devops-network-calculator-for-azure

Azure network planning, CIDR calculation, subnet sizing, and best-practices tool. Use this skill whenever the user asks about subnet sizing, CIDR planning, AKS networking, NSG rules, network segmentation, IP address management, VNet planning, address space analysis, overlap detection, or any Azure networking topic. Also trigger when the user mentions network calculator, net-calc, calculate hosts, plan subnets, or asks about Azure network best practices, even if they don't explicitly say 'networ…

First seen Mar 29, 2026

Installation

$ npx skills add julianobarbosa/claude-code-skills --skill devops-network-calculator-for-azure

Summary

Azure network planning, CIDR calculation, subnet sizing, and best-practices tool.
Use this skill whenever the user asks about subnet sizing, CIDR planning, AKS networking, NSG rules, network segmentation, IP address management, VNet planning, address space analysis, overlap detection, or any Azure networking topic.
Also trigger when the user mentions network calculator, net-calc, calculate hosts, plan subnets, or asks about Azure network best practices, even if they don't explicitly say 'network calculator'.

Agent compatibility

Declared targets from SKILL.md / docs. Unmarked agents are not listed — the skill may still install via the CLI.

Claude Code Declared

Cursor Not declared

Codex Not declared

GitHub Copilot Not declared

Windsurf Not declared

Gemini CLI Not declared

Cline Not declared

OpenCode Not declared

Repository health

Stars 10

License LICENSE

Default branch main

Open issues 1

Status Active

Package contents

Files included with this skill beyond the listing page.

skill md SKILL.md 4,848 B

docs SUMMARY.md 556 B

History

Mar 29, 2026 First seen on skills.sh

Sep 9, 2026 First recorded snapshot · 63 installs

SKILL.md

Azure Network Calculator

Offline Azure network planning tool. Calculates CIDRs, detects overlaps, analyzes VNet utilization, plans AKS networking, and generates Terraform-ready output. Zero external dependencies — uses Python stdlib only.

Quick Start

# What CIDR do I need for 500 hosts?
python3 scripts/network-calc.py calculate --from-hosts 500

# Analyze current VNet
python3 scripts/network-calc.py analyze --from-tfvars terraform/terraform.tfvars

# Validate for overlaps (pre-commit compatible)
python3 scripts/network-calc.py validate --from-tfvars terraform/terraform.tfvars

# Find where to place a new subnet
python3 scripts/network-calc.py first-fit --vnet 10.248.0.0/20 \
  --subnets "10.248.0.0/22,10.248.4.0/22,10.248.8.0/26,10.248.9.0/24" --hosts 500

Commands

Command	Purpose	Reference
`calculate`	CIDR info, host sizing, subnet splitting	[CIDR Guide](./references/cidr-calculation-guide.md)
`analyze`	VNet utilization, gap analysis	[CIDR Guide](./references/cidr-calculation-guide.md)
`validate`	Overlap detection, Azure constraint checks	[Azure Constraints](./references/azure-constraints.md)
`first-fit`	Find optimal placement for new subnet	[CIDR Guide](./references/cidr-calculation-guide.md)
`plan-multi`	Multi-environment VNet allocation	[Segmentation](./references/segmentation-patterns.md)

Project Context

This project's current VNet: 10.248.0.0/20 (4,096 IPs, 57.8% utilized)

Subnet	CIDR	Usable
GatewaySubnet	10.248.0.0/22	1,019
PublicSubnet	10.248.4.0/22	1,019
AzureBastionSubnet	10.248.8.0/26	59
PrivateSubnet	10.248.9.0/24	251
Available gaps		1,708

Key files: terraform/terraform.tfvars, terraform/networking.tf, terraform/nsg.tf

Azure Quick Reference

5 reserved IPs per subnet (.0, .1, .2, .3, broadcast)
Bastion: min /26 | Gateway: min /27 | Firewall: min /26
Max subnets/VNet: 3,000 | Max NSG rules: 1,000
Full reference: [Azure Constraints](./references/azure-constraints.md)

Reference Guides

Guide	When to Read
[CIDR Calculation Guide](./references/cidr-calculation-guide.md)	Subnet sizing, gap analysis, overlap detection
[AKS Networking Guide](./references/aks-networking-guide.md)	CNI comparison, pod/service CIDR, node sizing
[Segmentation Patterns](./references/segmentation-patterns.md)	Design patterns, anti-patterns, decision matrices
[Azure Constraints](./references/azure-constraints.md)	Hard limits, naming rules, reserved addresses

Templates

Template	Purpose
[VNet Layout](./templates/vnet-layout.tfvars.tpl)	Terraform variable blocks for VNet config
[AKS NSG Rules](./templates/nsg-rules-aks.tfvars.tpl)	NSG rules for AKS workloads
[Multi-Env Plan](./templates/multi-env-plan.md.tpl)	Multi-environment planning output

Execution

Follow the instructions in ./workflow.md.

Gotchas

Azure reserves 5 IPs per subnet, not 2: A standard /29 gives you 3 usable IPs, not 6. Sizing AKS node pools with /29 starves scaling and surfaces as InsufficientFreeAddressesInSubnet mid-scale.
GatewaySubnet name is literal: Azure refuses VPN Gateway attach unless the subnet is named exactly GatewaySubnet. Same for AzureBastionSubnet and AzureFirewallSubnet. Typo breaks at apply, not plan.
AKS Azure CNI eats one subnet IP per pod: A 30-node cluster at 30 pods/node needs 900+ subnet IPs, not 30. Plan --max-pods first; switching CNI later requires cluster rebuild.
first-fit picks lowest gap, not smartest: Places a /24 in a /22 gap and leaves fragmented unusable /25 leftovers. For long-lived VNets, use plan-multi and reserve growth gaps explicitly.
CIDR overlap with on-prem fails silently until peering: A 10.0.0.0/16 VNet looks fine alone, but ExpressRoute peering black-holes routes overlapping corporate ranges. Validate against full corporate IPAM.
NSG rule limit is 1,000 total, not per-direction: Inbound + outbound + default + Azure-auto rules share the budget. Leave headroom or hit a hard wall during scale.