What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its network prefix length as one string, e.g. 192.168.1.0/24. The number after the slash is how many bits are fixed in the network address.

What does /24 mean in CIDR?

A /24 prefix reserves 24 bits for the network and 8 bits for hosts: 256 total addresses, 254 usable hosts (network and broadcast addresses are reserved and cannot be assigned).

What is the difference between network address and broadcast address?

The network address (first IP) identifies the subnet and cannot be assigned to a host. The broadcast address (last IP) sends packets to all hosts on the subnet and is also unassignable.

Does the CIDR calculator support IPv6?

Yes. Enter any IPv6 CIDR block (e.g. 2001:db8::/32) to get the network address, prefix length, total addresses and usable range.

CIDR & Subnet Calculator — IPv4 / IPv6