I've got a WD My Passport Ultra 1TB (USB) plugged into my router...
Have you gone to the drive's web interface on your local net? (http://%5Bip of drive]) It has been my experience that these network storage devices typically come pre-configured for smb/sftp/(and one other i can't remember). The drive itself has a web interface in most cases allowing you to configure users and permissions. After you configure (if needed) a network discovery on the CentOS systems should show the NSD and allow a connection as you desire. Mine does a smb connection to my Windows system while I use sftp on all my Linux systems integrating file share seamlessly through the NSD. I don't care to put smb on my Linux machines as it seems to cause more trouble than it is worth; but, that is just a personal preference.
My 2 bits, Fred