On Sat, Feb 14, 2004 at 02:26:23PM +0000, Shevek wrote:
- The resulting addresses MUST have PTR records, and these PTR records
MUST match the host. The following lookups will still work but are
discouraged:
somehost -> a.b.c.d; a.b.c.d -> otherhost; otherhost -> a.b.c.d
This is absolutely standard setup for many places. domain.com => a.b.c.d
=> mailhost.comain.com => a.b.c.d. This happens because domain.com might
be needed as a www or telnet server, and this might be on a separate
system to the MX. I've always considered it peculiar that DNS specified
what is effectively a TCP redirect for port 25, but it does, and that's
how it's used.
$origin example.tld
@ MX 0 mailhost.example.tld.
mailhost A a.b.c.d
d.c.b.a.in-addr.arpa PTR mailhost.example.tld.
I don't see why an www or telnet server would clash with above setup.
Please explain.
I am saying something about the following (at least I tried to do so):
$origin domain.com
@ MX 0 mailhost.example.tld.
mailhost A a.b.c.d
crypticname A a.b.c.d
d.c.b.a.in-addr.arpa PTR crypticname.example.tld.
The following will NOT result in a valid lookup:
somehost -> a.b.c.d; a.b.c.d -> otherhost; otherhost -> p.q.r.s
These last conditions are naturally required of any DNS-based lookup.
Plenty of domains seem to get it wrong. Leave out the A record for
crypticname in my 2nd example above, and you get something that's seen
in the wild.
cheers,
Alex
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