subnet
termnetworking
A slice of a larger network, defined by how many address bits are fixed.
Subnetting splits an address block into smaller networks so traffic and broadcast stay contained and routing stays sane. The mask (or CIDR prefix) draws the line between the network part and the host part of each address. Every subnet spans a contiguous range: the first address identifies the network itself, the last is the subnet's broadcast address, and the usable host range sits between them, so a /24 holds 256 addresses of which 254 are assignable. Point-to-point /31 links (RFC 3021) are the deliberate exception, using both addresses as hosts.
Also known as: subnetwork, subnet mask, subnet range