Practitioner-built, privacy-first
The network and security toolbox that keeps your data on your machine.
Subnet math, DNS and email diagnostics, certificate inspection, and more, computed locally in your browser. No upload, no logging, no account required for the everyday tools.
Currently serving
Built by someone who has done the work since 1996.
Thirty years in enterprise networking and security, delivered as a working instructor rather than a marketing page. The comparisons here are made honestly, not sold.
The chapters lived from inside
These fourteen are also chapters of my own record - each timeline carries a My chapter marker. The full telling lives at the career record.
- Cabletron and Enterasys1996 – 2007
- Riverstone Networks2000 – 2002
- Cisco Systems2003 – 2008
- IronPort Systems2004 – 2005
- NetScreen and Juniper2009 – 2014
- Extreme Networks2013 – 2014
- FireEye, McAfee and Ixia2015 – 2019
- Pulse Secure2018 – 2019
- Palo Alto Networks2013 – 2015
- F52015 – present
- Fortinet2022 – present
- Netskope2024 – present
- Ping Identity and ForgeRock2025 – present
- Zscaler2026 – present
- Check Point2026 – present
Platforms taught and held current.
What is here
Six sections, built over years rather than assembled for a launch. Every count below is read from the thing itself at build time, so none of them can drift from what you will actually find.
Vendor hubs →
One door per platform: the tools, articles and certification material for that vendor, gathered in one place.
Tools →
Deterministic calculators and explainers for networks, security and identity. They compute in your browser and send nothing anywhere.
138 live
Learn →
Technical articles on the protocols and products behind the tools, written to be read rather than skimmed.
528 articles
Glossary →
Every term and acronym used across this site, defined once and cross-referenced. The thing to open mid-article.
Industry →
Company histories from the beginning of networking to now, including the ones that failed and the ones nobody remembers.
164 companies4 of them turn 50 this year
The Practice →
How the work is actually done rather than how the technology works. Triage, escalation, evidence, handover.
15 of 48 published
Certification guides →
What each exam tests and what to study for it. Free, and useful whether or not you ever book a course.
105 guides
Study guides →
Objective-by-objective walkthroughs for the exams, showing what is covered here and, honestly, what is not.
Training I teach →
Authorized instructor-led courses across four platforms, delivered through Red Education.
Advisory →
Independent judgement on decisions that have not been made yet. Scoped work, written answer, no on-call.
By engagement
About →
Who is writing all of this, what I have done, and why any of it should be trusted.
The career record →
Fifteen chapters from 1996 onward, each told from inside the company it happened in.
Red Education →
The global authorized training centre my courses are delivered through, and the story of how it got there.
Why local-first matters for security work.
When you paste a configuration, a packet capture, or a certificate into a tool, that data often contains secrets. Here, the everyday tools run entirely in your browser. The input never leaves your device, so there is nothing to log, leak, or subpoena.
Try a tool right now.
The CIDR calculator below runs locally. Type a network and prefix to see the address range, host count, and mask. Nothing is sent anywhere.
CIDR Calculator
Analyze a single IPv4 CIDR block: network, broadcast, mask, and host range.
Runs locally. Nothing is sent to any server.