What is the common reason for using telnet to troubleshoot AD Sync?

Using telnet to troubleshoot Active Directory Synchronization is primarily focused on confirming connectivity to the LDAP (Lightweight Directory Access Protocol) port. LDAP is essential for directory services, including user authentication and directory lookups in an Active Directory environment. When synchronization issues arise, it’s critical to verify that the server can communicate properly with the Active Directory by checking if the LDAP port (typically 389 for standard LDAP and 636 for LDAPS) is accessible.

By utilizing telnet to connect to the LDAP port, technicians can quickly identify if network issues or firewall restrictions are preventing the synchronization process. If the connection attempt is successful, it indicates that the basic network connectivity to the AD server is functional, allowing further investigation into potential misconfigurations or other issues that might be affecting sync.

In contrast, checking disk space on a Domain Controller or analyzing user permissions does not directly address connectivity issues related to AD sync. While viewing security logs can provide valuable insights into events and actions taken within Active Directory, it doesn't specifically confirm the operational capability to sync data—hence, they are not the common reason for using telnet in this context.