A Read-Only Domain Controller (RODC) is a type of domain controller in Active Directory that provides a subset of the domain’s directory services. As the name suggests, an RODC is read-only, meaning it cannot be used to make changes to the domain’s directory. Instead, it is primarily used to provide domain services to branch offices or other remote locations where a full domain controller may not be practical or secure.
RODCs are designed to be used in environments where security is a concern, as they can help to prevent the spread of malware or unauthorized access to sensitive domain information. They also help to reduce the administrative overhead of managing a full domain controller in a remote location.
Here are some of the key features and benefits of RODCs:
- Reduced attack surface: Because RODCs are read-only, they cannot be used to modify the domain’s directory services. This helps to reduce the risk of malicious attacks that could compromise the security of the domain.
- Credential caching: RODCs can cache user credentials, which can help to improve login times and reduce the load on the WAN link.
- Password replication policies: Administrators can configure password replication policies to control which user passwords are cached on the RODC. This can help to prevent password-based attacks and limit the impact of compromised credentials.
- Unidirectional replication: By default, RODCs only replicate changes from the hub site to the branch office. This helps to prevent unauthorized changes from being made at the branch office and ensures that the RODC always has the latest domain information.
To install and configure an RODC, you can follow these general steps:
- Install the Windows Server operating system on the hardware or virtual machine that will serve as the RODC.
- Join the server to the domain.
- Install the Active Directory Domain Services (AD DS) role on the server.
- Run the AD DS Configuration Wizard to promote the server to a domain controller.
- Select the Read-Only Domain Controller option and follow the prompts to configure the RODC.
- Configure the password replication policies for the RODC.
- Configure any other settings or options as needed for your specific environment.
Here are some examples of PowerShell commands that can be used to manage RODCs:
- Install-WindowsFeature -Name AD-Domain-Services -IncludeManagementTools This command installs the AD DS role and management tools on a Windows Server that will be used as an RODC.
- Install-ADDSDomainController -DomainName “contoso.com” -SiteName “Site-1” -InstallDNS:$true -ReadOnlyReplica:$true This command promotes a Windows Server to an RODC in the Site-1 site of the contoso.com domain and installs DNS.
- Get-ADReplicationSite -Filter “Name -eq ‘Site-1′” | Set-ADSite -ReplicationSchedule “Daily 4:00 AM-5:00 AM” This command sets the replication schedule for the Site-1 site to occur daily from 4:00 AM to 5:00 AM.
- Get-ADReplicationSiteLink -Filter “Name -eq ‘SiteLink-1′” | Set-ADReplicationSiteLink -ReplicationSchedule “Never” This command sets the replication schedule for the SiteLink-1 site link to never replicate.
Overall, RODCs are a powerful tool for improving the security and efficiency of Active Directory in branch office or remote locations. With careful planning and configuration, they can provide a secure and reliable way to extend domain services to these locations while minimizing the risk of compromise or data loss.
