"SIP/2.0 504 Cannot connect to gateway" error message when a PSTN call is routed to a Mediation server in Lync Server 2010

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Article ID: 2539642 - View products that this article applies to.
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Consider the following scenario:
  • In a Microsoft Lync Server 2010 environment, more than one Mediation server and a Public Switched Telephone Network (PSTN) gateway are deployed. The Mediation servers are configured to use dual network adapters.
  • A Mediation server cannot connect to the PSTN gateway because of a network issue that is specific to the Mediation server.
  • You call a PSTN number by using Lync 2010.
  • The call is routed to the Mediation server.
In this scenario, the Outbound Route application in Lync Server 2010 does not route the calls to a different Mediation server. Additionally, the Mediation server returns the following error:

SIP/2.0 504 Cannot connect to gateway. Socket error: TimedOut


To resolve this issue, install the following cumulative update:
2502810 Description of the cumulative update for Lync Server 2010, Mediation server: April 2011


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Article ID: 2539642 - Last Review: June 21, 2011 - Revision: 2.0
  • Microsoft Lync Server 2010 Enterprise Edition
  • Microsoft Lync Server 2010 Standard Edition
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