Inbound calls to internal branch users fail when WAN connection is unavailable


When a WAN connection to a central site is unavailable, the inbound calls to internal branch users fail. When the WAN connection becomes available, full functionality is restored to the branch site users.

For example, consider the following scenario:
  • You configure the branch site survivable branch appliance (SBA) with an Edge server for media relay.
  • A user signs in to the branch office.
  • You interrupt WAN connectivity between the central site and the branch.
  • You place an inbound call to the branch user.

In this scenario, the inbound call fails.


When the WAN connection goes down, the Mediation server can't reach the media relay. The Mediation server tries to resolve the media relay FQDN so that it can set the list of media relay IP addresses. If DNS resolution of the media relay FQDN fails, or if the media relay can't be contacted, the Mediation server raises an API exception, and the media session fails. 


To resolve this issue, install the April 2016 cumulative update 5.0.8308.956 for the Lync Server 2013, Mediation Server on the SBA. This allows inbound calls to proceed without media relay candidates.

More Information

Check with the SBA vendor for the latest available cumulative update for your model and the required upgrade method.

Article ID: 3174893 - Last Review: Jun 29, 2016 - Revision: 1