First of all, monitoring the Windows Event Viewer is a must. Take the time to check through all of the Event Log queues including the Application, Security and System log. On Domain Controllers the DFS Replication, Directory Service and DNS Server logs should also be reviewed. Leverage the sort and error fields to filter out the information you don’t need to see.
Next, run command line diagnostics and pipe the results to a text document for in-depth review. This allows you to analyze the results in detail and compare results after you’ve fixed any issues you identify. Its also much easier to read the logs in aNotePad++ window and search for events then trying to dig through command line output.
The following reports can be ran from the Windows command prompt:
This report will identify issues with domain controllers and any services associated with them:
C:\>dcdiag.exe /v >> c:\pre_dcdiag.txt
This test will assess the health of DNS services, records and entries for the entire Enterprise.
C:\>dcdiag.exe /Dnsall >> c:\pre_dnsdiag.txt
Net Diag will identify problems with network components and configuration. Note that this tool has been depreciated in Windows 2008 but can still be used in compatibility mode.
C:\>netdiag.exe /v >> c:\pre_netdiag.txt
This command, ran within netsh, will show the status of the local DHCP server.
C:\>netsh dhcp show server >> c:\pre_dhcp.txt
This command will show the status of inter-domain replication and wether or not it is successful. Be aware that DC’s holding the global catalog role will return additional information:
C:\>repadmin /showreps >> c:\pre_rep_partners.txt
A more exhaustive report can be ran using:
C:\>repadmin /replsum /errorsonly >> c:\pre_repadmin_err.txt
Once you have ran your reports, analyze them then re-run the checks and pipe the output to post_ rather than pre_, for example:
C:\>dcdiag.exe /v >> c:\post_dcdiag.txt
Don’t forget about you member servers. Whilst your Domain Controllers, Global Catalog and Operations Master (FSMO) role holders are the heart of your Active Directory domain, member servers provide services and information to your user. At a minimum you should be running a AD Health Check once per week and a Event Log assessment on your Member Servers at least once a fortnight.