What is a CIDR?

What is CIDR?

Most common for home networks: /24 (e.g. 192.168.1.0/24)

CIDR (Classless Inter‑Domain Routing) is a shorthand way to describe a range of IP addresses.
It combines an IP address with a prefix length that tells you how many bits are fixed.

Format: IP/Prefix

Examples:

• 192.168.1.0/24
• 10.0.0.0/16

How it works (quick intuition)

An IPv4 address has 32 bits. The prefix says how many bits are “network” bits.

• /24 → first 24 bits fixed → 8 bits vary → 256 addresses
• /26 → 6 bits vary → 64 addresses
• /30 → 2 bits vary → 4 addresses

So a smaller prefix number (e.g. /16) means a larger range.

Common CIDR sizes (IPv4)

CIDR	Addresses	Typical Use
/24	256	Home / small office LAN
/25	128	Half of a /24
/26	64	Small subnet
/27	32	Small subnet
/28	16	Devices / static reservations
/29	8	Very small segments
/30	4	Point‑to‑point

Usable hosts are usually fewer because the network and broadcast addresses are reserved.

Example: 192.168.10.0/24

• Network: 192.168.10.0
• Broadcast: 192.168.10.255
• Usable range: 192.168.10.1 → 192.168.10.254

Example: 192.168.10.0/28

• Addresses: 16 total
• Usable range: 192.168.10.1 → 192.168.10.14
• Broadcast: 192.168.10.15

Why Netory uses CIDR

CIDR is the most consistent way to describe IP pools and ranges.
In Netory, using CIDR lets you:

• define the size of an IP pool precisely
• avoid overlaps between pools
• calculate usable addresses automatically

Quick tips

• Use /24 for standard home networks.
• Use /28 or /29 for device‑specific pools.
• If you don’t know your prefix, your router usually shows it (often /24).