cnames & mx records on the root of a zone

Mark.Andrews at nominum.com Mark.Andrews at nominum.com
Mon Oct 30 04:11:03 UTC 2000


> In case anyone else didn't notice, the original questions remain unanswered,
> and I'd like to restate them for clarity..
> 
> Statements:
> 
> 1) Bind4 and Bind8 both support CNAME's at the root of the zone.  They
> *complain in various ways*, but they both support it.  We have clients using
> both versions to get external dynamic DNS servers to respond to the root of
> their zone.

	BIND 4 and BIND 8 don't support it.

	i.e.
	     if you file a bug about it to bind-bugs at isc.org
	     *I* will respond that it is an unsupported, illegal
	     configuration, as will anyone else here.

> 
> 2) Bind4, apparently, supported MX records mixed with CNAME's at the root.
> It whined about it, and spat our log errors, but it *supported* it.

	No.  It does not.  Just because it did not make the server
	die does to mean that it was supported.  I've got enough
	bugs logged over unexpected behaviour w.r.t. to CNAME and
	other data, and the answer to everyone of the was to fix
	your zone as it is an illegal configuration.

> Sendmail, Outlook, and other popular SMTP clients seemed to obey the MX at
> the root, rather than follow the CNAME first.  Bind 8 rejects this entry.
> 
> (( Maybe this is the wrong forum for these questions, however ))
> 
> Questions:
> 
> 1) Does anyone know why it was necessary, as a part of the DNS protocol, to
> reject this information?

	Because CNAME say that one name is an alias for another.

	It you have a CNAME record cached you know not to ask for
	records of a different type with the same owner name as that
	of the CNAME record because they are not supposed to exist,
	rather you follow the CNAME.

> 
> 2) since the previous implementations of BIND complained but supported this
> info and it seems that the DNS clients also supported it, is it possible to
> set a flag in the conf to get BIND8 to behave the same way as BIND4 did?

	No.
> 
>                                    - Erik
	
	Mark
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com



More information about the bind-users mailing list