DNS: Question about setting abc.com record

Daniel B. Thurman dant at cdkkt.com
Wed Jun 18 16:52:13 UTC 2008


Howard Wilkinson wrote:
> Daniel B. Thurman wrote:
>> Howard Wilkinson wrote:
>>>
>>> Daniel B. Thurman wrote:
>>> >
>>> > I have several DNS servers and wondered if the following
>>> > record entry is properly set for all of my DNS servers:
>>> >
>>> > $TTL 172800
>>> > @        IN SOA ns1.abc.com. admin.abc.com. (
>>> >                1               ; serial
>>> >                3H            ; refresh
>>> >                15M          ; retry
>>> >                1W            ; expiry
>>> >                1D )           ; minimum
>>> > ;============ Nameserver ================
>>> > @               IN NS           ns1.abc.com.
>>> > @               IN NS           ns2.abc.com.
>>> > @               IN NS           ns3.abc.com.
>>> > ;============ Mail Exchange =============
>>> > @               IN MX   10      mail1.abc.com.
>>> > @               IN MX   20      mail2.abc.com.
>>> > @               IN MX   30      mail3.abc.com.
>>> > @               IN TXT          v=spf1 a mx -all
>>> > ;============ Hosts ======================
>>> > @               IN A            10.1.0.1
>>> > mail1           IN A            10.1.0.1
>>> > mail2           IN A            10.1.0.2
>>> > mail3           IN A            10.1.0.3
>>> > ns1             IN A            10.1.0.1
>>> > ns2             IN A            10.1.0.2
>>> > ns3             IN A            10.1.0.2
>>> > ;========================================
>>> >
>>> > In particular, I am focusing on record:
>>> > @               IN A            10.1.0.1
>>> >
>>> > The reason I have set all of my DNS zones for the above record
>>> > for all of my DNS servers is because if had I set this record for the
>>> > actual localhost IP address, it appears that if I send mail on the
>>> > localhost, the localhost would receive the email I sent. For example,
>>> > sending mail to: joe at abc.com would be received at the localhost 
>>> instead
>>> > of being sent to mail{1,2,3}.abc.com.  Worse, any localhost programs
>>> > attempting to send emails to "root at abc.com" would fail to be 
>>> delivered
>>> > to one of the MX list.
>>> >
>>> > So, the question is, must each DNS server have it's own real IP 
>>> address
>>> > in the '@' record?  If so, how do I get around this?
>>> >
>>> > Kind regards,
>>> > Dan
>>> >
>>> Dan,
>>>
>>> do you have any other services with the network address 10.1.0.1 which
>>> you want to refer to as 'abc.com'? If not you do not need the 'A' 
>>> record
>>> just after the Hosts line. Otherwise for a simple internal network this
>>> look reasonable. However, do you not have any other hosts you need to
>>> address? If so the you need their 'A' records.
>>>
>>> Howard.
>>>
>> Yes, I have services at 10.1.0.1 as well as at several other
>> hosts.  The main reason that I use the @ is so that I can
>> use 'abc.com' such as dan at abc.com or to simply type
>> abc.com in the web-browser's URL line and it would get
>> resolved.
>>
>> What I found was, if I was at host one.abc.com, which had
>> a DNS server and had @ record set to it's own IP address,
>> and a local account "dan", sending mail to dan at abc.com
>> would be received locally instead of being delivered
>> according to the MX records.  That is why I set the @
>> record for all of my DNS servers to the same IP address
>> and not to each DNS servers actual IP address.
>>
>> Does this make sense?
>>
>> Thanks!
>> Dan
>>
> The point I was making was that the address associated with the '@' 
> record is independent of the name server information. The name server 
> address data is correctly listed later in the file. Thus you could if 
> you did not have any other services list the name servers without that 
> record.
>
> Your email SHOULD be delivered using the MX records data. Which again 
> is independent from the '@' address record. I say SHOULD because you 
> may have a mail routing issues depending on the mailer you use and how 
> it it configured. Sendmail can be set up so that it will deliver 
> locally even in the presence of relevant MX records. This has been the 
> default in some distributions. I do not know about the current Fedora 
> set up as we use custom configurations for all of our systems.
>
> So I suspect you need to look at the mailer set up not the address 
> record entries in the DNS arena.
>
> Howard.
>
> P.S. I have copied this back to the mailing list, but I suspect we 
> have broken the thread.
>
Ok, thanks for this information!  I was not sure what was going
on and why.  I will look into sendmail to see what is going on.

Thanks for your help!
Dan

P.S. I noticed that you have email receipt requests turned on and
if that was intended, never mind.

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