Free and open-source network labs with Containerlab: an intro, an update, a workshop#

Gordon Gidofalvy, Nokia

• Why: Lab-as-code is the closest thing network engineering has to CI for topology and config change — useful for prototyping fabrics, regression-testing config, and reproducing vendor claims before they touch production. This is the tool's 5-year status review plus a hands-on workshop.
• What: Containerlab at ~300K installations, 140+ contributors, 35+ supported network OSes (13 added in the last 12 months). Node types span containerized NOSes (SR Linux, SR OS, cEOS, XRd, cRPD, and more), VM-based NOSes wrapped in containers via vrnetlab (Juniper vMX/vJunosRouter, Arista vEOS, Cisco XRv9k/NX-OS, Fortinet, Palo Alto, OcNOS), and arbitrary regular containers — FRR, traffic generators, telemetry stacks, IPAM/DCIM, flow collectors. Declarative YAML topologies make labs versionable, shareable artifacts.
• How: Docker-based; a topology file defines nodes and links; the workshop walks from a first FRR lab through expanding topologies to collaboratively building a working "Internet". Requires a Linux host on kernel 5.4+ (physical or VM).
• Where applicable: Broadly applicable anywhere Docker runs; the intro half is 101 material, but the ecosystem update (including non-labbing use cases like the SIDN routing-security audit prototype) is where the value is for someone already past the basics.