CALCULATE / IP40BPS / MODULE
IPV4 SUBNET
Calculate IPv4 network boundaries, masks and host capacity from an address and CIDR prefix. All arithmetic stays in this browser.
COMMON PREFIXES
Traditional IPv4 subnets reserve network and broadcast addresses. /31 is interpreted as a point-to-point pair and /32 as one host address. Private/public scope is descriptive only and does not test reachability.
REFERENCE / FAQ
COMMON QUESTIONS
What does an IPv4 CIDR prefix mean?
The prefix length tells you how many of the 32 IPv4 bits identify the network. For example, /24 leaves eight host bits and covers 256 total addresses.
Why does /31 show two usable addresses?
RFC 3021 allows /31 networks on point-to-point links, where the two addresses can be used by the two endpoints instead of reserving network and broadcast host slots.
Does the calculator send my IP address anywhere?
No. IPv4 subnet arithmetic is performed locally in your browser.
The calculator performs deterministic 32-bit IPv4 subnet arithmetic locally in the browser. No address is sent to the server.
/31 networks are treated as point-to-point address pairs and /32 represents one host address.
PRACTICAL / EXAMPLES
PUT THE NUMBER IN CONTEXT.
Short examples using the same units and assumptions as this module.
Network 192.168.1.0, broadcast 192.168.1.255 and 254 traditional usable host addresses.
A /30 covers four addresses: network, two host addresses and broadcast.