Creates a routing circuit reachable address entity instance
    which contains information about a manually entered address
    prefix accessible over that circuit. It exists only on L2
    routers and end nodes.

    create  [node node-id] routing circuit circuit-name -
         reachable address simple-name -
         address prefix address-prefix

    On an end system, the type may be "outbound" or (for a
    broadcast circuit only) "filter".  A reachable address of
    type outbound behaves in a way similar to that on an L2
    router except that the routing information is used to
    control the operation of the ES cache.  A reachable address
    of type filter (for the broadcast circuit only) specifies
    the permitted LAN addresses of routers on the LAN that will
    be used by the reverse path cache algorithm.  To switch
    between outbound and filter types, the reachable address
    must first be disabled.  For either outbound or filter type,
    the mapping attribute should be set to manual because the
    default is X.121.

    The address prefix argument is required.  It specifies the
    address prefix to which this reachable address corresponds.

    Example:

    create routing circuit csmacd-1 reachable address to-bulean -
           address prefix 49::4