Bygget af en fagperson, med privatliv først
Værktøjskassen til netværk og sikkerhed, der holder dine data på din maskine.
Subnetberegninger, DNS- og e-maildiagnostik, certifikatinspektion og meget mere, beregnet lokalt i din browser. Ingen upload, ingen logning, ingen konto nødvendig til de daglige værktøjer.
Around the tools: sourced articles on how the technology works, a record of the companies that built this industry, the practice of doing the work, and the roles that do it.
Tilgængelige nu
Bygget af en, der har gjort arbejdet siden 1996.
Tredive år inden for virksomhedsnetværk og sikkerhed, leveret af en aktiv instruktør og ikke af en marketingside. Certificeret på platforme, så sammenligningerne her er lavet ærligt, ikke for at sælge.
The chapters lived from inside
In every one of these, employer or vendor, the work was the same shape: facing the end customer, in pre-sales and in post-sales technical support, and very often acting as the technical proxy and enablement facilitator for the partners who had to carry the product themselves. The job was to leave the customer with something that worked better than it did before — an innovation, a solution, an improvement they could keep running after I left. The full telling lives at the career record.
- Cabletron og Enterasys1996 – 2007
- Riverstone Networks2000 – 2002
- Cisco Systems2003 – 2008
- IronPort Systems2004 – 2005
- NetScreen og 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
The roles I have held
Eight positions across the path a product takes, each linking to what that job answers for, who it serves and how it is measured. The years are the ones on each entry, including the spans that are not continuous.
- Field network engineer1996-2000, 2005-2007
- Product support engineer2000-2002
- Knowledge base manager2000-2002
- High-touch operations manager2003-2004
- Systems engineer2004-2005, 2009-2010
- Network consulting engineer2008, 2010-2011, 2012, 2013-2014, 2020
- Channel systems engineer2015-2019
- Technical instructor2020-present
Platformene, undervist og holdt aktuelle.
What is here
Vendor hubs →
One door per platform: the tools, articles and certification material for that vendor, gathered in one place.
8 vendor hubs
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 →
Curated reading paths through the Learn library: an ordered route through a subject, built for understanding it rather than for passing an exam.
105 guides
Glossary →
Every term and acronym used across this site, defined once and cross-referenced. The thing to open mid-article.
1242 entries
The Practice →
How the work is actually done rather than how the technology works. Triage, escalation, evidence, handover.
64 published
The Roles →
The positions this industry is made of, grouped by the path a product takes from the company that builds it to the person who depends on it.
39 positions
Tools →
Deterministic calculators and explainers for networks, security and identity. They compute in your browser and send nothing anywhere.
152 live
Learn →
Technical articles on the protocols and products behind the tools, written to be read rather than skimmed.
553 articles
Industry →
Company histories from the beginning of networking to now, including the ones that failed and the ones nobody remembers.
289 companies4 of them turn 50 this year
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.
15 chapters
Advisory →
Independent judgement on decisions that have not been made yet. Scoped work, written answer, no on-call.
By engagement
Training I teach →
Authorized instructor-led courses across four platforms, delivered through Red Education.
28 courses across 4 vendors
Red Education →
The global authorized training centre my courses are delivered through, and the story of how it got there.
Hvorfor lokal kørsel betyder noget i sikkerhedsarbejde.
Når du indsætter en konfiguration, en pakkeoptagelse eller et certifikat i et værktøj, indeholder de data ofte hemmeligheder. Her kører de daglige værktøjer helt i din browser. Inddata forlader aldrig din enhed, så der er intet at logge, lække eller udlevere efter en retskendelse.
Prøv et værktøj nu.
CIDR-beregneren nedenfor kører lokalt. Indtast et net og et præfiks for at se adresseintervallet, antallet af værter og masken. Intet sendes nogen steder hen.
CIDR-beregner
Analyserer en enkelt IPv4-CIDR-blok: net, broadcast, maske og værtsinterval.
Kører lokalt, intet sendes til nogen server.
All results are computed locally from the address and prefix you enter, using standard IPv4 addressing arithmetic. Nothing is looked up remotely and nothing is sent anywhere.
- RFC 4632 (CIDR)Classless Inter-Domain Routing address aggregation
- RFC 1918Private address ranges
- RFC 791 (IPv4)The Internet Protocol