IP subnet calculator

Prefix details

Accepts CIDR, dotted netmask, wildcard mask, address length, or a bare address.

Split a prefix

Results are paged. Huge splits report the exact total without enumerating it.

VLSM allocation

One per line, or comma-separated. Either a bare count or name: count.

Aggregate

Free space

Compare two prefixes

EUI-64 and SLAAC

Reverse DNS

Handles non-octet-aligned IPv4 (RFC 2317) and non-nibble-aligned IPv6.

Cross-family embedding

RFC 6052 prefix lengths /32, /40, /48, /56, /64 and /96 are supported.

Batch

Blank lines and lines starting with # are ignored. A line that fails keeps its place in the table and shows the reason instead of results.