subnet-allocator

Overview

This project provides a subnet allocation tool that takes a pool of a given network (e.g., a Class B like 172.16.0.0/16) and, based on a customer’s host requirement, allocates:

• The tightest subnet mask possible (just enough addresses to satisfy the demand).
• The first available subnet inside the pool.

The allocation logic ensures no overlap with previously assigned prefixes.

On top of that, the tool integrates with NetBox (a popular IP Address Management tool), overcoming a limitation of NetBox:

NetBox is excellent at managing IP prefixes and metadata, but it does not allocate subnets for you.

This project bridges that gap:

• Allocates the subnet automatically.
• Creates the prefix entry in NetBox via its REST API.
• Lets you view existing allocations for a customer.
• Allows deallocation of prefixes when no longer needed.

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Features

• Standalone Subnet Allocation: Read customer requests from CSV, allocate subnets, and output results to CSV.
• NetBox Integration: Automatically create prefixes in NetBox after allocation.
• View Allocations: Query NetBox for subnets allocated to a specific customer.
• Deallocate Subnets: Free up or shrink a prefix in NetBox when a customer no longer needs it.
• Tight Masking: Always allocates the smallest possible subnet to fit the demand.

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Files in the Repo

• subnet_allocator.py
  Standalone version.

  • Reads input from requests.csv (customer name and number of hosts).
  • Outputs allocated subnets into allocations.csv.
  • Good for testing or offline subnet planning.

• netbox_allocator.py
  NetBox-integrated version.

  • Reads API token and NetBox URL from config.json.
  • Allocates subnets, creates prefixes in NetBox, and provides a menu for:
    • Adding a new prefix for a customer.
    • Viewing existing allocations.
    • Deallocating a prefix.

• config.json
  Stores NetBox API connection details. Example:

  {
    "NETBOX_URL": "https://demo.netbox.dev/api",
    "NETBOX_TOKEN": "YOUR_API_TOKEN_HERE"
  }
  

Usage Screenshots

1. Running subnet_allocator.py

• Input file: requests.csv with customer demands.
• Output file: allocations.csv with allocated subnets.

requests.csv

allocations.csv (after running subnet_allocator.py)

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2. NetBox Before and After Allocation

When you start, your NetBox IPAM may be empty:

NetBox (before allocation)

After running netbox_allocator.py and allocating prefixes, the subnets are created automatically in NetBox:

NetBox (after allocation)

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3. Using netbox_allocator.py

The tool provides a simple command-line menu for managing allocations.

Main Menu

Setting up a NetBox Account

Follow these steps to create a free NetBox Cloud account and generate your API token for use with the subnet allocator tool.

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1. Create a NetBox Cloud Account

• Go to NetBox Cloud Free Tier.
• Sign up for a free account or log in if you already have one.
• Once created, you’ll have access to your own NetBox instance (e.g., https://your-tenant.netbox.dev).

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2. Generate an API Token

1. Log in to your NetBox instance.
2. Click on your username in the top-right corner.
3. Select API Tokens from the dropdown menu.
4. Click Add Token.
5. Enter a name/description for the token (e.g., Subnet Allocator).
6. Ensure Read/Write permissions are enabled.
7. Save the token and copy the value (you’ll need it for config).

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3. Configure the Tool

• Open the config.json file in your repo.
• Add your NetBox instance URL and the token you just generated:

{
  "NETBOX_URL": "https://your-tenant.netbox.dev/api",
  "NETBOX_TOKEN": "YOUR_API_TOKEN_HERE"
}