Active Directory Basics

This article provides a foundational understanding of Microsoft Active Directory (AD), its core components, and its role in managing network resources.

What is Active Directory?

Active Directory is a directory service developed by Microsoft for Windows domain networks. It is included in most Windows Server operating systems as a set of processes and services. The primary purpose of Active Directory is to provide centralized authentication and authorization of all users and computers on a network, manage network resources, and enforce security policies.

Key Concepts

Domain

A domain is a fundamental security boundary within an Active Directory network. It's a logical grouping of network objects (like computers, users, and devices) that share a common directory database and security policies. Each domain has a unique name, for example, contoso.com.

Forest

A forest is a collection of one or more Active Directory domains that share a common schema, configuration, and trust relationships. The first domain created in a forest is called the forest root domain.

Tree

A tree is a collection of one or more domains that share a contiguous DNS namespace. For example, contoso.com and emea.contoso.com form a tree.

Domain Controller (DC)

A domain controller is a server that runs Active Directory Domain Services (AD DS) and is responsible for managing directory information and authenticating users and computers within a domain. There should always be at least two domain controllers in a domain for redundancy and fault tolerance.

Schema

The Active Directory schema defines the types of objects that can be stored in the directory and the attributes that objects can have. It's the blueprint for the entire directory.

Global Catalog

The Global Catalog (GC) is a distributed data repository that contains a searchable, partial replica of every object in every domain in an Active Directory forest. It allows users to search for objects across the entire forest without needing to know which domain the object resides in.

Core Components

• AD DS (Active Directory Domain Services): The core service that provides the directory store, authentication, and authorization.
• DNS (Domain Name System): Essential for AD DS to function, as it's used to locate domain controllers and other resources.
• Replication: The process by which changes made to the directory database on one domain controller are propagated to other domain controllers in the same domain or forest.

Benefits of Using Active Directory

• Centralized Management: Manage users, computers, and resources from a single console.
• Enhanced Security: Enforce security policies, manage permissions, and control access to resources.
• Single Sign-On (SSO): Users can log in once to access multiple network resources.
• Scalability: AD can scale from small office networks to very large enterprise environments.
• Resource Discovery: Easily find and access network resources.

Illustrative Example

Consider a company named "Innovate Solutions" with the domain name innovatesolutions.com. This domain would have one or more Domain Controllers managing user accounts, computer accounts, and security policies. Users logging into a computer within this domain are authenticated by a Domain Controller. The Domain Controller verifies their credentials and grants them access based on their assigned permissions.

If "Innovate Solutions" acquires another company with the domain techgrow.net, they might choose to create a new forest for techgrow.net and establish a trust relationship with the innovatesolutions.com forest, or they might integrate techgrow.net as a new domain within the existing forest if the DNS namespaces allow for it.

For more in-depth information on specific Active Directory features and configurations, please refer to the Advanced Topics section.