Active Directory Design Overview

Active Directory (AD) is a cornerstone of IT infrastructure for many organizations, providing essential services for managing and securing resources. This guide will take you through the essentials of Active Directory design, covering key considerations, structural components, and best practices to ensure your Active Directory environment is robust and scalable. We will explore the fundamentals of Active Directory, discuss the factors you need to consider before starting your design and provide detailed strategies for designing forest and domain structures. Additionally, we will delve into implementing trust relationships and designing Group Policy Objects (GPOs), and end with general best practices for keeping your Active Directory infrastructure in top shape.

Understanding Active Directory Design

Active Directory is often the linchpin of identity and access management (IAM) in an enterprise setting. It centralizes the management of user accounts, security groups, computers, and other network objects, streamlining administrative tasks and enhancing security. By providing a single point of control for authentication and authorization, Active Directory simplifies the management of complex IT environments.

Although Active Directory may not be the sole component of your IAM infrastructure, it is likely still present in some capacity, serving as a foundational element for managing on-premises resources and legacy systems. This is particularly true in today’s diverse IT environments that often include cloud-based solutions such as Microsoft Entra ID (formerly Azure AD) or other IAM products such as Saviynt, Okta, and SailPoint. Even as organizations adopt more hybrid or fully cloud-based IAM strategies, Active Directory continues to play a critical role in ensuring seamless integration and interoperability between different platforms, providing a bridge between traditional and modern IT landscapes. This dual presence allows businesses to leverage existing investments in Active Directory while transitioning to more flexible, scalable solutions.

In all cases, Active Directory has a set of common structures and elements. Let’s dive in.

The Hierarchical Structure of Active Directory

Active Directory’s hierarchical structure is both logical and flexible, designed to accommodate various organizational needs. Here’s a breakdown of the key components.

• Forests: The top-level container in an Active Directory environment, encompassing one or more domains.
• Domains: The subdivisions within a forest, each maintaining its own set of directory objects and security policies.
• Organizational Units (OUs): The containers within a domain used to organize and manage objects, such as users and computers, often in a way that mirrors the organization’s structure.

A well-planned Active Directory hierarchy not only simplifies management but also enhances security and scalability. We’ll talk more about the design of this structure a little later.

Factors to Consider Before Designing Your Active Directory Environment

Before diving into Active Directory design, you need to evaluate several critical factors:

• Business Requirements: Identify specific needs, such as regulatory compliance, security mandates, and operational workflows, to tailor your Active Directory design accordingly.
• Management Model: Define a clear management model outlining who will delegate permissions and manage different parts of the Active Directory infrastructure. Establishing roles and responsibilities for Active Directory administration ensures effective governance and prevents security lapses. If multiple teams will be managing Active Directory, such as one team managing the data in Active Directory and another team managing the infrastructure Active Directory runs on, ensure there is clear coordination and communication between the teams to maintain consistency and security. Within Active Directory, determine how permissions will be delegated to different administrative teams and ensure there is a clear process for managing and auditing permissions.
• Network Topology: Understanding the physical and logical layout of your network, including the geographic distribution of your sites and the connectivity between them, is essential. Think beyond your network boundary. For example, do you have remote workers that will need to connect to your domain?
• Domain Controller (DCs) Placement: DCs are the backbone of an Active Directory domain. Their placement is critical for ensuring high availability, fault tolerance, and optimal performance. Consider factors such as geographic distribution, network latency, and redundancy when planning for DC placement.
• Organizational Structure: Your Active Directory design should reflect your organization’s structure. This alignment facilitates efficient management and policy enforcement.

Understanding Your Existing IT Infrastructure

A thorough assessment of your current IT infrastructure is crucial. Evaluate your existing network configurations, hardware, and software dependencies. Understanding these elements will help you design an Active Directory environment that integrates seamlessly with your existing systems while addressing any gaps or weaknesses. Additionally, review any existing IAM tools you are currently using to ensure compatibility and integration with your Active Directory design. Leveraging these tools can enhance security, streamline user management, and provide a unified approach to IAM across your organization. In areas where there is overlapping functionality, you will want to consider if you are going to use Active Directory to augment this functionality or replace it entirely.

Planning for Future Growth and Scalability

An effective Active Directory design must accommodate future growth. As your organization grows, whether through organic growth or mergers and acquisitions, your Active Directory infrastructure must be able to scale accordingly. You must be able to add new users, groups, and devices seamlessly. Consider the potential geographic expansion, which may necessitate DCs in new locations to maintain optimal performance and availability. Historically, there was a need for additional domains for new geographical regions; however, these days there are very few locations that do not have sufficient connectivity to handle replication traffic.

