One network engineer, 24 calculators, no account system

Network engineer. Builds the calculators on this site because the ones available were either cloud-hosted, ad-walled, or quietly wrong about a vendor detail. Everything here runs in the browser and is tested against known answers on every commit.

Name

Alex Xu

Role

Network engineer

Credential

CCIE #13192

Email

alex.xu@ccie13192.com

Code

github.com/Alex13192

The longer pieces — the reasoning behind the calculators rather than instructions for using them — are collected under Writing.

Address plans, device configurations and secrets are the three things a network engineer is least able to paste into a stranger’s server. Most online calculators require exactly that, because a server is the easy way to build one. Every tool here is a pure function of its input, so there is no reason for a server to exist: the calculation is exported as a static site, and a service worker keeps it working after the first visit even with no network at all.

The one thing on the site that is not local is the advertising. It is disclosed on every page, described in full in the privacy policy, and no tool depends on it.

• Known-answer tests. The calculation kernel is tested against values worked out by hand or taken from a standard, on every commit. A formula that is subtly wrong fails the suite rather than shipping.
• A build that fails on a broken promise. Each tool declares in code whether it touches the network. The build scans the source and fails if the declaration and the implementation disagree — in either direction. There is also a CI job that deliberately breaks the rule to prove the gate still catches it.
• Evidence labels on vendor detail. Where a CLI syntax or a byte layout is confirmed on real hardware, the page says so. Where it is taken from documentation, or reported by the community and not confirmed, the page says that instead and asks you to verify it in your own lab.
• A standards reference, not an opinion. Where an RFC or an IEEE standard decides the answer — a /31, a special-purpose prefix, an EUI-64 bit flip — the page names it, so a disagreement can be settled by reading the source rather than by trusting the tool.

The tools on this site are free to use and always will be. Two things pay for them:

• Advertising. Google AdSense, labelled as advertising, never inside a tool’s input or output and never on the privacy or terms pages. What it collects is set out in the privacy policy.
• NetSmith Pro. A one-time in-app purchase that unlocks the remaining tools in the iOS and iPadOS app, the same kernel on a phone.

There are no affiliate links, no sponsored tools, no paid placement in any result, and no feature withheld from the free tools in order to sell an upgrade. If that changes, it will change on this page first.

A wrong number here is not a cosmetic bug: someone acts on it with a change window open. If you find one, email alex.xu@ccie13192.com with the input and the result you expected. Substantive corrections are made on the page and noted there, not quietly edited.

NetKit is independent. It is not affiliated with, endorsed by or sponsored by Cisco, Arista, Juniper, Huawei, HPE or any other vendor named in the reference tables; those names are trademarks of their owners and are used to describe interoperability. Nothing here is engineering advice, and generated configuration must be validated on a lab device before it reaches production — a mis-planned subnet, aggregate or power budget can take a network or a rack offline.