MX and A Records/CNAMES

[Koehler, Charles]

My thanks to those that responded.

1) I did err in putting host#@ucsf.edu rather than host#.ucsf.edu but
most of you caught that one just as I did ... after I sent it.
2) I was able to firmly state to my insistent client that they had to
use alternate methods to condense their various web services into single
server scenario w/o interrupting current email.

Thanks, Again
Charles
=================================================================
-----Original Message-----
From: Danny Mayer [mailto:mayer at ntp.isc.org] 
Sent: Friday, April 21, 2006 7:29 PM
To: Koehler, Charles
Cc: bind-users at isc.org
Subject: Re: MX and A Records/CNAMES

Koehler, Charles wrote:
> I need assistance to see if this is acceptable practice.
> 
> Currently we have three separate hosts that serve web and email w/ A
> record and two MX records:
> 
> host1 at ucsf.edu. IN A     192.5.5.4
> host1 at ucsf.edu. IN MX 0  localmailhost at ucsf.edu.
> host1 at ucsf.edu. IN MX 10 remotemailhost at outsidemail.net.
> 
> host2 at ucsf.edu. IN A     192.5.5.10
> host2 at ucsf.edu. IN MX 0  localmailhost at ucsf.edu.
> host2 at ucsf.edu. IN MX 10 remotemailhost at outsidemail.net.
> 
> host3 at ucsf.edu. IN A     192.5.5.20
> host3 at ucsf.edu. IN MX 0  localmailhost at ucsf.edu.
> host3 at ucsf.edu. IN MX 10 remotemailhost at outsidemail.net.
> 

This makes absolutely no sense. DNS only knows about host names. You
should never see email addresses in any DNS record (with the exception
of the SOA record which doesn't even have an @ in it).
> 
> 
> The server group wants to merge the web services to from these three
> hosts to a new server, mainwebhost.ucsf.edu.
> mainwebhost.ucsf.edu. IN A 192.5.5.50
> 
> I did the following:
> 1) Remove A Record (object) for host1.ucsf.edu
> 2) Add CNAME of host1.ucsf.edu to mainwebhost.ucsf.edu
> 3) Attempted to add MX record to MX host1.ucsf.edu to host1.ucsf.edu
but
> encountered an error stating that the mail host did not exist.
> 
> QIP requires that there be an A Record rather than CNAME for the MX
but
> can I do an exception as follows? And if not what specific RFC can I
> reference?
> 

No. QIP is correct. It's illegal for an MX record to reference a CNAME.

Danny