You should also think about how you will manage your Active Directory environment in the long run. Manually creating and removing users may work to start for a small organization but consider automating tasks wherever possible. Implementing automation for repetitive tasks such as user provisioning and deprovisioning can save significant time and reduce the risk of human error. Additionally, monitoring tools that provide real-time insights into the performance and security of your Active Directory infrastructure are essential. These tools can help identify potential issues before they become critical and ensure that your Active Directory environment is running smoothly.

Additionally, as we all know, the IT landscape is continually evolving, with new technologies and solutions emerging regularly. Your Active Directory design should be adaptable to incorporate these advancements without requiring a complete overhaul. For instance, integrating cloud-based solutions such as Entra ID can enhance your existing Active Directory infrastructure, providing additional features and capabilities such as single sign-on (SSO) and enhanced security measures.

Keeping factors such as automation, organizational expansion, mergers, and technological advancements in mind prevents the need for frequent redesigns, saving time and resources in the long run.

Now you are ready to start figuring out the overall logical design of your Active Directory environment.

Designing the Forest Structure

An Active Directory forest is the highest level of the Active Directory hierarchy, representing a security boundary for all objects within it. It allows for resource sharing, administrative autonomy, and isolation when needed. The following are a couple of best practices for designing your forest structure.

• Single Forest vs. Multiple Forests: A single forest simplifies administration and reduces complexity. However, multiple forests may be necessary for regulatory compliance, data isolation, or distinct administrative control.
• Hierarchy of Domains: Plan your domain hierarchy with care. The root domain should be stable and secure, serving as the anchor for the entire forest. Historically, child domains can be created based on factors such as geographic location or major business units. However, in a modern Active Directory design, a single domain forest should be the starting point. Additional domains should be considered only in specialized circumstances.

Designing the Domain Structure

An Active Directory domain is a logical grouping of objects, such as users and computers. It acts as a unit of replication, security, and administration. A security boundary does not exist between other domains in a forest. The following are a few domain design considerations.

• Naming Conventions: Use clear and consistent naming conventions for domains to avoid confusion and ensure easy identification of domains within the forest.
• OU Structure: Design organizational units (OUs) to reflect your administrative and policy needs. OUs should generally be used as the boundary of delegated administration. Grouping similar objects into OUs can also simplify management and Group Policy application.
• Group Policy Design: Develop a comprehensive strategy for Group Policy Objects (GPOs) to manage user and computer configurations effectively.

Once the domain structure is in place, you can start to think about how the domains are going to talk to each other. Do you have domains that should “trust” the users from another domain? If so, how do you go about configuring that “relationship”?

Implementing Trust Relationships

Trust relationships in Active Directory enable domains to share resources and authenticate users across boundaries. They are essential for facilitating interactions between different Active Directory domains and forests. Let’s look at different types of trust relationships.

• Transitive Trusts: This type of trust extends to other domains within the same forest, simplifying resource access. The transitive nature of the trust means there does not need to be an explicit trust between all domains. For example, if Domain A trusts Domain B and Domain B trusts Domain C, then Domain A automatically trusts Domain C. A transitive trust is automatically created when a new child domain is added to a parent domain within the same forest. This trust is bidirectional, facilitating resource access between parent and child domains.
• External Trusts: This type of trust connects domains in different forests or standalone domains, providing specific resource access. External trusts are non-transitive and can be one-way or two-way, depending on the access requirements.
• Realm Trusts: This type of trust connects an Active Directory domain to a Kerberos realm, facilitating interoperability with non-Windows environments that use Kerberos authentication.
• Forest Trusts: This type of trust is transitive and is established between two Active Directory forests. Forest trusts allow for resource sharing and user authentication across all domains in both forests, which is useful for large organizations or those undergoing mergers.

By understanding and implementing the appropriate types of trust relationships, you can ensure efficient resource access and authentication across your Active Directory environment, enhancing both performance and security.

But implementing trust relationships requires careful planning. Define clear policies and access controls to manage these trusts and regularly review their configurations to maintain security and efficiency.

You have your forest, domains, and trust relationships between them (perhaps even externally). But you need to implement some controls to lock down what users can or cannot do inside the domain. You can use GPOs to implement these policies.

Designing Group Policy Objects (GPOs)

GPOs are used to manage user and computer configurations centrally. They provide a mechanism for enforcing security settings, software installation, and other administrative tasks. GPOs play a critical role in standardizing configurations, enhancing security, and simplifying management across the Active Directory environment. Well-designed GPOs ensure consistent policy application and compliance.

Best Practices for Designing and Implementing GPOs

The following are a few best practices to follow when designing and implementing GPOs.

