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Saturday, October 29, 2011

Prevent Registration of Certain Domain Controller DNS Records

There are times when you want to restrict a Domain Controller from registering certain resource records in the DNS. One of the scenario is when you have hub - spoke topology, it is preferable that if all domain controllers/global catalogs in a satellite site become unavailable, a client that is searching for a domain controller/global catalog in that site will fail over to a domain controller/global catalog in a central hub and not in another satellite site.
To achieve this behavior, the domain controllers/global catalogs in the satellite offices should not register generic (non-site-specific) domain controller locator DNS records

To restrict the DNS resource records that are updated by NetlLogon
  1. Open Registry Editor.
  2. In Registry Editor, navigate to the following registry key:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
  3. Add the following multistring value (REG_MULTI_SZ) value:
    DnsAvoidRegisterRecords
  4. In this value, specify the list of data corresponding to the DNS resource records that should not be registered for this domain controller by the Net Logon service. The following table contains the list of data.
<>
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Domain Controller -Specific Records
Mnemonic
Type
DNS Record
LdapIpAddress
A
Ldap
SRV
_ldap._tcp.
DcByGuid
SRV
_ldap._tcp..domains._msdcs.
Kdc
SRV
_kerberos._tcp.dc._msdcs.
Dc
SRV
_ldap._tcp.dc._msdcs.
Rfc1510Kdc
SRV
_kerberos._tcp.
Rfc1510UdpKdcSRV_kerberos._udp.
Rfc1510KpwdSRV_kpasswd._tcp.
Rfc1510UdpKpwdSRV_kpasswd._udp.

Global Catalog-Specific Records
Mnemonic
Type
DNS Record
GcSRV_ldap._tcp.gc._msdcs.
GcIpAddressAgc._msdcs.
GenericGcSRV_gc._tcp.

Sunday, October 9, 2011

Infrastructure Master & Global Catalog placement

Infrastructure Master (IM) is FSMO role that responsible to updates cross-domain references and phantoms from the global catalog. It is comparing objects of the local domain against objects in other domains of the same forest.

  • Single domain forest:

    In a forest that contains a single Active Directory domain, there are no phantoms. Therefore, the infrastructure master has no work to do. The infrastructure master may be placed on any domain controller in the domain, regardless of whether that domain controller hosts the global catalog or not.


  • Multidomain forest:

    If every domain controller in a domain that is part of a multidomain forest also hosts the global catalog, IM won't ever see any differences, since the global catalog holds a partitial copy of every object in the forest itself. So there are no phantoms or work for the infrastructure master to do.

  • In this case, the infrastructure master may be put on any domain controller in that domain. In practical terms, most administrators host the global catalog on every domain controller in the forest.

    When do you require a Global Catalog?

    There are certain time when you would need Global Catalog role available instead of just Domain Controller role.

    The following events require a global catalog server:
    • Forest-wide searches. The global catalog provides a resource for searching an AD DS forest. Forest-wide searches are identified by the LDAP port that they use. If the search query uses port 3268, the query is sent to a global catalog server.
    • User logon. In a forest that has more than one domain (multidomain), two conditions require the global catalog during user authentication:
      • In a domain that operates at the Windows 2000 native domain functional level or higher, domain controllers must request universal group membership enumeration from a global catalog server.
      • When a user principal name (UPN) is used at logon and the forest has more than one domain, a global catalog server is required to resolve the name.
    • Universal Group Membership Caching: In a forest that has more than one domain, in sites that have domain users but no global catalog server, Universal Group Membership Caching can be used to enable caching of logon credentials so that the global catalog does not have to be contacted for subsequent user logons. This feature eliminates the need to retrieve universal group memberships across a WAN link from a global catalog server in a different site.
      noteNote
      Universal groups are available only in a domain that operates at the Windows 2000 native domain functional level or higher.
    • Exchange Address Book lookups. Servers running Microsoft Exchange Server rely on access to the global catalog for address information. Users use global catalog servers to access the global address list (GAL).

    Quote of the Day