To determine the appropriate procedure, first determine whether it is desirable to block unwanted calls based on Automatic Number Identifier (ANI), or Dialed Number Identification Service (DNIS) information, or both. Then, make sure to consider any limitations of the gateway being used.
If an H.323 gateway is used, incoming calls can be blocked based on ANI and DNIS information through translation rules on the gateway configuration.
If a Media Gateway Control Protocol (MGCP) gateway (controlled by Cisco CallManager) is used, the only way to block unwanted calls is based on the DNIS information. This is accomplished through translation patterns in the Cisco CallManager configuration.
An x-lation pattern in Cisco CallManager must be created to match the inbound DNIS information (called party number). Then, the gateway in Cisco CallManager must be configured to have a Content Services Switch (CSS) with access to this x-lation pattern first, based on the x-lation pattern partition. Give the x-lation pattern a CSS that has access to NOTHING. This sends the call nowhere, and the calling party receives a reorder tone.
Note: This method of blocking calls can only be accomplished based on the DNIS information (called party number) and not on the ANI (calling party number) information.
To block calls in the same manner at the Cisco CallManager level, use translation patterns. To do this, the DNIS or called number can be specified in a route pattern, then applied to the gateway. In this case, the "knob" that is used to block the call is the Route or Block this pattern option.
Note: This can only block unwanted calls based on DNIS information and not on the ANI information.