Before diving into the error, let’s recap the tool. Cisco IP Communicator (version 7.0, 7.1, 8.6) is a software-based application that mimics the hardware Cisco Unified IP Phones (like the 7975 or 7965). It uses Session Initiation Protocol (SIP) or Skinny Client Control Protocol (SCCP) to register with a Cisco Unified Communications Manager (CUCM).