Daniel Dib asked an interesting question on LinkedIn when considering an RT5-only EVPN design:

I’m curious what EVPN provides if all you need is L3. For example, you could run pure L3 BGP fabric if you don’t need VRFs or a limited amount of them. If many VRFs are needed, there is MPLS/VPN, SR-MPLS, and SRv6.

I received a similar question numerous times in my previous life as a consultant. It’s usually caused by vendor marketing polluting PowerPoint slide decks with acronyms without explaining the fundamentals¹. Let’s fix that.

Dmytro Shypovalov wrote a fantastic article explaining the basics of MPLS-based Segment Routing. It’s pretty much equivalent to everything I ever wrote about SR-MPLS but in a much nicer package. Definitely a must-read.

Ben asked an interesting question:

Do you think, realistically in 2024, netlab would suffice to prepare the CCIE lab exam? Particulary for the SP flavor, since netlab supports a lot of routing protocols. Thanks!

TL&DR: No.

netlab would be a great tool to streamline your CCIE preparation studies. You could:

Here’s another AI rant to spice your summer: AI Is Still a Delusion, including an excellent example of how the latest LLMs flunk simple logical reasoning. I particularly liked this one-line summary:

The real danger today is not that computers are smarter than us but that we think computers are smarter than us and consequently trust them to make decisions they should not be trusted to make.

It might be worth remembering that quote when an AI-powered management appliance messes up your network because of a false positive ;)

The first BGP load balancing lab exercise described the basics of EBGP equal-cost load balancing. Now for the fun part: what if you want to spread traffic across multiple links in an unequal ratio? There’s a nerd knob for that: the BGP Link Bandwidth extended community that you can test-drive in this lab exercise.

In Matt Duggan’s blog post, you’ll find a scathing review of another attempt to throw AI spaghetti at the wall to see if they stick: the GitHub Copilot Workspace.

He also succinctly summarized everything I ever wanted to say about the idea of using AI tools to generate networking configurations:

Having a tool that makes stuff that looks right but ends up broken is worse than not having the tool at all.

Daniel Dib went on another deep dive: Why Do We Have Native VLANs? What I loved most was that he went through the whole 802.1 standard (quite an undertaking) and explained the reasoning that VLAN-aware switches behave the way they do.

You should also read the follow-up post: what happens if a VLAN-unaware switch receives an 802.1Q-tagged frame?

Brad Casemore published an interesting analysis explaining why Cisco should accept being a mature company with mature products (yeah, you have to subscribe to view it). I always loved reading his articles, but unfortunately, this time, he briefly ventured into the “I don’t think this word means what you think it means” territory:

MPLS worked – and it still works – but it provided optimal value in an earlier time when the center of gravity was not the cloud. The cloud challenged the efficacy of MPLS, and it wasn’t long before SD-WAN, cloud connects, and interconnects […] represented an implacable threat to a status quo that had once seemed unassailable.

The second part of the paragraph is (almost) true, but it had nothing to do with MPLS.

In another wonderful deep dive, Julia Evans explains why you can’t edit the command line in some Linux utilities like the ancient sh.

You’ll also figure out:

• Why does CTRL-A jump to the beginning of the line?
• How can you enable command line editing in ancient utilities?

Have fun!

Last summer, I started a long-term project to revive the BGP labs I created in the mid-1990s. I completed the original lab exercises (BGP sessions, IBGP, local preference, MED, communities) in late 2023 but then kept going. This is how far I got in a year:

• Twenty-six deploy BGP exercises, including advanced settings like AS path manipulations, MD5 passwords and BFD, and new technologies like TCP/AO and interface EBGP sessions.
• Fifteen BGP routing policies exercises, covering the basic mechanisms as well as dirty tricks like route disaggregation
• Four load balancing exercises, from EBGP ECMP to BGP Link Bandwidth and BGP Additional Paths.
• Five challenges for everyone who got bored doing the simple stuff ;)

That completes the BGP technologies I wanted to cover. I’ll keep adding the challenge labs and advanced scenarios. Here are some ideas; if you have others, please leave a comment.