I love open-source tools (and their GitHub repositories). Someone launches a cool idea, and you can dig through their source code to figure out how it works. It beats reading documentation or fixing AI hallucinations every day of the week ;)

Not too long ago, the containerlab team launched the ability to run containerlab within a free¹ container² running on GitHub, and that seemed like a perfect solution to run the BGP labs (Jeroen van Bemmel pointing me in the right direction was another significant step forward).

I don’t think I ever created two netlab releases in a week, but last week, I stumbled upon a motherlode of goodies, and it would be a shame not to make them available.

Someone tried to use netlab with vrnetlab containers for CSR 1000v and Nexus 9300v. We got it to work, but when I started integrating his changes into the development branch, I wanted to test them, so I installed vrnetlab to create my own container images. vrnetlab is an excellent tool, and building containers is a breeze (running them is a different story), so I added support for vrnetlab containers for every device supported by that tool and netlab for which I happened to have a disk image.

Here’s another rant to spice up your weekend: focus on fixing your company’s problems instead of chanting the AI mantra. Have fun ;)

In late 2023, I started playing with the idea of having automated validation in netlab. The early implementation was used in BGP labs, and a user liked it so much that he opened an issue saying:

I would suggest providing netlab validate for each lab.

Numerous rounds of yak-shaving later, I merged a humongous commit that adds automated validation to these lab exercises:

During the ITNOG8 netlab presentation, I jokingly said something along the lines “all that’s missing is RIPv2 and Babel.” That’s no longer true; someone asked me how hard it would be to add RIPv2 to netlab, and I said, “give me a few days 😎”

Other new features in netlab release 1.8.3 include support for BGP route servers (and route server clients), BGP Link Bandwidth community, and OSPF/BGP validation plugins for Arista EOS, Cumulus Linux and FRR. We also fixed the installation scripts to work with Ubuntu 24.04 and Debian Bookworm.

For more details, read the release notes.

Dan Massameno wrote a series of blog posts describing the challenges you might encounter when connecting Internet-of-Things¹ devices to a Cisco SD-Access network. It is an absolute must-read if you have to deal with IoT devices.

Vendor product managers love discussing mythical use cases to warrant complex functionality in their gear. Long-distance VM mobility was one of those (using it for disaster avoidance was Mission Impossible under any real-world assumptions), and high-volume network-based backups seems to be another. Here’s what someone had to say about that particular unicorn in a LinkedIn comment when discussing whether we need traffic engineering in a data center fabric.

When you’re dealing with a large cluster on a fabric, you will see things like inband backup. The most common one I’ve seen is VEEAM. Those inband backups can flood a single link, and no amount of link scheduling really solves that; depending on the source, they can saturate 100G. There are a couple of solutions; IPv6 or eBGP SID has been used to avoid these links or schedule avoidance for other traffic.

It is true that (A) in-band backups can be bandwidth intensive and that (B) well-written applications can saturate 100G server links. However:

Marc Brooker published an interesting blog post arguing that we need distributed systems for more than just scale.

Keep that in mind the next time someone tries to sell you the beauties of a centralized control plane – an idea that should be dead by now regardless of what ONF keeps preaching but will inevitably reappear in some form or other due to RFC 1925 Rule 11.

A year or two after Damien Garros told me that “he moved to France and is working on something new” we can admire the results: Infrahub, a version-control-based system that includes a data store and a repository of all source code you use in your network automation environment. Or, straight from the GitHub repository,

A central hub to manage the data, templates and playbooks that powers your infrastructure by combining the version control and branch management capabilities of Git with the flexible data model and UI of a graph database.

I’ve seen an early demo, and it looks highly promising and absolutely worth exploring. Have fun ;)

I mostly gave up on LLMs being any help (apart from generating copious amounts of bullshit), but I still thought that generating summaries might be an interesting use case. I was wrong.

As Gerben Wierda explains in his recent “When ChatGPT summarises, it actually does nothing of the kind” blog post, you have to understand a text if you want to generate a useful summary, and that’s not what LLMs do. They can generate a shorter version of the text, which might not focus on the significant bits.

Using the typical default router configurations, it can take minutes between a failure of an inter-AS link and the convergence of BGP routes. You can fine-tune that behavior with BGP timers and BFD (and still get pwned by Graceful Restart). While you can’t influence link failures, you could drain the traffic from a link before starting maintenance operations on it, and it would be a shame not to do that considering there’s a standard way to do that – the GRACEFUL_SHUTDOWN BGP community defined in RFC 8326. That’s what you’ll practice in the next BGP lab exercise.

Tom Limoncelli wrote another must-read masterpiece: sometimes you’ll save time if you make two trips instead of one.

The same lesson applies to network design: cramming too many features into a single device will inevitably result in complex, hard-to-understand configurations and weird bugs. Sometimes, it’s cheaper to split the required functionality across multiple devices.

The recent IBGP Full Mesh Between EVPN Leaf Switches blog post generated an interesting discussion on LinkedIn focused on whether we need route reflectors (in small fabrics) and whether they do more harm than good. Here are some of the highlights of that discussion, together with a running commentary.

Many network automation solutions generate device configurations from a data model and deploy those configurations. Last week, we focused on “how do we know the device data model is correct?” This time, we’ll take a step further and ask ourselves, “how do we know the device configurations work as expected?”

There are four (increasingly complex) questions our tests should answer:

AWS started charging for public IPv4 addresses a few months ago, supposedly to encourage users to move to IPv6. As it turns out, you need public IPv4 addresses (or a private link) to access many AWS services, clearly demonstrating that it’s just another way of fleecing the sheep Hotel California tax. I’m so glad I moved my videos to Cloudflare ;)

For more details, read AWS: Egress Traffic and Using AWS Services via IPv6 (rendered in beautiful, easy-to-read teletype font).