Subnetting, Explained
Plain-English guides to IP subnetting — what a subnet really is, and how to read the CIDR notation that describes one. No jargon, no sign-up.
The three articles below build on each other: start with what a subnet actually is if the network/host split is still fuzzy, move to CIDR notation once you're comfortable with masks, and keep the CIDR chart open as a reference while you work. Every example uses real CIDR blocks — such as 192.168.1.0/24 or 2001:db8::/48 — that you can paste straight into the subnet calculator to see the network address, broadcast address, usable host range and mask worked out with exact 32-bit or 128-bit arithmetic, for both IPv4 and IPv6.
If you'd rather learn by doing than by reading, the calculator itself doubles as a check on your own math: work out a subnet on paper, then paste the same CIDR block in and compare the result. That habit catches the off-by-one mistakes that are easy to make with broadcast addresses and usable host ranges long before they end up in a real network plan.
What Is a Subnet? IP Networks Explained Simply
How a single IP address splits into a network part and a host part, why networks are divided into subnets, and how the mask draws the line — explained from scratch with examples you can run in the calculator.
Read ConceptCIDR Notation Explained: Reading /24, /26 and /64
What the slash-number really means, how prefix length maps to mask and host count, and the quick mental math for sizing IPv4 and IPv6 networks without a lookup table.
Read ReferenceCIDR Notation Chart: /0 to /32 Cheat Sheet
A complete reference table of every IPv4 prefix with its subnet mask, wildcard mask, host bits and usable host count — plus the common IPv6 prefixes. Bookmark it.
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