About SubnetTool

SubnetTool is a small infrastructure-focused website built to make subnet planning faster, clearer, and less error-prone.

The site focuses on practical networking questions such as:

  • How many usable IPs are available in a cloud subnet?
  • How large should a Kubernetes node subnet be?
  • How large should a pod CIDR be?
  • How do Azure, AWS, and Google Cloud reserve addresses differently?

The goal is simple:

Help operators make better subnet and CIDR decisions before they hit scaling problems in production.

Who Operates the Site

SubnetTool.com is operated by EDB og Sånt AS
Org.nr 835 999 432

The site is created and maintained by Kristoffer Hatland.

It is built as a practical resource for:

  • Platform engineers
  • Cloud architects
  • DevOps teams
  • Consultants
  • Anyone who regularly works with subnet sizing and Kubernetes networking

Why This Site Exists

Subnet planning is one of those tasks that looks simple on paper and becomes messy very quickly in real environments.

Traditional subnetting references often do not help enough when you are dealing with:

  • Azure reserved IPs
  • AWS reserved IPs
  • Google Cloud alias ranges
  • AKS, EKS, GKE, and ARO networking behavior
  • Pod CIDRs and service CIDRs
  • Cluster scaling and autoscaler headroom

SubnetTool exists to bridge that gap with focused tools and plain-language guides.

How the Calculators Work

The calculators on this site are designed for quick planning and estimation.

In general, they:

  • Run locally in your browser
  • Apply cloud-specific reservation logic where relevant
  • Estimate CIDR sizes based on node count, pod density, and growth headroom
  • Help identify obviously undersized subnets before deployment

They are intended to support architecture and operations work, not replace official provider documentation.

You should still validate final network designs against:

  • Your cloud provider’s current documentation
  • Your organization’s IP standards
  • Service-specific networking requirements

Content Approach

SubnetTool focuses on content that is:

  • Narrowly scoped
  • Practical
  • Written for real deployment decisions
  • Centered on cloud networking and Kubernetes CIDR planning

The aim is not to publish broad, generic cloud content.

The aim is to publish pages that help answer very specific operational questions well.

Contact

If you have questions about the site, feedback on the calculators, or suggestions for new subnet and CIDR tools, you can contact the site operator here:

You can also review the site policies here: