On Windows 8.1 and Server 2012 R2, SMB 1.0 (aka CIFS) is no longer enabled by default. This means clients that don't support at least SMB 2.0 (for Windows: everything predating Vista/2008) can no longer directly connect to a 8.1/2012R2 server, and instead, are presented with an error if they attempt to do so:
The specified network name is no longer available.
You can re-enable SMB 1.0 support by installing the SMB 1.0/CIFS support feature on your server.
Some users reported that even after enabling this feature, they could not access shares on the server. Apparently, the SMB 1.0 driver is not loaded properly, because of a missing dependency on the Server service (aka LanmanServer). ...
SMB (Server Message Block) is an application protocol, most commonly used for file and printer sharing. Although it was originally designed by IBM for use in OS/2, it has been adopted and improved upon by Microsoft as the primary protocol for file and printer sharing in their Windows for Workgroup. It has been in use ever since on Windows and a myriad of other OS flavours.
Although SMB is proprietary to Microsoft, SMB is also available on linux (through Samba), Apple (first Samba, then later, Apple's own SMBX), and a myriad of other OS vendors. In fact, Apple has replaced their own AFP in favour of SMB in their latest releases of Mac OSX. SMB has become the most commonly used protocol for f ...
A while back, Microsoft has introduced new security defaults in Windows 10 and Server 2019, disallowing unauthenticated guest access to shares. While this is a good security best practice, it can also break Samba implementations running on Linux. Older versions of Windows (and versions with this policy disabled) can still access the shares, but with the policy in effect, connections immediately fail.
While it would be possible to disable the policy, it's not a very good idea as it is a potential security flaw. A better solution is to fix it on your Linux Samba server, which can be easily done by completely disabling guest access and enforcing SMB3 and password encryption.