The Test-CsPstnPeerToPeerCall synthetic transaction does not run through a NET gateway successfully in a Microsoft Lync Server 2010 deployment.
This issue occurs because the volume value of the dual tone multi-frequency (DTMF) digits is too low. Therefore, the DTMF digits that are sent through the NET gateway cannot be recognized by the client.
To resolve this issue, install the following cumulative update:
2514981 Description of the cumulative update for Lync Server 2010, Core Components: November 2011
Note After the update is installed, the volume value of the DTMF digits increased from -32dB to 10 dB.
For more information about the Test-CsPstnPeerToPeerCall command, visit the following Microsoft website: