active directory engineer Interview Questions and Answers

1. What is Active Directory?

   • Answer: Active Directory is a directory service developed by Microsoft that provides centralized management and authentication for users, computers, and other resources within a Windows-based network. It stores information about these objects in a hierarchical structure called a directory tree.

2. Explain the concept of domains and forests in Active Directory.

   • Answer: A domain is a security boundary within an Active Directory forest. It's a collection of users, computers, and other resources that share a common directory database. A forest is a top-level logical grouping of one or more domains. Forests allow for organizational structures with separate but related domains.

3. What are Organizational Units (OUs)? Why are they useful?

   • Answer: Organizational Units are containers within Active Directory that allow you to logically group users, computers, and other objects. They're useful for delegating administrative control, applying Group Policy settings to specific sets of users or computers, and improving organizational structure and management.

4. Describe the different types of Active Directory objects.

   • Answer: Common Active Directory objects include users, computers, groups, OUs, contacts, printers, and shares. Each object has specific attributes and properties.

5. What are Group Policy Objects (GPOs)? How do they work?

   • Answer: Group Policy Objects are sets of rules and settings that can be applied to users and computers to manage their configurations and security settings. They work by linking GPOs to OUs, and when a user or computer logs in or starts, the policies linked to their respective OUs are applied.

6. Explain the difference between User and Computer accounts in Active Directory.

   • Answer: User accounts represent individual users who can log on to the network. Computer accounts represent computers that are part of the domain and can access network resources. They have different security attributes and settings.

7. What are different types of groups in Active Directory?

   • Answer: Common group types include security groups (for access control), distribution groups (for email distribution), and universal groups (which can span domains in a forest).

8. What is a Domain Controller (DC)?

   • Answer: A Domain Controller is a server that holds a replica of the Active Directory database and provides authentication, authorization, and other directory services to clients within a domain.

9. Explain the process of promoting a server to a Domain Controller.

   • Answer: Promoting a server to a DC involves installing the Active Directory Domain Services (AD DS) role and then running the Active Directory Domain Services Installation Wizard (dcpromo - older versions, now Server Manager). This replicates the Active Directory database onto the new server.

10. What are Global Catalog Servers?

    • Answer: Global Catalog servers hold a partial replica of every object in the forest. This allows users to search for objects across the entire forest, regardless of the domain they are in.

11. What is the role of a Schema Master?

    • Answer: The Schema Master is a domain controller that holds the master copy of the Active Directory schema. Changes to the schema must be made through this server.

12. What is the role of a PDC Emulator?

    • Answer: The PDC Emulator is a domain controller that acts as a backup domain controller in older style backwards compatibility scenarios. In modern deployments, its role is less critical.

13. What is replication in Active Directory?

    • Answer: Replication is the process by which changes made to the Active Directory database on one domain controller are copied to other domain controllers in the same domain and/or forest. This ensures consistency and high availability.

14. Explain the different replication topologies in Active Directory.

    • Answer: Common topologies include site-based, tree-based, and domain-based. Site-based replication prioritizes replication within geographic locations. The other topologies define replication based on the AD forest structure.

15. What is DNS and its role in Active Directory?

    • Answer: DNS (Domain Name System) is crucial for Active Directory. It translates domain names into IP addresses, allowing clients to locate and authenticate with domain controllers.

16. How do you troubleshoot Active Directory replication issues?

    • Answer: Troubleshooting involves checking replication logs (Repadmin), verifying DNS settings, checking network connectivity between domain controllers, and using Active Directory diagnostic tools.

17. What are some common Active Directory security best practices?

    • Answer: Best practices include strong passwords, regular password changes, least privilege access, multi-factor authentication, regular security audits, and patching of domain controllers.

18. Explain the concept of Kerberos authentication.

    • Answer: Kerberos is a network authentication protocol that uses tickets to grant access to network resources. It's a key component of Active Directory authentication.

19. What is NTLM authentication? When is it used?

    • Answer: NTLM is an older authentication protocol. It's used as a fallback when Kerberos authentication fails or when a Kerberos infrastructure isn't in place.

