IPv6用RIPng（制御機能）

   This section describes administrative controls.  These are not part
   of the protocol per se; however, experience with existing networks
   suggests that they are important.  Because they are not a necessary
   part of the protocol, they are considered optional.  However, it is
   strongly recommend that at least some of them be included in every
   implementation.  These controls are intended primarily to allow RIPng
   to be connected to networks whose routing may be unstable or subject
   to errors.  Here are some examples:

   - It is sometimes desirable to restrict the routers from which
     updates will be accepted, or to which updates will be sent.  This
     is usually done for administrative, routing policy reasons.

   - A number of sites limit the set of networks that they allow in
     Response messages.  Organization A may have a connection to
     organization B that they use for direct communication.  For security
     or performance reasons A may not be willing to give other
     organizations access to that connection.  In such a case, A should
     not include B's networks in updates that A sends to third parties.

   Here are some typical controls.  Note, however, that the RIPng
   protocol does not require these or any other controls.

   - A neighbor list which allows the network administrator to be able
     to define a list of neighbors for each router.  A router would
     accept response messages only from routers on its list of
     neighbors.  A similar list for target routers should also be
     available to the administrator.  By default, no restrictions are
     defined.

   - A filter for specific destinations would permit the network admin-
     istrator to be able to specify a list of destination prefixes to
     allow or disallow.  The list would be associated with a particular
     interface in the incoming and/or outgoing directions.  Only allowed
     networks would be mentioned in Response messages going out or
     processed in Response messages coming in.  If a list of allowed
     prefixes is specified, all other prefixes are disallowed.  If a list
     of disallowed prefixes is specified, all other prefixes are
     allowed.  By default, no filters are applied.