AD & Dynamic DNS Updates Registration Rules of engagement

Keep in mind, for the most part it automatically works “out of the box” without much administrative overhead.

Original Compilation: 11/19/2012
Updated: 9/5/2013

Prologue

What I’ve tried to do is accumulate all pertinent information about configuring dynamic DNS registration in an AD environment. I hope I haven’t missed anything, and that I’ve explained each numbered bullet point well enough and removed all ambiguity, to fully understand each point.

And yes, this blog is regarding an AD environment. If you have a non-AD environment with a Windows DNS server that you want your computers to register, please read the following blog:

DNS Dynamic Updates in a Workgroup
https://blogs.msmvps.com/acefekay/2013/06/12/dns-dynamic-updates-in-a-workgroup/

 

===

Summary

  1. The machine’s DNS entries in the NIC, must be ONLY configured to use the internal DNS servers that host the zone. No others.
        a. DHCP Option 006 MUST only be the internal DNS server(s) you want to use, otherwise if using an ISP’s DNS or your router, expect undesired results.
  2. The Primary DNS Suffix on the machine MUST match the zone name in DNS.
    1. For joined machines, this is default. 
    2. For non-joined machines, the Primary DNS Suffix must be manually configured or scripted.
  3. If using DHCP Option 015 (Connection Specific Suffix), it must match the zone name and have “Use This Connection’s DNS Suffix in DNS Registration” along with “Register This Connection’s Addresses in DNS” checked in the NIC’s IPv4, Advanced, DNS tab.
    1. For additional information on how to configure updates in a workgroup:
      DNS Dynamic Updates in a Workgroup
      https://blogs.msmvps.com/acefekay/2013/06/12/dns-dynamic-updates-in-a-workgroup/
  4. The Zone must be configured to allow updates.
  5. For AD Integrated Zones where you have it configured for “Secure and Unsecure Updates:
    1. If the machine’s network card DNS address entries have been statically configured:
            – They must only point to the internal DNS servers that host the AD zone or to servers that have a reference to the zone (such as stubs, secondary zones, conditional forwarders, or forwarders)
            – It must be joined to the domain in order to authenticate using Kerberos to update.
    2. If statically configured and not joined to the domain, the client can’t update its record if the zone is set to Secure Only. 
    3. For non-joined domain DHCP clients, you can configure DHCP to update in lieu of the client updating into a Secure Only zone.
  6. For any non-Windows statically configured machine, it must support the DNS Dynamic Updates feature and the zone configured to allow Secure and Unsecure updates.
  7. If the DNS server is multihomed and not configured properly to work with multihoming, it may cause problems with Dynamic Updates.
    1. Read the following for more info:
      Multihomed DCs (with more than one unteamed NIC or multiple IPs) with DNS, RRAS, iSCSI, Clustering interfaces, management interfaces, backup interfaces, and/or PPPoE adapters – A multihomed DC is not a recommended configuration, however there are ways to configure a DC with registry mods:
      http://msmvps.com/blogs/acefekay/archive/2009/08/17/multihomed-dcs-with-dns-rras-and-or-pppoe-adapters.aspx
  8. If the zone is single label name, such as ‘domain’ instead of the proper minimal format of ‘domain.com,’ ‘domain.net,’ etc., it will NOT update.
  9. The client will “look” for the SOA of the zone when it attempts registration. If the SOA is not available or resolvable, it won’t register. Keep in mind with AD integrated zones the SOA rotates among the DCs because of the multimaster feature. This is default and expected behavior, but if there are any DCs that have any problems, and the client resolved the SOA to that DC, it may not accept the update.
  10. The zone in DNS must NOT be a single lable name, such as “DOMAIN” instead of the required minimum of two hierarchal levels such as domain.com, domain.local, domain.me, domain.you, etc. Single label name zones are problematic, do not conform to the DNS RFC, and causes excessive internet traffic to the Root Servers when DNS tries to resolve a single label name query, such as querying for computername.domain – in such a query, the domain name is actually treated as a TLD. ISC has made a note of the excessive traffic generated by Microsoft DNS servers configured with a single label name in 2004 with Microsoft, which in turn disabled the ability for Microsoft DNS in Windows 2000 SP4 and newer to resolve single label names without a registry band aid. More info on this:
    1. Active Directory DNS Domain Name Single Label Names – Problematic
      Published by Ace Fekay, MCT, MVP DS on Nov 12, 2009 at 6:25 PM  641  0
      http://msmvps.com/blogs/acefekay/archive/2009/11/12/active-directory-dns-domain-name-single-label-names.aspx
  11. For Windows 2008 and all newer operating systems, IPv6 must not be disabled. If disabled, it will cause other problems:
    The Cable Guy – Support for IPv6 in Windows Server 2008 R2 and Windows 7, by Joseph Davies, Microsoft, Inc.
    Quoted by Joseph Davies, MSFT:
    “IPv6 is a mandatory part of the Windows operating system and it is enabled and included in standard Windows service and application testing during the operating system development process. Because Windows was designed specifically with IPv6 present, Microsoft does not perform any testing to determine the effects of disabling IPv6. If IPv6 is disabled on Windows Vista, Windows Server 2008, or later versions, some components will not function. “Moreover, applications that you might not think are using IPv6—such as Remote Assistance, HomeGroup, DirectAccess, and Windows Mail—could be.”
    http://technet.microsoft.com/en-us/magazine/2009.07.cableguy.aspx
    1. Arguments against disabling IPv6
      Demoire, [MSFT], 24 Nov 2010 12:37 AM
      http://blogs.technet.com/b/netro/archive/2010/11/24/arguments-against-disabling-ipv6.aspx
    2. IPv6 for Microsoft Windows: Frequently Asked Questions
      (Basically Microsoft is saying in this KB article to not disable IPv6)
      http://technet.microsoft.com/en-us/network/cc987595.aspx