• Security: Design GPOs with security in mind, applying the principle of least privilege and enforcing strict access controls.
• Delegation: Delegate GPO management responsibilities appropriately to balance administrative workload and maintain control.
• Inheritance: Understand and manage GPO inheritance to avoid conflicts and ensure predictable policy application.

Common GPO Configurations

Let’s look at a few common GPO configurations.

• Security Policies: Enforce password policies, account lockout settings, and other security measures.
• User Settings: Configure desktop environments, start menu layouts, and other user-specific settings.
• Computer Configuration: Manage system settings, network configurations, and hardware policies.
• Software Deployment: Automate software installation and updates to ensure consistency and compliance. Note that there are other, more intuitive, ways to deploy software now, such as leveraging Microsoft Intune, that you may want to consider instead.

Best Practices for Planning and Designing Active Directory

Designing an effective Active Directory environment is a huge undertaking, and there is far more to it than this short guide can cover. But before we wrap up, here are a few additional best practices we recommend following.

• Design with Security in Mind: Prioritize security in every aspect of Active Directory design, from naming conventions to GPO configurations. Implement measures to protect sensitive data, such as encryption, access controls, and regular audits to ensure data integrity and security. Consider implementing a tiered administrative model (Tier 0, Tier 1, Tier 2) to minimize the risk of lateral movement by attackers. This model segregates high-privilege accounts and resources from lower-tiered administrative tasks, enhancing security. You should also always apply the principle of least privilege when assigning permissions. Regularly review and audit access rights to ensure they are aligned with current roles and responsibilities.

• Ensure Compliance: Identify the regulations that apply to your organization, such as GDPR, HIPAA, or SOX, and ensure your Active Directory design complies with these standards. Often these standards include requirements such as implementing auditing mechanisms to track changes and access to critical Active Directory objects; regularly reviewing audit logs to detect and respond to potential security incidents; and/or maintaining thorough documentation of your Active Directory design, policies, and procedures. These practices will help aid in compliance audits and help ensure consistency in management procedures.
• Monitoring and Regular Maintenance: This is perhaps the most important practice to consider. Once your Active Directory environment is deployed, your job is not done. Performing regular maintenance tasks is essential to ensure the reliability and performance of your Active Directory environment. Here are a few you should focus on:
  • Backups: Regularly back up your Active Directory environment and other critical components and dependencies. Ensure that backups are stored securely and can be quickly restored in the event of data loss or corruption.
  • Disaster Recovery Testing: Establish and regularly test an incident response plan to quickly address and mitigate security incidents or performance issues. There are tools that can assist with this if needed.
  • Updates and Patches: Keep your Active Directory infrastructure, including Windows Server and related components, up to date with the latest patches and updates. This helps protect against known vulnerabilities and ensures compatibility with new features and improvements.
  • Security Audits: Conduct regular security audits to identify vulnerabilities and ensure compliance with security policies. These audits should include reviews of user activities, access rights, and configuration changes.
  • Health Checks: Perform routine health checks to verify the integrity and performance of your Active Directory environment. Check the replication status, verify DNS server configurations, and review DC performance.
  • Cleanup: Periodically clean up inactive or obsolete Active Directory objects, such as user accounts, computer accounts, and groups. This helps maintain a streamlined and efficient Active Directory structure.
  • Review and Adjust: Regularly review and adjust your Active Directory design and configurations based on changing business needs, security requirements, and technological advancements. This proactive approach ensures that your Active Directory environment remains robust and relevant.

Check out our other Active Directory articles for more details on specific topics:

• How to Mitigate Privilege Escalation with the Tiered Access Model for Active Directory Security – Ravenswood Technology Group
• TEC Talk: What Should and Should Not Be in Your Active Directory Disaster Recovery Plan (ravenswoodtechnology.com)
• Active Directory Maintenance Schedule – Ravenswood Technology Group
• Review Your Privileged Users & Groups – Ravenswood Technology Group
• Active Directory Forest Recovery | Disaster Prevention Strategies (ravenswoodtechnology.com)

Conclusion

In this guide, we explored the essentials of Active Directory design, from understanding its hierarchical structure to implementing trust relationships and designing effective GPOs. Proper Active Directory design is crucial for efficient identity management, security, and scalability.

At Ravenswood Technology Group, we specialize in helping organizations design, implement, and manage their Active Directory environments. Our principal architect, Brian Desmond, even co-authored the book on it. Our services include Active Directory design and implementation, security audits, compliance assessments, and ongoing support. With our expertise, you can ensure that your Active Directory infrastructure is robust, secure, and aligned with your business needs. Whether you are starting from scratch or working with a 20-year-old forest you inherited, we have you covered.

Get in touch with Ravenswood Technology Group today to learn how we can help you achieve a well-designed, secure, and efficient Active Directory environment.