Welcome to the third installment of Learn Active Directory Design and Administration in 15 Minutes a Week, a weekly series aimed at current IT professionals preparing to write the new Windows Active Directory Design and Administration exams (70-219 and 70-217 respectively), as well as newcomers to the field who are trying to get a solid grasp on this new and emerging directory service from Microsoft. This week's topic is the Active Directory Logical Architecture, specifically, Forests and Trees and the Trust Relationships between them.
Active Directory Logical Architecture
As you make preparations for the installation of your first Windows 2000 Domain Controller into your environment, whether that be a pristine new forest or into an existing domain, you need to have a solid understanding of all the different parts that make up the Windows 2000 Active Directory.
By definition, the Windows 2000 Active Directory forest is the collection of one or more Microsoft Windows 2000 domains that share a common schema, configuration, and global catalog.
This is not true of the domain namespace of the domain trees in the forest. If there is a single tree in the forest, it will have a common domain namespace. Since there can be more than one domain tree in a forest (it is not a requirement, but it is allowed) these different domain trees will have their own individual contiguous namespaces.
All of the domains in a domain tree and all of the trees in a single forest have the connectivity benefit of the two-way, transitive trust relationship, which is the default trust relationship between Windows 2000 domains. A two-way, transitive trust, by definition, is really the combination of a transitive trust and a two-way trust. This complete trust between all domains in an Active Directory domain hierarchy helps to form the forest as a single unit via its common schema, configuration, and global catalog.
The first Windows 2000 domain installed in the forest is considered to be the forest root domain.
[NOTES FROM THE FIELD] - Much of this information is an Exam Requirement for both the 70-217 AND the 70-219 exams. Some would argue it is more so for the 217 and I would agree, but if you do not have the underpinnings from the Administration pieces of 70-217, you'll be hard pressed to pull off the Design requirements for 70-219.
By definition, a Windows 2000 Active Directory domain tree is a set of Windows 2000 domains connected together via a two-way transitive trust, sharing a common schema, configuration, and global catalog.
In order to be considered a true Windows 2000 domain tree, the domains must form a contiguous hierarchical namespace with one domain being the domain root.
The first Windows 2000 domain installed in a tree is considered to be the root domain of that tree. It would only be considered the forest root domain if it was also the first domain in the forest.
Let's say that zandri.net is the first Windows 2000 domain in a pristine forest. This would make zandri.net the first Windows 2000 domain installed in the forest and as such it would be considered as the forest root domain. Since it is also the first Windows 2000 domain installed in this tree, it is considered to be the root domain of the tree zandri.net tree.
[NOTES FROM THE FIELD] - A single domain, where there is but a single domain in a tree is called a standalone domain tree. That single tree constitutes a forest of one tree.
After the zandri.net domain has been deployed, a child domain called data.zandri.net is then created as well as sales.zandri.net. Since these two new domains are children of the parent, zandri.net, they would be located below it in the hierarchy and it would appear as it does below, with the zandri.net domain at the top.
If we were to then create a new domain tree called madison.net and two child trees of sales.madison.net and data.madison.net, the forest structure would look something like this:
The root of the whole forest would be zandri.net (zandri.net is also the root of the entire zandri.net tree) and the root of the second tree would be madison.net (madison.net would be only the root of the madison tree). The child domains of sales.madison.net and data.madison.net would be directly below madison.net in the hierarchy.