GNS3 alternatives: EVE-NG, Containerlab, CML and more

People look for a GNS3 alternative when the GNS3 VM, nested virtualization or image imports get in the way, or when they want labs as code. GNS3 is a great tool, and for many labs it is still the right one. This page compares the main options as of October 2026, using each project's own site or repository.

What to compare

Four questions separate these tools more than any feature list:

• What does it run? Vendor VM images (QEMU/KVM), containers, or both.
• How do you build labs? A GUI you draw in, or a YAML file you keep in Git.
• Where does it run? A desktop app, a browser UI on a server, or a CLI on Linux.
• What does it cost? Free and open source, freemium, or a paid licence.

At a glance

GNS3

GNS3 is free and open source (GPL-3.0). It has a desktop GUI and a server; the server drives Dynamips, IOU, QEMU/KVM, VirtualBox, VMware and Docker, and a web UI client also exists. The latest stable releases are 2.2.61 (July 2026) and 3.0.6 (January 2026). On Windows and macOS, modern images such as IOSv run inside the GNS3 VM, which GNS3 recommends running in VMware.

Fits: anyone who wants a free GUI, a huge appliance catalogue and many emulator types in one place. The cost is setup: the VM, KVM and image checksums. Our GNS3 troubleshooting guide covers those.

EVE-NG

EVE-NG is a browser-based emulator that you install as its own server, based on Ubuntu 24.04, on bare metal or as a VM. Client packs add local telnet, VNC and Wireshark.

The editions changed this year. The download page lists Community Edition 6.2.0-4 as end of support and end of life in June 2026. The current build is Professional 7.2.0-18, which runs as a free Freemium edition until you add a licence. The comparison page gives Freemium the same feature list as the paid editions (Docker nodes, integrated Wireshark, hot links, link quality with delay, jitter and loss, clustering) but limits it to 7 running nodes per instance. The paid Base licence (listed at 150 EUR) raises that to 1024 nodes per lab, and RBL adds user roles such as editors and users. Licences are time-limited: a new one does not extend the old one.

Fits: teams and trainers who want one shared lab server with a browser UI and multi-user access, and who are fine with a paid licence for larger labs.

Containerlab

Containerlab is a free CLI (BSD-3-Clause) that builds labs from a YAML topology file. It runs container network OSes such as Nokia SR Linux and Arista cEOS natively. VM-based images run through vrnetlab, which wraps a VM disk you supply in a container; the docs say this needs nested virtualization. It runs on Linux, on macOS (Intel and ARM, with Rosetta for x86 images) and on Windows through WSL. A VS Code extension adds a graphical view.

Fits: network engineers who want labs in Git and in CI pipelines, and whose devices exist as containers.

Cisco Modeling Labs (CML)

CML is Cisco's lab platform, with an HTML5 UI and a full API. Its big difference is legal Cisco images: reference platforms come with the licence. It also runs third-party KVM VMs and Docker containers.

• CML-Free costs nothing and runs up to 5 nodes at once (unmanaged switches and external connectors don't count). Its images include IOL, IOL-L2 and ASAv plus Linux hosts. You need a Cisco.com account, and telemetry cannot be turned off.
• Personal is listed at $199 for 20 nodes and Personal Plus at $349 for 40 nodes, single user.
• Enterprise (multi-user, up to 300 nodes, clustering) and Education are sold through Cisco.

Personal editions run as a VM on VMware Workstation, Player or Fusion Pro. The system requirements say Intel CPUs are fully supported, AMD is best effort, and CML does not work on M series Macs.

Fits: Cisco certification study (CCNA to CCIE) and Cisco-centric teams that need licensed images.

Kathará

Kathará is a free, GPL-3.0 emulator from the Netkit lineage. Every device is a Docker container, with built-in images for FRRouting, Quagga, Bind, P4 and Open vSwitch, or your own images. A lab is a folder with a topology file and per-device config files. It runs on Windows, macOS and Linux, and on Kubernetes for large labs. It does not run VM images.

Fits: teachers and students, protocol research, and anyone whose lab is Linux routing and services.

netlab

netlab is a free, open-source tool that works one level up. You describe the topology and the routing design in YAML, and it creates the containerlab or Vagrant/libvirt files, an addressing plan and the device configs (OSPF, BGP, IS-IS, EVPN, MPLS and more), then deploys them. It runs on Linux, in WSL, or in a Multipass VM on macOS. VirtualBox support has been removed.

Fits: engineers who want a working, preconfigured lab in minutes and care about the design, not the cabling.

Isothrum

Isothrum is our free editor. Here it is with the same honesty. You draw a lab in the browser with no account, and the engine runs locally as WebAssembly. A lab holds containers from any Docker image, Linux and Windows VMs, switches with VLANs and trunks, and an automatic router or your own (FRR, or Cisco images you supply, built with vrnetlab). Links can carry latency, jitter, loss and bandwidth limits. It exports isoloom.yml plus Docker Compose, Vagrant, Proxmox, Kubernetes and cloud files, and it opens GNS3 .gns3 projects.

The limits: the editor does not run the lab. You run the exported files with Docker, Vagrant or the target platform. A desktop app with consoles, VNC, Wireshark capture and live status is coming soon, but there is no released download yet. It ships no vendor images, and IOSv, CSR 1000v and Catalyst 8000v still need KVM.

Fits: people who want to sketch a lab visually and get plain, portable files, especially container labs that need no hypervisor.

How to choose

• You need licensed Cisco images and run an Intel PC: CML, starting with CML-Free.
• You want a shared browser lab server for a team or a class: EVE-NG.
• Your devices are containers and you want labs in Git: Containerlab, or netlab on top of it for automatic configs.
• You teach Linux routing and services: Kathará.
• You want one free GUI for everything and accept some setup: stay with GNS3.
• You want to draw a lab and export files for Docker or Vagrant: Isothrum.

Many people use two of these. A network lab for study and a lab for testing changes rarely need the same tool.