A simple application and Elm library for inspecting and subtracting CIDR blocks. Try it out: https://bluekeyes.github.io/cidrtool/
Two reasons:
- Subtracting CIDR blocks seemed like an interesting problem
- I wanted to build a thing with Elm
If you find yourself also needing to subtract CIDR blocks, something's probably gone wrong already. But one place where it might be useful is when you have an ALLOW-only firewall (like an EC2 security group) but you really want to DENY a specific IP range. Take the overall allowed range, subtract out the deny range(s), and add ALLOW rules for the result.
This will quickly become difficult to maintain and will probably run into limitations on the number of allowed rules per security group. But until then, it will (probably) work!
Clone the repository, then run:
npm install
npm run start
You can view the application at http://localhost:8080 and it will live-reload
as changes are made.
To build a production version for distribution, run:
npm run build