First of all, you should not confuse transitive Kerberos trust relationships established in Windows and Windows. NET doma ins with non-transitive secure channels trust links. Although you can, for example, log on to a domain that belongs to one forest tree on a computer that has a machine account in another forest tree, this does not mean that domain controllers from the corresponding domains have direct trust relationships.
You can, however, manually establish such a relationship named a shortcut trust. See Chapter 5, "Deploying Active Directory. This output means that the computer has been authenticated by a domain controller, and a secure channel exists between the client computer and the domain controller. If a user has been logged on locally, or for some reason a network logon has not been performed e.
The following message indicates that the Netlogon service failed to start or is not running on the computer since it is stopped or disabled :. In that case, you should open the Services snap-in and check the status of the service. If there are multiple DCs in the domain, the client computer will establish a secure channel with the DC that responds first. In a trust relationship, a trusting domain allows accounts in a trusted domain to authenticate in its domain.
For example, assume that domain A trusts domain B. Domain A is the trusting domain and domain B is the trusted domain. Domain A will allow user accounts in domain B to be used to authenticate and access resources in domain A. Trust relationships like this one simplify domain and Active Directory structuring and management. In this example, you do not have to provide accounts in domain A to users in domain B and deal with the synchronization and management headaches that would entail.
In Windows NT, trust relationships are always one-way. Domain A trusts domain B, for example, but domain B does not trust domain A unless you create a trust relationship in that direction. In addition, Windows NT trusts are non-transitive , meaning the trust does not cross to adjacent domains. For example, assume that domain A trusts domain B and domain B trusts domain C.
In Windows Server and Windows Server , all trusts are transitive by default. However, access to resources in trusted domains doesn't happen automatically. You must configure permissions for resources in the trusting domain to enable users in the trusted domain to access them. Although all trust relationships accomplish essentially the same result—enabling one domain to trust another—different types of trust relationships do exist.
You need to understand the role these trust relationships play before you can begin structuring a large network. The domain above another in a domain tree is the parent domain; the one below is the child domain.
For example, in my domain boyce. When you create a new child domain in the Active Directory, that child domain automatically has a transitive trust relationship with its parent domain and vice-versa. Tree-root trusts The tree and forest analogy can confuse some Active Directory newcomers, at least until they realize that domain trees grow upside-down. The root domain resides at the logical top of the forest and the trees branch out underneath the root domain.
Let's use techrepublic. We then add two more domain trees; the first sales. The sales. A tree-root trust establishes trust between a domain tree and the forest root. Because these relationships are two-way and transitive, tree-root trusts ultimately enable one domain tree in a forest to trust another domain tree in a forest. For example, users in sales. External and realm trusts An external trust enables you to create trusts with Windows NT domains.
You can also create external trusts with an Active Directory domain in another forest that is not connected by a forest trust. External trusts can be one-way or two-way, but are always non-transitive. When you create an external trust, security principals user, group, computer, or service in the external domain can access resources in the internal domain.
In addition, domain local groups in the internal domain can contain security principals from the external domain. A realm trust establishes a trust relationship to an external, non-Windows Kerberos v5 realm.
Realm trusts support cross-platform authentication and resource sharing between Active Directory domains and UNIX-based security services.
Realm trusts can be either transitive or non-transitive and can be either one-way or two-way. Forest trusts A forest trust enables trust between a forest root domain in one forest and the forest root domain in another forest.
A forest trust is transitive and can be either one-way or two-way. Forest trust TDOs store additional information to identify all of the trusted namespaces from its partner forest. When you establish a forest trust, each forest collects all of the trusted namespaces in its partner forest and stores the information in a TDO.
This information includes:. When a workstation requests a service and the service cannot be located in the domain or the forest in which the workstation is a member, TDOs locate the service in all trusted forests. How trusts enable users When a user attempts to access a resource in another domain, the Kerberos to access resources in a version 5 authentication protocol must determine whether the trusting forest domain—that is, the domain that contains the resource that the user is trying to access—has a trust relationship with the trusted domain—that is, the domain that the user is logging on to.
To determine this relationship, the Kerberos version 5 protocol travels the trust path utilizing the Trusted Domain Object TDO to obtain a referral to the target domain's domain controller. The target domain controller issues a service ticket for the requested service. The trust path is the shortest path in the trust hierarchy. When the user in the trusted domain attempts to access the resource in the other domain, the user's computer first contacts the domain controller in its domain to get authentication to the resource.
If the resource is not in the user's domain, the domain controller uses the trust relationship with its parent and refers the user's computer to a domain controller in its parent domain.
This attempt to locate a resource continues up the trust hierarchy, possibly to the forest root domain, and down the trust hierarchy until contact occurs with a domain controller in the domain where the resource is located.
Introduction Windows Server supports cross-forest trusts , which allow users in one forest to access resources in another forest. When a user attempts to access a resource in a trusted forest, Active Directory must first locate the resource.
After the resource is located, the user can be authenticated and allowed to access the resource. Understanding how this process works will help you troubleshoot problems that may arise with cross-forest trusts.
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