PSTN call is disconnected in Lync 2013 when you enable the media bypass setting


Consider the following schenario:

  • You enable the media bypass setting in a Microsoft Lync Server 2010 or Lync Server 2013 environment.

  • A user signs in to Microsoft Lync 2013.

  • The user makes a call to a public switched telephone network (PSTN) telephone that is connected to version 8.6 of Cisco Unified Communications Manager (CUCM).

In this situation, the call is disconnected.


This issue occurs becauseĀ a 151 kilobits per second (Kbps) value of bandwidth is required by G.711 u-Law. Therefore, when a call is in an environment in which bandwidth is less than 151 Kbps, media manager sets the bandwidth to 151 Kbps incorrectly.


To resolve this issue, install the following update:

2889929 October 2014 update for Lync 2013 (KB2889929)

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