active directory administrator Interview Questions and Answers

1. What is Active Directory?

   • Answer: Active Directory (AD) is a directory service developed by Microsoft that provides centralized management and authentication for users, computers, and other resources within a network. It uses a hierarchical database to store information and allows administrators to manage access to resources based on user roles and permissions.

2. Explain the difference between a Domain and a Forest.

   • Answer: A domain is a collection of users, computers, and other resources that share a common directory database. A forest is a collection of one or more domains that share a common schema, configuration, and global catalog. A forest represents the highest level of organizational structure in Active Directory.

3. What is a Global Catalog?

   • Answer: The Global Catalog (GC) is a partial replica of the directory database that contains a subset of attributes for every object in the forest. It allows users to search for objects across multiple domains without having to query each domain individually. It is essential for cross-domain authentication and searches.

4. What are Organizational Units (OUs)?

   • Answer: OUs are containers within Active Directory that are used to organize users, computers, and other objects. They allow administrators to delegate administrative control and apply Group Policy settings to specific groups of objects.

5. Explain the different types of Active Directory Replication.

   • Answer: Active Directory uses multi-master replication, meaning that changes made on one domain controller are replicated to all other domain controllers in the domain. There are several replication topologies, including single-master operation (SMO) for certain types of data, but generally, it's multi-master.

6. What is Group Policy?

   • Answer: Group Policy is a powerful tool that allows administrators to configure settings for users and computers within Active Directory. These settings can control things like software installations, security settings, desktop configurations, and much more. Group Policy settings are applied based on the user's or computer's membership in various OUs or security groups.

7. What are the different types of Group Policy Objects (GPOs)?

   • Answer: GPOs can be linked to OUs or directly to Sites. They can be applied to users or computers, and their inheritance can be blocked or modified using link order and filtering. There are no inherent "types" beyond their scope and target (user or computer).

8. How do you troubleshoot Active Directory replication issues?

   • Answer: Troubleshooting replication issues involves using tools like repadmin, dcdiag, and event logs. You need to identify the replication failures, check for connectivity problems, review the directory service event logs on the domain controllers, and examine the replication topology to determine where the bottleneck is. Tools like Repadmin show replication status and errors.

9. What are Security Groups in Active Directory?

   • Answer: Security groups are used to assign permissions and access rights to users and computers. They allow administrators to manage access control efficiently by assigning permissions to the group rather than individual users or computers.

10. What are Distribution Groups in Active Directory?

    • Answer: Distribution groups are used for sending emails to a group of users or computers. Unlike security groups, they do not have any specific security permissions associated with them.

11. Explain the concept of Single Sign-On (SSO).

    • Answer: SSO allows users to authenticate once and access multiple resources without having to re-enter their credentials. Active Directory plays a crucial role in enabling SSO through Kerberos authentication.

12. What is Kerberos authentication?

    • Answer: Kerberos is a network authentication protocol that uses tickets to verify the identity of users and computers. It's a critical part of Active Directory's security model, ensuring secure access to network resources without transmitting passwords across the network in clear text.

13. What is NTLM authentication?

    • Answer: NTLM (NT LAN Manager) is an older authentication protocol that is still used in some situations, especially when Kerberos is not available or configured correctly. It's less secure than Kerberos.

14. What is a Domain Controller?

    • Answer: A Domain Controller (DC) is a server that holds a copy of the Active Directory database for a domain. It is responsible for authenticating users and computers and providing access to network resources.

15. What is the Schema in Active Directory?

    • Answer: The schema defines the structure and attributes of objects in Active Directory. It dictates what types of objects can exist and what properties they can have.

16. Explain the concept of Delegation of Control.

    • Answer: Delegation of Control allows administrators to grant specific permissions to other users or groups without giving them full administrative rights. This enhances security and allows for more efficient management of Active Directory.

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

    • Answer: User accounts are managed using tools like Active Directory Users and Computers (ADUC) or PowerShell cmdlets. You can create, modify, disable, or delete user accounts, as well as manage their group memberships and attributes.

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

    • Answer: Computer accounts are managed similarly to user accounts, using ADUC or PowerShell. These accounts represent the computers joining the domain and are essential for authentication and management.

19. What is the role of the DNS in Active Directory?

    • Answer: DNS is crucial for locating domain controllers and other resources within the network. Active Directory uses DNS to resolve names to IP addresses and vice-versa.

20. What is a Site in Active Directory?

    • Answer: A site represents a physical location or a group of subnets that are connected by a high-speed network. Sites are used to optimize replication and improve performance.

