IPv6用RIPng（アドレッシングの考慮）

   The distinction between network, subnet and host routes does not need
   to be made for RIPng because an IPv6 address prefix is unambiguous.

   Any prefix with a prefix length of zero is used to designate a
   default route.  It is suggested that the prefix 0:0:0:0:0:0:0:0 be
   used when specifying the default route, though the prefix is
   essentially ignored.  A default route is used when it is not
   convenient to list every possible network in the RIPng updates, and
   when one or more routers in the system are prepared to handle traffic
   to the networks that are not explicitly listed.  These "default
   routers" use the default route as a path for all datagrams for which
   they have no explicit route.  The decision as to how a router becomes
   a default router (i.e., how a default route entry is created) is left
   to the implementor.  In general, the system administrator will be
   provided with a way to specify which routers should create and
   advertise default route entries.  If this mechanism is used, the
   implementation should allow the network administrator to choose the
   metric associated with the default route advertisement.  This will
   make it possible to establish a precedence amoung multiple default
   routers.  The default route entries are handled by RIPng in exactly
   the same manner as any other destination prefix.  System
   administrators should take care to make sure that default routes do
   not propagate further than is intended.  Generally, each AS has its
   own preferred default router.  Therefore, default routes should
   generally not leave the boundary of an AS.  The mechanisms for
   enforcing this restriction are not specified in this document.