Sure you have run DCDIAG before, but do you know what it actually does?
Here’s the DCDIAG syntax:
dcdiag /test:DNS [/DnsBasic | /DnsForwarders | /DnsDelegation | /DnsDynamicUpdate | /DnsRecordRegistration | /DnsResolveExtName [/DnsInternetName:<InternetName>] | /DnsAll] [/f:<LogFile>] [/x:<XMLLog.xml>] [/xsl:<XSLFile.xsl> or <XSLTFile.xslt>] [/s:<DomainController>] [/e] [/v]
I usually run DCDIAG with the following switches to check the health of a DC:
DCDIAG /c /v /f:c:\DCDIAG.Log
- /v: Provides verbose logging displaying additional information on what is being tested and the result.
- /c: Performs a comprehensive suite of tests.
- /a: Test all DCs in the site. This is useful if your local Exchange team thinks something is going on with the DCs since Exchange is acting up.
- /e: Tests ALL the DCs in the enterprise. Use with caution.
Here’s an excellent in-depth post on DCDIAG and what happens behind the scenes when running it: