This series of interactive documents uses a typical head office and branch office in order to demonstrate some common voice network configurations. This interactive diagram allows you to view network configurations:
| This image is interactive! |
Click a component to view configuration
and troubleshooting information.
Refer to Unified CallManager Interactive Voice Network Configuration and Troubleshooting Case Study for requirements assumed by this series of interactive documents.
In order to configure CAC, complete these steps:
- Configure Locations and Bandwidth
- Configure an Alternative Automatic Rerouting (AAR) Group
- Enable AAR in Unified CallManager
- Configure AAR Calling Search Space on the IP Phones
- Ensure that IP Phones Contain an External Phone Number Mask
Note: AAR uses the prefix configured under the AAR group and the external phone number mask of the destination phone in order to construct the full E164 number.
For example, if phone 1 (5005) calls remote phone 2 (4002), phone 1 uses prefix 91, as configured under the AAR group, and adds it to the mask for the remote phone, which is 9195014002. The number becomes 919195014002.
Make sure that you do not include the long distance digit (1) in the external phone number mask; otherwise, the number is included as part of the caller ID.
Configure Locations and Bandwidth
Configure locations and bandwith per remote location as described in this section.
- Click System > Location > Add a New Location.
- Configure the location as shown in this image:
This example uses the default location of None for the San Jose head office. The bandwidth for the head office is left at default and unlimited. For the remote location (RTP), this example configures a location Remote.
Note: This example configures a bandwidth of 48 kbps, which allows 2 x G.729 call over the WAN. This does not include Layer 2 overhead. For information on how different codec use different bandwidth values, refer to the Call Admission Control chapter of the Cisco Unified Communications SRND Based on Cisco Unified CallManager 4.x.
Configure an Alternative Automatic Rerouting (AAR) Group
In order to configure an AAR group, complete these steps:
- Click Route Plan > AAR Group > Add a New AAR Group.
- Configure the group as shown in this image:
Note: The AAR Group name is assigned to directory numbers for each IP phone. The prefix nine (9) is used for external calls, and one (1) is used for long distance numbers in the United States.
Enable AAR in Unified CallManager
By default, AAR is disabled in Unified CallManager. You must enable AAR in order to perform PSTN rerouting during congestion.
In order to enable AAR, complete these steps:
- Click Service > Service Parameters > CallManager.
- Select True from the Automated Alternate Routing Enable drop-down list.
Configure AAR Calling Search Space on the IP Phones
For each IP phone, ensure that you configure a Calling Search Space for AAR and assign the directory number (DN) to the AAR group as shown in these images:
Ensure that IP Phones Contain an External Phone Number Mask
Ensure that IP phones contain an external phone number mask that contain the full E164 number (for example, 4085015005).
In order to verify the AAR configuration, place two phone calls from one site. (For this example, place two calls from San Jose to RTP). The first two calls are still within our bandwidth limitation and will traverse the WAN link. However, a third call should be rerouted via PSTN. This is indicated by this message that appears on the calling phone:
"Network Congestion, Rerouting..."
Note: This message can be changed in the Unified CallManager service parameters. If the call does not succeed, review the procedure described in this document. The most common reasons that AAR calls fail is because AAR is not enabled within the Unified CallManager service parameters or the incorrect partitions are configured within the AAR Calling Search Space. The AAR Calling Search Space should contain partitions that include route groups that point to gateways that are local to the calling site.
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