1. A system ( 1 ) for managing management data of plant ( 5 ) of a communications network, each unit of the plant including a management information base ( 6 ) containing values of fields and associated with a management information base definition ( 7 ) including fields and accessible in a network management system (NMS), which system is characterized in that it includes at least one automatic descriptor ( 8 ) that: i) includes first data designating at least one type of network plant ( 5 ) and second data designating management information base definitions ( 7 ) associated with said type of plant ( 5 ), and ii) is adapted, in the event of receiving data designating said type of plant ( 5 ), to access the fields of said management information base definitions ( 7 ) associated with the designated type and then to deliver third data representative of the fields of the plant ( 5 ) of the designated type.