A year ago, I was complaining about SR Linux breaking its configuration data model with a new software release. At that time, I was promised it would only happen once a year, and, like clockwork, that moment arrived with the SR Linux release 26.03.

However, this year Miguel Redondo fixed the netlab SR Linux configuration templates (VRF export policies, LocPref routing policy changes) before I could even start looking at them, and Roman Dodin released a tool that tells you exactly what changed between software releases and how to fix it.

Avery Pennarun published yet another excellent article: every layer of review makes you 10x slower, effectively reiterating what I’ve been saying for decades: all the technology in the world won’t help you unless you re-architect the broken processes.

AI is no exception, but of course, the AI evangelists, LinkedIn AI Wranglers¹, and Thought Leaders will never tell you that (or even admit it).

read more add comment

TL&DR: With the recent changes to online BGP labs, you can also use Aruba CX, Cisco IOS, Cisco IOS XE, Cisco IOS XR, Dell OS10, Junos, or VyOS as external lab devices in most lab exercises (you could always use these devices for the routers you worked on). Previously, you could choose between Arista EOS and FRRouting, both of which are (obviously) still supported.

One of the goals of the Online BGP Labs project was to create an environment in which you could practice the BGP features you were interested in without spending an inordinate amount of time preparing the lab.

For example, if you want to figure out why BGP wedgies work the way they do, you need at least four additional autonomous systems, two of them acting as upstream ISPs for your customer router, and at least one of them implementing BGP policies using BGP communities.

Some netlab users want to accurately replicate their physical network’s topology in a virtual lab. Ignoring the obvious caveats for a moment, the first hiccup is usually the interface naming. All bets are off if you’re using anything but Ethernet in your actual network, but even if you did standardize on Ethernet, the container/VM interface names might not match the physical ones.

netlab provided a solution for a long time – you can specify interface ifindex when attaching a node to a link. For example, use the following topology to connect Ethernet3 on R1 to Ethernet6 on R2:

Geoff Huston published an article supposedly describing the challenge of securing NTP, but as is usually the case, he couldn’t skip the prior art going all the way back (almost) to the formation of Earth.

Before coming to the how do we secure NTP section, you’ll learn everything about the wobbly Earth rotation, the changes in the Earth’s angular speed, the impact of tides, the smearing of leap seconds, the differences between UT1 and UTC, why we use quasars to measure time, and everything there is to know about NTP. Have fun!

The never-ending “we will replace developers” (or networking engineers) pipe dream didn’t start with the latest bout of AI hype (or SDN). As Stephan Schwab explains in his Why We’ve Tried to Replace Developers Every Decade article, it started with COBOL, the magic high-level programming language that businesspeople would use to write their own programs.

At least some of us know how well that ended. I was also unfortunate to be there for the 5GL hype, the forms-driven programming hype, the “everyone will solve every problem out there with Excel macros” (it does work for networking inventory, doesn’t it?), and a few others. So please excuse me if I remain a bit skeptical about the latest fad, even though I find it (like all the previous ones) very useful when used conservatively in limited domains.

I work on a laptop that loves to power down when not used (the right thing to do), which often breaks the SSH session to my netlab server (not so good).

Reconnecting is trivial. Figuring out which lab I was working on and where it lives on the disk after a few hours? That’s the annoying part.

We solved most of that ages ago with the netlab status --all command. It shows all running labs¹ and their directories, so you can quickly jump back to where you were. However, even that gets tedious the 100th time you have to do it.

Most vendors “discovered” anycast gateways when they tried implementing routing between MAC-VRFs in an EVPN environment and hit all the usual tripwires (more about that later). A few exceptions (like Arista) supported them on VLAN segments for over a decade, and it was a no-brainer to extend that support to VXLAN segments.

Want to try out how that works? The Anycast Gateways on VXLAN Segments lab exercise is just what you need.

Something didn’t feel right as I tried to check whether the IPv4 ECMP I observed in the latest version of Arista cEOS containers works with my MPLS/anycast scenario. The forwarding tables seemed OK, but I wasn’t getting MPLS labels in the ICMP replies (see RFC 4950 for details), even though I know Arista EOS can generate them.

I decided to go down that rabbit hole and built the simplest possible BGP-free core (the addition of BGP will become evident in a few seconds) to investigate PE/P-router behavior:

When I started the Online BGP Labs project in mid-2023, Cumulus Linux still seemed like a good platform to use. You could run devices as virtual machines (we were still supporting VirtualBox) or in containers (containerlab was improving with every release), and it looked more polished than bare-bones FRRouting.

Things only went downhill from there (from the perspective of offering a free and easy-to-use solution with a CLI resembling commonly-used devices):