Lync 2013 (Skype for Business) connects through the DirectAccess tunnel when you connect to an external network

To fix this issue, use one of the following methods:

For Lync 2013 (Skype for Business) MSI clients

To fix this issue, apply the following update: This issue is fixed in build 15.0.4867.1000 and later builds.

For Skype for Business 2016 MSI clients

To fix this issue, apply the following update:This issue is fixed in build 16.0.4442.1000 and later builds.

After you install the update, you can set a registry as follows if you still prefer internal network:

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 restorationin case problems occur.

1. Start Registry Editor:
   • In Windows 10, go to Start, enter regedit in the Search Windows box, and then select regedit.exe in the search results.
   • In Windows 8 or Windows 8.1, move your mouse to the upper-right corner, click Search, type regedit in the search text box, and then click regedit.exe in the search results.
   • In Windows 7 or Windows Vista, click Start, type regedit in the Search programs and files text box, and then click regedit.exe in the search results.
2. Locate and then select the following registry subkey:
   For Lync 2013 (Skype for Business)

   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Office\15.0\Lync
   For Skype for Business 2016

   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Office\16.0\Lync
   Note If it doesn't exist, you can create it.
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type PreferInternalServer, and then press Enter.
5. In the Details pane, right-click PreferInternalServer, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Exit Registry Editor.

Note Lync 2013 was upgraded to Skype for Business in April 2015.