Call Forwarding Calling Search Spaces
A directory number (DN) configuration include various call forwarding operations which can be restricted using calling search that are different than those used at the directory number of phone configuration levels. If a calling search space is not chosen for a call forwarding operation, the forwarded call may fail. The first configuration item in the Call Forward and Call Pickup Settings configuration of a directory number is the Calling Search Space Activation Policy. Beware that this configuration item only applies to call forward all (CFA) and not any of the other call forwarding operations. The activation policy is initially set to Use System Default, but can be configured with either of the following:
- With Configured CSS
- With Activating Device/Line CSS
The Use System Default operation in Cisco Unified Communications Manager (CUCM) indicates that there is a service parameter configuration that controls the setting for each server. The CFA CSS Activation Policy setting is set to With Configured CSS by default. It can be changed to With Activating Device/Line CSS if desired. The With Configured CSS explicitly uses the Forward All CSS and Secondary Calling Search Space for Forward All CSS configurations. All call forwarding fields are set to
by default which indicates all forwarded calls will fail by default unless the CSS is explicitly configured for each call forwarding operation. The call forward all field indicates two calling search space options to accommodate the line/device CSS deployment approach. If using the line/device approach, configure the Forward All CSS to match the line CSS and the Secondary Calling Search Space for Forward All to the device CSS. It is recommended to configure a CSS on CFA that does not include long distance or international patterns to avoid toll fraud situations (requirements may vary). All other call forwarding fields use the With Configured CSS option and the default operation cannot be changed. Each call forwarding operation will have to have a CSS configured with the traditional CSS approach to allow call forwarding operations. Most of the following call forwarding fields are identified by Internal or External to indicate whether the CUCM call classification feature classified the call as OnNet (internal) of OffNet (external). All calls received from a gateway are classified as OffNet by default. The internal and external options allow the organization to forward calls differently dependent on whether the call was from an external or internal customer. The call forwarding fields include the following:
- Call Forward Busy (CFB)
- Call Forward No Answer (CFNA)
- Call Forward No Coverage (CFNC)
- Forward on CTI Failure
- Call Forward Unregistered (CFUR)
For more information, read the Call-Forward Calling Search Spaces section of the CUCM 7.x SRND Dial Plan chapter: http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/6x/dialplan.html. We’ll have some more fun with calling search spaces in the next blog. There are plenty of conversations we can have on this topic.
