Re: A newbie question: what is SOA for?

From: Lei Hu (leihu_at_nojunk.com)
Date: 12/09/04 

Date: Thu, 9 Dec 2004 11:46:41 +1100

Hi there,

This is to follow up my preivous question about primary server name in a SOA
record.

Q1: Must the DNS server that holds the master copy of a .dns file be the
primary server for the zone? Or put it another way, is it possible for a
server to be the primary DNS server for a zone with the .dns file hosted in
another server?

Q2: A DNS server always knows that it is the primary server or a secondary
server. If it is the primary, it resolves names by looking up its dns file.
No client specifies its primary and secondary DNS servers by their names,
rather, by their IP addresses. Therefore, DNS server's name doesn't need to
be resolved. So, my question is, what is the primary server name in the SOA
recored for? Who uses this info?

Thanks a lot!!

"Herb Martin" <news@LearnQuick.com> wrote in message
news:%23Pf7dKT3EHA.2788@TK2MSFTNGP15.phx.gbl...
> "Lei Hu" <leihu@nojunk.com> wrote in message
> news:41b6e39a$0$25786$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
>> Dear Experts,
>>
>> I've just started learning DNS, and I'm sorry if this is a stupid
> question.
>>
>> Can anyone out there please explain SOA to me?
>
> SOA stands for "start of authority" but the simplest way to
> understand the SOA record of a zone is to think of it as the
> "header record".
>
> As the header record, the SOA declares and defines some
> information about the zone as a whole, including the name
> of the zone, the responsible person (an email address with
> the "@" sign replaced by a "."), and some time out values
> like the Default TTL (time to live AKA time to cache)
> records which don't have a specific override for the TTL.
>
> Think of the SOA as the header record for the zone.
>
>> Can one zone have only one SOA record or can have more?
>
> Only One.
>
> But recognize that secondary servers copy the entire zone
> file and so, each COPY has a copy of the SOA.
>
>> Books say that SOA should point to the primary
>> DNS server for the zone,
>
> Yes, that is another item in the SOA.
>
>> and there should be an A record for the server
>> pointed to by SOA.
>
> Yes. If you give a name but don't give the A (or address)
> record it would be difficult to find (maybe.)
>
>> In the win2k DNS server which I'm playing with, if I open
>> the properties page of SOA and change the name of the primary server (w2k
>> allows me to do this), what will this result in?
>
> Probably nothing (nothing bad anyway).
>
> The SOA record was invented before the GUI and so
> reflects the need to define everything in a text file.
>
> It might cause trouble if you only had one Primary (were
> not using AD-integrated DNS) and your clients needed to
> find the ONLY truly dynamic DNS server for the zone.
>
> BTW, don't do that. <grin> - Leave it set to the Primary
> or to the main AD-integrated DNS server for the zone.
>
>

Relevant Pages

  • Re: How Registrant down affect our DNS?
    ... how do I know which has the SOA of the zone. ... Also, the consultant does not host any Domain Name servers for us, and does ... The DNS server I have in our own server room is the primary (how do I ...
    (microsoft.public.windows.server.dns)
  • Re: Primary + Secondary DNS
    ... SOA primary server is "web01.clever4.net" but it is NOT RESOLVABLE. ... someone (some DNS server) somewhere think that his Authoritative ... resolve it. ...
    (microsoft.public.windows.server.dns)
  • Re: Meaning of "primary server" option, "SOA" tab
    ... >>option "primary server" under the SOA tab? ... > The server with the master primary zone should be listed on the SOA. ... SOA records are by RFC and describe what server has the only writeable copy of the zone. ...
    (microsoft.public.windows.server.dns)
  • Re: Setting up NS2
    ... I have my primary server setup and has been running for years. ... and ns2) I created a zone on my secondary server exactly like the xyzdomain ... the records of my DNS server are not propogating. ...
    (microsoft.public.windows.server.dns)
  • Re: Is every user a member of Users?
    ... When looking at an instance of a zone on some DNS server ... If so it is SOA, or "source host" whatever you should choose ...
    (microsoft.public.win2000.security)
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