Category: Tags

Networking Fundamentals

I firmly believe that you cannot be a good networking engineer1 without a firm grasp of the networking fundamentals, and I couldn’t resist pointing that out a few times (see also certifications-related posts):

Regardless of how far down this page you’ll get, these blog posts are a must-read:

I would also suggest exploring these series of blog posts as well as textbooks and other resources I collected:

The rest of the fundamentals-related blog posts are collected on this page.

Network Addressing

Addresses and routes are the basic concepts anyone dealing with a network must (eventually) grasp. These blog posts describe how we got a hierarchy of addresses:

Deep Dives

These blog posts dive deeper into interesting topics:

If you like them, it’s probably time you start exploring the deep-dive series I already mentioned.

A Bit of a History

These blog posts might help you figure out some less obvious details or give you a historical perspective on why networking technologies evolved to where we are right now:

If you want to dive deeper into historical technologies, you might enjoy the comparison of TCP/IP and OSI (CLNP) protocol stacks:

There Be Rants

Long-time readers know I can’t resist a good rant:

Everything Is a Graph

You can represent every network as a graph of network devices (nodes) and links2. Rachel Traylor covered the graph theory in the (free) Network Connectivity, Graph Theory, and Reliable Network Design and Graph Algorithms in Networks webinars; these blog posts might provide some extra details:

Networking Fundamentals Videos

Finally, I published dozens of videos describing the networking concepts as part of the How Networks Really Work webinar that got at least some minor positive feedback. The videos describe:

Business aspects of networking technologies

Some people liked the non-technical take on networking I recorded in 2019 and 2020:

More videos

Fallacies of distributed computing

More videos

Networking challenges and the importance of a layered approach

Network Addressing

Switching, Routing, and Bridging

Routing Protocols

More videos

Lessons Learned from 35 Years of Networking

More videos

  1. In the stricter sense, not in the “every CLI jockey is called an engineer these days” one ↩︎

  2. Multi-access networks are represented as pseudo-nodes ↩︎

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AI

Artificial Intelligence (AI) and Machine Learning (ML) are the next big hype in networking following Software-Defined Everything and Intent-Based Everything. Like with the previous hype bubbles it’s worth figuring out

  • How much of the hype is real (TL&DR: not much)?
  • Whether the technology is ready to be used in production networks (TL&DR: some of it)
  • How you could use the technology to make your life easier

How Real Is It?

Like with the previous hype tsunamis I’ll do my best to help you figure out the answers to the above questions with a hefty dose of skepticism and snark1, starting with:

I also decided to “kick the tires” and document my (often less-than-stellar) experience with the most-overhyped products:

AI/ML in Networking: The Good, the Bad and the Ugly

Javier Antich created a wonderful AI/ML in Networking in 2021. If you know nothing about AI/ML and wonder whether you should care about it, you MUST watch these videos from his webinar:

In 2023, Javier published a book covering the same set of topics in way more details. I would highly recommend you read it if you want to know more.

What Others Are Saying

I keep collecting interesting articles talking about AI in general and (lately) ChatGPT. I found these interesting enough to mention them in worth reading blog posts:

These are not bad either:

Finally, a few real-life uses of large language models:

Blog Posts I Forgot to Categorize

  1. Please don’t blame me for pointing out the ever-lasting validity of Sturgeon’s law. Contrary to what some people think, I’m not trying hard to pick up dismal examples of AI failures, I’m just good at looking in the wrong places. Also, I’m too old to be wearing rosy glasses and drinking Kool-Aid. ↩︎

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OSPF

OSPF is like a traffic director for the internet. Imagine a city with many roads - OSPF helps routers (the traffic directors) figure out the best paths for data to travel from one place to another. It’s like a smart GPS for computers, making sure information takes the shortest and fastest routes. OSPF routers talk to each other, share maps of the internet, and decide the best ways to send data. It’s a cool system that keeps the internet running smoothly!

ChatGPT explaining OSPF to a high-school kid

Configuration Tips

This blog started as a collection of (hopefully) helpful configuration tricks, and I documented numerous Cisco IOS configuration tips in the early 2000s.

Implementation Details

Let’s start with the elephant in the room: OSPF areas – a simple concept that got way too convoluted when OSPF started accreting nerd knobs like NSSA areas:

OSPF default routes are another confusing topic. You could have inter-area default routes (used in stub areas) or external default routes that could be conditional or unconditional.

OSPF adjacencies are another fun troubleshooting topic:

The inimitable forwarding address in type-5 LSA will make your head explode when combined with the NSSA areas.

Want even more OSPF details? I documented way too many of them since I started blogging, including:

Deploying OSPF

Creative networking engineers often forget an unpleasant truth: OSPF is a single security domain. You should never run it with less-trusted peers, be it your customers, data center servers, or virtual machines.

OSPF by itself is complex enough, but the real fun starts when you combine it with other protocols (for example, BGP and LDP):

Running OSPF in large hub-and-spoke networks (for example, large DMVPN networks) is another tough challenge:

While you could use OSPF to get unequal-cost multipathing, you might be tripped by numerous caveats; no wonder there are few implementations of this concept.

Finally, you can run OSPF over unnumbered interfaces, be it point-to-point serial links or Ethernet segments:

Rants

Now and then, I couldn’t resist writing an OSPF-related rant:

What Others Are Writing About OSPF

Other OSPF Blog Posts

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EVPN

EVPN, or Ethernet Virtual Private Network, is like a smart system that helps computers and devices in a network talk to each other better. It’s like having a super organized mail system where each computer has its own address, and EVPN makes sure messages get to the right place quickly and safely. So, it’s kind of like a traffic manager for information on a computer network, making everything run smoothly and securely.

ChatGPT trying (and failing) to explain EVPN

What Is EVPN?

Before going into the technical details, let’s start with the basics: What is EVPN, how does it work, and where can you use it?

EVPN Designs

EVPN was designed to be used in an IBGP environment on top of an IGP. With the eruption of EBGP as better IGP hype, many vendors tried to adapt EVPN to an environment running EBGP instead of OSPF. We covered some of the typical EVPN designs in these blog posts:

Other blog posts focus on various design details:

Finally, several blog posts describe various EVPN VPN topologies:

EVPN Implementation Details

There are tons of tiny little things that can go wrong when you try to deploy EVPN. I documented them as I stumbled upon them:

Beyond VXLAN

While EVPN is often used with VXLAN today, it was designed to work with the MPLS data plane, resulting in a few quirks:

EVPN Rants

Some vendors’ marketing engineers (or Senior Directors) can’t stand anyone telling them their implementation might be suboptimal, going to great lengths to prove to themselves they’re right, and generating beautiful fodder for rants.

Videos

You can watch numerous videos from the EVPN Technical Deep Dive webinar without an ipSpace.net account:

What Others Wrote About EVPN

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