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I started my part of the Segment Routing workshop @ ITNOG10 exploring SR-MPLS with IS-IS (simple SR-MPLS, dual-stack SR-MPLS, SR-MPLS over unnumbered IPv4 interfaces).

I always wanted to find someone who is more positive about AI than I am, while having solid “can deliver working stuff at scale” credentials.

Leo Fleskes sent me an interesting question after reading my Generate Partial Device Configurations with netlab blog post: What is stopping us from eventually, given enough usage and coverage, using netlab to configure devices in the live network?

A friend of mine sent me links to a new paper published by AWS engineers, and an associated LinkedIn post which claims: We got lean, resilient, massive aggregation fabrics that provide 33% better throughput with 69% fewer routers, savings 27% of costs, cu…

Following a link in Martin Fowler’s Fragments, I stumbled upon Genie Tarpit by Kent Beck – a perfect summary of my experiences with AI coding (code reviews are OK, new code less so).

netlab release 26.06 adds OSPFv3 support on FortiOS (by @a-v-popov) and MPLS/VPN support on SR Linux.

Did you know that you can implement a VRF-Lite design with VXLAN?

A happy netlab user sent me an unexpected use case: they successfully used its multi-vendor capabilities to argue with a vendor TAC.

A month ago, I described ARP issues in EVPN centralized routing design, and Naveen Kumar Devaraj was kind enough to add some Arista EOS implementation details.

Tony Mattke built several networking-focused CLI tools and released them on GitHub.

After the simple SR-MPLS demo and the dual-stack SR-MPLS setup, it was time for the next obvious question: Does SR-MPLS work over unnumbered IPv4 interfaces1, assuming the implementation of the underlying routing protocol supports them?

Here’s a short glimpse into the history of telecommunications: in a building at the top of this mountain (barely noticeable blip across the saddle from the radio tower; search for Capo Figari for more details), Guglielmo Marconi conducted experiments in t…

Doug Madory wrote an interesting article (published on APNIC blog) arguing that we shouldn’t worry about ephemeral BGP leaks that can be observed only during the BGP path hunting process that follows a route withdrawal.

After fixing the SR Linux LDP configuration template, I decided to add MPLS/VPN to the netlab SR Linux MPLS features.

Did you manage not to stumble on a dramatic post explaining how someone generated 10,000 lines of code with AI while wasting time on your LinkedIn feed?

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?

Most of the hyperventilated AI “success stories” are as useful as the “ANSIBLE!!!”

netlab release 26.05 is out.

netlab release 26.05 is out.

I postponed the discussion of ARP issues with EVPN anycast gateways to keep yesterday’s blog post reasonably short.

In a previous blog post, I described the ARP issues you’ll encounter when using centralized routing (on a spine switch) between two EVPN MAC-VRF instances (a fancy name for a VLAN encapsulated in VXLAN or MPLS).

The second demo1 I did during the Segment Routing workshop @ ITNOG10 illustrated how easy it is to set up and explore a small SR-MPLS network with netlab.

Kyle Kingsbury published a long (10-part) article about his frustrations with AI, aptly named The Future of Everything is Lies, I Guess.

I created nine sample SR-MPLS topologies for the ITNOG 10 SR-MPLS workshop, and of course, we ran out of time.

Naveen Kumar Devaraj mentioned an interesting fact in his EVPN-related comment: The EOS default ARP timeout is 4 hours, and MAC aging is 5 minutes.

A while ago, I found the How Automatic Return Routing solves IP overlap article on Cloudflare’s blog.

Adding IRB to a EVPN MAC-VRFs (the fancy way of saying stretched VLANs) seems like a no-brainer: Add IP addresses to VLAN interfaces Optionally add a shared anycast gateway Declare “Mission Accomplished” (and try to ignore the inevitable phone call at 2 AM

Last week’s SwiNOG was (as expected) great fun at a phenomenal location, starting with the first slide of the first presentation: “6 Stages of Network De-sh*tification”.

At ITNOG 10, I’ve seen something that I haven’t seen in a very long time: a mini-Interop-style physical lab using a dozen devices from different vendors.

Naveen Kumar Devaraj was reading my Integrated Routing and Bridging (IRB) with EVPN MAC-VRF Instances lab exercise and spotted this detail: Arista EOS originates MAC-IP routes with and without IP addresses, effectively doubling the size of the EVPN BGP ta…

@sjhloco wrote an excellent in-depth description of how you can use containerlab and netlab to manage your labs as code.

I stopped tracking the (lack of) progress in network automation years ago, when I realized I had nothing new to say.

Another week, another interesting AI article (is anyone writing about anything else these days?)

I spent the last two days in Bologna at ITNOG 10 in the excellent company of Italian networking engineers (many of them personal friends) and a few guests from around the world.

Phil Gervasi wrote an interesting article describing Rail-Optimized Networking for AI Training Workloads.

We had a wonderful SR-MPLS workshop @ ITNOG 10 in Bologna on April 20th 2025.

Most EVPN documentation rushes into the complexities of symmetric IRB, type-5 EVPN routes, and EVPN IP-VRFs, but if you want to master a technology, it’s better to take it slow and proceed with small steps.

Every other blue moon, I discover a bug in FRRouting (example).

A few weeks ago, I described the changes in the online BGP labs that allow you to use most of the common network operating systems as “external” routers1.

Milan Zapletal, the author of the biggest netlab topology I’ve seen so far (full story), has published a nice introductory article explaining What is Netlab and Why Network Engineers Should Care.

netlab release 26.04 is out.

FRRouting release 10.6 promised “BGP IPv6 VTEP support,” claiming “it enables EVPN deployments using IPv6 tunnel endpoints while maintaining full backward compatibility with IPv4 VTEPs.”

In a recent article, Scott Alexander made an interesting point: What AI produces are not hallucinations but shameless guesses (also known as bullshit) because the training process rewards the correct answers but does not penalize the incorrect ones.

IS-IS was designed to carry node addresses (NSAPs) between level-1 routers (called Intermediate Systems) within an area and area prefixes between level-2 routers, resulting in a perfect separation of concerns and forwarding information summarization.

A year ago, I was complaining about SR Linux breaking its configuration data model with a new software release.

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.

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).

Some netlab users want to accurately replicate their physical network’s topology in a virtual lab.

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.

The never-ending “we will replace developers” (or networking engineers) pipe dream didn’t start with the latest bout of AI hype (or SDN).