About IPv6 Subnet Calculator

Calculates IPv6 network information from an address and prefix length, using exact 128-bit BigInt math. Computes the network address, first and last address, total address count (exact for small subnets, 2^N notation for large ones), RFC 5952 compressed and fully expanded forms, a bit-accurate address-type classification, and the ip6.arpa reverse DNS zone. A subnet generator splits the network into smaller subnets at a chosen prefix (up to 1,000), listing each with its first and last address.

• Exact 128-bit BigInt arithmetic — no float precision loss on large blocks
• RFC 5952 compression (longest zero-run collapses to ::) and full expansion
• Bit-accurate range classification: Global Unicast (2000::/3), Unique Local (fc00::/7), Link-Local (fe80::/10), Multicast (ff00::/8), Documentation (2001:db8::/32), 6to4, NAT64, IPv4-mapped, Loopback, Unspecified
• Total count is exact for prefixes ≥ /75 and shown as 2^N above that
• Reverse DNS zone generated in ip6.arpa nibble format
• Subnet generator splits the parent into up to 1,000 child subnets, each with first/last address

Frequently Asked Questions

How does it classify the address type?

By bit-range, not string prefix — so a random Unique Local address like fd12:3456::1 is correctly identified as fc00::/7, not misread. It distinguishes Global Unicast, ULA, Link-Local, Multicast, Documentation, 6to4, NAT64, IPv4-mapped, Loopback and Unspecified.

How is the total address count shown?

Exactly (e.g. a /126 shows 4) when the count fits in a safe integer, and as 2^N (e.g. a /64 shows 2^64) for larger blocks where an exact decimal would be unwieldy.

What’s the maximum number of subnets it will generate?

1,000. A larger prefix difference returns an error to keep the browser responsive; each generated subnet lists its first and last address.