This holds the distinguished name of the underlying physical port endpoint object that this logical FC PIo entry actually maps to. Because UCS Manager separates the logical port configuration object from the physical hardware endpoint it controls, this field is how software correlates the two when, for example, matching a fault reported against the endpoint back to this port's configuration. For example, following epDn from this port record leads to the specific physical port endpoint object carrying the hardware-level fault and inventory detail for that same port.