SMB 1.0 Support in Windows Server 2012 R2

A new version of SMB 3 protocol was presented in Windows Server 2012 R2 (technically, it is SMB 3.02,  since SMB 3.0 appeared in Windows Server 2012), the driver of the outdated SMB 1.0 is now disabled and its components are not loaded. Since SMB 1.0 is not supported, the outdated OS versions (Windows XP, Server 2003, etc.) and compatible clients (Mac OSX 10.8 Mountain Lion, Snow Leopard, Mavericks, earlier Linux versions) won’t be able to access files located on the file server running Windows 2012 R2.

Different SMB versions appeared in the following Windows versions:

• CIFS - Windows NT 4.0
• SMB 1.0 – Windows 2000
• SMB 2.0 – Windows Server 2008 and Windows Vista SP1
• SMB 2.1 – Windows Server 2008 R2 and Windows 7
• SMB 3.0 – Windows Server 2012 and Windows 8
• SMB 3.02 – Windows Server 2012 R2 and Windows 8.1

In the network interaction over SMB, a client and a server use the maximum version of the SMB protocol supported both by the client and the server.

The summary table of SMB version compatibility on the side of a client and a server looks like this:

For example, if a client computer running Windows 7 connects to a file server running Windows Server 2012, SMB 2.1 will be used.

Get-SmbConnection

According to the table, Windows XP and Windows Server 2003 can use only SMB 1.0 to access folders and files, but by default it is disabled in Windows Server 2012 R2. So, if your infrastructure has computers running Windows XP ( no longer supported ), Windows Server 2003 / R2 and servers running Windows Server 2012 R2, you should understand that the older clients will not be able to access files and folders on a file server running new OS. If Windows 2012 R2 is used as a domain controller, it means that Windows XP / Server 2003 clients won’t be able to execute logon scripts (NETLOGON) and run some of the group policies stored in the network folders on the domain controllers (for example, when using the Central Store for ADM templates). When trying to connect to any resource on the file server, the clients receive the following error message:

If you look through the default Windows Server 2012 R2 features, you’ll notice SMB 1.0/CIFS File Sharing Support. If you install this role, the Computer Browser appears in the system, but SMB 1.0 driver is inactive. 

Remove-WindowsFeature FS-SMB1

By default, both drivers SMB 1 and SMB 2 are loaded in Windows Server 2012. To confirm this, open the properties of a system service Server (LanmanServer) and in the Dependencies tab you can see that Server SMB 1.xxx Driver and  SMB 2.xxx Driver are running on the server at the same time.

If you open Server properties in Windows 2012 R2, you’ll see that there is no driver that supports SMB 1.0 and it is excluded from dependencies.

To restore the access of XP/2003 clients over SMB to the file servers/domain controllers on Windows Server 2012 R2, you can activate SMB 1 support through the registry.

To enable SMB 1.0 support in Windows Server 2012 R2, open the Registry Editor, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer and change the value of DependOnService from SamSS Srv2 to SamSS Srv.

After that you have to restart the server and make sure that SMB 1.0 driver is working.

This actions should be performed on all file servers and domain controllers, to which older OS versions connect.