Question

A newly deployed Cisco IP Phone 8865 is configured for SIP and set to use DNS to locate its call-processing servers. The phone completes DHCP, obtains an IP address, and downloads its configuration file from TFTP, but it fails to register. Packet captures show the phone sending SIP REGISTER messages to an IP address that does not match any CUCM node, and the registrations time out. The CUCM group and device pool are correctly configured on the cluster. What is the most likely cause of the registration failure?

Accepted Answer

The DNS SRV or A record used to resolve the CUCM server name is missing or resolving to an incorrect address

Answer

The phone firmware load specified in the device configuration is incompatible with the 8865 model

Answer

The phone's device security profile is set to Encrypted instead of Non-Secure

Answer

The SIP dial rules assigned to the phone are preventing outbound REGISTER messages