Yeah, that looks a lot more familiar now. I recall working with several of the hotfixes for a similar issue.
Thanks Guido and Steve for taking the time and Steve for suggesting to the owners that recommendations get updated.
As I've mentioned before, the thinking changes but I'd still prefer to keep the DC a client of itself and to make it therefore as autonomous as possible. I can accept putting a centrally accessible DNS server in some other site as the secondary client. I can also accept the reboot times Guido mentioned. The clients have other servers to use anyway and if the DC's are rebooting constantly or more frequently than monthly (patches and all) then I've got bigger issues to deal with.
Al
On 7/14/06, Grillenmeier, Guido <[EMAIL PROTECTED]> wrote:
just found the description of the error and the pre-SP1 hotfix to the duplicate DNS app-partitions issue:
From: Grillenmeier, Guido
Sent: Freitag, 14. Juli 2006 20:34
To: 'ActiveDir@mail.activedir.org 'Subject: RE: [ActiveDir] Always point a DC with DNS installed to itself as the preferred DNS server...always?
there was no need to check on this issue again - with SP1 it doesn't happen ;-)I'm sure there were several pre-SP1 fixes targeted at this issue and were then integrated into SP1.but rgd. the startup behaviour of DNS in SP1, I'm rather sure that's unchanged at this point.Would be happy to be corrected.
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] ] On Behalf Of Al MulnickSent: Freitag, 14. Juli 2006 19:46To: ActiveDir@mail.activedir.org
Subject: Re: [ActiveDir] Always point a DC with DNS installed to itself as the preferred DNS server...always?
Guido, have you checked this lately? I know there were several changes to that behavior in several revs IIRC. The problems you describe were better than a challenge, as I recall. they had a tenedancy to wreak havoc with integrated dns zones when a dc would come up and create a new zone and then replicate that. There were several fixes related though and that behavior might have changed several times.
On 7/14/06, Grillenmeier, Guido < [EMAIL PROTECTED]> wrote:I'd have to do some more digging as to *why* the duplicate
app-partitions were created, but I've had to troubleshoot this prior to
SP1. This was during a global Win2003 DC rollout - we used the IFM
feature to rollout the DCs. But prior to SP1 you couldn't add the
application partitions to the dcpromo process (IFM in SP1 now offers an
the options to include app partitions during the promotion).
During this rollout a couple of DCs actually re-created the
DomainDnsZones app-partiontion right after their first reboot, causing
some interesting challenges. Agree they should have contacted the DN
master - not sure why either they didn't, or why the DN master allowed
them to re-create this well-known app-partition.
Anyways, to avoid similar issues, SP1 ensures that AD completes the
replication with one partner prior to allowing the DNS service to read
it's records and to register anything. This is actually similar to the
change that was done with either Win2000 SP2 or SP3 to avoid DCs to
advertise their GC status prior to finishing a replication cycle with
another GC or one DC of every domain in their site.
The challenge here is that you get into a "race-condition" when using
the DC itself as the primary DNS server - ofcourse this will still work,
but you have to wait for many more timeouts during the reboot of the AD
DC: for every DNS query prior to a successful replication, the DC will
first try to query it's own DNS server and won't use the secondary until
a DNS timeout... I've seen the boot-times of DCs go up to 10 and more
minutes. This can usually be fixed by setting the primary DNS server of
the DC to another DNS server (naturally won't help, if both are booted
at once - consider this during your DR planning...)
/Guido
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto: [EMAIL PROTECTED]] On Behalf Of Paul Williams
Sent: Freitag, 14. Juli 2006 12:33
To: ActiveDir@mail.activedir.org
Subject: Re: [ActiveDir] Always point a DC with DNS installed to itself
as the preferred DNS server...always?
I can't see how you can get a duplicate NDNC as the creation of such
objects
is targetted at the DN master. The DN master will check the existing
crossRefs and stop this happening, as we can't rely on the DS stopping
it as
the RDN is different for each NDNC (unless they've used "well-known"
GUIDs
for the DNS NCs?).
Although the behaviour you speak of is new to me, and another one of
those
slight, interesting changes, so thanks for that.
Can you elaborate on this new behaviour? What, exactly, happens and in
what
order?
