Can't transfer files to legacy Office Communicator clients from a Windows 10 computer with multiple network adapters

Symptoms

Assume that you're using the Microsoft Skype for Business 2016 client on a Windows 10 computer that has multiple network adapters. When you try to transfer a file to a legacy Office Communicator client, the file transfer fails.

Cause

The changes in Windows 10 expose an issue that affects the IP address selection logic that's used by the legacy file transfer process.

Resolution

Important

Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

To fix this issue, install the September 1, 2020, update (KB4484501) for Microsoft Skype for Business 2016.

To enable this fix, create a policy by using one of the following options:

• Create the following registry key on the client computers:
  
  Root: HKEY_LOCAL_MACHINE or HKEY_CURRENT_USER
  Subkey: Software\Policies\Microsoft\Office\16.0\Lync
  Value Type: DWORD
  Value Name: EnableGetSuitableIPWithMultipleAdapters
  Value Data: 0x00000001
  
  

• Create the following client policy entry by using the Skype for Business PowerShell:
  
  $x = New-CsClientPolicyEntry -Name "EnableGetSuitableIPWithMultipleAdapters" -Value "true"
  
  Set-CsClientPolicy -Identity "<ClientPolicyName>" -PolicyEntry @{Add=$x}