Jeroen Massar wrote:
<IPv6 whine mode>
But what about IPv6?
The receiver MX knows the IP of the client, either IPv4 or
IPv6. There's also a clause in the spec. about IPv4 mapped
to IPv6:
<http://www.schlitt.net/spf/spf_classic/?M=D>
| When any mechanism fetches host addresses to compare with
| <ip>, when <ip> is an IPv4 address, A records are fetched,
| when <ip> is an IPv6 address, AAAA records are fetched.
| Even if the SMTP connection is via IPv6, an IPv4-mapped
| IPv6 IP address (see [RFC3513] section 2.5.5) MUST still
| be considered an IPv4 address.
the 'a' mechanism gets redefined so that it requires apps
to also check for a valid IPv6 address.
Either IPv4 or IPv6. Comparing IPv4 directly with IPv6 is
a waste of time, they are different. If the connection is
IPv4 compare IPv4 (=> A), else IPv6 (=> AAAA).
what about host.example.com/24 IPv4 or IPv6?
It depends on the connection, either IPv4 or IPv6. If you
have both A and AAAA with different CIDRs you'd use the
"dual-cidr-length" notation, e.g. a:host.example.com/24//48
You almost always have //nn to identify an IPv6 CIDR, only
for ip6: you'd use one slash /nn for an IPv6 CIDR, because
then it's clear.
Your original a:host.example.com/24 is in fact the same as
a:host.example.com/24//128 (24 for A, default 128 for AAAA)
Bye, Frank