subnet --calc | praneeth.me

praneeth@website:~$ subnet --calc [beta]

This page is a tool rather than a document, so it needs JavaScript to do anything — the parsing, the masking and the arithmetic all happen in your browser. That is also why nothing is sent anywhere: enabling JavaScript only lets the work happen locally, it does not introduce a server.

address or network

CIDR, a subnet mask, or a Cisco wildcard — 10.0.0.0/24, 10.0.0.5 255.255.255.0, 10.0.0.5 0.0.0.255, 2001:db8::/48.

Paste a network in any notation — CIDR, a subnet mask, a Cisco wildcard, IPv4 or IPv6. You get the mask, wildcard, range, broadcast and host count, a ruler showing exactly where the prefix cuts the address, and a plain answer to what is this address for: private, loopback, documentation, carrier-grade NAT, multicast. Then divide it into subnets, or check whether two blocks overlap.

notation: RFC 4632
scope data: IANA special-purpose registry
families: IPv4 + IPv6
what's collected: nothing

Nothing you type is sent anywhere. This is bit arithmetic — parsing, masking and counting all happen in your browser. There is no server, no analytics and no lookup of any kind; once this page has loaded it makes no network requests at all. It also does no guessing. An address with host bits set is shown as the host it is — the network address is one click away, never silently substituted — and a bare address stays a single address rather than being snapped to a classful mask that stopped being meaningful in 1993.

# divide

Split the network above into smaller blocks. Everything stays aligned inside the parent.

new prefix

# compare

Does one block contain, sit next to, or miss the other? A bare address works too — ask whether an IP is inside a range.