The MIB's DESCRIPTION for cucsLsFcZoneGroupRn is only the auto-generated stub 'Cisco UCS ls:FcZoneGroup:rn managed object property', but the 'rn' property name together with its SnmpAdminString type tell us this column, on a group of FC zones bundled together within a service profile's storage configuration, holds this object's relative name as UCS Manager's data model defines it, exposed here as a read-only SNMP value (read-only). The Rn is just the last arc of that same Dn — the naming-coordinate segment specific to this one service-profile FC zone group, which is what changes from row to row while the parent path stays fixed, so it is useful for telling sibling service-profile FC zone group entries apart under the same parent without printing the whole Dn. Continuing the earlier example, the Rn here would just be the trailing segment, something like 'fc-zone-group-A'.