Active Directory is extremely popular for organizing a company’s network objects in a secure and scalable hierarchy. Active Directory or AD is used by 95% of the top Fortune 1000 companies. It offers seamless authentication and authorization for an unlimited number of users and other AD objects.
If you’re not familiar with Active Directory, don’t worry.
This guide outlines the basic terms, structure, and benefits of AD and domain controllers. Then you’ll learn about Active Directory Replication including when you should use it. Lastly, you’ll learn three methods to force Active Directory Replication, following step-by-step instructions.
What is Active Directory?
Active Directory is Microsoft software that stores information for all of the objects in an organization’s network. These Active Directory objects include Users, Computers, Printers, and Shared Folders.
Active directory arranges and stores information, providing access and permissions as requested. When a user or computer needs to access another Active Directory object, like a printer, on the organization’s network, then AD authenticates and authorizes that User.
All Active Directory objects are arranged into logical hierarchical groupings. Active Directory objects are just physical entities of a network, such as:
- Forest, Domain, Organizational Unit, User, Group, Contact, Computer, Shared folder, Printer, Site, and Subnet
Active Directory Advantages
Active Directory is a popular technology for network administration because:
- Highly Secure – policies and permissions can be set at different security levels
- Scalability – A single domain can handle an unlimited number of users and other AD objects
- Searchable – it’s very easy and efficient to locate a specific AD object using the search mechanism
- Location Independent – AD objects can be located all over the work landscape and still securely access the organization’s network resources
- Centralized Storage – all user information is stored on the AD, so backup and restoration are easy and efficient
- Mandatory Profiles – organizations can restrict or allow specific applications and services to specific sets of users or groups.
Active Directory is great for organizations that are operating in many locations and where the number of AD objects is constantly changing. AD protects data and information while providing a 24/7 uptime.
What is a Forest?
Within Active Directory, a forest is the highest level of organization. A forest is a collection of multiple domain trees, that do not share a common namespace. Every domain in the forest, known as a tree, has a separate database. Trees have a trust relationship.` `
What are Domain Controllers?
A domain is just a logical grouping of objects. There is an unlimited number of objects that can be contained within a domain, making Active Directory domains great at scaling to the size of the organization. Objects do not need to be in the same physical location to be on the same domain.
A domain controller is the domain’s supreme authority.
AD domains are identified using a domain name system (DNS), which is usually the company’s public domain name. The domain controller is responsible for all authentications and authorizations, as well as all additions, deletions, and edits within a domain. Any user that has access to a domain can log on from any computer in that domain.
What is Active Directory Replication?
Active Directory offers a method for replicating a domain controller and transferring all AD objects to another domain controller. Replication is fully automated and generally does not require any manual replication.
Most administrators won’t have any need to manually force a replication if they are only managing a handful of domains. For larger organizations, where there are hundreds of domain controllers on the network, replication errors are much more common. Administrators may need to intervene to fix replication errors or force replication when necessary.
Active Directory replication occurs across three directory partitions:
- Schema Partition – contains the object definitions and object attributes
- Configuration Partition – contains the physical layout of sites
- Domain Partition – contains the actual AD objects
Active Directory replication is needed to push changes from one domain controller to another within an organization’s network environment. It’s best to keep directory partitions synchronized across multiple domains. Replication is managed using the Knowledge Consistency Checker (KCC) which reads all configuration and connection objects.
Main Components of Active Directory Replication
Active Directory replication can be broken into four major components:
- Multimaster Replication – each domain controller receives updates for all objects that it has authority over.
- Store-and-forward Replication – balances replication load by having every domain controller communicate with a subset of DCs to transfer object changes.
- State-based Replication – domain controllers track replication updates to prevent unnecessary replication or conflicts.
- Pull Replication – domain controllers must request object changes instead of them being pushed out
What is the Repadmin tool? How does it help with Active Directory Replication?
Repadmin is a command-line tool that can help if you have issues with Active Directory replication. Starting with Windows Server 2008 and Windows Server 2008 R2, Repadmin.exe is a built-in repair utility.