21. Explain the process of joining a computer to a domain.

    • Answer: A computer joins a domain by providing domain credentials and being authenticated by a domain controller. This establishes trust and allows the computer to access domain resources.

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

    • Answer: Best practices include using strong passwords, enabling multi-factor authentication (MFA), regularly patching domain controllers, applying least privilege principles, regularly backing up the Active Directory database, monitoring for suspicious activity, and implementing robust access controls.

23. How do you recover a corrupted Active Directory database?

    • Answer: Recovery involves using Active Directory backups or potentially using ntdsutil to perform metadata cleanup or authoritative restores. This is a complex process and requires careful planning and testing.

24. What are some common Active Directory performance issues and how to resolve them?

    • Answer: Performance issues can stem from replication problems, excessive log file sizes, inefficient Group Policy settings, insufficient resources on domain controllers, or network bottlenecks. Troubleshooting involves using performance monitoring tools, analyzing event logs, and optimizing settings.

25. What is the difference between a read-only domain controller (RODC) and a writable domain controller (WDC)?

    • Answer: A WDC is a fully functional domain controller that can modify the Active Directory database. A RODC is a domain controller that can only read data; it cannot modify the database, improving security in branch offices.

26. What is the role of a Global Catalog Server?

    • Answer: A Global Catalog server holds a partial replica of the directory, containing attributes for every object in the forest, allowing for universal searches across the entire forest.

27. How do you manage user passwords in Active Directory?

    • Answer: Password management involves setting password policies (complexity, length, history), enforcing password changes, resetting passwords, and potentially using self-service password reset tools.

28. What is the purpose of the `repadmin` command?

    • Answer: `repadmin` is a command-line tool used to diagnose and troubleshoot Active Directory replication issues. It provides information about replication status, topology, and errors.

29. What is the purpose of the `dcdiag` command?

    • Answer: `dcdiag` is a command-line tool that performs a diagnostic test of a domain controller, identifying potential problems with the configuration and functionality of the DC.

30. What is Active Directory Lightweight Directory Services (AD LDS)?

    • Answer: AD LDS is a lightweight version of Active Directory that can be used for storing and managing data outside of a traditional Active Directory domain.

31. How do you create a new OU in Active Directory?

    • Answer: A new OU is created through the Active Directory Users and Computers (ADUC) console by right-clicking an existing OU and selecting "New" -> "Organizational Unit".

32. How do you create a new Security Group in Active Directory?

    • Answer: A new security group is created in ADUC by right-clicking an OU and selecting "New" -> "Group". You then specify that it's a security group.

33. How do you create a new Distribution Group in Active Directory?

    • Answer: A new distribution group is created similarly to a security group, but specifying it's a distribution group during the creation process in ADUC.

34. What are the different types of domain trusts?

    • Answer: There are several types of domain trusts, including one-way, two-way, transitive, and non-transitive trusts. They govern how authentication and access are handled between domains.

35. Explain the concept of forest functional levels.

    • Answer: Forest functional levels determine which Active Directory features are available and enabled across the entire forest. Raising the functional level unlocks new features and improvements.

36. Explain the concept of domain functional levels.

    • Answer: Domain functional levels determine which features are available and enabled within a specific domain. Raising the functional level within a domain enables new capabilities and features within that domain.

37. What is the command to promote a server to a domain controller?

    • Answer: The process is initiated through the Server Manager in the GUI, not a single command. It involves using the Active Directory Domain Services installation wizard.

38. What is the difference between a user's SID and their username?

    • Answer: A SID (Security Identifier) is a unique, persistent identifier for a user or group, while the username is a human-readable name that can be changed. SIDs are essential for security.

39. How can you track changes made to Active Directory?

    • Answer: Changes can be tracked using auditing, which logs actions like account creation, modification, and deletion. Tools like event viewer can be used to examine audit logs.

40. What are some common issues related to Group Policy?

    • Answer: Issues can include slow logon times, policy conflicts, unexpected settings, and problems applying policies. Troubleshooting often involves checking for loopback processing, policy inheritance, and GPO link order.

41. How do you manage Group Policy settings?

    • Answer: Group Policy settings are managed through the Group Policy Management Console (GPMC.msc). You can edit, create, link, and delete GPOs, and modify their settings.

42. What is the difference between User and Computer Group Policy?

    • Answer: User GPOs apply settings to users when they log on, while Computer GPOs apply settings to computers regardless of who is logged on.

43. What is a Site-Link Bridge?

    • Answer: A Site-Link Bridge connects two sites in Active Directory, allowing for replication between domain controllers in different sites. This can be a physical connection or a virtual connection.