20. What is Active Directory Recycle Bin?

    • Answer: The Active Directory Recycle Bin is a feature that allows administrators to restore accidentally deleted objects, improving data recovery capabilities.

21. Explain the concept of delegated administration in Active Directory.

    • Answer: Delegated administration allows administrators to grant specific permissions to other users or groups, allowing them to manage certain aspects of Active Directory without having full domain administrator privileges.

22. How do you manage user accounts in Active Directory?

    • Answer: User accounts are managed using Active Directory Users and Computers (ADUC) or PowerShell cmdlets.

23. How do you manage computer accounts in Active Directory?

    • Answer: Computer accounts are managed using ADUC or PowerShell cmdlets. Computers typically automatically register with the domain when they join.

24. What are some common Active Directory troubleshooting tools?

    • Answer: Common tools include ADUC, PowerShell, repadmin, nltest, dcdiag, and event viewer.

25. What is the command to check Active Directory replication status?

    • Answer: `repadmin /showrepl`

26. What is the command to check DNS server health?

    • Answer: `nslookup` or `ipconfig /all` (to verify DNS settings) and DNS management tools.

27. What is the difference between a read-only domain controller (RODC) and a regular domain controller?

    • Answer: RODCs are domain controllers that only hold a read-only copy of the Active Directory database. They're useful in branch offices to improve performance and security, but they can't be used for certain administrative tasks.

28. What are some security considerations when deploying RODCs?

    • Answer: Security considerations include protecting the RODC from unauthorized access and carefully managing password replication settings.

29. What are some best practices for designing an Active Directory infrastructure?

    • Answer: Best practices include proper site design for replication, careful planning of OUs for delegation, and consideration of scalability and security.

30. How do you perform a metadata cleanup in Active Directory?

    • Answer: Metadata cleanup involves using tools and scripts to remove unnecessary or orphaned objects and attributes from Active Directory to improve performance and efficiency. This often requires specialized tools and expertise.

31. How do you troubleshoot slow logon times in Active Directory?

    • Answer: Troubleshooting slow logon times involves examining event logs, checking DNS resolution, analyzing Group Policy processing time, and verifying network connectivity.

32. Explain the concept of fine-grained password policy.

    • Answer: Fine-grained password policy allows administrators to define different password policies for different groups of users, giving more control over password complexity and expiration.

33. What is a trust relationship in Active Directory?

    • Answer: A trust relationship allows users and computers in one domain to access resources in another domain without requiring separate accounts in each domain.

34. What are the different types of trust relationships?

    • Answer: Types include one-way, two-way, transitive, and non-transitive trusts.

35. How do you create a trust relationship between two domains?

    • Answer: Trust relationships are created using Active Directory administrative tools or PowerShell cmdlets.

36. What is the role of the RID Master?

    • Answer: The RID Master assigns Relative IDentifiers (RIDs) which uniquely identify objects within a domain. It's important for maintaining object uniqueness.

37. What is the role of the Infrastructure Master?

    • Answer: The Infrastructure Master updates references to objects in other domains within the forest, ensuring consistency across domains.

38. What is the command to check the FSMO roles?

    • Answer: `netdom query fsmo`

39. How do you transfer FSMO roles?

    • Answer: FSMO roles are transferred using Active Directory administrative tools or PowerShell cmdlets.

40. What is Active Directory Certificate Services (AD CS)?

    • Answer: AD CS is a role service that issues and manages digital certificates. These certificates are used for authentication, encryption, and other security functions.

41. What is a certificate template?

    • Answer: A certificate template defines the characteristics of certificates issued by AD CS, such as the key length, validity period, and intended use.

42. How do you troubleshoot certificate-related issues in Active Directory?

    • Answer: Troubleshooting involves checking certificate validity, reviewing certificate revocation lists (CRLs), and using certificate management tools.

43. What is Azure Active Directory (Azure AD)?

    • Answer: Azure AD is Microsoft's cloud-based directory service. It provides authentication and authorization services for cloud-based applications and resources.

44. How does Azure AD integrate with on-premises Active Directory?

    • Answer: Azure AD integrates with on-premises AD using Azure AD Connect, which synchronizes user accounts and other information between the two directories.

