IPv4 or IPv6. Leave the prefix off to treat it as a single host.
Normalised CIDR: 192.168.1.0/24
First host – Last host: 192.168.1.1-192.168.1.254
Network
24bit
Host
8bit
11000000.10101000.00000001.00000000
- Broadcast
- 192.168.1.255
- Block size
- 256
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Type
- Private (internal)
Enter something like 192.168.1.10/24 and get the network address, broadcast, usable host range and subnet mask. IPv6 prefixes work too.
Formats
IPv4 / IPv6
Questions
Is what I type sent anywhere?
No. It is all computed in the browser, so internal addressing plans stay on your machine.
Why does /31 show two hosts?
That is correct. RFC 3021 allows both addresses of a /31 to be used on a point-to-point link between routers.
Why is the IPv6 host count so large?
A /64 holds about 18 quintillion addresses. That size is the normal unit in IPv6; the design does not try to conserve them.
The network address shown is not the address I typed.
That is correct. Given 192.168.1.10/24, the network that host belongs to is 192.168.1.0/24, so the result is normalised to it. The point of the calculation is the block the host sits in, not the host itself.
Which range should I use for an internal network?
One of the reserved private ranges: 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16. None of the three is routed on the internet, so nothing you assign collides with the outside world. At small scale, laying out 192.168.x.0/24 blocks is the easiest to live with; sites tend to move to 10.x.x.x once there are enough locations to want summarised routes.
Can it tell me whether two CIDRs overlap?
It expands one CIDR at a time. To check an overlap, run both and compare the first and last addresses: if either range starts inside the other, they overlap. Handing out two blocks that overlap without noticing is the most common failure in network design.