An IPv4 address is 32 bits, usually written as four decimal octets (for example 192.168.1.10). Subnetting splits that space into networks. Classless Inter-Domain Routing (CIDR) writes the split as a prefix length after a slash: 192.168.1.0/24 means the first 24 bits are the network portion.
A /24 mask is 255.255.255.0 — twenty-four 1-bits then eight 0-bits. The network address has host bits all zero; the broadcast has host bits all one. Those two addresses are not assigned to hosts on classical IPv4 subnets.
For prefix length p, there are 2^(32−p) addresses in the block. Usable hosts = that count minus 2 (network + broadcast), except on /31 and /32 where conventions differ (point-to-point links may use /31 with no broadcast).
10.0.0.0/26 has 32 − 26 = 6 host bits → 2^6 = 64 addresses. Network: 10.0.0.0. Broadcast: 10.0.0.63. Usable hosts: 10.0.0.1 through 10.0.0.62 (62 hosts). Enter the same CIDR in our IPv4 Subnet calculator to see mask, wildcard, and range in dotted decimal and hex.
These are not routed on the public internet; home and office LANs use them behind NAT.
RFC 4632 (CIDR); RFC 1918 (private addressing); RFC 3021 (/31 links).
Last updated: June 2026