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What is CIDR notation?

CIDR (Classless Inter-Domain Routing) is a standard format used to represent a range of IP addresses in a single, compact line.

Think of it as shorthand for defining a whole "street" or "neighborhood" of IP addresses, rather than just a single "house."

How to Read CIDR Notation

Let's break down a common example: 123.45.67.0/24

This notation has two parts:

The IP Address (123.45.67.0): This is the starting address of the block. It tells you where the IP range begins.

The Suffix (/24): This is called the prefix size. It specifies the size of the block. A smaller number means a larger block of IP addresses.

Here’s a simple guide to what some common suffixes mean:

Why This is Essential for Your Protection

Using CIDR notation is critical for efficiently managing the 500-slot IP exclusion limit in Google Ads.

Instead of using up 256 of your valuable exclusion slots to block 256 individual fraudulent IPs, we can use just one slot by blocking their entire /24 range.

This allows our system to provide a much broader and more durable defense against large-scale botnets and malicious data center networks. In short, CIDR is the technical language we use to block entire bad neighborhoods on the internet, not just individual bad actors.