also prepare:
✅ A companion guide for configuring VirtualBox network adapters
✅ A troubleshooting section for common GNS3 VM errors
✅ A printable PDF version of this guide
