You enter an IPv4 address and a CIDR prefix length (or dotted-decimal mask). The tool converts the IP to a 32-bit integer, builds a bitmask from the prefix, then performs bitwise AND to get the network address and bitwise OR with the inverted mask to get the broadcast. Host count is 2^(32 − prefix) minus 2 for network and broadcast. It does not handle IPv6 or non-contiguous masks.
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by the number of leading 1-bits in the subnet mask. For example, /24 means the first 24 bits are the network portion, leaving 8 bits (256 addresses, 254 usable) for hosts.
The first address is reserved as the network identifier and the last as the broadcast address. Neither can be assigned to a device, so usable hosts = 2^(host bits) − 2. The exception is /31 (RFC 3021), where both addresses are usable on point-to-point links.
The wildcard mask is the inverse of the subnet mask (all 0s become 1s and vice versa). It tells a router which bits to "don't care" about when matching an ACL rule. For example, a /24 subnet mask of 255.255.255.0 has a wildcard of 0.0.0.255.
No. This calculator handles IPv4 only. IPv6 addresses are 128 bits with different notation and prefix rules. CIDR concepts still apply, but the math uses a much larger address space.
A /31 has only 2 addresses and no broadcast — it is used for point-to-point links per RFC 3021. A /32 is a single host route with exactly one address and zero usable hosts, typically used in routing tables or loopback interfaces.
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.