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🚩AD Forests

Idea of AD Forests ?

What is Active Directory Forests

An Active Directory Forest is the highest-level logical container in Active Directory, consisting of one or more domain trees that share a common schema, configuration, and global catalog, but may have different "DNS" namespaces. A forest defines the ultimate security and administrative boundary in an AD environment(Objects in one forest cannot natively access resources in another forest unless an explicit trust is created.), enabling centralized management, resource sharing, and cross-domain collaboration across its domains and trees while maintaining a unified framework

Idea of the Forests

Key characteristics of an AD forest

  1. Collection of Domain Trees: A forest contains one or more domain trees, each with its own contiguous namespace (example.com and anothercorp.com).

  2. Common Schema: All domains in the forest share a single schema, defining object types and attributes.

  3. Global Catalog: A forest-wide database that stores a partial replica of objects from all domains, facilitating cross-domain searches and authentication.

  4. Transitive Trusts: Automatic, two-way, transitive trusts connect all domains within the forest, enabling seamless resource access.

  5. Security Boundary: The forest is the ultimate security boundary; objects, policies, and permissions are confined within it unless explicitly shared via external trusts.

  6. Administrative Scope: The forest provides overarching administrative control, with Enterprise Admins having forest-wide authority.

Components of Active Directory Forests

To understand forests, let’s deep Dive into key components and related elements:

  1. Domain Trees

    • Definition: A hierarchical collection of domains sharing a contiguous DNS namespace ( example.com, sales.example.com).

    • Role: Domain trees organize domains within the forest, with each tree having its own root domain and namespace.

    • Example: The example.com tree includes example.com and sales.example.com.

  2. Domains

    • Definition: Logical groupings of objects (users, computers, groups, OUs) with a common AD database and security policies.

    • Role: Domains are the building blocks of domain trees and forests, each with its own domain controllers and administrative scope.

    • Example: example.com, sales.example.com, anothercorp.com.

  3. Forest Root Domain

    • Definition: The first ever domain created in the forest, which serves as the root of the first domain tree and holds special forest-wide roles.

    • Role: Hosts critical Flexible Single Master Operation (FSMO) roles (Schema Master, Domain Naming Master) and is managed by Enterprise Admins.

    • Example: example.com as the forest root domain in a forest with trees example.com and anothercorp.com.

  1. Schema

    • Definition: A forest-wide set of rules defining the types of objects (users, groups) and their attributes (email, name) in AD.

    • Role: Ensures consistency across all domains in the forest.

    • Management: Schema updates are controlled by the Schema Master role, typically in the forest root domain.

    • Example: The schema defines that a user object can have a userPrincipalName attribute.

  1. Global Catalog

    • Definition: A distributed database that stores a partial replica of attributes for all objects in every domain in the forest.

    • Role: Enables cross-domain searches (finding a user in another domain) and authentication (resolving group memberships).

    • Global Catalog Servers: Domain controllers designated to host the global catalog.

    • Example: A user in sales.example.com queries the global catalog to locate a printer in anothercorp.com.

  1. Trust Relationships

    • Definition: Automatic, two-way, transitive trusts that connect all domains within the forest.

    • Types:

      • Parent-Child Trusts: Connect domains within a tree (example.com ↔ sales.example.com).

      • Tree-Root Trusts: Connect root domains of different trees (example.com ↔ anothercorp.com).

      • Cross-Forest Trusts: Explicit trusts with other forests (not automatic).

    • Purpose: Enable authentication and resource access across domains using Kerberos.

    • Example: A user in sales.example.com accesses a resource in hr.anothercorp.com via transitive trusts.

  1. Domain Controllers

    • Definition: Servers hosting the AD database for a specific domain in the forest.

    • Role: Manage authentication, replication, and object storage for their domain, with some hosting the global catalog.

    • Example: dc1.example.com for example.com, dc1.sales.example.com for sales.example.com.

  1. Groups and OUs

    • Groups: Manage permissions and policy application across domains in the forest (universal groups like U_AllEmployees).

