The early October 2021 Facebook outage generated a predictable phenomenon – couch epidemiologists became experts in little-known Bridging the Gap Protocol (BGP), including its Introvert and Extrovert variants. Unfortunately, I also witnessed several unexpected trips to Mount Stupid by people who should have known better.

To set the record straight: everyone’s been there, and the more vocal you tend to be on social media (including mailing lists), the more probable it is that you’ll take a wrong turn and end there. What matters is how gracefully you descend and what you’ve learned on the way back.

When I started creating the How Networks Really Work series, I wondered whether our subscribers (mostly seasoned networking engineers) would find it useful. Turns out at least some of them do; this is what a long-time subscriber sent me:

How Networks Really Work is great, it’s like looking from a plane and seeing how all the roads are connected to each other. I know networking just enough to design and manage a corporate network, but there are many things I have learned, used and forgotten along the way.

Two weeks ago I replied to a battle-scar reaction to 7-layer OSI model, this time I’ll address a much more nuanced view from Russ White. Please read his article first (as always, it’s well worth reading) and when you come back we’ll focus on this claim:

The OSI Model does not accurately describe networks.

Like with any tool in your toolbox, you can view the 7-layer OSI model in a number of ways. In the case of OSI model, it can be used:

I should have known better, but I got pulled into another stretched VLANs for disaster recovery tweetfest. Surprisingly, most of the tweets were along the lines of you really shouldn’t be doing that and that would never work well, but then I guess I was only exposed to a small curated bubble of common sense… until this gem appeared in my timeline:

Interestingly, that’s exactly how IP works:

One of my readers sent me this interesting question:

It begs the question in how far graduated students with a degree in computer science or applied IT infrastructure courses (on university or college level or equivalent) are actually aware of networking fundamentals. I work for a vendor independent networking firm and a lot of my new colleagues are college graduates. Positively, they are very well versed in automation, scripting and other programming skills, but I never asked them what actually happens when a packet traverses a network. I wonder what the result would be…

I can tell you what the result would be in my days: blank stares and confusion. I “enjoyed” a half-year course in computer networking that focused exclusively on history of networking and academic view of layering, and whatever I know about networking I learned after finishing my studies.

I was speaking with a participant of an SDN event in Zurich after the presentations, and he made an interesting comment: whenever he experienced serious troubleshooting problems in his career, it was due to lack of understanding of networking fundamentals.

Let me give you a few examples: Do you know how ARP works? What is proxy ARP? How does TCP offload work and why is it useful? What is an Ethernet collision and when would you see one? Why do we need MLD in IPv6 neighbor discovery?

Remember OpenFlow, the One Protocol to Bind Them All¹? I haven’t heard anyone even mention it in ages, and I never bothered to ask whether anyone is still using it after the dismal results of the 2022 poll.

Anyway, if you still have to deal with that ancient blunder, six hours of deep dive videos I recorded a decade ago might still be useful. You can watch them without an ipSpace.net account.

Looking for more binge-watching materials? You’ll find them here.

After the introduction to SR-MPLS demo I did during the Segment Routing workshop @ ITNOG10, we moved to dual-stack SR-MPLS – can we assign node segment identifiers (SIDs) to IPv4 and IPv6 prefixes? The demo used the same three-router network as the previous one, with IPv4 SIDs starting at one and IPv6 SIDs starting at 101:

Most of the hyperventilated AI “success stories” are as useful as the “ANSIBLE!!!” movement was a few years ago. It’s thus always a pleasure to find someone with well-established software development chops who took the time to describe what works for them.

One cannot argue with Mike McQuaid’s credentials (at least if you happen to be using homebrew on MacOS, which you REALLY SHOULD), and his Sandboxes and Worktrees: My secure Agentic AI Setup in 2026 article is full of relevant recommendations in case you’re brave enough to let AI agents loose on your GitHub repository.

netlab release 26.05 is out. Here are the highlights:

• Support for global BGP routes with SRv6 next hops (inspired by proof-of-concept by @jvbemmel) on FRR and IOS XR
• Junos OSPF/IS-IS route redistribution, VRF IS-IS instances, and OSPF interface parameters
• Streamline and speed up the FortiOS initial device configuration by @a-v-popov
• Support for Juniper cSRX container by @leec-666