BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT "Illegal"

[Frank Bulk]

Al:

 

If you read RFC 2181 section 10.3, RFC 1034 section 3.6, RFC 1912 (page 6),
the average person would understand that it's strongly discouraged.  Perhaps
"illegal" is too strong a word, but the weight of the RFCs and best
practices appears to disagree with your assessment that "there is no such
standard nor requirement prohibiting the use of CNAME/alias in an MX
record.".

 

Frank

 

From: bind-users-bounces at lists.isc.org
[mailto:bind-users-bounces at lists.isc.org] On Behalf Of Al Stu
Sent: Sunday, January 25, 2009 12:11 AM
To: bind-users at lists.isc.org
Subject: BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT "Illegal"

 

BIND 9.6 'named' throws the following message during startup claiming that
it is illegal to use a CNAME/alias in the MX record.  I beg to differ.
There is no such standard nor requirement prohibiting the use of CNAME/alias
in an MX record.

 

Message thrown at startup:

"named[3307]: zone MyDomain.com/IN: MyDomain.com/MX 'MX1.MyDomain.com' is a
CNAME (illegal)"

 

Additionally in Chapter 6 - BIND Configuration Reference, Zone File,
Discussion of MX Records states the MX records "must have an associated
address record (A or AAAA) - CNAME is not sufficient."

 

Some people seem to think RFC 974 creates a standard which prohibits the use
of CNAME/alias in MX records.  But very much to the contrary RFC 974
demonstrates that CNAME/alias is permitted in MX records.

 

ISC's message that a CNAME/alias in an MX record is illegal is incorrect and
just an attempt by ISC to get people to go along with what is only a
perceived rather than actual standard/requirement, and should be removed so
as not to further the fallacy of this perceived perception of a
standard/requirement, as it is neither a standard nor a requirement, and
certainly not illegal.

 

Al Stu

 

 

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