    • OUs: Organize objects within each domain, not replicated forest-wide but accessible via trusts and the global catalog.

Logical Structure of Active Directory Forests

The logical structure of an AD forest is a collection of domain trees, unified by a shared schema, configuration, and global catalog, with transitive trusts connecting all domains, independent of physical network topology.

  1. Collection of Domain Trees

    • Structure: A forest contains one or more domain trees, each with its own contiguous namespace.

    • Namespace: Each tree has a unique namespace (example.com, anothercorp.com), unlike a domain tree’s single namespace.

    • Example:

Forest
├── Tree 1: example.com
│ ├── example.com (Root Domain)
│ ├── sales.example.com (Child Domain)
│ └── marketing.example.com (Child Domain)
└── Tree 2: anothercorp.com
├── anothercorp.com (Root Domain)
└── hr.anothercorp.com (Child Domain)

  1. Trust Relationships

    • Intra-Tree Trusts: Parent-child trusts connect domains within a tree (example.com ↔ sales.example.com).

    • Inter-Tree Trusts: Tree-root trusts connect root domains of different trees (example.com ↔ anothercorp.com).

    • Transitivity: All domains in the forest are implicitly trusted via transitive trusts.

    • Example: A user in sales.example.com accesses a resource in hr.anothercorp.com through the trust path: sales.example.com → example.com → anothercorp.com → hr.anothercorp.com.

  1. Global Catalog

    • Contents: Partial attributes of all objects (user names, group memberships) from every domain and also their context Within the Forest .

    • Purpose: Enables forest-wide searches and cross-domain authentication.

    • Example: A user in example.com queries the global catalog to find a group in anothercorp.com.

  1. Administrative Hierarchy

    • Forest-Wide Admins: Enterprise Admins (in the forest root domain) have authority over the entire forest.

    • Domain Admins: Manage specific domains within the forest.

    • Delegated Admins: Manage OUs or groups within domains.

    • Example: Enterprise Admins in example.com can add a new domain, while Domain Admins in sales.example.com manage only their domain.

Forests in the Context of Active Directory

Forests are the top-level structure in AD, encompassing domains, domain trees, OUs, and groups, providing a unified framework for management and security.

  1. Role of Forests

    • Security Boundary: The forest is the ultimate boundary for security policies, schema, and object access.

    • Administrative Boundary: Defines the scope of Enterprise Admins and forest-wide roles.

    • Unification: Combines multiple domain trees with different namespaces into a single management structure.

    • Example: A forest unifies example.com and anothercorp.com trees for resource sharing.

  1. Logical Structure of Forests

    • Hierarchy: Forests contain domain trees, which contain domains, which contain OUs and groups.

    • Trusts: Transitive trusts connect all domains, enabling forest-wide collaboration.

    • Shared Resources:

      • Schema: Ensures consistent object definitions.

      • Global Catalog: Facilitates cross-domain operations.

      • Configuration: Standardizes forest-wide settings.

    • Example:

Forest
├── Tree 1: example.com
│   ├── example.com
│   │   ├── Sales (OU)
│   │   │   ├── Users (OU, User: john.doe)
│   │   │   └── Groups (OU, Group: G_SalesUsers)
│   │   └── Resources (OU, Group: DL_FileAccess)
│   └── sales.example.com
│       ├── Marketing (OU)
│       └── Groups (OU, Group: G_MarketingUsers)
└── Tree 2: anothercorp.com
    ├── anothercorp.com
    │   ├── Finance (OU)
    │   └── Groups (OU, Group: U_AllEmployees)
    └── hr.anothercorp.com

  1. How Forests Interact with Other AD Components

    • Domains: Forests group domains into trees, with each domain maintaining its own database and policies.

    • Domain Trees: Forests contain one or more trees, each with a unique namespace, connected by tree-root trusts.

    • OUs: Exist within domains, organizing objects, but accessible forest-wide via the global catalog and trusts.

    • Groups: Manage permissions and policies, with universal groups enabling forest-wide access.

    • Resource Access:

      • A user in sales.example.com accesses a resource in hr.anothercorp.com via transitive trusts.

