You need to identify all of the authentication requests that originate from client computers that are not associated to an Active Directory subnet

Your network contains an Active Directory forest named contoso.com. The functional level of
the forest is Windows Server 2008 R2.
You have four Active Directory sites. Each site has multiple Active Directory subnets.
You need to identify all of the authentication requests that originate from client computers
that are not associated to an Active Directory subnet.
What should you use?

A.
The %Systemroot%\System32\Network_llu.log log file

B.
The %Systemroot%\Debug\Netsetup.log log file

C.
The Authentication User Interface operational log

D.
The %Systemroot%\Debug\Netlogon.log log file

Explanation:
Identifying Whether You Have a Problem Authenticating
You can identify whether you have a problem authenticating (or joining) a computer to a
domain by verifying that the local workstation is working. Do this by running the Netdiag tool.
Read the output from the top, and look for the words “ERROR” or “FATAL.” (Many failures

are not relevant to the domain itself; but you should follow up on them because they involve
network connectivity issues.) If you don’t find these words in the output, continue as follows:
Run netdiag /v (verbose mode). Do you receive any specific error messages or FATAL
errors?
If the answer to the preceding question is “No,” run netdiag /debug. Do you receive any
specific error messages or FATAL errors?
If Netdiag displays an error or failure with the domain itself, check the % SystemRoot
%\debug\netsetup.log file for join errors.