cucsSwEtherPortRn (syntax SnmpAdminString) holds the Relative Name (RN) of this Ethernet port -- the naming component that distinguishes it from sibling instances of the same class under the same parent object. Since this Ethernet port is a physical Ethernet port object on a UCS fabric interconnect switch, several such instances can exist side by side under one parent, so the RN is what UCSM concatenates with the parent's DN to build this instance's own unique DN. For example, comparing the RN values returned for two sibling instances under the same parent tells an admin which specific one they are looking at without walking the full DN string.