With Cisco CallManager, you might experience a one-way voice issue after you transfer a call or place a call on hold, if the H.323 endpoint that is configured on the CallManager is a FastEthernet subinterface of the gateway. This occurs especially when music on hold (MOH) is enabled.
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The IP phone sends Real-Time Transport Protocol (RTP) packets to the wrong IP address after it resumes a transferred or on-hold call.
Complete these steps in order to solve the problem:
On the gateway, configure a loopback interface and the h323-gateway voip bind srcaddr ip_address command, as described in H.323 Support for Virtual Interfaces. Ensure that you use this loopback IP address when you configure the Cisco IOS H.323 gateway.
Globally configure voice rtp send-recv on the gateway.
This command is documented in Cisco IOS Voice, Video, and Fax Commands: Si through Z.
Verify that you have selected correct MOH codecs in the service parameters for Cisco IP Voice Media Streaming Applications.
See the Related Information
When you use Cisco CallManager with an H.323 gateway, you might experience one-way voice after you transfer the call or put the call on hold or conferencing followed by the error message no mtp resources available.
This problem can occur if the Media Termination Point Required checkbox in the gateway configuration page is not checked. Complete these steps in order to check Media Termination Point Required:
Open the Cisco CallManager Administration page.
Choose Device > Gateway.
Select the Gateway and open the Gateway Configuration page.
Click in the Media Termination Point Required checkbox.
Click Reset Gateway for the changes to take effect.
For more information on Media Termination Points and their configuration in Cisco CallManager, refer to the Media Termination Point Configuration section of Cisco CallManager Administration Guide, Release 4.1(3).
- TAC Case Collection - Solution K10611272 (How to resolve one-way and no-way audio problems)
- TAC Case Collection - Solution K15163588 (One-way audio is experienced when cRTP is configured)
- Troubleshooting One Way Voice Issues
- Services - Cisco CallManager
- Voice Technology Support
- Voice and Unified Communications Product Support
- Troubleshooting Cisco IP Telephony
- Technical Support & Documentation - Cisco Systems
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