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Keep in mind that a CNAME record isn't just an A record by another
Re: No A Records Needed for Virtual Domains?
From: Men & Mice Support
Date: Thursday, February 8, 2001
Time: 2:54:04 pm
name. For example, if your main domain has these records:
lists.maindomain.com. A 192.168.0.1
lists.maindomain.com. MX 10 lists.maindomain.com.
Then you can accomplish a virtual domain's list server using either
(but not both) of the following:
lists.virtualdomain.com. CNAME lists.maindomain.com.
-> The alias picks up the MX record property of the original.
lists.virtualdomain.com. MX lists.maindomain.com.
-> The virtual listserv name has its own MX record.
Because of this, a CNAME record can't have the same name as any other
record - the alias must be strictly an alias, adding no properties of
its own. Furthermore, it can't have any subnames - anything of the
form x.alias.name.
Lastly, for speedier processing, an alias name can't be used in the
record data of any other record except another CNAME record. In other
words, you can't use the name of an alias as a name server or mail
server, and you can't use it in a SRV record.
On another topic, for various reasons, you should only ever refer to
a given mail server by one single name, throughout your zones. So,
for example, these records that you gave:
VirtualDomain.com. MX 10 mail.VirtualDomain.com.
is a bad idea. You should always refer to that mail server by the
name used in the PTR record for its address.
____________________________________________________________________
Chris Buxton Men & Mice
cbuxton@menandmice.com We Make DNS Easy!
At 1:35 PM -0700 2/8/01, Warren Michelsen wrote:
>This is a DNS question more than a QDNS Pro question.
>
>DNS Expert Pro told me that I had a CNAME record and a record of
>another type for the same host name. This is bad, it said.
>
>What I had was both a MX record and CNAME record for my list server.
>Both records in this virtual domain listed the MainDomain host, i.e.,
>
>Main domain has A record for lists.MainDomain.com.
>Virtual domain had CNAME record for lists.VirtualDomain.com that
>pointed to lists.MainDomain.com
>and had
>MX record for lists.VirtualDomain.com that again listed the mail
>exchanger as lists.MainDomain.com.
>
>Per DNS Expert, I eliminated the CNAME record, since I definitely
>need the MX record for a list server.
>
>Now DNS Expert is happy, my list server still works with virtual
>domains and I guess I'm happy.
>
>So my question is (finally), as long as my MainDomain.com has A
>records for its "www" and "lists" hosts, can all of my virtual
>domain zones contain only NS, MX and CNAME records?
>
>I started off way back when by adding A records for each new virtual
>host, creating a "mail.VirtualDomain.com A record, etc. Then
>creating an MX record for VirtualDomain.com that listed
>mail.VirtualDomain.com.
>
>Could I have instead been simply creating a MX record for
>VirtualDomain.com that referenced mail.MainDomain.com?
>
>This would result in only one zone file that had any IP addresses in
>it instead of 50 zones that need updating when IP addresses change.
>
>So, can I get by with no A records at all except in my MainDomain
>zone? Any drawbacks to doing this?
>
>Yeah, I know. You folks probably already knew this long ago. I'm a
>slow learner...
>
>--
>
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