About AAR Group Setup
In Cisco Unified Communications Manager Administration, use the menu path to configure AAR groups.
Automated alternate routing (AAR) provides a mechanism to reroute calls through the PSTN or other network by using an alternate number when Cisco Unified Communications Manager blocks a call due to insufficient location bandwidth. With automated alternate routing, the caller does not need to hang up and redial the called party. The AAR group represents the dialing area where the line/directory number (DN), the Cisco voice mail port, and the gateway are located.
For each AAR group, you enter the prefix digits that are used for automated alternate routing within the AAR group, as well as the prefix digits used for automated alternate routing between a given AAR group and other AAR groups. Devices, such as gateways, phones (by means of directory numbers), and trunks, associate with AAR groups. If automated alternate routing of calls takes place, you may also associate devices with an AAR calling search space.
For AAR to function, you must configure AAR groups and also ensure that the Automated Alternate Routing Enable clusterwide service parameter is set to True. (The default value for this service parameter specifies False.)