I’ll be honest with you. I made this mistake.

And I’m not talking about my early days as a DevOps engineer.

I was already a few years into my career when I finally understood the importance of networking.

Computer networking.

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You often hear me mention building networks of people. However, I haven’t shared much about computer networks.

In this newsletter, I’m sharing my complete guide on how I would learn networking if I had to start over. Including free resources.

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Before we start:

My team has some spots open for the next few days.

Apply for KubeCraft (limited spots) → CLICK HERE​

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The best starting point

If you like rabbit holes, start here.

How does your main workstation get its IP address?

How does it connect to other devices?

Those two questions should start a delightful rabbit hole for you. (I will explain further on if you just want me to show you).

After you figured those two out, dive into this one:

I want to segment my home network into separate VLAN’s.

One for my homelab, one for my main devices, and one for my guests.

And the traffic between those should be restricted.

This means: my guests should not be able to see my homelab devices, for example.

If you like doing research, stop reading now.

Have fun in your rabbit hole!

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If you want more structure, keep reading.

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Why Networking Matters

DevOps engineers often create and manage virtual networks in the cloud (AWS VPCs, Azure VNets, GCP VPCs).

You will troubleshoot connectivity between services, debug routing issues, and configure firewalls or security groups.

A clear grasp of networking makes everything from CI/CD runners to Kubernetes clusters far easier.

You do not need to become a full network engineer. You just need practical, working knowledge.

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Core Concepts to Master

IP Addresses and Subnetting

Understand IPv4 addresses: four octets (for example 192.168.1.15).

Learn CIDR notation and how to calculate networks like /24, /16, /20.

Instantly know how many usable hosts fit in a subnet and where network and broadcast addresses are.

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Private vs Public Address Spaces

Memorize the private IPv4 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).

Understand NAT (Network Address Translation) and why it exists.

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Routing Basics

How a host decides where to send packets (default gateway, routing table).

Difference between Layer 2 switching and Layer 3 routing.

Why overlapping subnets break things.

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Security Boundaries

Security groups, firewalls, and ACLs: how to allow or block traffic.

Inbound vs outbound rules, port ranges, and quick testing methods.

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Practical Troubleshooting Commands

ping, traceroute, ip a, ip route, netstat or ss, curl, nc.

DNS tools: dig, nslookup.

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Hands-On Practice Plan

Step 1 — Build a Simple Lab

  • Start with an old laptop or desktop running Ubuntu Server
  • Figure out the IP address of your lab device and your main workstation
  • Try pinging your main workstation from the lab device
  • Give your lab device a static IP and reboot it
  • Try to ping it again
  • Ping your lab device from your main workstation
  • Play with nc & traceroute between these devices

Step 2 — Explore Your Home Network

  • Log in to your home router and find the DHCP leases table (see which IP your main workstation device gets).
  • Change a device to a static IP and test connectivity.
  • Play with your router’s firewall rules to allow or block traffic (not all routers do this)

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VERY IMPORTANT NOTE: NEVER OPEN PORTS ON YOUR ROUTER

Unless you know what you’re doing, never open any ports on your main router.

You have been warned.

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Step 3 — Create Separate VLANs

This is one of the best real-world networking exercises you can do.

  • Hard way (recommended if you like tinkering):

  • Recycle an old desktop PC with two network cards.

  • Install pfSense or OPNsense and configure VLANs.

  • Put your laptop on one VLAN and another machine or VM on another, then control how they talk.

  • Easier way:

  • Buy a UniFi router such as the Dream Machine.

  • Use its UI to create VLANs and see how isolation works.

Step 4 — Cloud Networking

  • Create a small AWS VPC or Azure VNet.
  • Build two subnets and test security group rules.
  • Simulate real-world DevOps tasks like opening ports or pairing networks.

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How I learned networking

In my own DevOps learning journey, I picked up networking bit by bit. (get it?)

I never had a period where I focused on networking early in my career. In hindsight, I should have done it much earlier.

I learned about IP addresses and subnetting doing my LPIC-1 studies.

After that, I started studying Microsoft Azure.

And to be honest, I learned most of my networking skills when studying for my AZ-104 exam.

That certification is 50% cloud networking, and the MS Learn modules are really good.

But if I could start over, I would start with an old PC, install OPNsense on it, and learn it in my home network.

This way you stick to open source tools and don’t get too locked in to vendors.

But the same skills apply when you dive into cloud engineering.

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Best free networking sources

You’ll learn most by taking the questions I gave you in the beginning of this newsletter and doing your own research.

Reverse engineer those questions and you will learn a ton.

Go hands-on and start building and experimenting as soon as possible.

However, if you prefer a more structured approach, this is what I recommend:

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​ For Azure, this means doing this module for the AZ-104 preparation.

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If this was helpful to you, reply to this mail. Even if it’s just a “Yes, thank you!”

I read all replies.

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🫡 Mischa

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PS: Spots for KubeCraft are limited. September got filled.

9 spots left for the October cohort. Apply before they run out - CLICK HERE​

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