Consider the following scenario:
You install a Microsoft Lync Server 2010 Front-end server on a computer that has multiple network adapters installed.
You configure the Front-end service to bind to a single specific IP address.
You configure the Front-end service to bind to another IP address that is not routable from the internal network.
You configure a Domain Name System (DNS) load balancer in this environment.
A user makes a call.
In this scenario, the call does not connect. Additionally, if the user waits for about 5 to 10 minutes, another call that is made by the user can connect successfully. Additionally, you receive the following error message in Lync Server Logging Tool:
Result-Code: 0x8007274d WSAECONNREFUSED
This issue occurs because the Lync Server 2010 DNS load balancer module incorrectly assumes that the Front-end service is bound to all the available network interfaces in the computer and all network interfaces are routable to clients.
To resolve this issue, change the order in which the network adapters are accessed by network services in the Windows network configuration. Make sure that the network adapter that the Front-end service is bind to has the highest priority, and then install either of the following cumulative updates:
2670430 Description of the update for Lync Server 2010: February 2012
2670352 Description of the cumulative update for Lync Server 2010: February 2012
For more information about DNS load balancing in Lync Server 2010, visit the following Microsoft website: