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Network Subnet Splitter

Visualise IPv4 subnet boundaries and calculate precise network splits interactively using a dense, terminal-style component.

Around 2 mins No account required Advanced level
Interactive utility

Run Subnet Splitter

Inputs stay in this browser and results are not saved.

CIDR Subnet Calculator

Network Address10.0.0.0
Broadcast Address10.0.255.255
Subnet Mask255.255.0.0
Total Usable IPs65,534
/16/24
Splitting into /24 subnets yields 256 networks.
Warning: The split generates 256 subnets. Showing only the first 100 for performance.
SubnetUsable RangeUsable IPs
10.0.0.0/2410.0.0.1 - 10.0.0.254254
10.0.1.0/2410.0.1.1 - 10.0.1.254254
10.0.2.0/2410.0.2.1 - 10.0.2.254254
10.0.3.0/2410.0.3.1 - 10.0.3.254254
10.0.4.0/2410.0.4.1 - 10.0.4.254254
10.0.5.0/2410.0.5.1 - 10.0.5.254254
10.0.6.0/2410.0.6.1 - 10.0.6.254254
10.0.7.0/2410.0.7.1 - 10.0.7.254254
10.0.8.0/2410.0.8.1 - 10.0.8.254254
10.0.9.0/2410.0.9.1 - 10.0.9.254254
10.0.10.0/2410.0.10.1 - 10.0.10.254254
10.0.11.0/2410.0.11.1 - 10.0.11.254254
10.0.12.0/2410.0.12.1 - 10.0.12.254254
10.0.13.0/2410.0.13.1 - 10.0.13.254254
10.0.14.0/2410.0.14.1 - 10.0.14.254254
10.0.15.0/2410.0.15.1 - 10.0.15.254254
10.0.16.0/2410.0.16.1 - 10.0.16.254254
10.0.17.0/2410.0.17.1 - 10.0.17.254254
10.0.18.0/2410.0.18.1 - 10.0.18.254254
10.0.19.0/2410.0.19.1 - 10.0.19.254254
10.0.20.0/2410.0.20.1 - 10.0.20.254254
10.0.21.0/2410.0.21.1 - 10.0.21.254254
10.0.22.0/2410.0.22.1 - 10.0.22.254254
10.0.23.0/2410.0.23.1 - 10.0.23.254254
10.0.24.0/2410.0.24.1 - 10.0.24.254254
10.0.25.0/2410.0.25.1 - 10.0.25.254254
10.0.26.0/2410.0.26.1 - 10.0.26.254254
10.0.27.0/2410.0.27.1 - 10.0.27.254254
10.0.28.0/2410.0.28.1 - 10.0.28.254254
10.0.29.0/2410.0.29.1 - 10.0.29.254254
10.0.30.0/2410.0.30.1 - 10.0.30.254254
10.0.31.0/2410.0.31.1 - 10.0.31.254254
10.0.32.0/2410.0.32.1 - 10.0.32.254254
10.0.33.0/2410.0.33.1 - 10.0.33.254254
10.0.34.0/2410.0.34.1 - 10.0.34.254254
10.0.35.0/2410.0.35.1 - 10.0.35.254254
10.0.36.0/2410.0.36.1 - 10.0.36.254254
10.0.37.0/2410.0.37.1 - 10.0.37.254254
10.0.38.0/2410.0.38.1 - 10.0.38.254254
10.0.39.0/2410.0.39.1 - 10.0.39.254254
10.0.40.0/2410.0.40.1 - 10.0.40.254254
10.0.41.0/2410.0.41.1 - 10.0.41.254254
10.0.42.0/2410.0.42.1 - 10.0.42.254254
10.0.43.0/2410.0.43.1 - 10.0.43.254254
10.0.44.0/2410.0.44.1 - 10.0.44.254254
10.0.45.0/2410.0.45.1 - 10.0.45.254254
10.0.46.0/2410.0.46.1 - 10.0.46.254254
10.0.47.0/2410.0.47.1 - 10.0.47.254254
10.0.48.0/2410.0.48.1 - 10.0.48.254254
10.0.49.0/2410.0.49.1 - 10.0.49.254254
10.0.50.0/2410.0.50.1 - 10.0.50.254254
10.0.51.0/2410.0.51.1 - 10.0.51.254254
10.0.52.0/2410.0.52.1 - 10.0.52.254254
10.0.53.0/2410.0.53.1 - 10.0.53.254254
10.0.54.0/2410.0.54.1 - 10.0.54.254254
10.0.55.0/2410.0.55.1 - 10.0.55.254254
10.0.56.0/2410.0.56.1 - 10.0.56.254254
10.0.57.0/2410.0.57.1 - 10.0.57.254254
10.0.58.0/2410.0.58.1 - 10.0.58.254254
10.0.59.0/2410.0.59.1 - 10.0.59.254254
10.0.60.0/2410.0.60.1 - 10.0.60.254254
10.0.61.0/2410.0.61.1 - 10.0.61.254254
10.0.62.0/2410.0.62.1 - 10.0.62.254254
10.0.63.0/2410.0.63.1 - 10.0.63.254254
10.0.64.0/2410.0.64.1 - 10.0.64.254254
10.0.65.0/2410.0.65.1 - 10.0.65.254254
10.0.66.0/2410.0.66.1 - 10.0.66.254254
10.0.67.0/2410.0.67.1 - 10.0.67.254254
10.0.68.0/2410.0.68.1 - 10.0.68.254254
10.0.69.0/2410.0.69.1 - 10.0.69.254254
10.0.70.0/2410.0.70.1 - 10.0.70.254254
10.0.71.0/2410.0.71.1 - 10.0.71.254254
10.0.72.0/2410.0.72.1 - 10.0.72.254254
10.0.73.0/2410.0.73.1 - 10.0.73.254254
10.0.74.0/2410.0.74.1 - 10.0.74.254254
10.0.75.0/2410.0.75.1 - 10.0.75.254254
10.0.76.0/2410.0.76.1 - 10.0.76.254254
10.0.77.0/2410.0.77.1 - 10.0.77.254254
10.0.78.0/2410.0.78.1 - 10.0.78.254254
10.0.79.0/2410.0.79.1 - 10.0.79.254254
10.0.80.0/2410.0.80.1 - 10.0.80.254254
10.0.81.0/2410.0.81.1 - 10.0.81.254254
10.0.82.0/2410.0.82.1 - 10.0.82.254254
10.0.83.0/2410.0.83.1 - 10.0.83.254254
10.0.84.0/2410.0.84.1 - 10.0.84.254254
10.0.85.0/2410.0.85.1 - 10.0.85.254254
10.0.86.0/2410.0.86.1 - 10.0.86.254254
10.0.87.0/2410.0.87.1 - 10.0.87.254254
10.0.88.0/2410.0.88.1 - 10.0.88.254254
10.0.89.0/2410.0.89.1 - 10.0.89.254254
10.0.90.0/2410.0.90.1 - 10.0.90.254254
10.0.91.0/2410.0.91.1 - 10.0.91.254254
10.0.92.0/2410.0.92.1 - 10.0.92.254254
10.0.93.0/2410.0.93.1 - 10.0.93.254254
10.0.94.0/2410.0.94.1 - 10.0.94.254254
10.0.95.0/2410.0.95.1 - 10.0.95.254254
10.0.96.0/2410.0.96.1 - 10.0.96.254254
10.0.97.0/2410.0.97.1 - 10.0.97.254254
10.0.98.0/2410.0.98.1 - 10.0.98.254254
10.0.99.0/2410.0.99.1 - 10.0.99.254254
Purpose and audience

