mount.cifs: mount error(112): Host is down
I found this link here which says SMB 2 and 3 is not supported for rhel and Centos 6. It can only mount SMB1. From Centos and rhel 7 this is supported.
I solved this problem by forcing version 1 of the smb protocol.
In my fstab this is done like this:
//192.168.0.XXX/elements/Videos /home/myuser/videos cifs uid=1000,username=myuser,password=mypwd,rw,nounix,noserverino,defaults,auto,vers=1.0 0 0
By default, the system certainly use SMB2 or 3, and it doesn't work with my box. In fact it depends on your NAS. You have to give the good version depending on the SMB server.