Problems that can occur with many Domain Controllers in Active Directory integrated DNS zones
Original KB number: 267855
Applies to: Supported versions of Windows Server
Symptoms
Domain Name System (DNS) registrations of SRV and domain controller (DC) locator A records (registered by Netlogon) and NS records (added by the authoritative DNS servers) in an Active Directory-integrated DNS zone for some DCs may not work in a domain that contains a large number of DCs (usually over 1200). If the Active Directory-integrated DNS zone has the same name as the Active Directory domain name, problems with the registration of A records and NS records at the zone root seem to occur in a domain with more than 400 DCs. Also, one or more of the following error messages may be logged in the Event log:
Event Type: Error
Event Source: DNS
Event Category: None
Event ID: 4011
Description: The DNS server was unable to add or write an update of domain name xyz in zone xyz.example.com to the Active Directory. Check that the Active Directory is functioning properly and add or update this domain name using the DNS console. The event data contains the error.
Data: 0000: 2a 23 00 00 *#..
Event Type: Error
Event Source: DNS
Event Category: None
Event ID: 4015
Description: The DNS server has encountered a critical error from the Active Directory. Check that the Active Directory is functioning properly. The event data contains the error.
Data: 0000: 0b 00 00 00 ....
The final status code from event 4015, 0x00000b, maps to error "LDAP_ADMIN_LIMIT_EXCEEDED Administration limit on the server has exceeded."
Event Type: Warning
Event Source: NTDS Replication
Event Category: Replication
Event ID: 1093
Description: The directory replication agent (DRA) could not apply changes to object DC=@,DC=xyz.example.com,CN=MicrosoftDNS,CN=System,DC=xyz,DC=example, DC=com (GUID <GUID>) because the incoming changes cause the object to exceed the database's record size limit. The incoming change to attribute 9017e (dnsRecord) will be backed out in an attempt to make the update fit. In addition to the change to the attribute not being applied locally, the current value of the attribute on this system will be sent out to all other systems to make that the definitive version. This has the effect of nullifying the change to the rest of the enterprise.
The reversal may be recognized as follows: version 5474, time of change 2000-06-28 19:33.24 and USN of 2873104.
Event Type: Information
Event Source: NTDS Replication
Event Category: Replication
Event ID: 1101
Description: The directory replication agent (DRA) was able to successfully apply the changes to object DC=@,DC=xyz.example.com,CN=MicrosoftDNS,CN=System, DC=xyz,DC=example,DC=com (GUID <GUID>) after backing out one or more of the attribute changes. Preceding messages will indicate which attributes were reversed. Please note that this will have the effect of nullifying the change where it was made, causing the original update not to take effect. The originator should be notified that their change was not accepted by the system.
Cause
This problem occurs because Active Directory has a limitation of approximately 1200 values that can be associated with a single object. In an Active Directory-integrated DNS zone, DNS names are represented by dnsNode objects, and DNS records are stored as values in the multi-valued dnsRecord attribute on dnsNode objects, causing the error messages listed earlier in this article to occur.
Resolution
You can use one of the following methods to resolve this issue.
Method 1
If you want to specify a list of DNS servers that can add NS records corresponding to themselves to a specified zone, choose one DNS server and then run Dnscmd.exe with the /AllowNSRecordsAutoCreation switch:
To set a list of TCP/IP addresses of DNS servers that have permission to automatically create NS records for a zone, use the
dnscmd servername /config zonename /AllowNSRecordsAutoCreation IPListcommand. For example:Dnscmd NS1 /config zonename.com /AllowNSRecordsAutoCreation 10.1.1.1 10.5.4.2To clear the list of TCP/IP addresses of DNS servers that have permission to automatically create NS records for a zone and return the zone to the default state when every primary DNS server automatically adds to a zone an NS record corresponding to it, use the
dnscmd servername /config zonename /AllowNSRecordsAutoCreationcommand. For example:Dnscmd NS1 /config zonename.com /AllowNSRecordsAutoCreationTo query the list of TCP/IP addresses of DNS servers that have permission to automatically create NS records for a zone, use the
dnscmd servername /zoneinfo zonename /AllowNSRecordsAutoCreationcommand. For example:Dnscmd NS1 /zoneinfo zonename.com /AllowNSRecordsAutoCreation
Note
Run this command on only one DNS server. Active Directory replication propagates the changes to all DNS servers that are running on DCs in the same domain.
