Skill v1.0.1
currentAutomated scan100/100+1 new
version: "1.0.1" name: azure-network-calculator description: Azure network planning — CIDR calculation, subnet allocation, VNet sizing, IP address planning, snet layout, network capacity, Azure networking, hub-spoke topology. USE WHEN CIDR, subnet, VNet, snet, network planning, IP address, Azure networking, calculate network, plan network, validate CIDR, network capacity, address space.
Customization
Before executing, check for user customizations at: ~/.claude/skills/PAI/USER/SKILLCUSTOMIZATIONS/azure-network-calculator-skill/
If this directory exists, load and apply any PREFERENCES.md, configurations, or resources found there. These override default behavior. If the directory does not exist, proceed with skill defaults.
MANDATORY: Voice Notification (REQUIRED BEFORE ANY ACTION)
You MUST send this notification BEFORE doing anything else when this skill is invoked.
- Send voice notification:
``bash curl -s -X POST http://localhost:8888/notify \ -H "Content-Type: application/json" \ -d '{"message": "Running the WORKFLOWNAME workflow in the azure-network-calculator-skill skill to ACTION"}' \ > /dev/null 2>&1 & ``
- Output text notification:
`` Running the **WorkflowName** workflow in the **azure-network-calculator-skill** skill to ACTION... ``
This is not optional. Execute this curl command immediately upon skill invocation.
azure-network-calculator-skill
Automates CIDR calculation, subnet allocation, and Terraform code generation for your organization's Azure hub-spoke infrastructure.
Workflow Routing
| Intent | Workflow | Description | |
|---|---|---|---|
| Plan a VNet + subnets for a new resource group | PlanNetwork | Design complete network layout with Terraform | |
| Check if a CIDR overlaps existing allocations | ValidateCidr | Overlap detection against master allocation | |
| Show remaining capacity in a subscription/VNet | CalculateCapacity | Available /20 and /24 blocks |
If the user's intent is ambiguous, ask which workflow to run.
Quick Reference
CIDR Hierarchy
/13 (subscription) = 524,288 addresses = 128 x /20 VNets/20 (VNet) = 4,096 addresses = 16 x /24 subnets/24 (subnet) = 256 addresses = 251 usable (Azure reserves 5)/22 (large subnet) = 1,024 addresses = 1,019 usable/27 (gateway) = 32 addresses = 27 usable/26 (firewall) = 64 addresses = 59 usable
VNet Index Formula
VNet[i] address = subscription_base + (i * 4096) # 4096 = 2^(32-20)VNet[i] CIDR = calculated_address/20
Each /13 subscription holds exactly 128 /20 VNets (index 0-127).
Azure Reserved IPs (5 per subnet)
| Offset | Purpose | |
|---|---|---|
| +0 | Network address | |
| +1 | Default gateway | |
| +2 | DNS mapping | |
| +3 | DNS mapping | |
| Last | Broadcast |
Naming Convention
snet-{purpose}-{rg}-{env}-{region}vnet-{rg}-{env}-{region}nsg-{purpose}-{rg}-{env}-{region}natg-{rg}-{env}-{region}
Where {rg} is the resource group name (without rg-example- prefix), {env} is dev/hlg/prd, {region} is the shortcode (e.g., eus).
Context Files
| File | Purpose | |
|---|---|---|
| your CIDR master allocation (maintained outside this skill) | All 16 subscriptions, known VNets, formulas | |
| SubnetTemplates.md | 4 workload archetype subnet layouts | |
| TerraformSnippets.md | AVM module HCL matching repo patterns |
Gotchas
- Azure reserves 5 IPs per subnet (network, gateway, DHCP, broadcast + 1 reserved): /29 has 3 usable, not 5; /28 has 11, not 13.
- NSG rule count cap: 1000 per NSG — ASGs reduce rule count but introduce coupling between resource groups.
- VNet peering doesn't support transitive routing — hub-spoke designs need Azure Firewall or NVA as an explicit hop; a hub-as-router assumption fails.
- IPv6 dual-stack on AKS: requires preview feature flag; subnet calculations must size both v4 AND v6 explicitly.
- Subnet delegation locks the subnet — once delegated to a service (e.g., AKS, App Service), it can't be undelegated without recreating.