Pytest for Automated Network Testing (I)

Pytest for Automated Network Testing (I)

Pytest is a Python testing framework. It is primarily used by developers to test their code and make sure it behaves as expected. For example, if you write a function that adds two numbers, you can write a test to verify that the function returns the correct result. If it does, the test passes. If not, the test fails, and pytest tells you exactly where things went wrong.

That is the traditional use case, but pytest is not limited to testing code. You can use it to test anything that can be scripted in Python, and that includes testing your network.

In this series, we will use pytest to write tests that connect to network devices and verify their state. For example, we can write a test that connects to a router and checks whether BGP is up. If BGP is up, the test passes. If not, the test fails. We can also check things like interface states, routing table entries, OSPF neighbours, or really anything else you can pull from a device.

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Pytest is not the only testing framework available in Python. unittest is another popular option and is actually built into the Python standard library, so you Continue reading

VM Migration to Kubernetes: What Breaks and How to Prevent It

Here is what nobody putting together the business case for a VM migration to Kubernetes will tell you upfront: the compute is the easy part.

Moving workloads off vSphere and onto Kubernetes is conceptually straightforward. The tooling has matured. The architecture is proven. Compute moves, storage remaps, and the platform team has a plan.

The network is where projects quietly stall.

Not because the technology does not work. Because nobody scoped the network properly before the project started. A platform migration turned into a multi-team coordination exercise. The firewall team needed a change window. The security team needed to review a network placement that changed when it should not have needed to. The application team discovered hardcoded IPs that nobody documented.

Six months later, half the VMs are still on vSphere and the project is technically “in progress.”

This is not a skills gap. It happens at the most mature organisations with capable teams. It is a scoping problem, and it has a specific cause: the gap between how VM networking works and how Kubernetes networking works is wider than it looks on a migration plan.

This post is for the people who approve these projects. Here is what Continue reading

SONiC Part 1: SONiC Lab Setup on Windows (Step-by-Step)

 

Introduction

 

This chapter explains how to build a SONiC virtual test environment on a Windows computer. First, we enable the required Windows features for WSL 2 and update and verify the WSL installation. Next, we install an Ubuntu distribution and validate that the Linux environment is working correctly, including basic resource checks (CPU, memory, and disk). After the Linux environment is ready, we install Docker Engine from Docker’s official repository and complete the required post-installation steps to run containers. We then install Containerlab, download the SONiC virtual switch image (docker-sonic-vs.gz), copy it into WSL, and load it into Docker. Finally, we install Visual Studio Code on Windows and connect it to WSL to make creating and editing the YAML topology files easier. The next chapter uses this environment to define and deploy a simple SONiC-based topology.



Phase 1: Enable Features for WSL



WSL 2 requires two Windows features to be enabled. The first feature, Microsoft-Windows-Subsystem-Linux (Example 1-1), enables WSL. The second feature, VirtualMachinePlatform (Example 1-2), is required to run WSL 2.

In this example, both features are enabled using Microsoft PowerShell (Run as Administrator) with the dism.exe command. The options used are:

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From system of record to system of control: How NetBox Labs is making network engineers “masters of intent.”

Early internet networks were small enough that a single engineer could hold the entire system in their head. You didn’t need a system of record — you were the system of record. As networks expanded into the cloud, that model broke down. Infrastructure now sprawls across regions, providers, and services. The live state of the network became both impossible to understand and critical to get right fully. Network infrastructure is now the backbone of the business, and configuration errors are no longer nuisances; they are business-critical events. AI agents are further pressuring network infrastructure to the extreme — so how are network engineers to keep it all running flawlessly? Bespoke tracking doesn’t scale Excel spreadsheets and cloud dashboards are no longer going to cut it. Running modern infrastructure requires a reliable representation of what the network should be — what systems and services exist, where they live, and how they connect. Without that, managing the network becomes high-risk. In the past, your mapping might have fit into an Excel spreadsheet, and everything could be configured in the terminal. But today’s networks need more than a wizard at the terminal; they need architects who can look at the big picture and Continue reading

Shutdowns, power outages, and conflict: a review of Q1 2026 Internet disruptions

In the first quarter of 2026, government-directed shutdowns figured prominently, with prolonged Internet blackouts in both Uganda and Iran, a stark contrast to the lack of observed government-directed shutdowns in the same quarter a year prior. This quarter, we also observed a number of Internet disruptions caused by power outages, including three separate collapses of Cuba's national electrical grid. Military action continued to disrupt connectivity in Ukraine and also impacted hyperscaler cloud infrastructure in the Middle East. Severe weather knocked out Internet connectivity in Portugal, while cable damage disrupted connectivity in the Republic of Congo. A technical problem hit Verizon Wireless in the United States, and unknown issues briefly disrupted connectivity for customers of providers in Guinea and the United Kingdom.

This post is intended as a summary overview of observed and confirmed disruptions and is not an exhaustive or complete list of issues that have occurred during the quarter. A larger list of detected traffic anomalies is available in the Cloudflare Radar Outage Center. Note that both bytes-based and request-based traffic graphs are used within this post to illustrate the impact of the observed disruptions, with the choice of metric generally made based on which better illustrates the Continue reading

You Can’t Patch People

One of the things I’ve noticed when it comes to IT is how quickly we’re willing to use software to solve people problems. Over my career I’ve seen all manner of crazy solutions to get around people being lazy or uneducated. Remember vMotion? Or OTV for stretched layer 2? Why do you think those solutions came about? I posit that it’s because it’s faster to write software than to patch people.

Hacking Humans

I see this most often in cybersecurity. Developers love to create software solutions that prevent things from happening. Phishing and all its various forms are some of the top priorities for solutions that prevent leaking of information. While we have invested a lot in phishing tests and education it’s also very likely that there are controls in place that prevent users from accidentally giving out information to threat actors.

Why are we so willing to write software to fix problems instead of teaching people to avoid those issues? I think in part it’s because software is predictable. If I create an app or write some controls into a platform it’s going to behave the same way every time. That’s the definition of deterministic. Every time the software Continue reading

State of Network Automation with Urs Baumann

I stopped tracking the (lack of) progress in network automation years ago, when I realized I had nothing new to say. As an eternal optimist, I hoped I was just missing something, but Urs Baumann (the guest of Software Gone Wild Episode 206) destroyed my hopes when he said, “I can still use the same slides I created 10 years ago”. On a more positive note, he recently completed his Master’s thesis on AI in network engineering, so we ended with a nice chat on its potential impact.

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