In an environment in which the majority of the DNS DCs for a domain are located in branch offices and a few are located in a central location, you may want to use the Dnscmd command described earlier in this article to set the IPList to include only the centrally located DNS DCs. By doing so, only the centrally located DNS DCs add their respective NS records to the Active Directory domain zone.
Method 2
Important
This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information, see How to back up and restore the registry in Windows.
If you want to choose which DNS server does not add NS records corresponding to themselves to any Active Directory-integrated DNS zone, use Registry Editor (Regedt32.exe) to configure the following registry value on each affected DNS server:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
Registry value: DisableNSRecordsAutoCreation
Data type: REG_DWORD
Data range: 0x0 | 0x1
Default value: 0x0
This value affects all Active Directory-integrated DNS zones. The values have the following meanings:
| Value | Meaning |
|---|---|
| 0 | DNS server automatically creates NS records for all Active Directory-integrated DNS zones unless any zone, that is hosted by the server, contains the AllowNSRecordsAutoCreation attribute (described earlier in this article) that does not include the server. In this situation, the server uses the AllowNSRecordsAutoCreation configuration. |
| 1 | DNS server does not automatically create NS records for all Active Directory-integrated DNS zones, regardless of the AllowNSRecordsAutoCreation configuration in the Active Directory-integrated DNS zones. |
Note
To apply the changes to this value, you must restart the DNS Server service.
If you want to prevent certain DNS servers from adding their corresponding NS records to Active Directory-integrated DNS zones that they host, you can use the DisableNSRecordsAutoCreation registry value described earlier in this article.
Note
If the DisableNSRecordsAutoCreation registry value is set to 0x1, none of the Active Directory-integrated DNS zones hosted by that DNS server will contain its NS records. Therefore, if this server must add its own NS record to at least one Active Directory-integrated DNS zone that it hosts, do not set the registry value to 0x1.
Netlogon Fix
Important
This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information, see How to back up and restore the registry in Windows.
The Netlogon portion of this hotfix gives administrators greater control as described earlier in this article. You should apply the fix to every DC. Also, to prevent a DC from attempting dynamic updates of certain DNS records that by default are dynamically updated by Netlogon, use Regedt32.exe to configure the following registry value:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
Registry value: DnsAvoidRegisterRecords
Data type: REG_MULTI_SZ
In this value, specify the list of mnemonics corresponding to the DNS records that should not be registered by this DC.
Note
Set the value to the list of the enter-delimited mnemonics that are specified in the following table.
The list of mnemonics includes:
| Mnemonic | Type | DNS Record |
|---|---|---|
| LdapIpAddress | A | <DnsDomainName> |
| Ldap | SRV | _ldap._tcp.<DnsDomainName> |
| LdapAtSite | SRV | _ldap._tcp.<SiteName>._sites.<DnsDomainName> |
| Pdc | SRV | _ldap._tcp.pdc._msdcs.<DnsDomainName> |
| Gc | SRV | _ldap._tcp.gc._msdcs.<DnsForestName> |
| GcAtSite | SRV | _ldap._tcp.<SiteName>._sites.gc._msdcs.<DnsForestName> |
| DcByGuid | SRV | _ldap._tcp.<DomainGuid>.domains._msdcs.<DnsForestName> |
| GcIpAddress | A | gc._msdcs.<DnsForestName> |
| DsaCname | CNAME | <DsaGuid>._msdcs.<DnsForestName> |
| Kdc | SRV | _kerberos._tcp.dc._msdcs.<DnsDomainName> |
| KdcAtSite | SRV | _kerberos._tcp.<SiteName>._sites.dc._msdcs.<DnsDomainName> |
| Dc | SRV | _ldap._tcp.dc._msdcs.<DnsDomainName> |
| DcAtSite | SRV | _ldap._tcp.<SiteName>._sites.dc._msdcs.<DnsDomainName> |
| Rfc1510Kdc | SRV | _kerberos._tcp.<DnsDomainName> |
| Rfc1510KdcAtSite | SRV | _kerberos._tcp.<SiteName>._sites.<DnsDomainName> |
| GenericGc | SRV | _gc._tcp.<DnsForestName> |
| GenericGcAtSite | SRV | _gc._tcp.<SiteName>._sites.<DnsForestName> |
| Rfc1510UdpKdc | SRV | _kerberos._udp.<DnsDomainName> |
| Rfc1510Kpwd | SRV | _kpasswd._tcp.<DnsDomainName> |
| Rfc1510UdpKpwd | SRV | _kpasswd._udp.<DnsDomainName> |
Note
It is not necessary to restart the Netlogon service. If the DnsAvoidRegisterRecords registry value is created or modified while the Netlogon service is stopped or within the first 15 minutes after Netlogon is started, appropriate DNS updates take place with a short delay (however, the delay is no later than 15 minutes after Netlogon starts).