--Paul
----- Original Message -----
From: "Grillenmeier, Guido" < [EMAIL PROTECTED]>
To: < ActiveDir@mail.activedir.org >
Sent: Thursday, July 13, 2006 6:52 PM
Subject: RE: [ActiveDir] Always point a DC with DNS installed to itself
as
the preferred DNS server...always?
> note that DNS startup behavious changes with SP1, which is another
> reason not to choose the DC itself as the preferred DNS server: with
> SP1, AD will not allow the DNS service to read any records, until it
has
> successfully replicated with one of it's replication partners. This
is
> to avoid false or duplicate registration of records (or even duplicate
> creation of the application partitions).
>
> As such, with SP1 it's better to point your DCs to a replication
partner
> as a primary DNS and to self as a secondary.
>
> /Guido
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto: [EMAIL PROTECTED]] On Behalf Of
> [EMAIL PROTECTED]
> Sent: Donnerstag, 13. Juli 2006 17:02
> To: ActiveDir@mail.activedir.org
> Cc: ActiveDir@mail.activedir.org ; [EMAIL PROTECTED]
> Subject: Re: [ActiveDir] Always point a DC with DNS installed to
itself
> as the preferred DNS server...always?
>
> Hi Al
>
> I did want to throw in a personl experience I had with W2K3 that
> validates
> the "Point your DNS server to a replication partner theory". I did
see
> in
> one environment where every DC had DNS and the msdcs partition was a
> forest
> partition. An unfortunate DNS scavenge was done deleting some of the
> GUID
> records in the MSCDCS partition. Replication started to fail shortly
> after
> that and the missing GUIDs were discovered. The netlogon service was
> restarted to make the DCs re-register but of course they re-registered
> the
> GUID on themselves. They could find themselves but not their
> replication
> partners. The replication partners could find them but not
themeselves.
> When the DCs were set to point to a hub replication partner for
primary
> and
> themselves as secondary the problem went away - the netlogon service
was
> restarted, the GUIDs registered on the central DNS server, the spokes
> did
> the lookup for replication parnters on the hub site DC and eventually
> things started working again.
>
> This was pre - SP1 so this may not be a problem anymore, but after
that
> experience I have seen value in doing the DNS configuration so that
the
> DCs
> all point to the hub first and themselves second. I have not seen any
> problems for the DC itself when the WAN link dropped for a length of
> time
> and the primary DNS server was not reachable.
>
> Of course, if there are never any changes to DC IPs or names and the
> MSDCS
> is never scavenged (or the interval is long enough not to recreate the
> above problem) then the above argument is moot.
>
> Regards;
>
> James R. Day
> Active Directory Core Team
> Office of the Chief Information Officer
> National Park Service
> 202-230-2983
> [EMAIL PROTECTED]
>
>
>
>
> "Al Mulnick"
>
> < [EMAIL PROTECTED]> To:
> ActiveDir@mail.activedir.org
>
> Sent by: cc: (bcc:
> James Day/Contractor/NPS)
> [EMAIL PROTECTED] Subject: Re:
> [ActiveDir] Always point a DC with DNS installed to itself as the
>
> tivedir.org preferred DNS
> server...always?
>
>
>
>
>
> 07/12/2006 09:58 PM AST
>
> Please respond to
>
> ActiveDir
>
>
>
>
>
>
>
> You don't work at the post office do you? ;)
>
>
> There are many many many ways to properly configure DNS. One thing
that
> helps is to think of the terms client and server vs. preferred and
> alternate only. You are configuring a preferred server and an
alternate
> server that you want this DC to be a client of.
>
> DNS is a standard. Windows 2003 DNS follows those standards (comments
> really, but let's not pick right?) Microsoft has done some
enhancements
> above and beyond that make DNS play very well in the Microsoft
> sphere[1].
> You can however have DNS that is a third party DNS system, such as
BIND.
> Active Directory plays very well with such third party DNS systems.
You
> could have your domain controllers not have any DNS hosted on them at
> all.
> You could have it hosted, but as a secondary zone. You could also
have
> it
> AD integrated meaning that you have a listener for DNS but the
> data(base)
> is stored in the active directory.
>
> Something to clarify: what you're talking about is making the DC a
> *client*
> to another DNS server that hosts the zones. You're also talking about
> making dc1 a client of dc2 and vice versa. That's silly, but I'll get
> to
> that.
