I can't seem to find any document describing the option interface.blocked.mgmt_data_traffic (found e.g. in Data ONTAP 7.3.6P2, default value: off). Google and now.netapp.com search did not return a single hit.
The option interface.blocked.mgmt_data_trafficcontrols the protocol filter for dedicated management ports, such as e0M on many platforms (not all platforms have a dedicated management port). If the option is set to on (the default for new installs), then NDMP, NFS, CIFS, iSCSI and the SNAP* family of data protocols will be blocked by the dedicated management port. "On" is the recommended setting because a dedicated management port is a low-bandwidth port that does not support jumbo frames, vlans or ifgrps. If a dedicated management port is used for data traffic, it can hide misconfigurations that might lead to serious loss of filer throughput. A dedicated management port should only be configured with addresses that are on isolated management-only subnets.