Hi All,

2 days back we found that People Picker is not working for the entire farm.
Same issue happened last week in our UAT server which has same AD and it automatically resolved within couple of hours.    Referred to following URLs
http://blogs.msdn.com/b/svarukala/archive/2014/03/26/issue-with-peoplepicker-searchadforests-stsadm.aspx
From the Blog:

STSADM.exe -o setproperty -pn peoplepicker-searchadforests -pv "domain:aaa.com; domain:bbb.com; domain:ccc.com;domain:ddd.com" -url http://webappurl

After running the above command you can check the property settings using below command:

STSADM.exe -o getproperty -pn peoplepicker-searchadforests -url http://webappurl We have only ONE AD domain.
Q: Do have to run this command for all web applications?  
https://technet.microsoft.com/en-us/library/gg602075.aspx?f=255&MSPPError=-2147217396  

Q: Could it be Network or AD issue?
Any help would be appreciated.     &nb

You'll want to set the ULS logging to Verbose, then attempt to query for a user via the People Picker. From there, you can start diagnosing the issue.

Are there any firewalls/routers between SharePoint and the Active Directory Domain Controllers?

Can you telnet to domain controller through port 389 or 636 from your SharePoint WFE server? Are trust scenario consistent between domains?