Does anyone know what 'VoIP Call Failure of "Unknown" (Error Code 1) occurred on Client 'xx:xx:xx:xx:xx:xx'. Each VoIP handset gets hundreds of these Information Events each day.  I am trying to determine if this is an issue with my wireless handsets...

Hi all, I have been searching endlessly for some kind of subscription model video training or up-to-date published books for CCNP wireless.  Can anyone recommend some study material for the 4 exams besides the White papers on the Cisco website.   Tha...