Strategy

Unused Cloud Subnets

July 04, 2026·2 min read·CloudBudgetMaster

Introduction to Cloud Subnets

Cloud subnets are a fundamental component of cloud infrastructure, allowing you to segment your virtual private cloud (VPC) into smaller, isolated networks. However, unused cloud subnets can accumulate over time, leading to unnecessary costs. In this post, we'll explore how to identify and eliminate unused cloud subnets in AWS, GCP, and Azure.

Identifying Unused Subnets in AWS

To identify unused subnets in AWS, you can use the AWS CLI command aws ec2 describe-subnets. This command will return a list of all subnets in your account, including their subnet IDs, CIDR blocks, and availability zones. You can then use the aws ec2 describe-instances command to check if any instances are running in each subnet. For example:

aws ec2 describe-subnets --query 'Subnets[]|{SubnetId, CidrBlock, AvailabilityZone}'
aws ec2 describe-instances --filters 'Name=subnet-id,Values=<subnet-id>' --query 'Reservations[]|{Instances[]|{InstanceId}}'

If no instances are running in a subnet, it's likely unused and can be deleted.

Identifying Unused Subnets in GCP

In GCP, you can use the gcloud compute networks subnets list command to list all subnets in your project. You can then use the gcloud compute instances list command to check if any instances are running in each subnet. For example:

gcloud compute networks subnets list
gcloud compute instances list --filter='subnet=<subnet-name>'

If no instances are running in a subnet, it's likely unused and can be deleted.

Identifying Unused Subnets in Azure

In Azure, you can use the az network vnet subnet list command to list all subnets in your virtual network. You can then use the az vm list command to check if any virtual machines are running in each subnet. For example:

az network vnet subnet list --resource-group <resource-group> --vnet-name <vnet-name>
az vm list --resource-group <resource-group> --subnet <subnet-name>

If no virtual machines are running in a subnet, it's likely unused and can be deleted.

Deleting Unused Subnets

Once you've identified unused subnets, you can delete them using the following commands: * AWS: aws ec2 delete-subnet --subnet-id <subnet-id> * GCP: gcloud compute networks subnets delete <subnet-name> --network <network-name> * Azure: az network vnet subnet delete --resource-group <resource-group> --vnet-name <vnet-name> --name <subnet-name>

Conclusion

Unused cloud subnets can accumulate over time, leading to unnecessary costs. By regularly identifying and deleting unused subnets in AWS, GCP, and Azure, you can optimize your cloud costs and improve your overall cloud infrastructure efficiency. CloudBudgetMaster automates the detection of unused cloud subnets, providing you with a clear view of the associated costs and allowing you to delete them with ease.