https://blog.it-learn.io/tags/cidr/Recent content in Cidr on it-learn.io | IT, Networking & Cybersecurity BlogHugoen-usTue, 09 Jun 2026 00:00:00 +0000https://blog.it-learn.io/posts/2026-06-09-subnetting-without-calculator-magic-number-method/Tue, 09 Jun 2026 00:00:00 +0000https://blog.it-learn.io/posts/2026-06-09-subnetting-without-calculator-magic-number-method/<p>There are two kinds of Network+ candidates. The ones who can subnet in their heads in under 30 seconds, and the ones who can&rsquo;t and run out of time on the exam. The gap between those two is one technique: the magic-number method.</p> <p>This post is the complete walkthrough — the trick, why it works, how to apply it to any prefix length, the worked example for /29 that comes up on every Network+ exam attempt, and the 5-minute practice routine that turns this from &ldquo;I sort of remember the trick&rdquo; into reflex.</p>