Who this Lab is for

Designed for

  • Network Engineers
  • Cloud Architects
  • DevOps Engineers

Use it when

  • Planning VPC networks
  • Designing IP allocations
  • Splitting large blocks into smaller subnets
How to use it

A complete run, step by step

1

Input Base CIDR

Provide an IPv4 block in CIDR notation (e.g. 10.0.0.0/16).

2

Select Target Prefix

Use the slider to choose how many bits to allocate to the new subnets.

3

Review Split Table

Examine the generated subnets, usable IP ranges, and total network capacity.

4

Export the result

Export the calculation for your own documentation.

Input guide

What you will need

Prepare the following information before starting. Use measured evidence where possible; defaults are examples and should not be treated as recommendations.

Results and methodology

What the result tells you

Your report includes

  • Network and Broadcast Addresses
  • Subnet Mask
  • Total Usable IPs
  • Split Network Table
  • Truncation status for very large splits

How it is determined

Calculates IP boundaries and steps using standardized IPv4 arithmetic via ipaddr.js, iterating efficiently without heavy bitwise overhead in JavaScript.

Deterministic calculation · high confidence · v2026.08.1

Canonical IPv4 parsing and subnet boundaries are calculated deterministically and covered by edge-case tests.

Model assumptions

  • • All calculations follow IPv4 standard prefix and mask definitions.
  • • Broadcast addresses are correctly calculated as the final IP in the range.
  • • Usable-host conventions depend on prefix and use case; /31 point-to-point links follow RFC 3021.

Authoritative references

IETF RFC 4632: Classless Inter-domain RoutingIETF RFC 3021: 31-Bit IPv4 Prefixes
Worked example

VPC Subnet Planning

Situation

You have a /16 block and need /24 subnets for application tiers.

Result

The tool instantly renders all 256 /24 subnets with precise start/end usable IPs, ready for configuration.

Important limitations

Use the result with engineering judgement

  • Currently supports only IPv4 blocks.
  • Large splits (>256 subnets) are truncated in the UI to prevent browser freezing.
  • Does not validate overlapping allocations against your existing cloud environment.
Frequently asked questions

Questions before you begin

Why does it truncate the output?

Splitting a /8 into /30s produces over 4 million subnets. Rendering this many DOM nodes will crash any browser, so the UI is capped to safely display the first 100 rows of very large splits.

Does it handle IPv6?

Currently, this calculator focuses specifically on IPv4 subnetting. For IPv6, use our CIDR Planner utility.

How are the broadcast addresses calculated?

The broadcast address is always the last IP in the given subnet block, calculated using bitwise OR against the inverse of the subnet mask.

Ready to run Subnet Splitter?

Open the interactive utility without an account. Inputs and results are not saved.

Open tool
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