Incoming calls from a PSTN to a IP Phone by way of MGCP or a Skinny gateway get disconnected

[TCC_2]

Core Issue

Incoming calls from a Public Switched Telephone Network (PSTN) to a Cisco IP Phone by way of a Media Gateway Control Protocol (MGCP) or a Skinny gateway could fail with any of these symptoms:

• Busy tone: By default, call waiting is enabled on the Cisco IP Phones. Cisco CallManager returns a busy signal to the caller if there are two calls on the same line appearance and no forwarding destination has been configured or if the forwarded destination is unavailable. Check or configure a forwarding destination for the phone in question. Also check the availability of the forwarded destination.
  • Wrong destination: The call might reach a wrong destination if the called phone has call forwarding configured and this information is not synchronized with the Structured Query Language (SQL) database. If the call is directed to a wrong destination, refer to the Resolution section.
• Reorder tone or without any tone: The resolution describes the problem. For more information, refer to One-way voice or failed call connections for inbound calls from the PSTN to Cisco CallManager through a Cisco IOS MGCP gateway.

Resolution

If you have a reorder tone or are without any tone, perform these steps:

1. Check the registration status of the gateway in the Cisco CallManager.
2. In the gateway configuration screen of Cisco CallManager, verify that the number of significant digits mentioned correspond to the number of digits in your dialing plan.
3. If the called Cisco IP Phone is in a partition, then the most common reason for receiving reorder (fast busy) is that the calling party does not have the rights to call the called party. In the case of calls from the PSTN, the Calling Search Space (CSS) that the gateway belongs to must include the partition of the called party. For more information on CSSs and partitions, refer to Understanding and Using Partitions and Calling Search Spaces with Cisco CallManager.
4. If the incoming circuit is an analog Foreign Exchange Office (FXO) port, then ensure the port direction is set to either inbound or both ways.
5. Also try resetting the gateway and the Cisco IP Phone.
6. If none of these steps resolve the issue, follow the procedure for setting up traces described in Set Up Cisco CallManager Traces for Cisco Technical Support and capture the failed call. These traces could be presented to the Cisco TAC for further analysis.