Subnet
A defined range of IP addresses forming one logical network segment.
Subnets are how networks are divided at the addressing layer, expressed with a mask or CIDR notation that determines how many addresses the range holds.
Planning matters more than it appears. Overlapping address ranges between sites, or between your network and a partner's, cause VPN problems that are painful to fix once both ends are in production.
Where this comes up
Subnet sits inside our networks and infrastructure work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.
Related terms
VLAN A logical network created on shared physical switching, keeping groups of devices separated from each other. NAT Translating private internal IP addresses to a public one so many devices can share a single internet address. DHCP The service that automatically assigns IP addresses and network settings to devices when they connect. Network segmentation Dividing a network into zones with controlled traffic between them, so a compromise in one does not reach the others.