 

Full explanation:

  1. Active Directory’s DNS Domain Name is NOT a single label name (“DOMAIN” vs. the minimal requirement of “domain.com.” “domain.local,” etc).
  2. The Primary DNS Suffix MUST matches the zone name that is allowing updates. Otherwise the client doesn’t know what zone name to register in. You can also have a different Connection Specific Suffix in addition to the Primary DNS Suffix to register into that zone as well.
  3. AD/DNS zone MUST be configured to allow dynamic updates, whether Secure or Secure and Non-Secure. For client machines, if a client is not joined to the domain, and the zone is set to Secure, it will not register either.
  4. You must ONLY use the DNS servers that host a copy of the AD zone name or have a reference to get to them.
    1. Do not use your ISP’s, an external DNS address, your router as a DNS address
    2. Do not use any DNS that does not have a copy of the AD zone.
    3. Internet resolution for your machines will be accomplished by the Root servers (Root Hints), however it’s recommended to configure a forwarder for efficient Internet resolution.
  5. The domain controller is multihomed (which means it has more than one unteamed, active NIC, more than one IP address, and/or RRAS is installed on the DC).
  6. The DNS addresses configured in the client’s IP properties must ONLY reference the DNS server(s) hosting the AD zone you want to update in.
    1. This means that you must NOT use an external DNS in any machine’s IP property in an AD environment.
    2. You can’t mix internal and external DNS server. This is because of the way the DNS Client side resolver service works. Even if you mix up internal DNS and ISP’s DNS addresses, the resolver algorithm may still pick the incorrect DNS to query. Based on how the algorithm works, it will ask the first one first. If it doesn’t get a response, it removes the first one from the eligible resolvers list and goes to the next in the list. It will not go back to the first one unless you restart the machine, restart the DNS Client service, or set a registry entry to cut the query TTL to 0. The rule is to ONLY use your internal DNS server(s) and configure a forwarder to your ISP’s DNS for efficient Internet resolution.
    3. There is a registry entry to cut the query to 0 TTL (normally this is not necessary, but I’m posting it as a reference).
      1. The DNS Client service does not revert to using the first server …The Windows 2000 Domain Name System (DNS) Client service (Dnscache) follows a certain algorithm when it decides the order in which to use the DNS servers …
        http://support.microsoft.com/kb/286834
    4. The DNS Client Service Does Not Revert to Using the First Server in the List in Windows XP (applies to all Operating Systems, too)
       http://support.microsoft.com/kb/320760
    5. For more info, please read the following on the client side resolver service:
      DNS, WINS NetBIOS & the Client Side Resolver, Browser Service, Disabling NetBIOS, Direct Hosted SMB (DirectSMB), If One DC is Down Does a Client logon to Another DC, and DNS Forwarders Algorithm if you have multiple forwarders.
      http://msmvps.com/blogs/acefekay/archive/2009/11/29/dns-wins-netbios-amp-the-client-side-resolver-browser-service-disabling-netbios-direct-hosted-smb-directsmb-if-one-dc-is-down-does-a-client-logon-to-another-dc-and-dns-forwarders-algorithm.aspx
