PTR records

[Joseph S D Yao]

On Fri, Sep 29, 2000 at 02:21:44PM -0300, Everton da Silva Marques wrote:
> Joseph wrote:
> > Again, there are certain times when you MAY NOT use CNAME records.
> > When there is another record for the same name (e.g., SOA, NS, MX).
> > When it is an NS or MX record target.
> >
> > Why have CNAMEs?  Single-stop changes.  Instead of having to stop at
> > each use of the name and decide whether it should be changed.  I could
> > have two sets of names:
> >
> >	franklin	IN A		...
> >	mail		IN CNAME	franklin
> >	pop3		IN CNAME	franklin
> >	mailhost	IN CNAME	franklin
> 
> I´m assuming the above zone also has an MX RR like the following:
> 
> 			IN MX 	10 mail
> 
> But the first paragraph seems to state the MX records can´t point to
> an CNAME RR. Am I missing anything?

Yes.  Lots.

(1) That was not a zone.  It was an example.  There are lots of things
in that zone that you'll never even see.  Neither will I.  (It's an
imaginary zone.)

(2) You are quite right, "mail" may not be a target for an MX record.
The obvious conclusion is that your assumption is absolutely wrong.
Why would I have to make the string "mail" the target of my MX record?
If that even were my mail machine [wouldn't it be evil to call it
"mail" and have it be my "news" machine? ;-}], that rule unequivocally
indicates that the MX record would then have to be:

	@	IN MX	42	franklin

Why "@"?  You never said where you imagined the record to be.  If it's
after one of the above, it's either illegal [after a CNAME] or refers
only to franklin [which would be legal, but perhaps not what you
wanted].

I do have

		IN MX	42	franklin

after each host name that is not set up to receive its own mail.

Why 42?  Why not?

-- 
Joe Yao				jsdy at cospo.osis.gov - Joseph S. D. Yao
COSPO/OSIS Computer Support					EMT-B
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