A short companion for IPv4 Range Expander: when it is useful, what it expects, and what to check before using the result.
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 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.
Related guide
For broader background, see Network Debugging Notes.