Assume that a user makes a PSTN call by using a Microsoft Lync 2010 client. The Outbound Routing (OBR) component does not receive a response that is between 180 and 183 from the first gateway within 10 seconds. In this situation, the OBR component on the Lync Server 2010 server does not route the PSTN call to other gateways.
This issue occurs because a Mediation server sends back a response that is between 180 and 183 for non-bypass calls when the Mediation server retrieves the INVITE message from the OBR component. The response stops the 10 second OBR call timer that is used to detect unresponsive gateways.
To resolve this issue, install the following cumulative update:
2592293 Description of the cumulative update for Lync Server 2010, Mediation Server: August 2011
Note After you apply this update, an ms-mediation-generated header is added to the response. The OBR component does not stop the 10 second call timer when the header is detected.
For more information about Lync Server 2010 Outbound Routing, visit the following Microsoft website: