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# IPv6 prefix calculator

First and last address, the exact 2^n address count, and the arpa prefix for any /0–/128 — BigInt-exact, computed in this tab.
a /64 is 18,446,744,073,709,551,616 addresses — printed in full, never roundedCalculateClearFirst address (canonical)2001:db8:dead::2001:0db8:dead:0000:0000:0000:0000:0000Last address (canonical)2001:db8:dead:ffff:ffff:ffff:ffff:ffff2001:0db8:dead:ffff:ffff:ffff:ffff:ffffTotal addresses (exact decimal)1208925819614629174706176Excluding the Subnet-Router anycast1208925819614629174706175ip6.arpa prefix (nibbles, reversed)d.a.e.d.8.b.d.0.1.0.0.2.ip6.arpa

- No broadcast reservation: every address in the block is assignable. The one convention worth knowing is the Subnet-Router anycast (RFC 4291 §2.6.1) — the first address — which is why both counts are shown; it is an addressing convention, not a reserved-invalid.
- Capacities are BigInt-exact: a /64 prints as 18,446,744,073,709,551,616 — the full decimal, because no float ever touches it.
- The arpa row is the reverse-nibble prefix used for reverse DNS zones. It is a text derivation — this tool never performs a DNS query.
- Host bits set in your input are named; the network is computed from the aligned base.
Done

Finished here in the tab. Nothing was uploaded.

same core as the IPv4 calculator — one tested implementation

## Next door in Network

- [IPv6 expand & compress](/network/ipv6-format)
- [IPv4 subnet calculator](/network/ipv4-subnet)
[All network tools](/network)

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