A subnet (subnetwork) is a logical subdivision of an IP network created by applying a subnet mask to an IP address. Subnetting divides a large network into smaller, more manageable segments for improved performance and security.

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask as a single string, e.g. 192.168.1.0/24. The /24 means the first 24 bits are the network address, leaving 8 bits for 256 host addresses (254 usable).

How many hosts does a /24 subnet have?

A /24 subnet has 256 addresses total (2^8). Two are reserved: the network address and the broadcast address. That leaves 254 usable host addresses.

What is a Subnet?

A subnet (subnetwork) is a logical subdivision of an IP network. Subnetting splits a large address block into smaller segments, keeping local traffic local and reducing broadcast domain size.

CIDR Notation

Subnets are expressed in CIDR (Classless Inter-Domain Routing) notation: an IP address followed by a prefix length, e.g. 192.168.1.0/24. The prefix length tells you how many bits are fixed as the network portion.

/8 — 16,777,214 usable hosts (Class A range)
/16 — 65,534 usable hosts (Class B range)
/24 — 254 usable hosts (most common LAN subnet)
/30 — 2 usable hosts (point-to-point links)
/32 — single host (loopback, specific route)

Subnet Mask vs CIDR

A subnet mask is the older dotted-decimal representation of the same information. /24 is equivalent to the mask 255.255.255.0. CIDR notation is more concise and universally preferred today.

Why Subnet?

Security — isolate segments (e.g. separate guest Wi-Fi from production servers)
Performance — reduce broadcast traffic within each segment
Address efficiency — allocate only the addresses a segment needs
Organisation — map network topology to physical or logical boundaries

Calculate subnet ranges, host counts, and broadcast addresses: Open Subnet Calculator →

Frequently Asked Questions

What is the difference between a subnet and a VLAN?

A subnet is a Layer 3 (IP) concept dividing address space. A VLAN is a Layer 2 (Ethernet) concept dividing switch ports into broadcast domains. In practice they're often paired — one VLAN per subnet — but they operate at different layers.

What are private IP address ranges?

RFC 1918 reserves three ranges for private networks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These are not routable on the public internet and are used in homes, offices, and cloud VPCs.

Related Terms

DNS — Resolves hostnames to IP addresses within subnets.
HTTP Headers — Network metadata sent over IP connections.