TL&DR: Of course, the title is clickbait. While the differences are amazing, you won’t notice them in small topologies or when using bloatware that takes minutes to boot.

Let’s start with the background story: due to the (now fixed) suboptimal behavior of bleeding-edge Ansible releases, I decided to generate the device configuration files within netlab (previously, netlab prepared the device data, and the configuration files were rendered in an Ansible playbook).

As we use bash scripts to configure Linux containers, it makes little sense (once the bash scripts are created) to use an Ansible playbook to execute docker exec script or ip netns container exec script. netlab release 26.01 runs the bash scripts to configure Linux, Bird, and dnsmasq containers directly within the netlab initial process.

Now for the juicy part.

Why do we need Infrahub, another network automation tool? What does it bring to the table, who should be using it, and why is it using a graph database internally?

I discussed these questions with Damien Garros, the driving force behind Infrahub, the founder of OpsMill (the company developing it), and a speaker in the ipSpace.net Network Automation course.

David Gee was time-pressed to set up a demo network to showcase his network automation solution and found that a Ubuntu VM running netlab to orchestrate Arista cEOS containers on his Apple Silicon laptop was exactly what he needed.

I fixed a few blog posts based on his feedback (I can’t tell you how much I appreciate receiving a detailed “you should fix this stuff” message, and how rare it is, so thanks a million!), and David was kind enough to add a delightful cherry on top of that cake with this wonderful blurb:

TL&DR: Most probably not, but if you do, you’d better not rely on random blogs for professional advice #justSaying 😜

Here’s an interesting question I got from a reader in the midst of an OSPF-to-IS-IS migration:

Why should one bother with different [IS-IS] areas when the routing hierarchy is induced by the two levels and the appropriate IS-IS circuit types on the links between the routers?

Well, if you think you need a routing hierarchy, you’re bound to use IS-IS areas because that’s how the routing hierarchy is implemented in IS-IS. However…

I completely rewrote netlab’s device configuration file generation during the New Year break. netlab Release 26.01 no longer uses Ansible Jinja2 functionality and works with Ansible releases 12/13, which are used solely for configuration deployment. I had to break a few eggs to get there; if you encounter any problems, please open an issue.

Other new features include:

• EVPN for VXLAN-over-IPv6
• The ‘skip_config’ node attribute that can be used to deploy partially-provisioned labs
• Lightweight netlab API HTTP server by Craig Johnson
• Rudimentary support for Citrix Netscaler by Seb d’Argoeuves

You’ll find more details (and goodies) in the release notes.

They say time goes faster as you get older, and it seems to be true. Another year has (almost) gone by.

Try to disconnect from the crazy pace of the networking world, forget the “vibe coding with AI will make engineers obsolete” stupidities (hint: Fifth Generation Languages and Natural Language Programming were all the rage in the 1980s and 1990s), and focus on your loved ones. I would also like to wish you all the best in 2026!

Want to look up various HTTP status/error codes when troubleshooting a DNS BGP network server problem? Start at http.pizza for badly-needed stress relief (HT: Networking Notes), then start a chat session with your new AI friend exploring more focused resources like the Wikipedia list of HTTP status codes.

A month ago, I described how Ansible release 12 broke the network device configuration modules, the little engines (that could) that brought us from the dark days of copy-and-paste into the more-survivable land of configuration templates.

Three releases later (they just released 13.1), the same bug is still there (at least it was on a fresh Python virtual environment install I made on a Ubuntu 24.04 server on December 13th, 2025), making all device_config modules unusable (without changing your Ansible playbooks) for configuration templating. Even worse:

I don’t know why I decided to allow underscores in netlab node names. Maybe it’s a leftover from the ancient days when some network devices refused to accept hyphens in hostnames, or perhaps it’s a programmer’s subconscious hatred of hyphens in identifiers (no programming language I’m aware of allows them for a very good reason).

Regardless, you can use underscores in netlab node names (and plugins like multilab use them to create unique hostnames), and they work great on Linux distributions we recommend… until they don’t.

What follows is a story about the weird dependencies that might bite you if you ignore ancient RFCs.

Like OSPF, IS-IS was designed when router memory was measured in megabytes and clock speeds in megahertz. Not surprisingly, it includes a scalability mechanism similar to OSPF areas. An IS-IS router could be a level-1 router (having in-area prefixes and a default route), a level-2 router (knowing just inter-area prefixes), or a level-1-2 router (equivalent to OSPF ABR).

Even though multilevel IS-IS is rarely used today, it always makes sense to understand how things work, and the Multilevel IS-IS Deployments lab exercise created by Dan Partelly gives you a perfect starting point.