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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 rounded
- First address (canonical)
- 2001:db8:dead::
- 2001:0db8:dead:0000:0000:0000:0000:0000
- Last address (canonical)
- 2001:db8:dead:ffff:ffff:ffff:ffff:ffff
- 2001:0db8:dead:ffff:ffff:ffff:ffff:ffff
- Total addresses (exact decimal)
- 1208925819614629174706176
- Excluding the Subnet-Router anycast
- 1208925819614629174706175
- ip6.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