netlab Release 1.5.3: libvirt Public Networks

containerlab release 0.41.0 that came out a few days ago changed a few topology attributes with no backward compatibility, breaking netlab for anyone doing a new installation. The only way out of that conundrum was to push out a new netlab release that uses the new attributes and requires containerlab release 0.41.0 (more about that in a minute).

On a more positive note, netlab release 1.5.3 brings a few interesting features, including:

I will cover the public libvirt networks in another blog post, today I want to explain how we’re dealing with containerlab changes.

Root cause: containerlab release 0.41.0 changed the name of management network attributes from mgmt_ipv4/ipv4_subnet to mgmt-ipv4/ipv4-subnet with no backward compatibility or deprecation period. Old topologies no longer work, and new topologies don’t work with older versions of containerlab.

Mitigation: The only safe way to deal with this change was to change the netlab containerlab topology template and enforce minimum containerlab version during netlab up virtualization provider tests. The netlab install installation scripts could use an older containerlab version, but that wouldn’t help users installing containerlab manually (without reading the smallprint). It would also break netlab the moment someone would upgrade containerlab.

Positive side effects: netlab up and netlab down already executed a number of commands to check the virtualization provider installation. I modified those probes to return a hopefully-useful error message when the executed command fails.

containerlab probes check the availability of containerlab command and containerlab version (using a bash command that looks like line noise). libvirt probes are more extensive and check that:

  • You installed KVM and KVM utilities like kvm-ok
  • KVM works (for example, you haven’t forgotten to turn on nested virtualization)
  • You installed libvirt and made yourself a member of libvirt group
  • You installed Vagrant and vagrant-libvirt plugin.


To get more details and learn about additional features included in release 1.5.3, read the release notes. To upgrade, execute pip3 install --upgrade networklab. You will also have to upgrade containerlab with sudo containerlab version upgrade.

New to netlab? Start with the Getting Started document and the installation guide.

Need help? Open a discussion or an issue in netlab GitHub repository. There’s also a netlab channel in networktocode Slack team, but you will get faster response time reporting your challenges in GitHub.

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