In the last post we summarized the content underlying domain 2, subobjective 3 (“Configure sites”) in the Microsoft 70-640 Active Directory Configuration certification exam blueprint. Today we will provide a sample practice question along with a detailed explanation and analysis.
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You are a domain administrator for your organization. The company recently established a second campus in another state and installed two new domain controllers at that location. You create a new Active Directory site for the second campus and establish a new site link that joins the local site to the second campus site.

What remaining tasks are necessary in order to complete the new site topology? (Select the two best choices)

A. Enable site link bridging on the site link.

B. Move the domain controller objects to the second campus site object.

C. Define subnet objects for the second campus.

D. Change the link cost for the site link object.

E. Edit the replication schedule by editing the properties of the second campus’ domain controller objects

The correct answer, explanation, and analysis

The two correct answers are B and C. To complete the site implementation topology in this scenario, we need to move the new domain controller objects to the newly created site object, and define subnet objects for the second campus.

Remember that our Active Directory site design should mirror our physical infrastructure. Because the domain controllers in the second campus are located on the same physical campus, we want to allow for intrasite (that is, almost instantaneous) replication between those DCs.

The Knowledge Consistency Checker (KCC) is an Active Directory component that exists on all domain controllers. The determines an optimal replication topology for all domain controllers both within and between sites. The Inter-Site Topology Generator (ISTG) role, which is held by one DC within each site, calculates intersite replication topology based upon administrator-specified schedules and link costs. The following screenshot points out where we configure these properties on a site link.

Configuring the properties of a site link

Configuring the properties of a site link

The reason why choice A is incorrect is because site link bridging is enabled by default with Active Directory site links. Site link bridging enables site links to be used transitively in much the same way that Active Directory domain trusts are transitive. Thus, if we have a site link between site 1 and site 2 and another link between site 2 and site 3, we can replicate Active Directory changes from site 1 to site 3 even though there is no explicit site link connecting those sites.

Choice D is incorrect because site link costing is relevant only when the topology includes more than one site link. In this scenario we have only two sites and one site link. By contrast, if we had a backup network link between the campuses, we could set the second link at a higher cost than the first link in order to force the ISTG to use the primary link first, and then the secondary link only when the first link is unavailable.

Choice E is incorrect on a technicality. In order to set a replication schedule, we edit the properties of the site link, not the domain controller. When tackling Microsoft certification exam items, we need to parse EVERY WORD and make sure that we understand what’s going on.


I hope that you found working through this sample practice question to be fruitful to your certification studies. If you remain unclear on how Active Directory sites work, then see the companion piece that I mentioned at the beginning of this blog post. You are also free to leave your questions, comments, and concerns in the comments portion of this post.

In the next part of this series I will cover Active Directory replication.


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