Exponential Complexity
12 accounts × 4 regions × 3 AZs × 6 subnet types = 864 unique subnets
Each one needs a carefully calculated CIDR block. One overlap, and traffic routes to the wrong place—or nowhere at all.
Subnetter
Plan your entire cloud network in minutes, not days. Generate thousands of conflict-free subnet allocations from a single config file.
The Problem
Every cloud network starts with a simple question: “What IP addresses should we use?”
What seems straightforward quickly becomes a nightmare at scale. A typical enterprise cloud deployment requires:
The Spreadsheet Trap
Teams resort to massive spreadsheets. Formulas break. Rows get deleted. Version control is “final_v3_REAL.xlsx”. The person who built it left the company.
Growth Breaks Everything
You allocated a /24 for production. Now you need 500 hosts. Re-IP the entire VPC? Migrate workloads? Explain to leadership why this “simple change” takes 3 months?
Multi-Cloud Multiplies Pain
AWS uses us-east-1a. Azure uses eastus-1. GCP uses us-central1-a. Three clouds means three naming conventions, three spreadsheets, and three times the chance for human error.
The Hidden Costs
🔥 Incident Response
Hours to days per incident
A developer deploys to staging, but traffic routes to production. Why? Overlapping CIDRs between VPCs. The on-call engineer spends 3am tracing packet flows, comparing subnet tables, and explaining to leadership why customer data might have been exposed.
🏗️ Re-IP Projects
Weeks to months of engineering time
You allocated a /24 for the data tier. Now the ML team needs 500 GPU instances. Options: re-architect the entire VPC, migrate every workload with downtime, or run a parallel network and maintain both. None are good. All are expensive.
🧠 Tribal Knowledge
Institutional risk
“Why is this subnet 10.47.128.0/22?” The answer lives in Sarah’s head. Sarah left 6 months ago. The wiki says “see network diagram” but the diagram is from 2019. New engineers take weeks to become productive because the network is a mystery.
📋 Compliance & Audits
Failed audits, delayed certifications
The auditor asks: “Show me your IP address management policy.” You show them a spreadsheet. They ask: “How do you prevent overlaps?” You say: “We’re careful.” They write: “Finding: No automated controls for IP allocation. Risk: High.”
🤝 M&A Integration
Months of delay, millions in cost
Your company acquires a competitor. Their production network is 10.0.0.0/8. So is yours. Every integration project—shared services, data migration, unified auth—is blocked until someone re-IPs an entire organization. The deal synergies are delayed by a year.
📈 Scaling Paralysis
Opportunity cost
The business wants to launch in 3 new regions by Q2. The network team says: “We need to plan the IP allocation first.” Planning takes 6 weeks. Implementation takes 4 more. The competitor launches first. The window closes.
There’s a Better Way
What if you could describe your entire network structure in a simple config file—and generate every subnet allocation automatically, with mathematical guarantees of zero conflicts?
That’s Subnetter.
Define your accounts, regions, and subnet types once. Subnetter handles the CIDR math, respects cloud provider conventions, and produces a complete allocation table in seconds. Add a new region? One line in the config. Need to audit your IP space? It’s all in version control.
Try It Now
Get your first allocation in under a minute:
# Install and runnpm install -g subnettersubnetter generate --config config.json --output allocations.csv# Run directly without installingnpx subnetter generate --config config.json --output allocations.csvSee It In Action
📄 Your Config (15 lines)
{ "baseCidr": "10.0.0.0/8", "accounts": [ { "name": "production", "clouds": { "aws": { "regions": ["us-east-1", "us-west-2", "eu-west-1"] } } }, { "name": "staging", "clouds": { "aws": { "regions": ["us-east-1"] } } }, { "name": "development", "clouds": { "azure": { "regions": ["eastus", "westeurope"] } } } ], "subnetTypes": { "Public": 24, "Private": 24, "Data": 26, "Management": 28 }}📊 Your Output (144 rows)
| Account | Cloud | Region | AZ | Subnet | CIDR |
|---|---|---|---|---|---|
| production | aws | us-east-1 | us-east-1a | Public | 10.0.0.0/24 |
| production | aws | us-east-1 | us-east-1a | Private | 10.0.1.0/24 |
| production | aws | us-east-1 | us-east-1a | Data | 10.0.2.0/26 |
| production | aws | us-east-1 | us-east-1a | Management | 10.0.2.64/28 |
| production | aws | us-east-1 | us-east-1b | Public | 10.0.4.0/24 |
| … | … | … | … | … | … |
| development | azure | westeurope | westeurope-3 | Management | 10.2.28.64/28 |
3 accounts × 6 regions × 3 AZs × 4 subnets = 144 allocations
Real-World Scenarios
Scenario: Global financial services company migrating to cloud
- 50+ AWS accounts (prod, staging, dev, sandbox per business unit)
- 8 regions for data residency compliance
- 6 subnet types per VPC (public, private, data, management, endpoints, transit)
- Strict audit requirements for IP allocation
Without Subnetter: 6-month planning project. Dedicated network team. Custom tooling.
