That is
what BIND is complaining about, and I in turn saying should be
changed/removed.
i.e. BIND should not complain about the following, but it does. It says
the
MX record is "illegal". But it is not.
srv1 300 IN A 1.2.3.4
mx1 300 IN CNAME srv1.xyz.com.
@ 300 IN MX 1 mx1.xyz.com.
The MX query for xyz.com delivers mx1.xyz.com which is a CNAME.
The A query for mx1.xyz.com delivers the address (A) record of
srv1.xyz.com,
1.2.3.4, and the alias (CNAME) record of "mx1.xyz.com".
*** PLEASE don't copy me on replies, I'll read them in the group ***
----- Original Message -----
From: "Mark Andrews" <mark_andr...@isc.org>
To: "Al Stu" <al_...@verizon.net>
Cc: <bind-users@lists.isc.org>
Sent: Monday, January 26, 2009 10:03 PM
Subject: Re: BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT
"Illegal"
>
> In message <b3ba5e37553642e28149093cdee78...@ahsnbw1>, "Al Stu" writes:
>>
>> Yes, the response to an MX query, that is the subject here. And a
>> CNAME
>> is
>> in fact permitted and specified by the RFC's to be accepted as the
>> response
>> to an MX lookup.
>
> No one is saying a CNAME is not permitted in response to a MX
> query.
>>
>> "If the response does not contain an error response, and does not
>> contain
>> aliases"
>> See there, alias is permitted. You just keep proving the my case.
>
> We are saying that when you lookup the address of the mail
> exchanger that you shouldn't get a CNAME record. MX ->
> CNAME is not permitted. Others have quoted similar text
> from more recent RFC's.
>
> RFC 974
>
> Note that the algorithm to delete irrelevant RRs breaks if LOCAL has
> a alias and the alias is listed in the MX records for REMOTE. (E.g.
> REMOTE has an MX of ALIAS, where ALIAS has a CNAME of LOCAL). This
> can be avoided if aliases are never used in the data section of MX
> RRs.
>
>> I am not taking it out of context. It is very explicitly stated. And
>> the
>> context is that of locating the target/remote host by first submitting
>> an
>> MX
>> query, then submitting an A query of the MX query result.
>
> The text you quote is ONLY talking about the MX query.
> There is no "then submitting an A query of the MX query
> result" at this point in the RFC.
>
>> The MX query
>> result is permitted to be and alias, which in turn when submitted for
>> an
>> A
>> query results in both the A and CNAME being returned. Thus meeting
>> the
>> SMTP
>> RFC requirements.
>
>> ----- Original Message -----
>> From: "Mark Andrews" <mark_andr...@isc.org>
>> To: "Al Stu" <al_...@verizon.net>
>> Cc: <bind-users@lists.isc.org>
>> Sent: Monday, January 26, 2009 8:41 PM
>> Subject: Re: BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT
>> "Illegal"
>>
>>
>> >
>> > In message <3c802402a28c4b2390b088242a91f...@ahsnbw1>, "Al Stu"
>> > writes:
>> >>
>> >> RFC 974:
>> >> "There is one other special case. If the response contains an
>> >> answer
>> >> which
>> >> is a CNAME RR, it indicates that REMOTE is actually an alias for
>> >> some
>> >> other
>> >> domain name. The query should be repeated with the canonical domain
>> >> name."
>> >
>> > And that is talking about the response to a MX query. The section
>> > from which you quote starts with:
>> >
>> > Issuing a Query
>> >
>> > The first step for the mailer at LOCAL is to issue a query for MX
>> > RRs
>> > for REMOTE. It is strongly urged that this step be taken every
>> > time
>> a mailer attempts to send the message. The hope is that changes in
>> > the domain database will rapidly be used by mailers, and thus
>> > domain
>> > administrators will be able to re-route in-transit messages for
>> > defective hosts by simply changing their domain databases.
>> >
>> > and the paragraph after that which you quote is:
>> >
>> > If the response does not contain an error response, and does not
>> > contain aliases, its answer section should be a (possibly zero
>> > length) list of MX RRs for domain name REMOTE (or REMOTE's true
>> > domain name if REMOTE was a alias). The next section describes
>> > how
>> > this list is interpreted.
>> >
>> > So I would suggest that you stop taking text out of context.
>> >
>> > CNAME -> MX is legal
>> > MX -> CNAME is illegal
>> >
>> > Mark
>> >
>> >> ----- Original Message -----
>> >> From: "Scott Haneda" <talkli...@newgeo.com>
>> >> To: "Al Stu" <al_...@verizon.net>
>> >> Cc: <bind-users@lists.isc.org>
>> >> Sent: Monday, January 26, 2009 8:09 PM
>> >> Subject: Re: BIND 9.6 Flaw - CNAME vs. A Record in MX Records are
>> >> NOT
>> >> "Illegal"
>> >>
>> >>
>> >> > On Jan 26, 2009, at 7:54 PM, Al Stu wrote:
>> >> >
>> >> >> If you refuse a CNAME then it is your SMTP server that is
>> >> >> broken.
>> >> >> The
>> >> >> SMTP RFC's clearly state that SMTP servers are to accept and
>> >> >> lookup a
>> >> >> CNAME.
>> >> >
>> >> >
>> >> > [RFC974] explicitly states that MX records shall not point to an
>> >> > alias
>> >> > defined by a CNAME. That is what I was talking about, are you
>> >> > saying
>> >> > this is not correct? As this is what I was under the impression
>> >> > for
>> >> > quite some time.
>> >> > --
>> >> > Scott
>> >> >
>> >>
>> >> _______________________________________________
>> >> bind-users mailing list
>> >> bind-users@lists.isc.org
>> >> https://lists.isc.org/mailman/listinfo/bind-users
>> > --
>> > Mark Andrews, ISC
>> > 1 Seymour St., Dundas Valley, NSW 2117, Australia
>> > PHONE: +61 2 9871 4742 INTERNET:
>> > mark_andr...@isc.org
>>
>> _______________________________________________
>> bind-users mailing list
>> bind-users@lists.isc.org
>> https://lists.isc.org/mailman/listinfo/bind-users
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742 INTERNET: mark_andr...@isc.org
> _______________________________________________
> bind-users mailing list
> bind-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/bind-users
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