Question

A newly deployed Cisco 8865 SIP phone fails to register with CUCM. Packet captures show the phone sends its REGISTER over UDP to port 5060, but CUCM never responds. Other phones in the same cluster register successfully. The phone's device configuration in CUCM uses a Device Security Profile named 'Non Secure SIP Profile - TCP'. What is the most likely cause of the registration failure?

Accepted Answer

The Device Security Profile specifies TCP transport, but the phone is attempting to register over UDP, causing a transport mismatch

Answer

The phone firmware does not support SIP and must be downgraded to SCCP

Answer

CUCM only accepts SIP registrations on TCP port 5061 for non-secure profiles

Answer

The phone is missing a digest credential, so CUCM silently drops the REGISTER