Subnet / CIDR calculator (IPv4 + IPv6)
Enter an address with a CIDR prefix, a netmask, or a wildcard mask. Get the network address, broadcast, usable host range and more, and split the block into smaller subnets. Everything is computed locally in your browser; nothing is sent to a server.
Accepts CIDR (/24), a dotted netmask
(255.255.255.0) or a wildcard mask
(0.0.0.255) after the address. IPv6 takes a prefix
length. Results update as you type.
Results
Split into smaller subnets
| # | Subnet | Range |
|---|
How it works
An IPv4 address is 32 bits; the prefix length says how many of those
bits name the network and how many are left for hosts. A
/24 keeps 8 host bits, which is 256 addresses: the first
is the network address, the last is the broadcast, and the 254 in
between are usable for hosts. Two special cases:
/31 networks have no broadcast and are used for
point-to-point links (both addresses usable, RFC 3021), and a
/32 is a single host.
IPv6 works the same way with 128 bits, but there is no broadcast
address and subnets are conventionally /64, which leaves
more addresses in one LAN than IPv4 has in total. The wildcard mask
is just the netmask inverted; Cisco ACLs use it, which is why it is
accepted as input here.