o  data link error

    An error was reported by the Data Link layer.

 o  unrecognized client

    There is no client with the specified identification in the MOP
    Client database.  Run net$configure to add that client entity
    to the MOP Client database.

 o  unrecognized circuit

    There is no circuit with the specified identification.

 o  required argument omitted

    An Address must be provided either in the command line or the
    MOP Client database.

 o  entity class not supported (OpenVMS)

    MOP is not registered with EMAA.  The NET$MOP process is probably
    not started.  For instructions on how to restart the MOP process,
    refer to HELP NETWORK_MANAGEMENT MOP.