  7. For DHCP clients, DHCP Option 006 for the clients are set to the same DNS server.
  8. If using DHCP, DHCP server must only be referencing the same exact DNS
    server(s) in it’s own IP properties in order for it to ‘force’ (if you set
    that setting) registration into DNS. Otherwise, how would it know which DNS
    to send the DNS registration request data to?
  9. If the AD DNS Domain name is a single label name, such as “EXAMPLE”, and not the proper format of “example.com” and/or any child of that format, such as “child1.example.com”, then we have a real big problem. DNS will not allow registration into a single label domain name.
    This is for two reasons:
    1. It’s not the proper hierarchal format. DNS is
                 hierarchal, but a single label name has no hierarchy.
                 It’s just a single name
    2. Registration attempts causes major Internet queries
                 to the Root servers. Why? Because it thinks the
                 single label name, such as “EXAMPLE”, is a TLD
                (Top Level Domain), such as “com”, “net”, etc. It
                will now try to find what Root name server out there
                handles that TLD. In the end it comes back to itself
               and then attempts to register. Unfortunately it doe NOT
               ask itself first for the mere reason it thinks it’s a TLD.
    3. Quoted from Alan Woods, Microsoft, 2004:
      “Due to this excessive Root query traffic, which ISC found from a study that discovered Microsoft DNS servers are causing excessive traffic because of single label names, Microsoft, being an internet friendly neighbor and wanting to stop this problem for their neighbors, stopped the ability to register into DNS with Windows 2000 SP4, XP SP1, (especially XP,which cause lookup problems too), and Windows 2003. After all, DNS is hierarchal, so therefore why even allow single label DNS domain names?”
    4. The above also *especially* applies to Windows Vista, Windows 7, &, 2008, 2008 R2, Windows 2012, and newer.
  10. ‘Register this connection’s address” on the client is not enabled under the NIC’s IP properties, DNS tab.
  11. Maybe there’s a GPO set to force Secure updates and the machine isn’t a joined member of the domain.
  12. With Windows 2000, 2003 and XP, the “DHCP client” Service is not running.  In Windows 2008, Windows Vista and all newer operating systems, it’s now the DNS Client Service.
    1. This is a requirement for DNS registration and DNS resolution even if the client is not actually using DHCP.
    2. Dynamic DNS Updates Do Not Work if the DHCP Client Service Stops (2000/2003/XP only)
      http://support.microsoft.com/?id=264539
  13. You can also configure DHCP to force register clients for you, as well as keep the DNS zone clean of old or duplicate entries. The following has more information on how to do that:
    1. DHCP, Dynamic DNS Updates, Scavenging, static entries & timestamps, and the DnsProxyUpdate Group (How to remove and prevent future duplicate DNS host records)
      Published by acefekay on Aug 20, 2009 at 10:36 AM  3758  2 
      http://msmvps.com/blogs/acefekay/archive/2009/08/20/dhcp-dynamic-dns-updates-scavenging-static-entries-amp-timestamps-and-the-dnsproxyupdate-group.aspx

 

What will stop AD SRV registration:

