In the spring of 2017, Jeff Tantsura, the IETF Routing Area chair, delivered a short “Introduction to Segment Routing” webinar. In mid-April 2026, we had ~100 people at ITNOG 10 attending the excellent “Segment Routing: From Theory to Practice” workshop by the great Tiziano Tofoni. The future is obviously not evenly distributed.

If you’re in the early stages of your Segment Routing journey, you might appreciate the videos from Jeff’s webinar; you can now watch them without an ipSpace.net account.

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.

Arista is not the only platform using these default values; did you ever wonder where they came from?

A while ago, I found the How Automatic Return Routing solves IP overlap article on Cloudflare’s blog. They evidently have a technology that addresses a pain point well worth solving (access to shared resources from clients using overlapping address ranges). I just hate how they’re selling it. Go read the article first; I’ll wait.

OK, here’s what bothers me: the “VRFs and NAT are bad” claims, while they use the same technology in disguise.

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 on a Sunday night)

Making that work in a multi-vendor environment is even more fun¹, as I sadly discovered when creating the EVPN lab exercises or trying to figure out why some EVPN implementations were failing netlab EVPN integration tests.

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”. I particularly loved the “talk less, chat more” schedule. The longer breaks gave us plenty of time to catch up with old friends and discuss interesting, sometimes completely unexpected, topics. For example, I learned that SIP MESSAGE is used to carry SMS messages these days.

As much as I loved chatting with fellow networking engineers, I also found these presentations highly interesting:

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. The network core was a leaf-and-spine fabric with off-path BGP route reflectors and numerous other devices attached to it.

I’ve configured a few networks in the past, so I know it must have been a beast to configure all those devices by hand (and fix all the IP addressing errors), but then a thought struck me: unless one wants to practice configuring IP addresses, it might be a good idea to use netlab to generate the IP addressing plan and partial device configurations.

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 table

He kindly wrote a LinkedIn comment explaining that behavior:

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

He also documented a few netlab shortcomings (one of which caused a crash); fortunately, I found his blog post (admittedly over a year later) and fixed most of them in release 26.04:

I stopped tracking the (lack of) progress in network automation years ago, when I realized I had nothing new to say. As an eternal optimist, I hoped I was just missing something, but Urs Baumann (the guest of Software Gone Wild Episode 206) destroyed my hopes when he said, “I can still use the same slides I created 10 years ago”. On a more positive note, he recently completed his Master’s thesis on AI in network engineering, so we ended with a nice chat on its potential impact.

Another week, another interesting AI article (is anyone writing about anything else these days?), this time from Noah Smith (another author worth following). I found this gem hidden in his weekly roundup:

Instead of trying to write a piece of code from scratch, or prove a math theorem from scratch, or figure out some piece of knowledge for yourself, you just ask AI to do it all for you. So everyone ends up getting the right answers to questions whose answers are already known, so they don’t end up adding anything new.