44. What is a DFS Namespace?

    • Answer: DFS Namespaces provides a single, unified namespace for accessing files and folders that are stored on multiple servers across the network. It simplifies access and management of shared resources.

45. How do you troubleshoot DNS issues related to Active Directory?

    • Answer: DNS troubleshooting involves checking DNS server configurations, zone transfers, forward and reverse lookup zones, and using tools like `nslookup` and `ipconfig` to check DNS resolution.

46. What are some tools used for monitoring Active Directory?

    • Answer: Tools include Performance Monitor, Event Viewer, Active Directory Administrative Center, ADUC, PowerShell cmdlets, and third-party monitoring tools.

47. How do you delegate control over specific OUs?

    • Answer: Delegation is accomplished using Active Directory Users and Computers (ADUC) or the Active Directory Administrative Center (ADAC) by right-clicking the OU, selecting "Delegate Control...", and specifying the users or groups and the permissions to grant.

48. What is the role of the SYSVOL folder?

    • Answer: The SYSVOL folder stores Group Policy files and other files that are replicated to all domain controllers. It's crucial for the consistency and proper functioning of Group Policy.

49. What are the different types of Active Directory backups?

    • Answer: There are various types of backups, including full, incremental, and differential backups. The strategy depends on recovery requirements and RTO/RPO.

50. How do you restore an Active Directory backup?

    • Answer: The process is performed using tools like ntdsutil and involves restoring the database to a domain controller. The process is complex and depends on the type of backup used.

51. What is the concept of "tombstoning" in Active Directory?

    • Answer: Tombstoning is the process of deleting an object from Active Directory, but retaining information about it for a specified period to aid in replication and recovery.

52. What is the purpose of the `netdom` command?

    • Answer: `netdom` is a command-line tool used to manage domain trusts and perform other domain-related tasks.

53. Explain the concept of a read-only domain controller (RODC) in a branch office scenario.

    • Answer: RODCs improve security in branch offices by providing authentication services without storing a writable copy of the entire Active Directory database, reducing the risk of data compromise.

54. What are some security considerations when implementing RODCs?

    • Answer: Security considerations include protecting the RODC's credentials, managing its access, and ensuring proper network security to protect it from unauthorized access.

55. What are some of the key performance indicators (KPIs) you would monitor in an Active Directory environment?

    • Answer: KPIs include logon times, replication latency, disk I/O on domain controllers, CPU utilization, network bandwidth usage, and the number of authentication failures.

56. How would you identify and resolve a slow logon issue in Active Directory?

    • Answer: Troubleshooting slow logons involves examining event logs, analyzing Group Policy processing times, checking DNS resolution times, and reviewing network latency. Tools like Process Monitor can assist in identifying bottlenecks.

57. Explain the concept of password filtering in Active Directory.

    • Answer: Password filtering allows administrators to enforce password complexity requirements and prevent users from choosing weak or easily guessable passwords.

58. How do you enforce password expiry policies in Active Directory?

    • Answer: Password expiry policies are enforced through Group Policy settings that define password age and the minimum password age.

59. What are some common tools used for Active Directory administration?

    • Answer: Tools include Active Directory Users and Computers (ADUC), Active Directory Administrative Center (ADAC), Group Policy Management Console (GPMC), PowerShell, and various command-line tools like `repadmin`, `dcdiag`, and `netdom`.

60. What is the difference between a domain local group and a global group?

    • Answer: Domain local groups are limited to members within the same domain, while global groups can contain members from other domains, making them useful in cross-domain administration.

61. How do you manage service accounts in Active Directory?

    • Answer: Service accounts are managed like regular user accounts, but with additional considerations for security and permissions. Managed Service Accounts (MSAs) and Group Managed Service Accounts (gMSAs) simplify the management of service account passwords.

62. Explain the concept of access control lists (ACLs) in Active Directory.

    • Answer: ACLs define the permissions granted to users and groups on specific objects, controlling access to those objects. They are used to implement fine-grained access control.

63. How do you monitor Active Directory replication health?

    • Answer: Monitoring replication health involves using tools like `repadmin`, examining replication event logs, and using monitoring tools to track replication latency and errors.

64. What is the role of the RID pool in Active Directory?

    • Answer: The RID pool manages the allocation of Relative Identifier (RID) numbers, which are used to uniquely identify objects within a domain.

65. How would you troubleshoot an issue where users cannot log on to a domain?

    • Answer: Troubleshooting login issues involves checking domain controller connectivity, verifying user account status, examining event logs for authentication failures, checking password policies, and ensuring DNS resolution is working correctly.

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