virtual domains and zone files

[Mark_Andrews at isc.org]

> Well, I did open a can of worms, didn't I? 'Virtual domain' is such a 
> common term when referring to email delivery I didn't think twice about 
> using it here. If there is a more acceptable term to DNS admins, I'd 
> like to know what it is because, right now, I have no other way to label 
> what I'm talking about.

	mail domain

> The zone file I posted really is for the arda.homelinux.net zone, 
> honest. It's purpose in life is to tell hosts on my network that if 
> someone sends mail to user at arda.homelinux.net, use 
> callisto.arda.homeunix.net as the mail exchanger. There are no A records 
> in this zone file because there are no hosts with the FQDN of 
> <hostname>.arda.homelinux.net on my network. The A records for io, 
> europa, and callisto reside in the arda.homeunix.net zone file. Which is 
> what you might expect given that their FQDNs all end in arda.homeunix.net.
> 
> All I wanted to know is whether the SOA and NS records in the 
> arda.homelinux.net zone file are really necessary. Having thought about 
> how hosts determine where to send mail addressed to 'virtual' domains, I 
> think that they are. Of course, the whole purpose of posting my question 
> was to allow people more knowledgeable than I to confirm or deny my 
> suspicion.

	You need the SOA and NS records if and only if arda.homelinux.net
	is a seperate zone.

	The MX record could just as easily been added to the homelinux.net
	zone.

> So I suppose I've answered my own question. I'm surprised at how much 
> consternation my question has caused, though, given the wide use of 
> 'virtual' domains in email delivery and the fact (as far as I know) that 
> DNS must be set up specifically to allow such delivery.
> 
> For those who are interested, all my zone files and my named.conf file 
> are posted on my web site. Go to:
> http://www.arda.homeunix.net/dnssetup.shtml
> 
> Andrew
> 
> Andrew wrote:
> 
> > My mail server hosts a virtual domain that does not include any hosts in 
> > it. Here is the zone file I use with this domain.
> > 
> > # cat /etc/namedb/master/arda.homelinux.net.zone
> > $ORIGIN .
> > $TTL 10800      ; 3 hours
> > arda.homelinux.net      IN SOA  europa.arda.homeunix.net. 
> > postmaster.arda.homeunix.net. (
> >                                  20030416   ; serial
> >                                  10800      ; refresh (3 hours)
> >                                  3600       ; retry (1 hour)
> >                                  604800     ; expire (1 week)
> >                                  3600       ; minimum (1 hour)
> >                                  )
> >                          NS      io.arda.homeunix.net.
> >                          NS      europa.arda.homeunix.net.
> >                          MX      10 callisto.arda.homeunix.net.
> > 
> > As things stand now, I can deliver mail to user at arda.homelinux.net but I 
> > would like to know if this zone file looks reasonable or if there are 
> > elements that don't need to be there.
> > 
> > Andrew
> > 
> > 
> > 
> > 
> 
> 
> 
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org