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CIDR Overlapping In AWS

In this article, we will discuss the CIDR overlapping in AWS.

What Is CIDR Overlapping?

The CIDR overlapping is when two or more CIDR blocks have IP addresses that fall within the same range.

CIDR Explained?

There are 2 parts of CIDR: -

IP Address
Subnet Mask

The IP address marks the beginning of the range. The subnet mask determines how many bits are used for the network portion. Consider an example of the 192.168.1.0/24 CIDR. The 192.168.1.0 is the IP address and /24 is the subnet mask.

Simple Overlap

Suppose you have two CIDR blocks: -

192.168.1.0/24 - This range covers 192.168.1.0 to 192.168.1.255.
192.168.1.128/25 - This range covers 192.168.1.128 to 192.168.1.255.

The IPs 192.168.1.128 to 192.168.1.255 overlap between the two CIDR blocks.

Nested Overlap

10.0.0.0/8 - This covers a large range: `10.0.0.0` to `10.255.255.255`.
10.0.1.0/24 - This smaller range covers `10.0.1.0` to `10.0.1.255`.

The second block, 10.0.1.0/24 is entirely within the larger 10.0.0.0/8 range, creating a nested overlap.

Posted By -	Karan Gupta

Posted On -	Friday, November 15, 2024

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