By Fathalla Ramadan
February 2026
If you’ve installed GNS3 on Windows 11, launched a router—and seen it stuck at “Starting” or showing “Nested virtualization not available”—you’re not alone.
This is one of the most frequent issues I hear from students in Cairo, Riyadh, Manama, and beyond. The good news? It’s not your fault, and it’s 100% fixable.
In this guide, I’ll walk you through the exact steps that have helped hundreds of learners get GNS3 running smoothly on Windows 11 and achieved “gns3 nested virtualization windows 11 fix”, without disabling security entirely.
Why This Happens
Windows 11 includes advanced security features like:
- Core Isolation / Memory Integrity
- Hyper-V (used by WSL2, Docker, Windows Sandbox)
These features block QEMU (the engine behind GNS3 nodes) from using hardware virtualization—because they assume nested VMs are a risk.
But for networking labs? We need that access.
Common Symptoms
- Router status: “Starting…” forever
- Console shows nothing or black screen
- Error: “Unable to start VM” or “Hypervisor error”
- Works on Windows 10—but not Windows 11
Step-by-Step Fixes (Tested on Dell, HP, Lenovo, Surface)
Try these in order—most users fix it at Step 1 or 2.
Fix 1: Disable Core Isolation (Memory Integrity)
This is the #1 cause on Windows 11.
- Open Windows Security
- Go to Device Security → Core Isolation
- Turn OFF “Memory Integrity”
- Restart your computer
This does not disable antivirus—it only relaxes a specific memory protection that conflicts with QEMU.
Fix 2: Disable Hyper-V (If You Use WSL2 or Docker)
Hyper-V reserves virtualization exclusively—blocking GNS3.
- Open PowerShell as Administrator
- Run
- bcdedit /set hypervisorlaunchtype off
- Restart your PC
To re-enable later (e.g., for Docker):
bcdedit /set hypervisorlaunchtype auto
Fix 3: Enable Virtualization in BIOS/UEFI
- Reboot your PC
- Press F2/Del/F12 (varies by brand) to enter BIOS
- Find settings like:
- Intel VT-x or AMD-V → Enable
- SVM Mode (on AMD) → Enable
- Virtualization Technology → Enable
- Save & exit
Most modern laptops have this enabled by default—but some brands (e.g., Lenovo ThinkPad) disable it for “security.”
Fix 4: Use the GNS3 VM (Recommended for Windows 11)
Instead of running nodes locally, offload to a pre-configured VM:
- In GNS3: Edit → Preferences → GNS3 VM
- Check “Enable the GNS3 VM”
- Download the appliance if prompted
- Set Server to “Run everything inside the GNS3 VM”
This avoids Windows virtualization conflicts entirely—and is more stable long-term.
The GNS3 VM avoids Windows virtualization conflicts—but you still need to add your own appliances (e.g., FRRouting) if available.
Fix 5: Run GNS3 as Administrator
Right-click the GNS3 shortcut → “Run as administrator”
This grants necessary permissions to access low-level virtualization.
Verify It’s Working
- Add a FRRouting node node to your workspace
- Start it
- Double-click → Console should show:
- frr-router#
- Run
show versionto confirm it’s responsive
Success! Your lab is ready, with real routing protocols, no licensing gray areas.
Pro Tips for Stability
- Don’t run Docker/WSL2 and GNS3 at the same time (they compete for virtualization)
- Use SSD storage—GNS3 is I/O heavy
- Allocate enough RAM: 8 GB minimum, 16 GB recommended
Next Step: Build Real Labs
Now by achieving “gns3 nested virtualization windows 11 fix” and that GNS3 works, try:
All 26 labs—with troubleshooting checklists—are in my IP Routing and Switching Lab Handout Book.
Final Thought
Technology should empower learning—not block it.
These Windows 11 “security” features are well-intentioned, but they shouldn’t stop you from building your future.
You’ve got this. And now—you’ve got a working lab.
—
Fathalla Ramadan
Network Architect & Educator
35+ years in IT, networking, and technology education across the Middle East and beyond