FF01::101                   a multicast address
         ::1                         the loopback address
         ::                          the unspecified addresses

   3. An alternative form that is sometimes more convenient when dealing
      with a mixed environment of IPv4 and IPv6 nodes is
      x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of
      the six high-order 16-bit pieces of the address, and the 'd's are
      the decimal values of the four low-order 8-bit pieces of the
      address (standard IPv4 representation).  Examples:

         0:0:0:0:0:0:13.1.68.3

         0:0:0:0:0:FFFF:129.144.52.38

      or in compressed form:

         ::13.1.68.3

         ::FFFF:129.144.52.38






 
RFC 2373              IPv6 Addressing Architecture             July 1998


2.3 Text Representation of Address Prefixes

   The text representation of IPv6 address prefixes is similar to the
   way IPv4 addresses prefixes are written in CIDR notation.  An IPv6
   address prefix is represented by the notation:

      ipv6-address/prefix-length

   where

      ipv6-address    is an IPv6 address in any of the notations listed
                      in section 2.2.

      prefix-length   is a decimal value specifying how many of the
                      leftmost contiguous bits of the address comprise
                      the prefix.

   For example, the following are legal representations of the 60-bit
   prefix 12AB00000000CD3 (hexadecimal):

      12AB:0000:0000:CD30:0000:0000:0000:0000/60
      12AB::CD30:0:0:0:0/60
      12AB:0:0:CD30::/60

   The following are NOT legal representations of the above prefix:

      12AB:0:0:CD3/60   may drop leading zeros, but not trailing zeros,
                        within any 16-bit chunk of the address

      12AB::CD30/60     address to left of "/" expands to
                        12AB:0000:0000:0000:0000:000:0000:CD30

      12AB::CD3/60      address to left of "/" expands to
                        12AB:0000:0000:0000:0000:000:0000:0CD3

   When writing both a node address and a prefix of that node address
   (e.g., the node's subnet prefix), the two can combined as follows:

      the node address      12AB:0:0:CD30:123:4567:89AB:CDEF
      and its subnet number 12AB:0:0:CD30::/60

      can be abbreviated as 12AB:0:0:CD30:123:4567:89AB:CDEF/60










 
RFC 2373              IPv6 Addressing Architecture             July 1998


2.4 Address Type Representation

   The specific type of an IPv6 address is indicated by the leading bits
   in the address.  The variable-length field comprising these leading
   bits is called the Format Prefix (FP).  The initial allocation of
   these prefixes is as follows:

    Allocation                            Prefix         Fraction of
                                          (binary)       Address Space
    -----------------------------------   --------       -------------
    Reserved                              0000 0000      1/256
    Unassigned                            0000 0001      1/256

    Reserved for NSAP Allocation          0000 001       1/128