On a Cisco Unified Communications Manager SIP trunk with a single remote device and OPTIONS ping feature enabled, which response from the SIP remote peer causes the trunk to be marked as "Out of Service"? 

Answer options:

A. 401 Unauthorized
B. 505 Version Not Supported
C. 406 Not Acceptable
D. 408 Request Timeout
E. 500 Server Internal Error

D

408 Request Timeout Couldn`t find the user in time. The server could not produce a response within a suitable amount of time, for example, if it could not determine the location of the user in time. The client MAY repeat the request without modifications at any later time References: http://en.wikipedia.org/wiki/List_of_SIP_response_codes