A browser-only IPv4 subnet learning tool with /0, /31 and /32 semantics and a 32-bit diagram. Created by an OpenAI AI research assistant.
<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><title>IPv4 CIDR range explorer</title><link rel="stylesheet" href="https://gbx-htmldrop-e.1007sandiego.com/htmldrop-e/5e671fe10dce4285b22f1437e1e9c455-layout.css">
</head><body><main><h1>IPv4, one range at a time.</h1><p>Explore how a CIDR prefix divides a 32-bit address into a fixed network and a host range. Everything you type stays in this browser.</p><form id="cidr"><label>IPv4 address<input id="ip" value="192.168.12.77" inputmode="decimal" autocomplete="off" spellcheck="false"></label><label>Prefix /<input id="prefix" value="24" inputmode="numeric" autocomplete="off"></label><button>Explore range</button></form><p id="error" role="alert"></p><section id="results" aria-live="polite"><dl><div><dt>Normalized network</dt><dd id="network"></dd></div><div><dt>Broadcast / upper endpoint</dt><dd id="broadcast"></dd></div><div><dt>Total addresses</dt><dd id="total"></dd></div><div><dt>First usable</dt><dd id="first"></dd></div><div><dt>Last usable</dt><dd id="last"></dd></div></dl><p id="semantics"></p><p id="bits"></p></section><figure><img src="https://gbx-htmldrop-e.1007sandiego.com/htmldrop-e/5e671fe10dce4285b22f1437e1e9c455-bits.svg" alt="32-bit IPv4 diagram: a /24 prefix fixes the first 24 blue network bits; the final 8 amber host bits vary from 0 to 255." width="864" height="184"><figcaption>A /24 example: three fixed octets and one variable octet. The selected prefix may differ.</figcaption></figure><p>A calculated usable range is not a promise that addresses are routable. Special-use ranges, local network policy and device configuration still apply.</p><footer>Created by an AI research assistant (OpenAI). No address lookup, scanning, analytics, or requests containing your input. This page loads a public educational diagram and its layout stylesheet from our server; ordinary web request logs may record IP address, time, user agent and referrer. <a href="https://gbx-htmldrop-e.1007sandiego.com/htmldrop-e/5e671fe10dce4285b22f1437e1e9c455-cidr.html" target="_blank" rel="noopener">Standalone tool and viewable HTML source</a>.</footer></main></body></html></a></footer></p></figcaption></figure></p></dd></dt></div></dl></section></p></button></label></form></p></h1></main></body></title></head></html>