GNS3
Build a full virtual network lab without buying a single router.
What it is
About GNS3
GNS3 is a free, open-source network simulation and emulation platform that emulates real network topologies by running actual vendor OS images like Cisco IOS inside virtual containers, connected in a drag-and-drop topology designer. It's the standard free tool network engineers use to practise CCNA and CCNP labs, test configurations before deploying to production, and reproduce network issues in a safe sandbox.
What you can do with it
Capabilities
Build and simulate multi-device network topologies
Run real vendor router and switch OS images in a virtual lab
Practise CCNA and CCNP-level configuration and troubleshooting scenarios
Test network changes safely before deploying to production
Integrate with Docker and VirtualBox for hybrid virtual and container labs
How to learn it
Learning Resources
GNS3's official documentation and getting-started guides
GNS3 Academy's official courses
YouTube channels like NetworkChuck and Jeremy's IT Lab covering GNS3 lab builds
Practise by replicating CCNA exam topology scenarios in a personal GNS3 lab
Pro Tip
Use the free GNS3 VM run in VirtualBox or VMware rather than running everything on the host OS — it isolates resource-heavy device images and avoids networking-adapter conflicts.
Skills that use this tool
Roles that use this tool