As mentioned above, a small point of clarification, the Drobo isn't by itself a NAS (Network Attached Storage) but rather an external RAID hard drive case or DAS (Direct Attached Storage).
You can turn a standard Drobo into a NAS with the optional DroboShare. The new DroboPro does have a built-in ethernet port for iSCSI but doesn't function as a NAS and is supposed to be segregated from the network.