Supported Cloud Providers:
- •Azure: VNets with subnets, optional hub-spoke peering
- •AWS: VPCs with subnets distributed across AZs
- •GCP: VPCs with subnets (hub-spoke supported)
- •Oracle Cloud: VCNs with subnets
- •AliCloud: VPCs with subnets
- •On-Premises: Basic IP calculations
Output Formats by Provider:
- •Azure: info, JSON, Terraform, Bicep, ARM, PowerShell, Azure CLI
- •AWS: info, JSON, Terraform, CloudFormation, AWS CLI
- •GCP: info, JSON, Terraform, gcloud
- •Oracle: info, JSON, Terraform, OCI CLI
- •AliCloud: info, JSON, Terraform, Aliyun CLI
- •On-Premises: info, JSON
Uses Python for deterministic IP calculations matching the TypeScript CLI implementation. </objective>
<quick_start> Basic usage - calculate subnets for a single VNet/VPC:
Show network information:
code
/ipcalc-for-cloud "azure, 10.0.0.0/16, 4 subnets"
Generate Terraform for AWS:
code
/ipcalc-for-cloud "aws, 10.0.0.0/16, 3 subnets, output: terraform"
Custom subnet prefix (to avoid filling entire network):
code
/ipcalc-for-cloud "azure, 172.16.1.0/24, 4 subnets, prefix: /26"
Hub-spoke topology for Azure:
code
/ipcalc-for-cloud "azure, 10.0.0.0/16, 2 subnets, spokes: 10.1.0.0/16,10.2.0.0/16, spoke-subnets: 2,2, output: terraform"
The skill will:
- •Calculate optimal CIDR splits based on provider constraints
- •Distribute subnets across availability zones (AWS/GCP)
- •Apply provider-specific reserved IP calculations
- •Validate IP allocations
- •Output in requested format </quick_start>
Accept user input specifying:
- •Cloud provider: azure, aws, gcp, oracle, alicloud, onpremises
- •Base CIDR: Network CIDR block (e.g., "10.0.0.0/16")
- •Number of subnets: How many subnets to create (1-256)
- •Output format: info (default), json, terraform, bicep, arm, powershell, cloudformation, cli, gcloud, oci, aliyun
- •Optional - Custom prefix: Desired subnet prefix (e.g., /26) to override auto-calculation
- •Optional - Hub-spoke: Spoke network CIDRs and subnet counts for hub-spoke topology
Extract:
- •Cloud provider selection
- •Base IP range (CIDR notation)
- •Number of subnets for primary network
- •Output format
- •Custom subnet prefix (if specified)
- •Spoke network specifications (if hub-spoke topology)
Step 2: Run IP Calculations
Execute the IP calculation script with cloud provider configuration:
bash
python ~/.claude/skills/ipcalc-for-cloud/scripts/ipcalc.py \ --provider azure \ --cidr "10.0.0.0/16" \ --subnets 4 \ --output terraform
With custom subnet prefix:
bash
python ~/.claude/skills/ipcalc-for-cloud/scripts/ipcalc.py \ --provider azure \ --cidr "172.16.1.0/24" \ --subnets 4 \ --prefix 26 \ --output info
With hub-spoke topology:
bash
python ~/.claude/skills/ipcalc-for-cloud/scripts/ipcalc.py \ --provider azure \ --cidr "10.0.0.0/16" \ --subnets 2 \ --spoke-cidrs "10.1.0.0/16,10.2.0.0/16,10.3.0.0/16" \ --spoke-subnets "2,2,2" \ --output terraform
The script will:
- •Validate base CIDR against provider constraints
- •Calculate optimal subnet prefix OR use custom prefix
- •Check capacity (can the network accommodate requested subnets?)
- •Generate subnet CIDR assignments
- •Distribute subnets across availability zones (AWS, GCP)
- •Calculate provider-specific reserved IPs (Azure: 5, AWS: 5, GCP: 4, Oracle: 3)
- •Calculate usable IP ranges
- •Detect any overlaps or invalid ranges
- •For hub-spoke: Calculate spoke networks and configure peering
- •Output structured data for template rendering
Step 3: Output Results
Based on requested output format and provider:
Info format (default):
- •Human-readable formatted table
- •Network details (CIDR, total IPs, address range)
- •Subnet details with availability zones
- •Reserved and usable IP information
- •Provider-specific formatting
JSON format:
- •Structured JSON data
- •Complete network and subnet information
- •Availability zone assignments
- •Reserved IP lists
- •Machine-readable for integration
Terraform format: Generate HCL code with:
- •Provider configuration (azurerm, aws, google, etc.)
