Reverse all thirty-two hexadecimal digits
04A reverse lookup starts with an IPv6 address. Expand it, reverse its hexadecimal digits one by one, separate them with dots, and append ip6.arpa.
An illustrative PTR answer points to picnic.example. It must be configured separately from the forward AAAA entries; no reverse record is guaranteed to exist.
Source for this drawing: RFC 3596 · Read RFC section 2.5 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
Reverse nibbles, not groups or bytes.
- A nibble is four bits, written as one hexadecimal digit. A 128-bit address has 32 nibbles, including all zeros hidden by ::.
- The lowest-order nibble comes first in the reverse DNS name. Each digit is a separate DNS label; the name ends under IP6.ARPA.
- A PTR (pointer) record can point from that name to a host name. Forward AAAA and reverse PTR data are separately maintained; neither automatically creates the other.
The four displayed digit rows are one continuous DNS name, not separate queries. RFC 3596 replaces the old IP6.INT suffix with IP6.ARPA and obsoletes RFCs 1886 and 3152. A PTR answer is directory data, not proof of ownership or authentication.
Read the RFC section ↗