These guides go deeper than a quick reference. Each one walks through the underlying mechanics — the binary arithmetic, the design decisions, the gotchas — using examples you can paste straight into the calculator to check. They are written for the moment you actually have to plan an address space, not just pass an exam.
Why an IP address is just 32 bits, how the mask splits network from host, and how to subnet a /24 by hand without memorising tables.
The hosts-to-prefix formula, the allocate-largest-first method, two fully worked plans, how to spot overlapping subnets, which routing protocols support VLSM, and a Packet Tracer lab walkthrough.
Hex notation and compression rules, the prefix types (GUA, ULA, link-local, multicast), SLAAC and EUI-64, and why there is no broadcast and no NAT.
Every prefix from /8 to /32 with its mask, wildcard, address count and usable hosts — plus a wildcard mask table for ACLs and OSPF, and how to convert between notations in your head.
The Learn subnetting page covers IPv4 basics, CIDR, masks, network and broadcast addresses, VLSM, supernetting, IPv6, EUI-64, MTU and TCP MSS in one long read, with a FAQ. The guides above break the trickier topics out into focused, example-heavy walkthroughs.