Dependency of Active Directory on DNS


DNS Records that are required for proper functionality of Active Directory


We know that DNS servers serves more than resolving Name to IP and IP into Name. It is core protocol or you can say daddy of all protocols over a network.

In this article I have tried to visualize and explain all the core records of DNS without which Active Directory cannot function properly.

Here are the list of all core SRV, A and C-Name records that are used by Active Directory and Domain clients.

Please Note: The Red marked records in below table are used by Non-SRV-Aware Clients


Mnemonic Type DNS Record Requirements
  1. PDC
SRV _ldap._tcp.pdc._msdcs.<DnsDomainName> One per domain
  1. GC
SRV _ldap._tcp.gc._msdcs.<DnsForestName> At least one per forest
  1. KDC
SRV _kerberos._tcp.dc._msdcs.<DnsDomainName> At least one per domain
  1. DC
SRV _ldap._tcp.dc._msdcs.<DnsDomainName> At least one per domain
A <DomainControllerFQDN> One per domain controller (domain controllers that have multiple IP addresses can have more than one A resource record)
  1. GcIpAddress
A gc._msdcs.<DnsForestName> At least one per forest
  1. DsaCname
CNAME <DsaGUID>._msdcs.<DnsForestName> One per domain controller


Below I have mentioned the location of all these important records, with their properties and NSLOOKUP commands to verify if the record exists correctly or not. I have taken screenshot from a single domain lab, on default site i.e. my domain itself represent the forest. So results may vary if you explore these in big infrastructure.



In the records Properties window, you will notice below few fields:

Priority-    The priority of the server. Clients attempt to contact the server with the lowest priority.

Weight –   A load-balancing mechanism that is used when selecting a target host from those that have the same priority. Clients randomly choose SRV records that specify target hosts to be contacted, with probability proportional to the weight

Port Number-    The port where the server is listening for this service.

Target –   The fully qualified domain name of the host computer.




Host Records for SRV-Aware Clients

  1. PDC Record – _ldap._tcp.pdc._msdcs.<DnsDomainName>

Allows a client to locate the server that is acting as the primary domain controller (also known as a “PDC”) in the mixed-mode domain named in DnsDomainName . Only the PDC emulator master of the domain registers this SRV record.




  1. GC Record – _ldap._tcp.gc._msdcs.<DnsForestName>

Allows a client to locate a Global Catalog (gc) server for this forest. Only domain controllers that are functioning as Global Catalog servers for the forest named in DnsForestName register this SRV record.



  1. KDC Record – _kerberos._tcp.dc._msdcs.<DnsDomainName>

Allows a client to locate a domain controller that is running the Windows implementation of the Kerberos KDC service for the domain named in DnsDomainName . All Windows Server–based domain controllers that are running the KDC service (that is, that implement a public key extension to the Kerberos v5 protocol Authentication Service Exchange subprotocol) register this SRV record.



  1. DC Record – _ldap._tcp.dc._msdcs.<DnsDomainName>

Allows a client to locate a domain controller (dc) of the domain named by DnsDomainName . All Windows Server–based domain controllers register this SRV record.



  1. Domain FQDN A Record  – <DomainControllerFQDN>

This record helps to locate the domain controllers IP address in a domain.


Host Records for Non-SRV-Aware Clients


  1. GC IP Address – gc._msdcs.<DnsForestName>

Allows a non-SRV-aware client to locate any Global Catalog server in the forest by looking up an A record. A name in this form is returned to the LDAP client through an LDAP referral. A non-SRV-aware client looks up this name; an SRV-aware client looks up the appropriate SRV resource record.

Net Logon also registers a DNS CNAME (alias) record for use by Active Directory replication The Locator does not use this record.



  1. DsaCname Record – <DsaGUID>._msdcs.<DnsForestName>

Allows a client to locate any domain controller in the forest by looking up an A record. The only information that is known about the domain controller is the GUID of the directory system agent (also known as the “DSA”) object for the domain controller and the name of the forest in which the domain controller is located. This record is used to facilitate renaming a domain controller.


To know more about SRV records in DNS , please refer to below article



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User Account Types


User Account Types

A user account identifies a single user, such as an employee. Windows has the following types of user accounts:




A local user account is created and stored on a local system and is not distributed to any other system.

  • Local user accounts are created with the Computer Management console.
  • The local Security Accounts Manager (SAM) manages the user account information.
  • Only local resources are accessible with local user accounts.


A domain user account is created and centrally managed through Active Directory, and is replicated between domain controllers in the domain.

  • Domain user accounts are created with Active Directory Users and Computers, command line tools, and PowerShell.
  • Each domain user account has a unique security identifier (SID) to identify the user. A
  • user can log on to the domain from any computer that is a member of the domain and can access resources on that computer or on other computers for which the domain user account has permissions.
  • Domain user accounts have a variety of properties, such as user information, group membership, user profiles, and dial-in settings.

Note: External users which need an e-mail account, can be represented through a contact object. A contact object is an account that does not have any security permissions. Users represented as contact objects cannot log on to the domain. Use contacts to add information about individuals, such as e-mail or phone number, to Active Directory. Applications, such as Exchange, can search for attributes of contact objects.

Active Directory uses the following name types to recognize each object:



User or Logon


The user or logon name is the name of the user account. It is typically a combination of the given name (first name) and surname (last name) of the user. For example, Habib Sheikh may have the following logon name, hsheikh.

User Principal

Name (UPN)

The User Principal Name (UPN) combines the user account name with the DNS domain name. For example, account hsheikh in the domain would have as the UPN.

  • The UPN format is also known as the SMTP address format.
  • The DNS domain name in the UPN is known as the UPN suffix.
  • By default, the domain that holds the user account is selected for the UPN suffix. However, you can configure different UPN suffixes to use instead of the domain name.

LDAP Distinguished Name (DN)

The LDAP Distinguished Name (DN) references the domain and related container(s)

Where the object resides. It has three basic attributes:

  • Domain Component (DC)
  • Organizational Unit (OU)
  • Common Name (CN)

An example LDAP Distinguished Name (DN) is:

 CN=hsheikh, OU=sales, DC=habib, DC=com

Relative Distinguished Name


The Relative Distinguished Name (RDN) is used to identify the object within its container. The RDN needs to be unique only within the object’s container. In the example above, the RDN is CN=hsheikh.