- •Variables for customization
- •Network resource (VNet/VPC)
- •Subnet resources with AZ distribution
- •Outputs for resource IDs
- •Hub-spoke peering resources (if applicable)
- •Comments with IP allocation table
Other IaC formats:
- •Bicep: Azure Bicep template with inline subnets
- •ARM: Azure Resource Manager JSON template
- •PowerShell: Azure PowerShell script with cmdlets
- •CloudFormation: AWS YAML template with intrinsic functions
- •CLI Scripts: Bash scripts with az/aws/gcloud commands
Step 4: Validate Output
Run validation checks:
- •IP range validation (no overlaps, proper nesting)
- •Provider constraint validation (prefix limits)
- •Capacity validation (requested subnets fit in network)
- •For Terraform: syntax validation (if terraform CLI available)
- •For hub-spoke: peering configuration correctness </workflow>
- •
IP Range Validation:
- •Verify all subnets fit within parent network
- •Confirm no overlapping ranges
- •Validate CIDR notation
- •Check provider constraints (min/max prefix)
- •
Provider Constraint Validation:
- •Azure: /8 to /29
- •AWS: /16 to /28
- •GCP: /8 to /29
- •Oracle: /16 to /30
- •AliCloud: /8 to /29
- •
Capacity Validation:
- •Requested subnets fit in network
- •Custom prefix (if specified) allows requested subnet count
- •No address space exhaustion
- •
Manual Review Checklist:
- • Subnets properly sized for intended use
- • Availability zone distribution is appropriate
- • Reserved IPs calculated correctly for provider
- • Usable IP counts are accurate
- • Hub-spoke peering configured correctly (if applicable)
Additional validation for IaC output:
- •
Syntax Validation (if CLI tools available):
bash# Terraform terraform init && terraform validate # Azure Bicep az bicep build --file output.bicep # AWS CloudFormation aws cloudformation validate-template --template-body file://output.yaml
- •
IaC Checklist:
- • Provider configuration present and correct version
- • Resource naming follows conventions
- • Variables defined for customization
- • Output variables defined for resource IDs
- • Hub-spoke peering resources complete (if applicable)
- • IP allocation documented in comments </validation>
<advanced_features> Custom Subnet Prefix: Specify exact subnet size instead of auto-calculation:
code
/ipcalc-for-cloud "azure, 172.16.1.0/24, 4 subnets, prefix: /26"
Use case: Avoid filling entire network, leave room for future expansion
Hub-Spoke Topology (Azure, GCP): Create centralized hub network with multiple spoke networks:
code
/ipcalc-for-cloud "azure, 10.0.0.0/16, 2 subnets, spokes: 10.1.0.0/16,10.2.0.0/16,10.3.0.0/16, spoke-subnets: 2,3,2, output: terraform"
Generates bidirectional peering between hub and each spoke
Multi-Provider Support: Same IP calculations work across all cloud providers with provider-specific adjustments:
- •Reserved IP counts
- •CIDR prefix constraints
- •Availability zone naming
- •Output format availability
Availability Zone Distribution (AWS, GCP): Automatic round-robin distribution of subnets across AZs for high availability
Legacy Compatibility: Old command-line options still supported for backward compatibility:
bash
python ipcalc.py --base-cidr "10.0.0.0/16" --vnets 3 --subnets-per-vnet 4
(Creates multiple VNets instead of single VNet with subnets) </advanced_features>
<scripts_reference>
scripts/ipcalc.py
Main IP calculator script supporting multiple cloud providers and output formats.
