Stefano’s notebook

my technical writings

netlab: the swiss knife for network simulations

Edit 2022-08: netsim-tools was renamed to netlab on release 1.3.

Edit 2023-06: new documentation url is

While working on the VXLAN and EVPN Series I started looking around searching for a good way to automate the configuration of my GNS3 appliances used in the different LABs.

Ansible was a natural choice, since I was already using it for configuring Dell OS10 and other devices at work. For that reason, I was thinking about deploying an Ansible instance as a VM (or as a container) on top of GNS3, keeping track of the different playbooks using GIT (or github), etcetera etcetera etcetera…

But then, I discovered this wonderful tool created by Ivan Pepelnjak @ NETLAB (formerly NETSIM-TOOLS).

When I approached it, the first word was: “Wow!”. A single toolkit to deploy virtual appliances, to configure them, and to manage links and IP address allocations! This would be a dream!

Then I started reading all the docs, having a look at the examples and the existing codebase, ansible playbooks and templates, and more time I spent working with it, more and more I was convinced that this is the perfect tool for me.

And the next phase was: let’s contribute to it! Let’s add some more devices, some more templates, let’s make it more useful also for my stuff!

This is why I added support for Mikrotik CHR and VyOS, and their configurations. And this is why, I am sure about that, I will continue to give my little contribution to this wonderful project.

If you are interested in discovering more about netlab, have a look at these links:

I promise you will like it! ;)

Creating a topology is as simple as creating a YAML file that describes it, using the infrastructure-as-code principle. You can describe nodes, links, and specific parameters:

module: [ bgp ]

  a: 65001
  b: 65002
  y: 65003
    device: linux
    module: []

links: [ a-b, b-y, y-linux ]

Going back to the original topic, EVPN support in netlab is still under development, and more other features are to be developed. But you can contribute to it, if you wish! ;)

In the meantime, I have a set of additional Ansible templates that you can use to configure an Arista EOS-based topology, and another example for MLAG as well.

On the same github repository, you can find additional netlab topology examples, like BGP with Route Reflectors, and MPLS/LDP L3VPN (VPNv4).

Oh! I forgot to say that netlab is also able to generate a graph of the topology. See the following example, based on the above YAML file:


Or, a more complex one:


I hope you will like netlab as much as I like it! And I hope to see you soon on the contributor list.