Reasons for a Single-Domain Environment
Most small/medium business choose a single domain for the following reasons:
–Easier access to resources
Reasons for a multi-Domain Environment
Using more than one domain makes sense or is even a necessity in the following circumstances:
–Need for differing account policies.
Also you can use password settings object (PSO) to apply different password policies for users or groups, it can be difficult to manage when many users are involved.
–Need for different name identities
–Need for internal versus external domains
–Need for tight security
Subdomain (child domain)
A subdomain maintains a common naming structure with the forest root
–Third-level domain name is different
When creating a subdomain, consider the following:
–What server will be the first DC for the new domain?
–What are the names of the subdomain and the new DC?
–What Active Directory-related roles will the new DC fill?
–In which site will the new DC be located?
–Are you going to install a second DC for the subdomain immediately?
–Who will administer the new domain?