Unable to connect MacBook to NAS server after OS/X upgrade

I have files on Western Digital NAS devices (MyBook Du0 and MyCloud acting as Windows file servers) that I share with Windows computers. My MacBook used to be able to access files on these devices without a hitch.

On May 17, 2016, I updated one of my MacBook to OS/X 10.11.5 El Capitan. Immediately after the update, I was not able to connect to  the NAS devices. I tried connecting with another MacBook that ran OS/X 10.11.4 El Capitan. Connection was flawless.

THE PROBLEM. When I accessed a NAS device, I was prompted for password.

After I entered a password, it either returned an error message or showed a list shares on the NAS device.

SOLUTION #1. To solve this problem, all you need to do is changing connecting protocol from SMB to CIFS. Just open Finder. Select Go | Connect to Server…. In the server address box, enter cifs://<server name> (e.g., cifs://leece).

NOTE: If you try to access a file server on a LAN, solution #2 is better.

I think OS/X 10.11.5 El Capitan changed the default SMB protocol to SMB2. Since my NAS devices are still using SMB1, so the connection failed.

SOLUTION #2. I came across another solution recently. It requires disabling SMB signing. It is a better solution if you are on a private network because SMB protocol is a lot faster than CIFS.

Apple updated SMB to require signing during connection establishment stage. That causes problem with servers that does not support such feature. SMB signing is a security feature to prevent man-in-the-middle attach. If you are accessing a server on a LAN at home or at work, you do not need to worry about such attach.

The solution is quite simple. You need to add a configuration file /etc/nsmb.conf and add two lines in the file. Then reboot you Mac.

[default]
signing_required=no

To create the configuration file, you need to open a terminal. Then, substitute current user as root.

$ sudo -s

Use vi to create the file and add the two lines.

$ vi /etc/nsmb.conf

Alternatively, you can create the file from command line.

$ echo >> "[default]" > /etc/nsmb.conf
$ echo >> "signing_required=no" >> /etc/nsmb.conf

Since you are root user, you can reboot from command line. You can also click the Apple icon and select Restart….

$ reboot

After you Mac reboots, login and connect to a server using smb://<server>. you should be able to do it now.

See Also: https://discussions.apple.com/message/30260816#30260816

Hope this help! Good luck.

Poon