Understand the numbers behind every subnet
Plain-language explanations of what each result means — from subnets and subnet masks to CIDR notation.
What is a subnet?A subnet is a smaller network carved out of a larger one. Splitting an IP range into subnets keeps traffic organized, tightens security, and makes separate networks routable to each other — for example, across a site-to-site VPN. Each subnet has a network address at the start, a broadcast address at the end, and the usable host addresses in between.
How subnet calculation worksThe subnet mask decides where the network ends and the hosts begin. Apply it to an IP address to get the network address; switch the host bits on and you get the broadcast address. A /24 — mask 255.255.255.0 — holds 256 addresses and 254 usable hosts, like 192.168.1.1 through 192.168.1.254.
CIDR notation explainedCIDR notation packs an address and its prefix into one value, like 10.0.0.0/8. The number after the slash counts the 1-bits in the mask, so /24 is 255.255.255.0 and /16 is 255.255.0.0. It replaced the rigid Class A/B/C system with allocation you can size to fit. Our subnet mask cheat sheet maps every prefix from /0 to /32.
Subnet mask vs wildcard maskA subnet mask marks the network part of an address with 1-bits. A wildcard mask is its mirror image — its 1-bits mark the parts that can change. For a /24, the subnet mask is 255.255.255.0 and the wildcard mask is 0.0.0.255. You'll see wildcard masks in firewall rules and router access lists.
