Your network contains an Active Directory forestnamed fabrikam.com.
The forestcontains the following domains:
Fabrikam.com
Eu.fabrikam.com
Na.fabrikam.com
Eu.contoso.com
Na.contoso.com
You need to configure the forest to ensure that the administrators of any of the domains can specify a
user principal name (UPN) suffix of contoso.com when they create user accounts from Active Directory
Users and Computers.
Which toolshould you use?

A.
Active Directory Sites and Services

B.
Set-ADDomain

C.
Set-ADForest

D.
Active Directory Administrative Center

Explanation:
We would use the following command to achieve this:
Set-ADForest -UPNSuffixes @{Add=”contoso.com”}
Reference 1:
http://technet.microsoft.com/en-us/library/dd391925.aspx
Creating a UPN Suffix for a Forest
This topic explains how to use the Active Directorymodule for Windows PowerShell to create a new user
principal name (UPN) suffix for the users in a forest. Creating an additional UPN suffix helps simplify the names
that are used to log on to another domain in the forest.
Example
The following example demonstrates how to create a new UPN suffix for the users in the Fabrikam.com forest:
Set-ADForest -UPNSuffixes @{Add=”headquarters.fabrikam.com”}
Reference 2
http://technet.microsoft.com/en-us/library/ee617221.aspx
Set-ADForest
Modifies an Active Directory forest.
Parameter
UPNSuffixes
Modifies the list of user principal name (UPN) suffixes of the forest. This parameter sets the multi-valued
msDS-UPNSuffixes property of the cross-reference container. This parameter uses the following syntax to add
remove, replace, or clear UPN suffix values.
Syntax:
To add values:
-UPNSuffixes @{Add=value1,value2,…}