Disjoint namespace scenarios

Applies to: Exchange Server 2013

This topic provides information about the concept of disjoint namespaces and the supported scenarios for deploying Microsoft Exchange 2013 in a ___domain that has a disjoint namespace.

DNS and NetBIOS ___domain names

First, some background. Every computer that is on the Internet has a Domain Name System (DNS) name. This is also known as the machine name or host name. Every computer running the Windows operating system with networking capabilities also has a NetBIOS name.

A computer running Windows in an Active Directory ___domain has both a DNS ___domain name and a NetBIOS ___domain name, as follows:

• DNS ___domain name: The DNS ___domain name consists of one or more subdomains separated by a dot (.) and is terminated by a top-level ___domain name. For example, in the DNS ___domain name corp.contoso.com, the subdomains are corp and contoso and the top-level ___domain name is com.

• NetBIOS ___domain name: Typically, the NetBIOS ___domain name is the subdomain of the DNS ___domain name. For example, if the DNS ___domain name is contoso.com, the NetBIOS ___domain name is contoso. If the DNS ___domain name is corp.contoso.com, the NetBIOS ___domain name is corp.

A computer in an Active Directory ___domain also has a primary DNS suffix and can have additional DNS suffixes. By default, the primary DNS suffix is the same as the DNS ___domain name. For detailed steps about how to change the primary DNS suffix, see the procedures later in this topic.

You define the DNS ___domain name and NetBIOS ___domain name of an Active Directory ___domain when you configure the first ___domain controller in the ___domain. For more information about configuring ___domain controllers, see Domain Controller Roles and Active Directory Domain Services Overview.

Disjoint namespaces

In most ___domain topologies, the primary DNS suffix of the computers in the ___domain is the same as the DNS ___domain name.

In some cases, you may require these namespaces to be different. This is called a disjoint namespace. For example, a merger or acquisition may cause you to have a topology with a disjoint namespace. In addition, if DNS management in your company is split between administrators who manage Active Directory and administrators who manage networks, you may need to have a topology with a disjoint namespace.

A disjoint namespace scenario is one in which the primary DNS suffix of a computer doesn't match the DNS ___domain name where that computer resides. The computer with the primary DNS suffix that doesn't match is said to be disjoint. Another disjoint namespace scenario occurs if the NetBIOS ___domain name of a ___domain controller doesn't match the DNS ___domain name.

Exchange 2013 and disjoint namespaces

Exchange 2013 supports the following three scenarios for deploying Exchange in a ___domain that has a disjoint namespace:

• Primary DNS suffix and DNS ___domain name are different: The primary DNS suffix of the ___domain controller isn't the same as the DNS ___domain name. Computers that are members of the ___domain can be either disjoint or not disjoint.

• Member computer is disjoint: A member computer in an Active Directory ___domain is disjoint, even though the ___domain controller is not disjoint.

• NetBIOS name of ___domain controller differs from subdomain of its DNS ___domain name: The NetBIOS ___domain name of the ___domain controller isn't the same as the subdomain of the DNS ___domain name of that ___domain controller.

These scenarios are detailed in the following sections.

Scenario: Primary DNS suffix and DNS ___domain name are different

In this scenario, the primary DNS suffix of the ___domain controller isn't the same as the DNS ___domain name. The ___domain controller is disjoint in this scenario. Computers that are members of the ___domain, including Exchange servers and Microsoft Outlook client computers, can have a primary DNS suffix that either matches the primary DNS suffix of the ___domain controller or matches the DNS ___domain name.

Scenario: Member computer is disjoint

In this scenario, the primary DNS suffix of a member computer on which Exchange 2013 is installed isn't the same as the DNS ___domain name, even though the primary DNS suffix of the ___domain controller is the same as the DNS ___domain name. In this scenario, you have a ___domain controller that isn't disjoint and a member computer that is disjoint. Member computers that are running Outlook can have a primary DNS suffix that either matches the primary DNS suffix of the disjoint Exchange server or matches the DNS ___domain name.

Scenario: NetBIOS name of ___domain controller differs from subdomain of its DNS ___domain name

In this scenario, the NetBIOS ___domain name of the ___domain controller isn't the same as the DNS ___domain name of the same ___domain controller.

NetBIOS ___domain name doesn't match DNS ___domain name

Allow Exchange 2013 servers to access ___domain controllers that are disjoint

To allow Exchange 2013 servers to access ___domain controllers that are disjoint, you must modify the msDS-AllowedDNSSuffixes Active Directory attribute on the ___domain object container. You must add both of the DNS suffixes to the attribute. For detailed steps about how to modify the attribute, see The computer's primary DNS suffix does not match the FQDN of the ___domain where it resides.

In addition, to make sure that the DNS suffix search list contains all DNS namespaces that are deployed within the organization, you must configure the search list for each computer in the ___domain that is disjoint. The list of namespaces should include not only the primary DNS suffix of the ___domain controller and the DNS ___domain name, but also any additional namespaces for other servers with which Exchange may interoperate (such as monitoring servers or servers for third-party applications). You can do this by setting Group Policy for the ___domain. For more information about Group Policy, see Group Policy Overview.

For detailed steps about how to configure the DNS suffix search list Group Policy, see Configure the DNS suffix search list for a disjoint namespace.

View DNS and NetBIOS name-related information of a computer running Windows Server 2008

1. Click Start, right-click Computer, and then click Properties.

2. In System, the DNS host name and primary DNS suffix are displayed under Computer name, ___domain, and workgroup settings next to Full computer name. The DNS ___domain name is displayed next to Domain.

3. Click Change settings.

4. In System Properties, on the Computer Name tab, click Change.

5. In Computer Name/Domain Changes, click More. The primary DNS suffix is displayed under Primary DNS suffix of this computer. The NetBIOS computer name is displayed under NetBIOS computer name.

   To change the primary DNS suffix, type the new primary DNS suffix under Primary DNS suffix of this computer, and then click OK.

6. From a Command Prompt window, type set. The variable USERDNSDOMAIN displays the DNS ___domain name. The variable USERDOMAIN displays the NetBIOS ___domain name.