  1. Any DNS server referenced in TCP/IP properties that does not host the AD zone name, or does not have a reference to the internal AD zones name.
    1. External DNS servers do not host or have a reference, therefore must NOT be used.
    2. AD Domain machines must never be pointed at an external (ISP) DNS server or even use an ISP DNS server as an “Alternate DNS server” because they do not host the internal AD zone, or have a reference to it.
      1. Only use internal DNS servers when part of an Active Directory domain. Active Directory’s Reliance on DNS, and why you should never use an ISP’s DNS address or your router as a DNS address, or any other DNS server that does not host the AD zone name
        http://msmvps.com/blogs/acefekay/archive/2009/08/17/ad-and-its-reliance-on-dns.aspx
  2. Are any services disabled such as the DHCP Client service or the DNS Client Service? They are required services, whether the machine is static or DHCP.
    1. No DNS registration functions if DHCP Client Service Is Not Running (2000/2003/XP only)
      http://support.microsoft.com/?id=268674
    2. Dynamic DNS Updates Do Not Work if the DHCP Client Service Stops (2000/2003/XP only)
      http://support.microsoft.com/?id=264539
    3. For all Windows 2008, Windows Vista and all newer operating systems, it’s the DNS Client Service.
  3. The AD/DNS zone not configured to allow dynamic updates.
  4. Make sure ‘Register this connection’s address” in DNS is enabled under TCP/IP properties.
  5. Missing or incorrect “Primary DNS suffix” or “Connection-specific DNS suffix” of the domain to which the machine belongs. 
    1. I one of these are incorrect, the client side service cannot find the correct zone to register into. If missing or incorrect, it is called a Disjointed Domain Namespace.
  6. Is the firewall service enabled? (disable it).
  7. Were the default C: drive permissions altered and was a hotfix installed a recently?
    1. “Systems that have changed the default Access Control List permissions on the %windir%\registration directory may experience various problems after you install the Microsoft Security Bulletin MS05-051 for COM+ and MS DTC”
      http://support.microsoft.com/kb/909444
    2. For more info about this issue, see:
      http://blogs.technet.com/steriley/archive/2005/11/08/414002.aspx
  8. If the zone is set to Secure Updates Only, the computer may not have authenticated to the domain (which can be due to DNS misconfiguration or DNS server problem), which of course causes more problems than just DNS  registration.
  9. Is the File and Print services enabled?
    1. It must be enabled.
  10. Microsoft Client Services enabled?
    1. If not,  it must be enabled.
  11. Is DNS service listening on the private LAN interface?
    1. Check under the Interfaces tab under DNS server properties in the DNS console.
  12. More than one NIC on a client?
    1. The wrong one may be registering.
  13. Updates allowed on the zone?
    1. This is an obvious one.
  14. Primary DNS suffix matches the zone name in DNS and the AD domain name?
    1. If not, then it won’t register into the zone.
  15. Was Zone Alarm ever installed on these machines?
    1. If so, ZA leaves SYS files and other remnants that continue to block traffic.
  16. Any Event log errors?
  17. Was a Registry entry configured to stop registration?
    1. 246804 – How to Enable-Disable Windows 2000 Dynamic DNS Registrations (per NIC too):
      http://support.microsoft.com/?id=246804
  18. Spyware or something else such as DotNetDns installed on it?
    1. Download the free tool at www.malwarebytes.com and run a malware scan.
    2. Download the free Malicious Software Scanner from Microsoft and run a scan
    3. Download TrendMicro HouseCall free scan tool and run it.
  19. Single Label Domain Name?
    1. Active Directory DNS Domain Name Single Label Names – Problematic – And this applies to any DNS zone name, not just AD.
      Published by Ace Fekay, MCT, MVP DS on Nov 12, 2009 at 6:25 PM  641  0
      http://msmvps.com/blogs/acefekay/archive/2009/11/12/active-directory-dns-domain-name-single-label-names.aspx
  20. Netlogon and DFS services must be started.
  21. Malware or virus altering network services preventing it from registering.
    1. Some sort of firewall in place, whether the Windows firewall disabling File and Print Services, or a 3rd party firewall, which many AV programs now have built in and must be adjusted to allow this sort of traffic and exclude the NTDS and SYSVOL folders.
    2. If Windows Firewall, run the following to see what settings are enabled:
      netsh firewall show config
  22. Is IPv6 disabled? That will stop registration.
    1. Enable it.
  23. Do any duplicate AD integrated zones exist in the AD database?
    1. This will cause major problems. Any duplicates found must be deleted. The cause must also be determined to eliminate it from occurring again.
    2. Using ADSI Edit to Resolve Conflicting or Duplicate AD Integrated DNS zones
      Published by acefekay on Sep 2, 2009 at 2:34 PM  7748  2
      http://msmvps.com/blogs/acefekay/archive/2009/09/02/using-adsi-edit-to-resolve-conflicting-or-duplicate-ad-integrated-dns-zones.aspx
  24. Were imaged machines cloned without the image being Sysprepped first? 
    1. If not, duplicate SIDs will cause machines to fail authentication to register into the zone.

 

Suggestions, Comments, Corrections are welcomed.

Ace Fekay, MCT, MVP, MCSE 2012/Cloud, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & 2010, Exchange 2010 Enterprise Administrator, MCSE 2003/2000, MCSA Messaging 2003
   Microsoft Certified Trainer
   Microsoft MVP: Directory Services
   Active Directory, Exchange and Windows Infrastructure Engineer and Janitor
   www.delcocomputerconsulting.com

Using ADSI Edit to Resolve Conflicting or Duplicate AD Integrated DNS zones

Using ADSI Edit to Resolve Conflicting or Duplicate AD Integrated DNS zones

Revisions:

Original publication 3/2006
Recompiled 6/10/2010
Updated 12/9/2010
Updated 8/31/2014

Prologue

Ace here again. I’m cleaning up my blogs for technical and syntax errors. If you see anything that needs correction, please let me know.

