BGP Graceful Restart Considered Harmful

A networking engineer with a picture-perfect implementation of a dual-homed enterprise site using BGP communities according to RFC 1998 to select primary- and backup uplinks contacted me because they experienced unacceptably long failover times.

They measured the failover times caused by the primary uplink loss and figured out it takes more than five minutes to reestablish Internet connectivity to their site.

Public Videos: Large Language Models (AI/ML)

All the Large Language Models videos from the AI/ML in Networking webinar with Javier Antich are now public. Enjoy!

Is It The End, Or Can You Do Something in 2024?

David Bombal invited me for another annual chat last December, focusing on (what else) networking careers in 2024. The results were published a few days ago, and I was amazed at how good it turned out. I always love chatting with David; this time, his editing team did a masterful job.

netlab 1.7.1: Eye Candy

What do you get when you write code next to a Christmas tree? You can expect to get tons of eye candy, and that’s what netlab release 1.7.1 is all about.

It all started with a cleanup idea: I could replace the internal ASCII table-drawing code with the prettytable library. Stefan was quick to point out that I should be looking at the rich library, and the rest is history:

Registration No Longer Needed to Download Free PDFs

I published dozens of free-to-download slide decks on ipSpace.net. Downloading them required the free ipSpace.net subscription which is no longer available because I refuse to play a whack-a-mole game with spammers.

You might like the workaround I had to implement to keep those PDFs accessible: they are no longer behind a regwall.

You can find the list of all the free content ipSpace.net content here. The Conferences and Presentations page is another source of links to public presentations.

BGP Labs: Reuse BGP AS Number Across Sites

When I published the Bidirectional Route Redistribution lab exercise, some readers were quick to point out that you’ll probably have to reuse the same AS number across multiple sites in a real-life MPLS/VPN deployment. That’s what you can practice in today’s lab exercise – an MPLS/VPN service provider allocated the same BGP AS number to all your sites and expects you to deal with the aftermath.

On Routing Protocol Metrics

This LinkedIn snippet just came in from the someone is not exactly right on the Internet department:

Unlike IGP protocols, BGP is not dependent on a single type of metric to choose the best path.

EIGRP is an immediate counterexample that brought the above quote to my attention, but it’s worth exploring the topic in more detail.

Public Videos: Routing Protocols

One of the delightful side effects of leaving the paid content business is that I no longer have to try to persuade anyone that my content is any good. That includes the “this video is now public” announcements – instead of elaborate introductions, I’ll just publish a short blog post with the links.

As of today, these videos (along with dozens of previously-released videos) from the Routing Protocols section of the How Networks Really Work webinar are no longer behind a login wall:

Upcoming BGP Labs, 2024 Edition

It’s that time of the year when we create unreachable goals and make empty promises to ourselves (or others) that we subconsciously know we’ll fail.

I tried to make that process a bit more structured and create external storage for my lab ideas – I started publishing more details on future BGP lab scenarios. The lab descriptions contain a high-level overview of the challenge and the lab topology; the details will be filled in later.

Want to know what’s coming in 2024? Check out the Upcoming Labs page of the BGP Labs project.

Public Cloud Networking Hands-On Exercises

I got this request from someone who just missed the opportunity to buy the ipSpace.net subscription (or so he claims) earlier today

I am inspired to learn AWS advanced networking concepts and came across your website and webinar resources. But I cannot access it.

That is not exactly true. I wrote more than 4000 blog posts in the past, and some of them dealt with public cloud networking. There are also the free videos, some of them addressing public cloud networking.

Goodbye, ipSpace.net Subscription

I ran the first webinar as an independent author almost exactly fourteen years ago¹, with the first ticket sold just before New Year’s Eve. I kept focusing on individual webinars until someone asked me, “Would it be possible to buy access to everything you did?” His question effectively created the ipSpace.net subscription, with the first one sold in late 2010 (I still have the email that triggered the whole process).

Happy Holidays and All the Best in 2024!

My video editor sent me the perfect let’s-wrap-up-this-year video:

I wish you a few quiet days disconnected from the technology and all the best in 2024!

End-of-Year Cleanup: OSPF Blog Posts

After procrastinating for months, I finally spent a few days cleaning up and organizing OSPF blog posts (it turns out I wrote almost 100 blog posts on the topic in the 18 years of blogging).

Setting Source IP Address on Traffic Started by a Multihomed Host

In the Path Failure Detection on Multi-Homed Servers blog post, I mentioned running BGP on servers as one of the best ways to detect server-to-network failures. As always, things aren’t as simple as they look, as Cathal Mooney quickly pointed out:

One annoyance is what IP address gets used by default by the system for outbound traffic. It would be nice to have a generic OS-level way to say, “This IP on lo0 should be default for outbound IP traffic unless to the connected link subnet itself.”

That’s definitely a tough nut to crack, and Cathal described a few solutions he used in the past:

BGP Challenge: Merge Autonomous Systems

Here’s a challenge in case you get bored during the Christmas break: merge two networks running BGP (two autonomous systems) without changing anything but the configurations of the routers connecting them (the red BGP session in the diagram). I won’t give you any hints; you can discuss it in the comments or a GitHub discussion.

Hopefully, you won’t have to deal with something similar in real life, but then we know that crazy requirements trump good designs any day of the week.

Review: Unnumbered Interfaces in netlab

A while ago, Chris Parker published a nice blog post explaining how to configure unnumbered interfaces with IS-IS in Junos. It’s well worth reading, but like my Unnumbered Ethernet Interfaces blog post, it only covers one network operating system. What if you want to do something similar on another platform?

How about using the collective efforts of the team developing device configuration templates for netlab? As of December 2023 netlab supports:

Worth Reading: The AI Supply Paradox

Eric Hoel published a spot-on analysis of AI disruptiveness, including this gem:

The easier it is to train an AI to do something, the less economically valuable that thing is. After all, the huge supply of the thing is how the AI got so good in the first place.

TL&DR: AI can easily disrupt things that are easy to generate and thus have little value. Seeing investors trying to recoup the billions pouring into the latest fad will be fun.

Worth Reading: State-of-the-Art AI

Gerben Wierda published another AI-buster article describing what exactly “state-of-the-art” means in AI benchmarks.

Hint: you give an AI model 32 step-by-step examples before asking a question, and it still gets it wrong 10% of the time.

Video: Language Model Basics

After a brief introduction of how the language models fit into the AI/ML landscape, Javier Antich explained the language model basics, including auto-regression, types of language models, the specifics of large language models, and potential use cases,

netlab: Version-Specific Topology Files

TL&DR: If you’re using netlab to build labs for your personal use, you can skip this one, but if you plan to use it to create training labs (like my BGP labs project), you might want to keep reading.

Like any complex enough tool, netlab eventually had to deal with inconsistent version-specific functionality and configuration syntax (OK, topology attributes). I stumbled upon this challenge when I wanted to make labs that use two types of configurable devices.