Calculate network addresses, broadcast IPs, subnet masks, wildcard masks, and usable host IP ranges with real-time binary breakdown and interactive subnet division.
Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing. In CIDR notation, an IP address is appended with a slash and a prefix number (e.g. 192.168.1.0/24), indicating how many contiguous leading bits belong to the network routing prefix.
In traditional IPv4 subnets (/0 through /30), the very first address with all host bits set to 0 is reserved as the Network Address, and the last address with all host bits set to 1 is reserved as the Broadcast Address. Therefore, usable hosts = 2^(32 - prefix) - 2.
RFC 3021 establishes the use of 31-bit prefixes for point-to-point router links. Because point-to-point links only connect exactly two router endpoints, broadcast is unnecessary. Both addresses are fully usable host endpoints, saving IPv4 addresses on backbone networks.
IPv6 uses 128-bit addresses. Standard subnets are allocated as /64, providing 64 bits for the network routing prefix and 64 bits for the Interface Identifier (IID). This enables Stateless Address Autoconfiguration (SLAAC) and privacy extensions.