Preface and Scope Of this Article

This blog explains how to use ADSI Edit to determine if duplicate zones exists in the AD database and to delete them.

When  using ADSI Edit, the duplicate zones show up in the partitions with names that are prefixed with an “In Progress….” or “CNF…” and suffixed with a long GUID number. You will be checking EACH DC. When you find them, you will simply delete them. because they are useless and cause substantial problems.

This blog also explains how duplicate zones will appear to make zone records disappear.

Introduction to Duplicate Zones

Duplicate zones can cause numerous issues for the mere fact that the DNS zone that DNS is showing you on a specific DC may not have the latest up to date data. It literally may be missing data that you see on other DCs. If there are duplicate or conflicting zones, the zone data can’t replicate, resulting in each DC may have a different copy of the zone, which then results in unreliability and AD issues.

And to further complicate it, there are three different storage locations that AD can store AD integrated DNS zones – DomainDnsZones, ForestDnsZones, and the DomainNC partitions. You can read more on specifics in one of my other blogs:

DNS Zone Types Explained, Storage Locations in the AD database, and their Significance in Active Directory.
https://blogs.msmvps.com/acefekay/2013/04/30/dns-zone-types-explained-and-their-significance-in-active-directory/

Symptoms?

You may have a duplicate zone or a conflicting zone if a zone exists in both the Domain NC and/or in one of the Application Partitions. Some of the symptoms include:

  • Trying to change the replication scope, you receive an unusual error message stating, “The name limit for the local computer network adapter card was exceeded.”

DNS Duplicate zone - Scope Replication error - The Replication scope could not be set- The name limit for the local computer network adapter was exceeded.

  • Event ID 4515
  • An admin may see the data on a different DC is not there and will manually create records.
  • Zone data is disappearing, or it appears to be. This can be caused by:
  • The data on each DC is different, and you are wondering why replication isn’t brining the zone data up to date, but it won’t because replication will either not occur or won’t occur if AD sees a duplicate.
  • Causes?

    • You’ve installed DNS on another DC and you don’t see the zone under DNS that is on the other DCs, so you manually created the AD zone because you didn’t have the patience to wait for replication to occur, which it would have automatically populated.
    • You’ve promoted a new DC in another site and didn’t have the patience to wait for the zone data to replicate.
    • Antivirus not configured to exclude AD communications (common cause).
    • At one time, or currently, the AD environment is a mixed Windows 2000/2003/2008 environment and DNS is installed on all operating system versions. On Windows 2000, if the zone is AD Integrated, it is in the DomainNC partition of the AD database, and should be set the same in Windows 2003’s or newer DC/DNS server to keep the zone data compatible and allow both operating system versions to be able to read and use them.
    • Someone must have attempted to change it in Windows 2003 or 2008 DNS to place the zone in the DomainDnsZones partition no realizing the implications, hence the duplicate. In a scenario such as this where you want to use the Windows 2003 application partitions, you then must insure the zone on the Windows 2003 is set to the DomainNC, then uninstall DNS off the Win2000 machine, then once that’s done and AD replication has been given time to occur, you can go to the Windows 2003 or newer DNS and change the partition’s replication scope to one of the application partitions.
    • A new domain controller was promoted into the domain, and the administrator manually created the zone name in DNS. This causes a duplicate. The proper way was to simply install DNS, and allow AD replication to occur. The zone will auto-populate into DNS.

    I usually don’t want to assume someone’s deleting data. That’s would be the far end of the spectrum, especially if more than one DC is showing inconsistent zone data.

    I feel the best approach to find out which is occurring is to first find out if there is a duplicate zone. This is because auditing is time consuming, and you need to parse through all the events generated in the Event Security Logs. It’s easier to run ADSI Edit to find if there are duplicates. Once you’ve determined it’s not a duplicate zone issue, then you can move on to DNS auditing. If it is a duplicate zone issue, follow the procedure below to remove them.

    *

    AD Integrated Zones Storage Locations

    First, a quick review on the partitions. Hopefully you’ve taken a few moments to read my blog link that I posted above to understand the partitions. If not, I’ll just touch base on it here so you understand it and can relate to it. For specifics and the nitty gritty, read my other blog above.