DNS registrations of A records performed by Netlogon can be also be modified by using the RegisterDnsARecords registry value. For more information, see How to enable or disable DNS updates in Windows.
Be aware that both the DnsAvoidRegisterRecords and the RegisterDnsARecords registry values need to allow registering the host (A) record:
- RegisterDnsARecords = 0x1
If you list LdapIpAddress and GcIpAddress in the DnsAvoidRegisterRecords registry value settings, A records are not registered. - RegisterDnsARecords = 0x0
No matter whether you list LdapIpAddress and GcIpAddress in the DnsAvoidRegisterRecords registry value settings, A records are not registered.
To prevent the problem described earlier in this article from occurring in an environment in which a set of DCs and/or global catalog (GC) servers are located in a central location and a large number of the DCs and/or GC servers are located in branch offices, the administrator can disable registration of some of the DNS records by Netlogon on the DCs/GCs in the branch offices. In this situation, the list of mnemonics that should not be registered includes:
DC-specific records:
| Mnemonic | Type | DNS Record |
|---|---|---|
| LdapIpAddress | A | <DnsDomainName> |
| Ldap | SRV | _ldap._tcp.<DnsDomainName> |
| DcByGuid | SRV | _ldap._tcp.<DomainGuid>.domains._msdcs.<DnsForestName> |
| Kdc | SRV | _kerberos._tcp.dc._msdcs.<DnsDomainName> |
| Dc | SRV | _ldap._tcp.dc._msdcs.<DnsDomainName> |
| Rfc1510Kdc | SRV | _kerberos._tcp.<DnsDomainName> |
| Rfc1510UdpKdc | SRV | _kerberos._udp.<DnsDomainName> |
| Rfc1510Kpwd | SRV | _kpasswd._tcp.<DnsDomainName> |
| Rfc1510UdpKpwd | SRV | _kpasswd._udp.<DnsDomainName> |
GC-specific records:
| Mnemonic | Type | DNS Record |
|---|---|---|
| Gc | SRV | _ldap._tcp.gc._msdcs.<DnsForestName> |
| GcIpAddress | A | gc._msdcs.<DnsForestName> |
| GenericGc | SRV | _gc._tcp.<DnsForestName> |
Note
These lists do not include the site-specific records. Therefore, DCs and GC servers in branch offices are located by site-specific records that are usually used by a DC locator. If a program searches for a DC/GC by using generic (non-site-specific) records such as any of the records in the lists that are listed earlier in this article, it finds a DC/GC in the central location.
An administrator may also choose to limit the number of the DC locator records such as SRV and A records registered by Netlogon for the same generic DNS name (_ldap._tcp.dc._msdcs.<DomainName>), even in a scenario with fewer than 1200 DCs in the same domain, to reduce the size of DNS responses to queries for such records.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More Information
Every DNS server that is authoritative for an Active Directory-integrated DNS zone adds an NS record. By default, every DC in a domain registers an SRV record for a set of non-site-specific names such as "_ldap._tcp.<domain_name>" and A record(s) that map(s) the Active Directory DNS domain name to the TCP/IP address(es) of the DC. When a DNS server tries to write a record after approximately 1200 records with the same shared name, Local Security Authority (LSA) runs at 100 percent CPU usage for approximately 10 seconds and the registration does not succeed. Netlogon retries this registration every hour; the 100 percent CPU usage spike reappears at least once an hour and the attempted registrations do not succeed.
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