Refer to the exhibit.

The exhibit shows an outgoing SIP 401 response message from Cisco Unified Communications
Manager to a SIP VoIP service provider gateway. Which action can the Cisco Unified
Communications Manager systems administrator use to change the response to “200 OK”?

A.
Make sure the gateway IP address of the SIP VoIP service provider is defined correctly in Cisco
Unified Communications Manager SIP trunk.

B.
Enable OPTIONS ping on Cisco Unified Communications Manager SIP trunk.

C.
Disable OPTIONS ping on Cisco Unified Communications Manager SIP trunk.

D.
Create an SIP response alias to force outgoing 401 messages to “200 OK”.

E.
Disable digest authentication on Cisco Unified Communications Manager SIP trunk.

Explanation:
Because Right now CUCM challenges the identity of a SIP user agent and must configure digest
credentials for the application user in CUCM or you have to disable it for stop challenging by CUCM.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/security/9_0_1/secugd/CUCM_BK_C
CB00C40_00_cucm-security-guide-90/CUCM_BK_CCB00C40_00_cucm-securityguide_chapter_011010.html