    Windows 2000:

    the physical AD database is broken up into 3 logical partitions, the DomainNC (Domain Name Context, or some call the Domain Name Container), the Configuration Partition, and the Schema Partition. The Schema and Configuration partitions replicate to all DCs in a forest.

    The DomainNC is specific only to the domain the DC belongs to. That’s where a user, domain local or global group is stored. The DomainNC only replicates to the DCs of that specific domain.

    When you create an AD Integrated zone in Windows 2000, it gets stored in the DomainNC. This causes a limitation if you want this zone to be available on a DC/DNS server that belongs to a different domain. The only way to get around that is for a little creative designing using either delegation, or secondary zones. This was a challenge for the _msdcs.contoso.com zone, which must be available forest wide to resolve the forest root domain, which contains the Schema and Domain Name Masters FSMO roles.

    Windows 2003 and newer:

    There were two additional storage locations added to the AD database for DNS storage use. These areas are called “partitions,” specifically the DomainDnsZones and ForestDnsZones Application Partitions, specifically to store DNS data. They were conceived to overcome the limitation of Windows 2000’s AD Integrated zones. Now you can store an AD Integrated zone in either of these new partitions instead of the DomainNC. If stored in the DomainDnsZones app partition, it is available only in that domain’s DomainDnsZones partition. If you store it in the ForestDnsZones app partition, it will be available to any DC/DNS server in the whole forest. This opens many more design options. It also ensures the availability of the _msdcs.contoso.com zone to all DCs in the forest. By default in Windows 2003, the _msdcs.contoso.com zone is stored in the ForestDnsZones application partition.

    Selecting the Replication Scope in Windows 2003 and newer:

    When selecting a zone replication scope in Win2003, in the zone’s properties, click on the “Change” button. Under that you will see 3 options:

    • “To all DNS servers in the AD forest example.com”  The top button. This option puts the zone is in the ForestDnsZones Application Partition. This setting will allow the zone data to replicate to all domain controllers to every domain in the forest, including if additional Trees exist in the forest.
    • “To all DNS servers in the AD domain example.com”  The middle button. This option means the zone is in the DomainDnsZones Application Partition. This setting allows the zone to be stored and replicated in the DomainDnsZones Application Partition in the specific domain that it exists in. This setting is not compatible with Windows 2000 domain controllers. If Windows 2000 domain controllers exist in the domain, then the bottom option (below) will need to be used.
    • “To all domain controllers in the AD domain example.com”  The bottom button. This option means the zone is in the DomainNC (Domain Name Context) portion of the actual AD database. This is only for Windows 2000 compatibility, that is if you have any Windows 2000 domain controllers in that specific domain you are administering.

    If you receive an Event ID 4015 or the following error, it may indicate there is a duplicate or conflicting zone that exists in the DomainNC, the DomainDnsZones Application partition and/or in the ForestDnsZones partition.

    DNS Duplicate zone - Scope Replication error - The Replication scope could not be set- The name limit for the local computer network adapter was exceeded.

    *

    Non-AD Integrated Primary and Secondary Zones

    A Primary or Secondary zone that is not stored in AD is stored in a text file in the system32\dns folder. This type of zone storage has nothing to do with the above types ONLY unless it is truly a secondary with the Master being a DC transferring a copy of the zone. This types of zone storage is obviously not secure.

    Now **IF** you did manually create a zone (whether intentionally or unknowingly) on one DC while it already existed on another DC, then you may have a duplicate.

    *

    Duplicate zone names will start with the letters,  “CNF…” or “InProgress…”

    If there is a duplicate, you can use either ntdsutil or ADSI Edit to take a look. I will outline in this article on how to use ADSI Edit to look for the duplicate.

    A duplicate zone name will appear in ADSI Edit that starts with an “In Progress….” or “CNF…” with a long GUID number after it.

    • The CNF…” means it’s in conflict due to a duplicate in the AD database.
    • The “In Progress….” means it is trying to replicate, but it can’t because there’s another identical zone name but with a different USN version number (USNs are used for replication control between DCs) on another domain controller, which also means there’s a duplicate zone.

    You can simply delete them, which will clean up the whole problem. Yep, a simple deletion. The “CNF” data is not used by AD, but yet it will conflict with the zone that is actually used, and needs to be deleted.

    But before doing anything about it just yet, let’s read on to explain more about this and what may have caused it.

