Understanding CIDR Ranges

Some of our plugins allow you to block or allow groups of IP addresses using CIDR ranges. If you have never encountered CIDR notation before, it can look confusing at first. This guide explains CIDR ranges in simple terms so that beginners can understand what they are and how to use them safely.

What Is an IP Address?

Every device connected to the internet or a local network uses an IP address. An IP address is similar to a postal address for a computer or device.

Examples of IPv4 addresses include:

  • 192.168.1.1
  • 10.0.0.25
  • 203.0.113.45

Sometimes you may want to block or allow:

  • A single IP address
  • A small group of addresses
  • An entire network or provider range

CIDR notation provides a compact way to describe these ranges.

What Does CIDR Mean?

CIDR stands for:

Classless Inter-Domain Routing

The important thing for most users is that CIDR notation lets you describe a range of IP addresses using a short format.

A CIDR range looks like this:

192.168.1.0/24

The /24 part tells the computer how large the range is.

A Simple Way to Think About CIDR

Think of an IP address as a street address.

  • A single IP address is like one house
  • A CIDR range is like a group of houses on the same street

The number after the slash controls how large the group is.

Common CIDR Examples

CIDR RangeWhat It Means
192.168.1.25/32One single IP address only
192.168.1.0/24All addresses from 192.168.1.0 to 192.168.1.255
10.0.0.0/8A very large private network
172.16.0.0/16A medium-sized network range

The Most Common CIDR Sizes

/32 — One IP Address

203.0.113.45/32

This means:

Only 203.0.113.45

Useful when blocking or allowing a single device.

/24 — A Typical Small Network

192.168.1.0/24

This includes:

192.168.1.0 → 192.168.1.255

This is one of the most common CIDR ranges.

/16 — A Larger Range

192.168.0.0/16

This includes:

192.168.0.0 → 192.168.255.255

This covers many smaller /24 networks.

Smaller Number = Larger Range

This often confuses beginners.

CIDRApproximate Size
/321 IP
/24256 IPs
/1665,536 IPs
/8Over 16 million IPs

So:

  • /32 is very specific
  • /8 is extremely broad

Should I Use CIDR Ranges Carefully?

Yes.

Blocking a large CIDR range can accidentally block legitimate visitors.

For example:

203.0.113.0/24

blocks 256 addresses, not just one.

If you only want to block a single address, use /32.

CIDR vs IP Ranges

Some plugins also support traditional dash ranges such as:

192.168.1.10-192.168.1.50

This means:

Every IP address between those two addresses

CIDR ranges are more compact and are commonly used in firewalls, hosting platforms and server administration tools.

Private Network CIDR Ranges

You may see these ranges on home or office networks:

CIDR RangeTypical Usage
192.168.0.0/16Home routers
10.0.0.0/8Large private networks
172.16.0.0/12Private internal networks

These addresses are not normally visible directly on the public internet.

Helpful CIDR Tools

If you want help calculating CIDR ranges, these free tools can help:

Quick Summary

  • CIDR notation defines a range of IP addresses
  • The format is:
IP_ADDRESS/NUMBER

Example:

192.168.1.0/24
  • Larger numbers after the slash mean smaller ranges
  • /32 means a single IP address
  • /24 is a common small network range
  • Use caution when blocking large ranges to avoid blocking legitimate users