Podcast: Network Automation Source(s) of Truth
Figuring out how to describe your network (also known as “create a source of truth”) is one of the most challenging tasks you’ll face when building a network automation solution (more). As always, the devil is in the details, starting with “and what exactly is The Truth?”.
We discussed those details in a lively Packet Pushers podcast with Claudia de Luna, David Sinn, Dinesh Dutt, Drew Conry-Murray and Ethan Banks. Have fun!
BGP Labs: Work with FRR and Cumulus Linux
FRR or (pre-NVUE) Cumulus Linux are the best bets if you want to run BGP labs in a resource-constrained environment like your laptop or a small public cloud instance. However, they both behave a bit differently from what one might expect from a networking device, including:
- Interfaces are created through standard Linux tools;
- You have to start the FRR management CLI from the Linux shell;
- If you need a routing daemon (for example, the BGP daemon), you must enable it in the FRR configuration file and restart FRR.
A new lab exercise covers these intricate details and will help you get fluent in configuring BGP on FRR or Cumulus Linux virtual machines or containers.
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.
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.
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).
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: