There are a couple of IPv6 address types that are somewhat special;
these are considered here.
The IPv6 addressing architecture [RFC4291] includes two kinds of
local-use addresses: link-local (fe80::/10) and site-local
(fec0::/10). The site-local addresses have been deprecated [RFC3879]
but are discussed with unique local addresses in Appendix A.
Link-local addresses should never be published in DNS (whether in
forward or reverse tree), because they have only local (to the
connected link) significance [WIP-DC2005].
Temporary addresses defined in RFC 3041prop [RFC3041] (sometimes called
"privacy addresses") use a random number as the interface identifier.
Having DNS AAAA records that are updated to always contain the
current value of a node's temporary address would defeat the purpose
of the mechanism and is not recommended. However, it would still be
possible to return a non-identifiable name (e.g., the IPv6 address in
hexadecimal format), as described in [RFC3041].
6to4 [RFC3056] specifies an automatic tunneling mechanism that maps a
public IPv4 address V4ADDR to an IPv6 prefix 2002:V4ADDR::/48.
If the reverse DNS population would be desirable (see Section 7.1 for
applicability), there are a number of possible ways to do so.
[WIP-H2005] aims to design an autonomous reverse-delegation system
that anyone being capable of communicating using a specific 6to4
address would be able to set up a reverse delegation to the
corresponding 6to4 prefix. This could be deployed by, e.g., Regional
Internet Registries (RIRs). This is a practical solution, but may
have some scalability concerns.
6to4 is mentioned as a case of an IPv6 transition mechanism requiring
special considerations. In general, mechanisms that include a
special prefix may need a custom solution; otherwise, for example,
when IPv4 address is embedded as the suffix or not embedded at all,
special solutions are likely not needed.
Note that it does not seem feasible to provide reverse DNS with
another automatic tunneling mechanism, Teredo [RFC4380]; this is
because the IPv6 address is based on the IPv4 address and UDP port of
the current Network Address Translation (NAT) mapping, which is
likely to be relatively short-lived.
