Existing registered phones all work fine. They can make and receive calls, speed dials work etc. However adding new phones or if an existing phone is reset, they do not register. The phone displays a spinning icon with the word ”Registering”. When you do a debug ephone register and debug tftp events, you only see the tftp debugs come through and no debug logs for ephone register.

This is caused by the SCCP listening socket being shutdown under the telephony-service menu. By default on the UC 560 and other versions of CME, the SCCP listening socket is enabled by default. However if shutdown, phones are unable to register, however existing registered phones maintain their operations.

Resolve the issue by entering the below commands. The confirm you start seeing debug messages for ephone register.

Commands

(config)#telephony-service
(config-telephony)#no shutdown

NOTE: This post also relates to all Cisco CME versions.