In plain words
Enter an IPv4 address followed by its prefix (/24) or its mask (255.255.255.0). The result updates as you type. Everything happens in your browser: nothing is sent anywhere.
What each line means
| Result | Meaning |
|---|---|
| Mask | The prefix in classic notation |
| Wildcard mask | Used in Cisco access lists and OSPF |
| Network address | First address of the range, it designates the network |
| Broadcast address | Last address, it reaches every machine on the network |
| First and last host | The range of addresses to give to machines |
| Address type | Private, public, loopback, APIPA, CGNAT, multicast, documentation… |
| Former class | Class A, B, C, D or E, useful for exercises and certifications |
| Split this network | The list of subnets obtained with a longer prefix |
The calculated address is added to the page address (?ip=…): you can bookmark or share a calculation.
To understand the calculations, see calculating a subnet step by step and the subnet mask cheat sheet.