With Subnetter: Single config file. Version-controlled. Auditable. Done in a day.
Scenario: Fast-growing SaaS company expanding internationally
- Started with 1 region, now need 5
- Adding new microservices weekly
- Can’t afford downtime for re-IP projects
- Small team wearing many hats
Without Subnetter: Outgrow your IP scheme. Painful re-architecture. Production incidents.
With Subnetter: Plan for 10x growth upfront. Add regions in minutes. Sleep at night.
Scenario: Healthcare company with multi-cloud strategy
- AWS for compute, Azure for AI/ML, GCP for analytics
- Need consistent IP strategy across all three
- Each cloud has different AZ naming conventions
- Compliance requires documented network architecture
Without Subnetter: Three different spreadsheets. Manual translation. Inevitable conflicts.
With Subnetter: One config. All clouds. Provider-aware AZ naming. Single source of truth.
How It Works
Subnetter divides your IP space hierarchically—no overlaps, guaranteed:
flowchart LR
A["🌐 Base CIDR<br/>10.0.0.0/8<br/><i>16M addresses</i>"] --> B["☁️ Accounts<br/>/16 each<br/><i>65K per account</i>"]
B --> C["🗺️ Regions<br/>/20 each<br/><i>4K per region</i>"]
C --> D["📍 AZs<br/>/22 each<br/><i>1K per AZ</i>"]
D --> E["🔲 Subnets<br/>/24-/28<br/><i>16-254 per subnet</i>"]
style A fill:#1a1a2e,color:#fff,stroke:#4a4a6a,stroke-width:2px
style B fill:#16213e,color:#fff,stroke:#4a4a6a,stroke-width:2px
style C fill:#0f3460,color:#fff,stroke:#4a4a6a,stroke-width:2px
style D fill:#1a5276,color:#fff,stroke:#4a4a6a,stroke-width:2px
style E fill:#1e8449,color:#fff,stroke:#4a4a6a,stroke-width:2px
Deterministic
Same config always produces the same output. Perfect for GitOps, disaster recovery, and reproducible infrastructure.
Extensible
Add new accounts or regions anytime. Subnetter finds the next available space without touching existing allocations.
Provider-Aware
Knows that AWS uses us-east-1a, Azure uses eastus-1, and GCP uses us-central1-a. You don’t have to.
Validation Built-In
Catches errors before they reach production: overlapping CIDRs, invalid prefixes, exhausted address space.
Why Teams Choose Subnetter
🕐 Save Days of Planning
What takes a team days in spreadsheets takes Subnetter seconds. Focus your engineers on building, not IP math.
🛡️ Eliminate Human Error
No more typos in CIDR notation. No more “oops, that overlaps with prod.” Mathematically guaranteed correctness.
📈 Scale Confidently
Plan for 10x growth from day one. Add accounts, regions, and subnets without re-architecting your network.
📋 Audit-Ready Documentation
Your network allocation is a version-controlled config file. Every change is tracked. Every allocation is explainable.
The Manual Approach vs. Subnetter
| Aspect | Manual (Spreadsheets) | Subnetter |
|---|---|---|
| Time to plan 100 subnets | Hours to days | Seconds |
| Risk of overlap | High (human error) | Zero (algorithmic) |
| Adding a new region | Recalculate everything | Add one line to config |
| Multi-cloud consistency | Three separate docs | One unified config |
| Onboarding new team members | ”Ask Sarah, she knows” | Self-documenting config |
| Disaster recovery | Hope the spreadsheet is current | Regenerate from Git |
| Audit trail | ”Check the wiki” | Git history |
Choose Your Path
🚀 New to Subnetter?
Start with the Quick Start guide for installation, configuration basics, and your first allocation.
📋 Ready to Configure?
Jump to the Configuration Reference for the complete schema and all available options.
🔧 Using Programmatically?
Check the API Documentation to integrate Subnetter into your Node.js applications.
🎓 Learn CIDR Basics?
New to IP subnetting? The CIDR Primer covers everything you need to know.
Key Capabilities
Multi-Cloud Native
First-class support for AWS, Azure, and GCP with provider-specific region and AZ naming conventions built in.
Flexible Subnet Sizing
Define different prefix lengths for different workloads. Large /24s for compute, small /28s for management.
Account-Level Overrides
Need a specific CIDR for one account? Override defaults without breaking the hierarchy.
CSV & Programmatic Output
Export to CSV for spreadsheet users, or use the TypeScript API for automation pipelines.
More Resources
Architecture
Understand Subnetter’s technical design and allocation algorithms.
Troubleshooting
Solutions for common issues and error messages.
Kubernetes Guide
Specialized network design for multi-AZ Kubernetes deployments.
Developer Guide
Contributing to Subnetter? Start here.