Windows 2012 R2 remote desktop cannot be connected by Linux rdsktop-vrdp
Ubuntu command
rdesktop-vrdp <IP>
Failed to connect, CredSSP required by server
Solution
On DOS mode execute below command
reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" /v UserAuthentication /t REG_DWORD /d 0 /f