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Service Parameters “Block Offnet To Offnet Transfer” For Toll Fraud

Frequent Contributor

A call coming from an external PSTN is classified as an OffNet. A call that is placed internally (from one phone to another, or between two CUCMs clusters, where the call is routed over the WAN) is classified as an OnNet. When you are using AAR in OnNet or OffNet implementations, it is important to know the source of the call. With AAR, the source can be the WAN connection or the PSTN connection.

When the call is routed over the WAN connection, the call is classified as an OnNet at the called site. If AAR reroutes the call over the PSTN, the call is classified as an Offnet call at the called site.

Gateway and trunks can be configured as OnNet (internal) or OffNet (external by using gateway configuration, using trunk configuration, or setting a clusterwide service parameters to classify devices. This parameter can be set in the Service Parameter Configuration page. When the feature is used with the clusterwide service parameter Block OffNet to OffNet Transfer, the configuration determines if calls can transfer over a gateway or trunk.

The following devices can be configured as internal and external to Cisco Unified Communication Manager.


  • H.323 gateway
  • MGCP FXO trunk
  • MGCP T1 or E1 trunk
  • Intercluster trunk
  • SIP trunk

To classify a call as OnNet or OffNet, you can set the Call Classification field in the Route Pattern Configuration page. You can override the route pattern setting and use the trunk or gateway setting by checking the Allow Device Override check box in the Route Pattern Configuration page.

By setting the devices as OffNet, you can restrict the transfer of an external call to an external device and thus help prevent toll fraud.

Assume that you are an employee (Office Phone 1 or Office Phone 2), and friend located in New Yorke (NY-Phone) want to place a call to a destination in United Kindom.

First you call your the NY-Phone from your office phone and then transfer the call to the destinatiion in United Kindom.

This behavior means that both PSTN calls are outbound and OffNet that the enterprise established and are therefore charged to the enterprise.

By default the OffNet to OffNet transfers are allowed, to prevent this behavior and toll fraud, the service parameter Block OffNet to OffNet Transfers should be be turned on.




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