Active Directory Health Check
        Active Directory helpful Command         Events View     Check event log in all DCs to find everything ok specifically DNS, system and Application events.     Dcdiag.exe     This is a must and will always tell you if there is trouble with DCs and/or services associated with it     Netdiag.exe     This will let me know if there are issues with the networking portion on the DC.     Netsh dhcp show server     This command identify DHCP in in AD infrastructure.     Repadmin /showreps     This shows all replication among DCs.     repadmin /replsum /errorsonly  reapadmin /syncall /AdeP     This will identify any issues with replication among DCs.   Active Directory DNS Check     Dnslint /ad domain_controller_ip_address /s dns_server_ip_address        Reference ..