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.
There are no specific requirements for this document.
This document is not restricted to specific software or hardware
Technical Tips Conventions for more information on document
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
command, as described in
Support for Virtual Interfaces. Ensure that you use this loopback IP
address when you
the Cisco IOS H.323 gateway.
on the gateway.
This command is documented in
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
See the "Related Information" section for additional solutions and
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
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
Open the Cisco CallManager Administration page.
Choose Device > Gateway.
Select the Gateway and open the Gateway Configuration
Click in the Media Termination Point Required
Click Reset Gateway for the changes to take
For more information on Media Termination Points and their
configuration in Cisco CallManager, refer to the
Termination Point Configuration section of
CallManager Administration Guide, Release 4.1(3).