What should Ivan verify before implementing Azure AD DS with a custom domain?

Before implementing Azure Active Directory Domain Services (Azure AD DS) with a custom domain, verifying that the Azure AD service is running and synchronizing is crucial. This step ensures that all necessary user accounts and directory information from Azure AD are in place and up to date, which is essential for the successful deployment of Azure AD DS.

Azure AD DS relies on Azure AD for identity and directory services, so it's important that the synchronization processes are functioning correctly. If the Azure AD service is not running or is not synchronizing properly, it could lead to issues with user authentication and access to resources once Azure AD DS is deployed. Ensuring that the service is operational and synchronized means Ivan can have confidence that the user accounts and policies will function as intended in the new environment, leading to a smoother transition to Azure AD DS.

In contrast, while migrating user accounts is important, it doesn't directly impact the initial setup of Azure AD DS with a custom domain. Ensuring that on-premises backups are completed, or firewall settings are configured properly, may be relevant but do not specifically address the prerequisite condition of having the Azure AD service running and in sync, which is critical for the successful implementation of Azure AD DS.