>
> If you have your dns hosted on a third party system such as BIND,
you'll
> have one server as the primary (not best practice, but you get the
idea;
> in
> practice you'd have multiple for failure tolerance wan traffic
> optimization) and your DC would be a client of that system.
>
> If you have a traditional DNS hierarchy that has primary and secondary
> transfers, you would be mimicking BIND topology and again could
> configure
> your DC's to be clients of the BIND or Microsoft DNS servers.
>
> If you have the the DNS AD-Integrated, then after initial replication
> you
> should have the client configured to use itself as the DNS server.
> That'd
> be the best practice. Before 2003 you could have an "island effect"
> where
> because you didn't have a full picture of the directory, you might not
> have
> all the records needed to fully *see* the entire DNS names list
> effectively
> creating an island of a DC. In 2003 some additional code was put in
to
> make sure that doesn't happen. You need to be a client of a working
DNS
> to
> join the domain and to find the other DC's when you get promoted.
After
> replication completes, you have a full list and there's no need to
> continue
> as a client of a server that has the same information you do.
>
> So, what's silly about having your server configured to be a client of
a
> dns server that has the same information? I find it amusing that if
the
> server wants to find something he'll ask his neighbor if he has the
> information when he could just ask himself. It's brain dead in my
> opinion
> and very difficult to troubleshoot. In addition, and more importantly
it
> breaks the idea of a fabric design because now dc1 and dc2 are reliant
> on
> each other to be operational. If either is down, both are down and
> that's
> ridiculous considering how easy it is to prevent that situation. But
> wait!
> you say? He should try the partner first and if that fails use himself
> right? Yes but. :) He'll try the neigbor first, because that's the
> preferred. He'll also register there etc. The worst part is that if
he
> tries the partner and the partner is not completely dead, he'll not
try
> himself even if he has the right information.
>
> Now, will it work? Yes. Is it a good idea? Absolutely not and shows a
> lack
> of understanding on the part of the folks that deployed it. From the
> sounds
> of it, an unwillingness to fix the underlying issues that led them
there
> as
> well. On the other hand, they're spot on if it's W2K vs. K3 :)
>
> Does that help?
>
>
> [1] unless you like a granular audit logging. But that's neither here
> nor
> there.
>
>
> On 7/12/06, Victor W. <[EMAIL PROTECTED] > wrote:
> Today a conversation at my job came up about setting the preferred
DNS
> server on the NIC of a DC with DNS installed.
> For as far as I know it's best to point the DC (with DNS installed)
to
> itself for DNS by specifying the internal IP address of the DC as the
> preferred DNS
> server on the NIC.
>
> Then I was told that this is not always necessary and this puzzled me
> a
> bit.
>
> Not everybody was convinced of the above and this got me thinking.
> Some
> people are claiming that it doesnt really matter if you set that DC
to
> be
> the preferred or the alternate DNS server.
>
> I was then showed an environment where all DC's in a child domain
(all
> had DNS installed), had the same DNS server set as preferred DNS
> server.
>
> Perhaps an example will make it more clear:
>
> a forest root domain with 4 child domains.
>
> child domain A, B, C, and D.
>
> Names of the Domain Controllers:
> root domain: DC-A & DC-B & DC-C & DC-D
> for child domain A: DC-A1 & DC-A2
> for child domain B: DC-B1 & DC-B2
> for child domain C: DC-C1 & DC-C2
> for child domain D: DC-D1 & DC-D2
>
>
> DC-A1 has specified DC-A2 as preferred DNS server and has specified
> DC-A1
> (itself) as alternate DNS server.
> DC-A2 has specified DC-A2 (itself) as preferred DNS server and has
> specified DC-A1 as alternate DNS server
>
> DC-B1 has specified DC-B2 as preferred DNS server and has specified
> DC-B1
> (itself) as alternate DNS server
> DC-B2 has specified DC-B2 (itself) as preferred DNS server and has
> specified DC-B1 as alternate DNS server
>
> And so on for the other child domains.
>
> I was told that this was done because this AD environment was not
> optimal
> and that by pointing all the dc's in a child domain to the same DNS
> server, other issues were prevented from occuring.
> This didnt sound all that good to me to be honoust :-)
>
> I am now wondering if there are scenario's thinkable when it would be
> better not to point a DC with DNS installed as the preferred server
on
> it's NIC.
>
> Does the term Island DNS also play a role in this?
>
>
>
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