A firewall rule may ask for a CIDR block instead of a start and end address. CIDR describes a group of addresses with a suffix such as /30. IPv4 Range Expander finds blocks that cover the exact range you type.
Cover four addresses
In IP range (start-end), type 192.168.1.0-192.168.1.3. Covering CIDR blocks should show 192.168.1.0/30. That one block contains .0, .1, .2, and .3. The /30 describes this group’s size; it is not a port number.
Now change the start to .1: 192.168.1.1-192.168.1.3. You should see 192.168.1.1/32 and 192.168.1.2/31. One /30 would also include .0, which you did not ask for, so the tool uses two smaller blocks.
Before using the result in a firewall
Check that the start and end are in the right order and that you intend to allow every address in the range. A CIDR list is just text until you put it in a firewall or route table. The tool does not change network access for you. If you see an error, check that both sides are complete IPv4 addresses with four numbers from 0 to 255.
Where your input goes
Processing runs in your browser. The tool does not upload your input to ilham.dev.
Related guide
For more background, read Network Debugging Notes.
Questions you might have
- 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.