    *

    Preventing Duplicate Zones

    AD Integrated Zones will auto-populate when adding replica domain controllers

    If an AD integrated zone exists on a DC, and the DNS service is install DNS on another DC in the domain or forest, depending on the replication scope, it will automatically appear on the new DNS installation without any interaction on your part. You may have to wait a certain period of time for it to populate depending on if the other DC is in the same AD Site or not, but it WILL AUTO-POPULATE.

    However, if you attempted to manually create the zone, believing that you need to do this to make the zone available on that DC, then you’ve just introduced a duplicate zone in the AD database. It doesn’t matter if the zone say originally exists in the DomainNC, and you manually create the zone on the other DC and put it into the DomainDnsZones application partition, AD will still recognize it in the AD database.

    Duplicate zones cause numerous AD communication and access problems.

    The point is, AD is smarter than you think. Let it do it’s thing.

    *

    An Example of what an AD Duplicate Zones looks like in ADSI Edit

    This image shows “In Progress…” entries. They need to be deleted.

    *

    Using ADSI Edit to look at  your AD Partitions

    This is a manual step by step. For a screenshot step by step, see the next section.

    This section assumes you have a little familiarity withe ADSI Edit. If not, I suggest to get yourself familiar with it once you’ve connected into the various partitions as outlined below. Be careful deleting anything, for once deleted, it’s a destructive process and basically it’s gone. There is no “Back Button” or “Undelete,” or “Undo”  button. To restore data, you will need to run an Authoritative Restore from your backup program restoring that specific object that was deleted.

    Determine if there are any duplicate zone.

    While in ADSI Edit, if you see the same exact named zone in multiple partitions, such as seeing the same zone name in the Domain NC (Name Container) Partition, in the DomainDnsZones App partition), and/or in the ForestDnsZones application partition, you have duplicate zones. If this is the case, then you must choose which zone you want to keep.

    I will select a DC that isn’t having a problem and delete the duplicates and conflicts off all other DCs.

    Multiple domains or multiple tree forest?

    If the AD forest is a multidomain forest with child domains and/or multiple trees, you must look at each domain’s DomainNC and DomainDnsZones partition, because each domain has one.

    To view the DomainNC Partition (Default Naming Context)

    • In ADSI Edit, rt-click ADSI Edit, choose “Connect To,” in the Connection Point click on “Well known Naming Context”, then in the drop-down box, select “Domain”.  If this is Windows 2003 or newer, this option shows up as “Default Naming Context”
    • Expand DomainNC or Default Naming Context, then expand your domain name. Drill down to CN=System. Under that you will see CN=MicrosoftDNS.
      You will see any zones that are in the DomainNC partition under the MicrosoftDNS folder.
    • If you see anything that starts with an “In Progress….” or “CNF…” with a long GUID number after it, that’s a duplicate zone. Delete them!
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    To view the ForestDnsZones Application Partition:

    [ForestDNSZones]

    1. Click Start, click Run, type adsiedit.msc, and then click OK.
    2. In the console tree, right-click ADSI Edit, and then click “Connect To.”
    3. Click Select or type a Distinguished Name or Naming Context, type the following text in the list, and then click OK:
      DC=ForestDNSZones, DC=contoso, DC=com
    4. In the console tree, double-click DC=ForestDNSZones, DC=contoso, DC=com.
      Double-click CN=MicrosoftDNS, and click the zone (contoso.com).
    5. You should now be able to view the DNS records which exist in this DNS partition.

    If you see anything that starts with anIn Progress….” or “CNF…” with a long GUID number after it, that’s a duplicate zone. Delete them!

    To view the DomainDnsZones Application Partition

    [DomainDNSZones]

    1. Click Start, click Run, type adsiedit.msc, and then click OK.
    2. In the console tree, right-click ADSI Edit, and then click “Connect To.”
    3. Click Select or type a Distinguished Name or Naming Context, type the following text in the list, and then click OK: DC=DomainDNSZones,DC=contoso,DC=com.
    4. In the console tree, double-click DC=DomainDNSZones,DC=contoso,DC=com
      Double-click CN=MicrosoftDNS, and click the zone (contoso.com).
    5. You should now be able to view the DNS records which exist in this DNS partition.

    If you see anything that starts with an “In Progress….” or “CNF…” with a long GUID number after it, that’s a duplicate zone. Delete them!

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    Procedure with Screenshots:

     

     

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    Procedure to Delete the Duplicate zones

    The easiest is to simply delete any duplicates you find in ADSI Edit. Choice #1, to delete them, can actually be safely done during production. Matter of fact, things may just start to work after you delete them! But Choice #2, which is a lengthy procedure, must be done during non-production hours.