      • Example: G_SalesUsers (in sales.example.com) is nested in DL_FileAccess (in example.com) for file server access.

    • Authentication:

      • Kerberos uses trust paths to authenticate users across domains in the forest.

      • The global catalog resolves universal group memberships.

    • Administration:

      • Enterprise Admins manage forest-wide tasks ( schema updates).

      • Domain Admins manage individual domains.

      • Delegated admins manage OUs or groups.

Functionality of Active Directory Forests

Forests serve critical functions in AD:

  1. Unified Management

  • Purpose: Provide a single framework for managing multiple domains and trees.

  • Example: A single schema ensures consistent user attributes across example.com and anothercorp.com.

  1. Resource Sharing

  • Purpose: Transitive trusts and the global catalog enable cross-domain resource access.

  • Example: A user in sales.example.com accesses a printer in hr.anothercorp.com.

  1. Security Boundary

  • Purpose: Confine security policies and objects within the forest, protecting against external access.

  • Example: A compromised account in example.com cannot affect another forest without an explicit trust.

  1. Cross-Domain Collaboration

    • Purpose: Enable authentication and resource access across domains using trusts.

    • Example: A universal group U_AllEmployees grants forest-wide application access.

  2. Centralized Administration

    • Purpose: Allow forest-wide tasks (schema updates) to be managed by Enterprise Admins.

    • Example: Adding a new domain tree to the forest is controlled by the Domain Naming Master(Flexible Single Master Operations (FSMO) ).

Real-World Example

Consider GlobalTech, a multinational corporation with a forest integrating multiple domain trees:

  • Forest Structure:

Forest
├── Tree 1: globaltech.com
│   ├── globaltech.com (Forest Root Domain)
│   │   ├── Resources (OU)
│   │   │   └── Groups (OU, Group: DL_FileAccess)
│   │   └── IT (OU, Group: G_ITAdmins)
│   ├── na.globaltech.com (Child Domain)
│   │   ├── Sales (OU)
│   │   │   ├── Users (OU, User: john.doe)
│   │   │   └── Groups (OU, Group: G_SalesUsers)
│   │   └── Marketing (OU)
│   └── eu.globaltech.com (Child Domain)
│       └── uk.eu.globaltech.com (Grandchild Domain, User: alice.smith)
└── Tree 2: acquiredcorp.com
    ├── acquiredcorp.com (Root Domain)
    │   ├── Finance (OU, Group: G_FinanceTeam)
    │   └── Groups (OU, Group: U_AllEmployees)
    └── hr.acquiredcorp.com (Child Domain)

  • Components:

    • Forest Root Domain: globaltech.com, hosting Schema Master and Domain Naming Master.

    • Domain Trees: globaltech.com (with child domains na.globaltech.com, eu.globaltech.com) and acquiredcorp.com.

    • Trusts:

      • Parent-child: globaltech.com ↔na.globaltech.com, eu.globaltech.com ↔ uk.eu.globaltech.com.

      • Tree-root: globaltech.com ↔ acquiredcorp.com.

      • Transitive: na.globaltech.com ↔ hr.acquiredcorp.com.

    • Groups:

      • U_AllEmployees (universal, in acquiredcorp.com): Includes G_SalesUsers and G_FinanceTeam.

      • DL_FileAccess (domain-local, in globaltech.com): Grants access to \\fileserver.globaltech.com\Shared, includes G_SalesUsers.

    • Global Catalog: Stores partial data from all domains, enabling searches for john.doe or U_AllEmployees.

  • Functionality:

    • Access: john.doe (in na.globaltech.com) accesses a file server in globaltech.com via G_SalesUsers membership in DL_FileAccess.

    • Authentication: alice.smith (in uk.eu.globaltech.com) authenticates to access a resource in hr.acquiredcorp.com using transitive trusts.

    • Administration: Enterprise Admins in globaltech.com add a new domain, while Domain Admins in na.globaltech.com manage Sales users.

    • Search: A user queries the global catalog to find G_FinanceTeam in acquiredcorp.com.

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