GNS3 is free, open-source software for emulating, configuring, testing, and troubleshooting virtual and real networks. It pairs a graphical client with a virtual machine, while its server can run locally or remotely. Network engineers can combine emulated devices using actual images with simulated devices, including a built-in layer 2 switch. Supported equipment includes appliances from Cisco, Brocade, Cumulus Linux, and HPE. GNS3 also works with Docker, QEMU-based appliances, VMware, VirtualBox, Hyper-V, and connections to real networks. Its Marketplace offers preconfigured appliance templates with recommended settings. There are no monthly or yearly license fees, and supported device count is limited in practice by the host computer's CPU and memory. Users must provide their own Cisco IOS images; GNS3 does not provide them. The software is available for Windows, macOS, and Linux. Documentation recommends the GNS3 VM for most Windows and macOS setups and for complex topologies. GNS3 is used for networking education, certification practice, proofs of concept, demonstrations, and interoperability testing. Its server has no authentication enabled by default and should be restricted at the network level.
Who it is for
GNS3 suits network engineers and learners working on network education, certification practice, proofs of concept, demonstrations, or interoperability testing. It also fits users who need to combine virtual appliances with real networks.
What is good
- Open-source software with no monthly or yearly license fees.
- Supports emulated and simulated devices.
- Works with Docker, QEMU, and several hypervisors.
- Marketplace offers preconfigured appliance templates.
What to know first
- Users must provide their own Cisco IOS images.
- Server authentication is disabled by default.
- Device capacity depends on host CPU and memory.
Verdict
GNS3 supports multi-vendor network lab work without license fees, with practical scale tied to the host computer. Users should plan for Cisco image requirements and restrict server access at the network level.
GNS3 plans and pricing
All plansCompared on network testing software
- Free plan
- Yes
- Simulation model
- hybrid
- Real-time emulation
- Yes
- Hardware-in-the-loop
- Yes
- Deployment options
- desktop
- Automation API
- Yes