45. What is password hash synchronization?

    • Answer: Password hash synchronization is a method of integrating Azure AD with on-premises AD by syncing password hashes. This allows users to use the same password for both on-premises and cloud resources.

46. What is pass-through authentication?

    • Answer: Pass-through authentication allows users to authenticate directly against on-premises AD from cloud applications, eliminating the need for password synchronization.

47. What is federation authentication?

    • Answer: Federation authentication uses a third-party identity provider (like Azure AD) to authenticate users accessing cloud resources. This allows organizations to use their existing identity infrastructure.

48. What are some common performance tuning techniques for Active Directory?

    • Answer: Techniques include optimizing Group Policy settings, optimizing DNS configuration, managing replication traffic, and improving hardware resources.

49. How do you monitor Active Directory performance?

    • Answer: Monitoring involves using performance counters, event logs, and dedicated monitoring tools to track key metrics like replication latency, CPU utilization, and network traffic.

50. What is the command to check Active Directory Domain Services health?

    • Answer: `dcdiag`

51. How do you restore an Active Directory domain controller?

    • Answer: Restoration involves using authoritative restores, non-authoritative restores, or using backups to recover the database and configuration.

52. What is the difference between an authoritative and non-authoritative restore?

    • Answer: An authoritative restore overwrites the existing directory data, while a non-authoritative restore merges the data into the existing directory.

53. What are some disaster recovery strategies for Active Directory?

    • Answer: Strategies include having multiple domain controllers in different locations, using replication to ensure data redundancy, and having a disaster recovery plan that details restoration procedures.

54. What is the process of demoting a domain controller?

    • Answer: Demoting a DC involves using the Active Directory Domain Services Installation Wizard (or Server Manager) to remove the Active Directory Domain Services role. This process removes the domain controller from the domain.

55. What are some considerations before demoting a domain controller?

    • Answer: Considerations include ensuring there are other domain controllers available, backing up the domain controller before demotion, and verifying the impact on replication and overall domain functionality.

56. What are security groups and distribution groups? Explain the difference.

    • Answer: Security groups are used for controlling access to resources. Distribution groups are used for sending emails to a group of recipients.

57. What is a site in Active Directory?

    • Answer: A site represents a physical location or a group of geographically close servers. It's essential for optimizing Active Directory replication.

58. What is a subnet in Active Directory?

    • Answer: Subnets are logical divisions within a network used to manage IP addresses and network traffic. They are linked to Active Directory sites for optimized replication.

59. What is the concept of a "writeable" domain controller?

    • Answer: A writeable domain controller is a fully functional domain controller that can accept write operations to the Active Directory database.

60. Explain the significance of the SYSVOL folder.

    • Answer: The SYSVOL folder stores Group Policy settings and other domain-wide configuration data that are replicated to all domain controllers.

61. What is the purpose of the DFSR service?

    • Answer: Distributed File System Replication (DFSR) is the service responsible for replicating the SYSVOL folder and other file shares across domain controllers.

62. How do you troubleshoot issues with DFSR?

    • Answer: Troubleshooting DFSR involves checking DFSR event logs, using the DFSR diagnostics tools, and analyzing replication health.

63. What is the difference between a forest and a tree in Active Directory?

    • Answer: A forest is the top-level structure, containing one or more trees. A tree consists of one or more domains, all sharing a common namespace.

64. What is a cross-forest trust?

    • Answer: A cross-forest trust allows users and groups in one forest to access resources in another forest.

65. What is the importance of auditing in Active Directory?

    • Answer: Auditing provides a record of changes and activities within Active Directory, allowing administrators to monitor security, troubleshoot issues, and comply with regulatory requirements.

66. How do you configure auditing in Active Directory?

    • Answer: Auditing is configured using Group Policy and specifying which events to audit.

67. What is the role of the domain naming master?

    • Answer: The domain naming master is the only domain controller that can create new domains in the forest.

68. What are some tools used for managing Active Directory from the command line?

    • Answer: PowerShell, `netdom`, `repadmin`, `nltest`, and others.

69. What is the importance of regular backups of Active Directory?

    • Answer: Regular backups are essential for disaster recovery, enabling the restoration of Active Directory in the event of data loss or corruption.

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