Help / Subnet calculator
Subnet calculator
A subnet calculator for IPv4 and IPv6: give it an address and a prefix or mask, get the network, mask, broadcast, usable host range and what kind of address space it is.
How to use it
- Type an address with a prefix (10.0.0.0/22), with a mask (10.0.0.5 255.255.252.0), or an IPv6 prefix (2001:db8::/48).
- Press Calculate.
Reading the results
- Network
- The first address of the block, written with its prefix length.
- Netmask / prefix
- How much of the address identifies the network. /24 = 255.255.255.0.
- Wildcard
- The inverse of the mask, used by Cisco ACLs and OSPF.
- Broadcast
- The last address of an IPv4 block, used to reach every host on it. /31 and /32 have none.
- Usable hosts
- Addresses you can assign to devices: total minus network and broadcast (except /31, where both are usable).
- Type
- Private (RFC 1918), carrier-grade NAT, documentation, link-local, multicast or public.
Examples
- 192.168.1.0/24 A typical home network
- 10.20.30.40 255.255.240.0 Address plus mask
- 2001:db8:abcd::/48 An IPv6 site prefix
From the command line
curl "https://tools.nexayori.com/subnet?q=192.168.1.0%2F24" curl "https://tools.nexayori.com/subnet?q=192.168.1.0%2F24&format=json"
| q | Address/prefix or “address mask” |
| format | text, json or html |
Questions
Why does a /31 have 2 usable hosts?
Point-to-point links (RFC 3021) don’t need network or broadcast addresses, so both addresses are usable.
What’s a /64 for in IPv6?
It’s the standard size for one network segment. A /48 holds 65,536 of them.