computer science

OPNsense

OPNsense is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand OPNsense rather than just read about it. In short: OPNsense is an open source, FreeBSD-based firewall and routing software developed by Deciso, a company in the Netherlands that makes hardware and sells support packages for OPNsense. Launched in 2015, it is a fork of pfSense, which in turn was forked from m0n0wall built on FreeBSD.

Key takeaways

OPNsense belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OPNsense to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OPNsense from memory before moving on to harder problems.

Reference excerpt

OPNsense is an open source, FreeBSD-based firewall and routing software developed by Deciso, a company in the Netherlands that makes hardware and sells support packages for OPNsense. Launched in 2015, it is a fork of pfSense, which in turn was forked from m0n0wall built on FreeBSD. When m0n0wall closed down in February 2015 its creator, Manuel Kasper, referred its developer community to OPNsense.

Features OPNsense has a web-based interface and can be used on the x86-64 platform. Along with acting as a firewall, it has traffic shaping, load balancing, captive portal and virtual private network capabilities, and others can be added via plugins. The software also offers next-generation firewall capabilities utilizing Zenarmor, a NGFW plugin developed by OPNsense partner Sunny Valley Networks.

Domain dispute In November 2017, a World Intellectual Property Organization panel found that Netgate, the copyright holder of pfSense, used the domain opnsense.com in bad faith to discredit OPNsense, and obligated Netgate to transfer domain ownership to Deciso.

Releases The OPNsense version naming system consists of year.month. Since the first release took place in January 2015, it was named release 15.1. OPNsense typically uses a 6 month major release cycle with new releases in January and July of each year.

Illustrations

Worked examples

Example 1 — a first encounter with OPNsense

Start with the simplest possible case. Write down what OPNsense claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OPNsense before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OPNsense ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OPNsense

In research: OPNsense appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OPNsense in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OPNsense is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2015 software, BSD software, FreeBSD, so understanding it makes those chapters shorter.
In everyday life: Look for OPNsense outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study OPNsense in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OPNsense means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OPNsense out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OPNsense in simple terms?

Why does OPNsense matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OPNsense?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OPNsense.