Repadmin can assist you with a variety of different tasks associated with managing your domain controllers and fixing replication problems:
- Identify the Root of Replication Issues
- Provide Detailed Replication Attempt Information
- Check Queue
- Checks for KCC
- Manage Password Replication Policy (PRP)
- Force Replication
There are many more uses of Repadmin. You can get a list of the most common command line options by entering:
Repadmin /?What causes Active Directory Replication Issues?
Active Directory replication issues can be caused by numerous things. We’ll outline a few of the possible causes below:
- DNS Problems – any issues with an organization’s DNS, such as a disabled server service, zone issues, or server setting issues
- Time Synchronization Issues – if time and date are not synced between domain controllers
- Out of Disk Space – not enough disk space on a domain controller’s C drive
- Firewall Interference – replication is blocked by the firewall
- Wrong AD site topology – poorly designed topology causes errors and inefficiencies
- Corrupt Registry Keys
- Malware Infection
There are many other reasons for Active Directory replication issues, if you want to learn more, check out this list.
Note: In most cases, you should try to resolve the root cause of the replication issues, instead of forcing replication.
Can you Force Active Directory Replication?
Yes, you can force Active Directory Replication using three different methods. In most cases, Active Directory replication proceeds automatically with low latency and without issues. But sometimes you may need to force replication because of some unknown problem.
Forcing replication does not cause topology to be recalculated. Instead, it forces replication of the existing topology.
How to Force Active Directory Replication: Using GUI, Command Prompt, and Powershell
There are three options available to you if you need to force Active Directory Replication for a domain controller:
1. Using Active Directory Sites and Services
To force replication between two domain controllers, you can use the graphical user interface tool Active Directory Sites and Services. This tool is essential for larger organizations.
- Log into a domain controller and open the Active Directory Site and Services administrative tool.
- Within Active Directory Sites and Services, navigate to the intended site containing the domain controllers you want to replicate, using the left-hand pane.
- Expand through Servers until you locate the domain controller that needs to be replicated. Click on NTDS settings.
- Now on the right-hand pane, right-click on the server and select Replicate Now.
- When the replication is finished, a pop-up notification will read Active Directory Domain Services has replicated the connections. This may take up to a few minutes. Click OK.
2. Using Command Prompt
If you need to force replication quickly and you’re more comfortable with the Windows command prompt, you can use the Repadmin tool.
- Login to a domain controller. Open command prompt using Windows Search and select Run as Administrator.
- Enter this command and press Enter:
repadmin /syncall /AdeP
- When the replication is complete, you’ll see the following message:
CALLBACK MESSAGE: SyncAll Finished.
SyncAll terminated with no errors.
3. Using Powershell
You can force replication using Powershell or Powershell ISE, by following these steps”
- Log on to a domain controller. Right-click on the Windows button to open Windows Search. Type “PowerShell” into the search bar and select Run as Administrator.
- To get a list of your domain controllers, type in the following command and press Enter:
(Get-ADDomainController -Filter*).Name
- The name of your domain controllers will be listed. Now add the following command to the end of the existing command:
| Foreach-Object { repadmin /syncall $_ (Get-ADDomain).DistinguishedName /AdeP }So the entire command should be as follows:
(Get-ADDomainController -Filter*).Name | Foreach-Object { repadmin /syncall $_ (Get-ADDomain).DistinguishedName /AdeP }
- When the replication is complete, you will see the following message:
CALLBACK MESSAGE: SyncAll Finished.
SyncAll terminated with no errors.
Replicating Active Directory Successful
If you’ve followed along with this guide, you’ve learned what Active Directory is and why it’s so popular among organizations of any size. We also covered domain controllers and forests before moving on to discuss Active Directory Replication and the Repadmin tool.
Replication issues can be caused by numerous issues. You learned how to use Active Directory Sites and Services, GUI, Windows Command Prompt, and Windows Powershell to force replication.
