[ILUG] CNAME and MX record with the same name

[Paul Jakma]

On Sun, 18 Dec 2005, Niall O Broin wrote:

> It seems that you cannot have a CNAME and MX record with the same name in a 
> zone

A CNAME node may not have *any* other data, not MX, NS, A, etc. Hence 
you can /not/ have a CNAME at the apex of a zone (for the apex /must/ 
list at least SOA, if not NS).

> e.g. this is an illegal zonefile extract:

> something  3600    IN      CNAME   @
> something  3600    IN      MX	99	 mail.wherever.com
>
> because of the two something records. If instead there was
>
> something  3600    IN      A       1.2.3.4
> something  3600    IN      MX	99	 mail.wherever.com
>
> this would be fine.

Correct.

> http://www.ietf.org/IESG/Implementations/RFC1886-Implementation/DNSrecords.html 
> but of course I might just be reading it all wrongly.

See RFC1034 3.6.2:

  "If a CNAME RR is present at a node, no other data should be
   present;"

It is also implied by RFC1035 3.3.1, "CNAME RDATA format":

"CNAME RRs cause no additional section processing, but name servers 
may choose to restart the query at the canonical name in certain 
cases."

This is elaborated on in 1034.

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
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 	Works equally poorly on all systems.