CNAME / MX Record question
Shawn Bakhtiar
shashaness at hotmail.com
Mon Aug 8 18:25:00 UTC 2011
HHmmm....
Maybe I'm not understanding this, we have two domains. inksystems.com and inksystemsinc.com They both point to the same IP address using A records, and point to the same MX records as well.
The web server, does not, but can destingwish based on the domain name (Apache), and for email, it is simply a matter of changing the sendmail configuration to forward all domain A to domain B by using the alias files. I'm sure exchange has that same kind of feature. Where the SMTP portion can simply forward (relay) other domains to the primary email domain.
I'm not sure what the point of the CNAME is in that case since you can point everything to the same records and have the server software do the parsing?
I'm a nooooob too, so maybe I'm missing something :)
Date: Sun, 7 Aug 2011 14:08:07 -0400
From: dmiller at tiggee.com
To: bind-users at lists.isc.org
Subject: Re: CNAME / MX Record question
On 8/7/2011 9:05 AM, Scott Hughes wrote:
All,
I have Googled and searched the archives for two days and
cannot find an answer to this question... just more confusion!
Please forgive me ahead of time as I run two name servers for
my mid-sized company and am by no means an expert in using bind
DNS. We have about eight domains but don't have a lot of records
for each zone. Here is my issue:
We are moving to a two Exchange server / two data center
model for auto-failover reasons. Both data centers are in to
different locations and have multiple internet pipes and tier 1
providers coming into their data centers.
Here is what I'm trying to do:
For example, our email domain name on the Exchange servers
is: mail.blahblah.us
Our spam filtering device is: spam.blahblah.us and is the
MX record. In the blahblah.us zone file I have A
records pointing to both correctly.
Our problem comes in on our other domains. I am trying to
point mail.company1.com
to mail.blahblah.us
and spam.company1.com
to spam.blahblah.us
using CNAME records. I'm obviously doing this wrong or trying
to do something that can't or shouldn't be done. Like I said, I
am fairly new to bind9 but I'd sure rather use it than something
link MS DNS servers!
What I am attempting to do is make it so that if an outside
email server or inside user goes to mail.company1.com or spam.company1.com
they are 'redirected' to the blahblah.us domain where our UCC
cert covers both of the Exchange servers.
Please let me know if I've left anything out that would be
helpful in answering these questions.
blahblah.us and company1.com are actual registered domain names. If
they are registered to you, then using these domains in examples is
fine... if not, then better to use RFC2606 names...
If I understand your environment correctly:
Your "main domain" - example.com - looks (in part) like this:
// Begin example.com
$TTL 86400
@ IN SOA ns1.example.com. contact.example.com. (
2011080701 ; serial number YYMMDDNN
28800 ; Refresh
7200 ; Retry
864000 ; Expire
86400 ; Min TTL
)
NS ns1.example.com.
NS ns2.example.com.
MX 10 spam.example.com.
MX 20 spam2.example.com.
$ORIGIN example.com.
spam IN A 192.0.2.25
spam2 IN A 192.0.2.26
mail IN A 192.0.2.30
// End example.com
There is no reason that example.net (another of your domains) can't
look like this:
// Begin example.net
$TTL 86400
@ IN SOA ns1.example.com. contact.example.net. (
2011080701 ; serial number YYMMDDNN
28800 ; Refresh
7200 ; Retry
864000 ; Expire
86400 ; Min TTL
)
NS ns1.example.com.
NS ns2.example.com.
MX 10 spam.example.com.
MX 20 spam2.example.com.
$ORIGIN example.net.
// End example.net
^^^ MX records in example.net point to example.com hosts (which are
A records).
If you have a 'requirement' that the users for example.net configure
their mail clients with example.net mail server hostnames, then you
can create a CNAME record in example.net that aliases
mail.example.net to mail.example.com.
If, however, you have a 'requirement' to make it 'seem' that
example.com and example.net have 'independent' mail servers at a DNS
level - i.e. you want to use MX records in example.net that are in
example.net, then you need to add A records for spam & spam2 in
example.net that point to the IP addresses of these hosts (and you
need to do this for all domains 'like' example.net as well -and-
update the A records in all of these domains if the IP addresses of
these hosts change in the future... c'est la DNS). Like so:
// Begin example.com
$TTL 86400
@ IN SOA ns1.example.com. contact.example.com. (
2011080701 ; serial number YYMMDDNN
28800 ; Refresh
7200 ; Retry
864000 ; Expire
86400 ; Min TTL
)
NS ns1.example.com.
NS ns2.example.com.
MX 10 spam.example.com.
MX 20 spam2.example.com.
$ORIGIN example.com.
spam IN A 192.0.2.25
spam2 IN A 192.0.2.26
mail IN A 192.0.2.30
// End example.com
// Begin example.net
$TTL 86400
@ IN SOA ns1.example.com. contact.example.net. (
2011080701 ; serial number YYMMDDNN
28800 ; Refresh
7200 ; Retry
864000 ; Expire
86400 ; Min TTL
)
NS ns1.example.com.
NS ns2.example.com.
MX 10 spam.example.net.
MX 20 spam2.example.net.
$ORIGIN example.net.
spam IN A 192.0.2.25
spam2 IN A 192.0.2.26
mail IN CNAME mail.example.com.
// End example.net
// Begin example.org
$TTL 86400
@ IN SOA ns1.example.com. contact.example.org. (
2011080701 ; serial number YYMMDDNN
28800 ; Refresh
7200 ; Retry
864000 ; Expire
86400 ; Min TTL
)
NS ns1.example.com.
NS ns2.example.com.
MX 10 spam.example.org.
MX 20 spam2.example.org.
$ORIGIN example.org.
spam IN A 192.0.2.25
spam2 IN A 192.0.2.26
mail IN CNAME mail.example.com.
// End example.org
HTH,
-DMM
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