Expanding a CIDR Block Subnet to Have More IP Addresses
Start course
1h 1m

This course has been designed to teach you how to manage networking and compute resources on Google Cloud Platform. The content in this course will help prepare you for the Associate Cloud Engineer exam.

The topics covered within this course include:

  • Adding subnets to a VPC
  • Expanding existing subnets
  • Reserving static addresses via the console and Cloud Shell
  • Managing, configuring, and connecting to VM instances
  • Adding GPUs and installing CUDA libraries
  • Creating and deploying from snapshots and images
  • Working with instance groups

Learning Objectives

  • Learn how to manage networking and compute resources on Google Cloud Platform
  • Prepare for the Google Associate Cloud Engineer Exam

Intended Audience

  • Those who are preparing for the Associate Cloud Engineer exam
  • Those looking to learn more about managing GCP networking and compute features


To get the most from this course, you should have some exposure to GCP resources, such as VCPs, VM Instances, Cloud Console, and Cloud Shell. However, this is not essential.



Hi everyone, welcome back. In this lecture, we're going to cover the expansion of a CIDR block subnet.

In a production environment and maybe even while sitting an exam, you may find yourself needing to expand a subnet. That being the case, it's important that you know how to do this.

To expand the primary IP range of an existing subnet, you need to modify its subnet mask. By setting the mask prefix length to a smaller number, you make more addresses available on the subnet itself. If you need to expand the range of an automatically created subnet within an auto mode network, the broadest subnet mask or prefix that you can use is /16. Using a subnet mask that's broader than /16 would conflict with the primary IP ranges of the other automatically created subnets. The same rule applies to a custom network that was previously an auto mode network.

It's important to know that you cannot undo the expansion of the primary IP range of a subnet, nor can you shrink the primary IP range of a subnet. That being the case, you should always be conservative when expanding primary IP ranges. If you find that you need even more addresses than expected, you can always expand again later.

You should also be sure to factor in any IP address space of any networks that will be connected to your VPC network when expanding the subnet's primary IP range. You need to ensure that you don't overlap any connected IP address spaces.

Join me in the next lesson where I'll show you how to expand a CIDR block subnet for an existing subnet within a VPC.

About the Author
Learning Paths

Tom is a 25+ year veteran of the IT industry, having worked in environments as large as 40k seats and as small as 50 seats. Throughout the course of a long an interesting career, he has built an in-depth skillset that spans numerous IT disciplines. Tom has designed and architected small, large, and global IT solutions.

In addition to the Cloud Platform and Infrastructure MCSE certification, Tom also carries several other Microsoft certifications. His ability to see things from a strategic perspective allows Tom to architect solutions that closely align with business needs.

In his spare time, Tom enjoys camping, fishing, and playing poker.