Category: Worth Reading

Justin Pietsch published another must-read article, this time dealing with operational complexity of load balancers and IP multicast. Here are just a few choice quotes to get you started:

• A critical lesson I learned is that running out of capacity is the worst thing you can do in networking
• You can prevent a lot of problems if you can deep dive into an architecture and understand it’s tradeoffs and limitations
• Magic infrastructure is often extremely hard to troubleshoot and debug

You might find what he learned useful the next time you’re facing a unicorn-colored slide deck from your favorite software-defined or intent-based vendor ;))

Greg Ferro is back with some great technical content, this time explaining why hardware-based packet capture might return unexpected results.

Justin Pietsch published a fantastic recap of his experience running OSPF in AWS infrastructure. You MUST read what he wrote, here’s the TL&DR summary:

• Contrary to popular myths, OSPF works well on very large leaf-and-spine networks.
• OSPF nuances are really hard to grasp intuitively, and the only way to know what will happen is to run tests with the same codebase you plan to use in a production environment.

Dinesh Dutt made similar claims on one of our podcasts, and I wrote numerous blog posts on the same topic. Not that anyone would care or listen; it’s so much better to watch vendor slide decks full of the latest unicorn dust… but in the end, it’s usually not the protocol that’s broken, but the network design.

Brett Lykins published an excellent description of what an automation Minimum Viable Product could be.

Not surprisingly, he’s almost perfectly in sync with what we’ve been telling networking engineers in ipSpace.net Network Automation online course:

• Start small
• Go for quick wins
• Do read-only stuff before modifying device configurations
• Test, test, test…

Here’s an interesting factoid: when using default IS-IS configuration (running L1 + L2 on all routers in your network), every router inserts every IP prefix from anywhere in your network into L2 topology… at least on Junos.

For more details read this article by Chris Parker. I also wrote about that same problem in 2011.

When someone sent me a presentation on seamless MPLS a long while ago my head (almost) exploded just by looking at the diagrams… or in the immortal words of @amyengineer:

“If it requires a very solid CCIE on an obscure protocol mix at 4am, it is a bad design” - Peter Welcher, genius crafter of networks, granter of sage advice.

Turns out I was not that far off… Dmytro Shypovalov documented the underlying complexity and a few things that can go wrong in Seamless Suffering.

I wanted to write a “SRv6 makes no little sense” blog post for a long while, but there were always more relevant topics to focus on. Fortunately, I won’t have to write it anytime soon; Ethan Banks did a fantastic job with SR(x)6 - Snake Oil Or Salvation?. Make sure you read it before attending the next “SRx6 will save the world” vendor presentation.

Robert Graham wrote a great article explaining why CEOs don’t care much about cybersecurity or any other non-core infrastructure (including networking, unless you happen to be working for a service provider). It’s a must-read if you want to understand the **** you have to deal with in enterprise environments.

Every now and then a security researcher “discovers” a tunneling protocol designed to be used over a protected transport core and “declares it vulnerable” assuming the attacker can connect to that transport network… even though the protocol was purposefully designed that way, and everyone with a bit of clue knew the whole story years ago (and/or it’s even documented in the RFC).

It was MPLS decades ago, then VXLAN a few years ago, and now someone “found” a “high-impact vulnerability” in GPRS Tunnel Protocol. Recommended countermeasures: whitelist-based IP filtering. Yeah, it’s amazing what a wonderful new tool they found.

Julia Evans recently described another awesome Linux tool: entr allows you to run a bash command every time a watched file changes (and it works on Linux and OSX).

I wish I found it years ago…