# IPv4 Range Expander Guide

Expand an IP range into the CIDR blocks that cover it.

- Tool: https://ilham.dev/tools/ipv4-range-expander/
- Guide URL: https://ilham.dev/guides/ipv4-range-expander/
- Tool guides index: https://ilham.dev/guides/tools/
- Broader guide: Network Debugging Notes (https://ilham.dev/guides/network-debugging/)

## What it does

Given a start and end address, list the CIDR blocks that cover the range exactly, so you can turn an arbitrary range into something a firewall or a route table will accept.

## Use the tool

Open https://ilham.dev/tools/ipv4-range-expander/, add the input the tool asks for, run it, and check the output before using it elsewhere.

## Input and output

- Input: text.
- Output: text.
- Category: Network.

## Privacy and processing
Processing happens locally in your browser. This tool does not upload the input to ilham.dev.

## Questions

### Why does it return several blocks instead of one?

CIDR blocks are always powers of two, so an arbitrary range almost never lands on one. The tool finds the smallest set of blocks that covers it without going over.