Class of Restrictions(COR)

Class of Restrictions (COR) is a Cisco voice gateway feature that enables Class of Service (COS) or calling privileges to be assigned. It is most commonly used with Cisco Survivable Remote Site Telephony (SRST) and Cisco CallManager Express but can be applied to any dial peer.

The COR feature provides the ability to deny certain call attempts based on the incoming and outgoing CORs provisioned on the dial-peers. COR is required only when you want to restrict the ability of some phones to make certain types of calls but allow other phones to place those calls.

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.

If the COR applied on an incoming dial-peer (for incoming calls) is a super set or equal to the COR applied to the outgoing dial-peer (for outgoing calls), the call goes through. Incoming and outgoing are terms used with respect to the "voice ports". COR is often described as a lock and key mechanism. Locks are assigned to dial peers with an outgoing COR list. Keys are assigned to dial peers with an incoming COR list.

For example, if you hook up a phone to one of the Foreign Exchange Station (FXS) ports of the router and try to make a call from that phone, it is an incoming call for the router/voice-port. Similarly, if you make a call to that FXS phone, then it is an outgoing call.

By default, an incoming call leg has the highest COR priority and the outgoing COR list has the lowest COR priority. This means that if there is no COR configuration for incoming calls on a dial-peer, then you can make a call from this dial-peer (a phone attached to this dial-peer) going out of any other dial-peer, irrespective of the COR configuration on that dial-peer.
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