i have two Cisco IP phones behind CCME, the first is logged with extension mobility and take a number, and he other is not logged and takes another number.
COR is used to specify which incoming dial-peer can use which outgoing dial-peer to make a call. Each dial-peer can be provisioned with an incoming and an outgoing COR list. The corlist command sets the dial-peer COR parameter for dial-peers and the directory numbers that are created for Cisco IP phones associated with the Cisco CallManager Express router. COR functionality provides the ability to deny certain call attempts on the basis of the incoming and outgoing CORs that are provisioned on the dial-peers. This functionality provides flexibility in network design, allows users to block calls (for example, calls to 900 numbers), and applies different restrictions to call attempts from different originators.
Configuring class of restriction is given briefly in this document.