For SIP phones the transport protocol that CUCM actually uses (UDP, TCP, or TLS) is taken from the device’s “Phone Security Profile.”

If the phone is still assigned to a Secure profile (TLS), CUCM will attempt to signal on TCP/5061. Because the administrator changed CUCM to use UDP, the signaling ports/protocols no longer match and the phone cannot set up calls.

Assigning or editing the phone to a Non-Secure SIP Phone Security Profile whose Transport Protocol is UDP restores registration and call establishment.

A. Common Phone Profile controls soft-key, feature and firmware parameters, not signaling transport; changing it will not affect UDP/TCP/TLS selection.

B. SIP Dial Rules manipulate digit strings dialed by the user; they have no impact on SIP transport.

C. SIP Profile adjusts timers, message contents and options; the transport protocol continues to be governed solely by the phone security profile.

1. Cisco Unified Communications Manager Security Guide, Release 14, “Configure SIP Phone Security Profiles,” Table 2-1: Device Security Mode vs. Transport Protocol, pp. 2-9–2-10.

2. Cisco Unified Communications Manager Administration Guide, Release 14, “Adding a SIP Phone,” step 7: “Select the appropriate Phone Security Profile; this setting determines whether UDP/TCP (Non-Secure) or TLS (Secure) is used,” pp. 2663-2664.

3. Cisco Unified Communications Manager Security Guide, Release 12.5(1), Chapter 3 “How CUCM Determines SIP Transport,” para. 2.