    Choice #1 (Recommended)

    Just go into ADSI Edit and delete the duplicate zones you’ve found.

    You can do this during production, and frankly, I’ve done it with a large infrastructure during production hours without any problems. This is my personal choice as long as there are no true duplicate zones, that is if there are duplicate zones without seeing any zone names prefixed with either an “In Progress….” or “CNF…” with a long GUID number after, and you truly see a duplicate of your actual zone, such as a domain.com in any of the partitions, then you must perform Choice #2.

    Choice #2 (Not recommended)

    This is a multi-step process to first change the zone to a Standard Primary Zone, which removes it from the AD database, allow AD replication to complete, delete the duplicates, then change the zone to AD integrated, and allow AD replication to complete.

    • Choose only one DC to perform this action.
      • For example, if the duplicate is in the DomainDnsZones partition or DomainNC partition of a child domain, perform it only on a DC in that domain.
      • If the Duplicate is in the ForestDnsZones partition, you can choose any DC in the forest.
    • Right-click the zone name, Choose Properties.
    • Under the General  tab, click on the “Change” button next to the “Type” section.
    • Then uncheck the box that says “Store the zone in Active Directory (available only if the DNS servers is a domain controller.”
    • Click Ok, Don’t click Ok again just yet. Just click on Apply.
    • IMPORTANT – You must allow AD replication to occur to replicate the change to all DCs that are in the replication scope of the zone. If you have DCs in another AD Site and have replication schedule set for example, to 3 hours, then you must WAIT for 3 hours.
    • This action makes the zone a Standard Primary zone. This means it is now stored in the system32\dns\ZoneName.com.dns text file and is no longer in the AD database.
    • You can also force replication, as well.  If there are AD Sites configured, and the replication schedule on the Site Connection objects is say 3 hours, you can reduce the replication schedule on the Site Connection objects to the minimal time allowed, which is 15 minutes. Then force replication by choosing the partner DC’s NTDS Setting, right –click, and choose Replicate Now.
    • Once confirmed that replication has occurred, and refreshing the ADSI Edit window and seeing the zones no longer exist in any of the partitions, then you can now safely delete the duplicate zones.
    • Note: Just to be clear, you will be deleting any zone names that you find that are prefixed with an “In Progress….” or “CNF…” and suffixed with a long GUID number after it.
    • Also Note: Deleting a zone is a destructive operation. Make sure you are only deleting duplicates!
  • Click Start, point to All Programs, point to Administrative Tools, and then click DNS.
  • In the console tree, right-click contoso.com, point to All Tasks, and then click Restart.
  • Change the zone back to AD Integrated into the Replication Scope it’s supposed to be in.
  • Once the duplicates have been deleted, once again, you MUST allow AD replication to occur. If you had changed the Replication Schedule on the Site Connection objects to quicken AD replication, you will want to reset them to their original setting.
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    References

    DNS zone replication in Active Directory
    http://technet.microsoft.com/en-us/library/cc779655(WS.10).aspx

    Oops, our AD Integrated DNS zone’s are missing in Windows 2003!
    http://blogs.technet.com/b/networking/archive/2007/05/10/oops-our-ad-integrated-dns-zone-s-are-missing-in-windows-2003.aspx

    Directory Partitions:
    http://www.microsoft.com/resources/documentation/Windows/2000/server/reskit/en-us/distrib/dsbg_dat_favt.asp

    kbAlertz- (867464) – Explains how to use ADSI Edit to resolve app partitions issues:
    http://www.kbalertz.com/kb_867464.aspx

    Event ID 4515 is logged in the DNS Server log in Windows Server 2003
    http://support.microsoft.com/kb/867464

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    Summary

    It seems like a lot of steps, but it really isn’t. Just read it over a few times to get familiar with the procedure. You may even want to change it into a numbered step by step list if you like. If you only have one DC, and one Site, then it’s much easier since you don’t have to mess with secondary zones or play with the site objects.

    I hope that helps!

    Ace Fekay
    MVP, MCT, MCSE 2012, MCITP EA & MCTS Windows 2008/R2, Exchange 2013, 2010 EA & 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
    Microsoft Certified Trainer
    Microsoft MVP – Directory Services
    Complete List of Technical Blogs and Videos: http://www.delawarecountycomputerconsulting.com/technicalblogs.php

    This blog is provided AS-IS with no warranties or guarantees and confers no rights.

    Suggestions, Comments and Corrections are Welcomed!