Key Functions:
- •
calculate_subnets(cidr, num_subnets, provider, desired_prefix)- Calculate subnet allocations - •
generate_hub_spoke_topology(hub_cidr, hub_subnets, spoke_cidrs, spoke_subnets, provider)- Hub-spoke networks - •
calculate_network_info(network, provider_config)- Detailed network information - •
format_network_info(cidr, subnets, provider)- Human-readable output
Usage:
bash
python scripts/ipcalc.py --provider PROVIDER --cidr CIDR --subnets N [OPTIONS]
Options:
- •
--provider: Cloud provider (azure, aws, gcp, oracle, alicloud, onpremises) - •
--cidr: Network CIDR block - •
--subnets: Number of subnets (1-256) - •
--prefix: Optional custom subnet prefix - •
--output: Output format (info, json, terraform, bicep, arm, powershell, cloudformation, cli, gcloud, oci, aliyun) - •
--file: Write output to file - •
--spoke-cidrs: Comma-separated spoke VNet/VPC CIDRs - •
--spoke-subnets: Comma-separated subnet counts per spoke
Output Format (JSON):
json
{
"vnetCidr": "10.0.0.0/16",
"provider": "azure",
"subnets": [
{
"name": "subnet1",
"cidr": "10.0.0.0/18",
"network": "10.0.0.0",
"mask": "255.255.192.0",
"total_ips": 16384,
"usable_ips": 16379,
"usable_range": "10.0.0.3 - 10.0.63.253",
"availabilityZone": "1",
"reserved": ["10.0.0.0", "10.0.0.1", "10.0.0.2", "10.0.63.254", "10.0.63.255"]
}
],
"peeringEnabled": false
}
scripts/cloud_provider_config.py
Cloud provider configuration module defining provider-specific settings.
Configurations:
- •Reserved IP counts (Azure: 5, AWS: 5, GCP: 4, Oracle: 3, etc.)
- •CIDR prefix limits (min/max)
- •Availability zone lists
- •Supported output formats
Functions:
- •
get_cloud_provider_config(provider)- Get provider configuration - •
validate_output_format(provider, output_format)- Validate output format support - •
get_availability_zone(provider, index)- Get AZ for subnet index (round-robin)
scripts/ipcalc_legacy.py
Legacy version supporting old multi-VNet split behavior. Use for backward compatibility:
bash
python scripts/ipcalc_legacy.py --base-cidr "10.0.0.0/16" --vnets 3 --subnets-per-vnet 4
Creates 3 separate VNets instead of 1 VNet with subnets. </scripts_reference>
<templates_reference>
Template Architecture
Templates are organized by provider and format:
code
templates/ ├── azure/ │ ├── terraform.template.tf │ ├── bicep.template.bicep │ ├── arm.template.json │ ├── powershell.template.ps1 │ └── cli.template.sh ├── aws/ │ ├── terraform.template.tf │ ├── cloudformation.template.yaml │ └── cli.template.sh └── ...
Template Placeholders: Common across all templates:
- •
{{vnetCidr}}/{{vpcCidr}}- Network CIDR - •
{{subnetVariables}}- Subnet variable declarations - •
{{subnetResources}}- Subnet resource definitions - •
{{subnetOutputs}}- Output definitions - •
{{spokeVnetResources}}/{{spokeVpcResources}}- Spoke network resources - •
{{vnetPeeringResources}}/{{vpcPeeringResources}}- Peering configurations
Template Processor:
The template processor module (template_processor.py) generates placeholder content:
- •Variable/parameter declarations
- •Resource definitions with proper syntax
- •Hub-spoke peering logic
- •Provider-specific formatting
Templates use simple string replacement for placeholders, maintaining exact output compatibility with TypeScript CLI. </templates_reference>
<anti_patterns>
<pitfall name="filling_entire_network">
❌ Auto-calculating subnet size fills entire network, no room for growth
✅ Use --prefix option to specify smaller subnets, leave address space for future
</pitfall>
<success_criteria> The skill successfully completes when:
For all providers and outputs:
- • IP calculations are mathematically correct and deterministic
- • Provider constraints are enforced (CIDR prefix limits)
- • Reserved IPs calculated correctly for provider
- • Subnets fit within parent network
- • No CIDR blocks overlap
- • Multiple invocations with same input produce identical output
- • Output format matches user request
For AWS and GCP:
- • Subnets distributed across availability zones using round-robin
- • AZ names match provider conventions
For hub-spoke topologies:
- • Hub network calculated correctly
- • All spoke networks calculated correctly
- • Bidirectional peering configured for each spoke
- • No overlapping CIDRs between hub and spokes or between spokes
For IaC template outputs:
- • Generated code passes syntax validation
- • Provider configuration is present and correct
- • Resource naming follows cloud provider conventions
- • Variables defined for customization
- • Outputs defined for resource IDs
- • Documentation included (IP allocation table in comments)
- • Hub-spoke peering resources complete (if applicable)
Compatibility:
- • Output matches TypeScript CLI output for same inputs
- • Legacy compatibility maintained via
ipcalc_legacy.py</success_criteria>