2.2 Text Representation of Addresses

   There are three conventional forms for representing IPv6 addresses as
   text strings:

   1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the
      hexadecimal values of the eight 16-bit pieces of the address.

      Examples:

         FEDC:BA98:7654:3210:FEDC:BA98:7654:3210

         1080:0:0:0:8:800:200C:417A

      Note that it is not necessary to write the leading zeros in an
      individual field, but there must be at least one numeral in every
      field (except for the case described in 2.).

   2. Due to some methods of allocating certain styles of IPv6
      addresses, it will be common for addresses to contain long strings
      of zero bits.  In order to make writing addresses containing zero
      bits easier a special syntax is available to compress the zeros.




 
RFC 3513              IPv6 Addressing Architecture            April 2003


      The use of "::" indicates one or more groups of 16 bits of zeros.
      The "::" can only appear once in an address.  The "::" can also be
      used to compress leading or trailing zeros in an address.

      For example, the following addresses:

         1080:0:0:0:8:800:200C:417A  a unicast address
         FF01:0:0:0:0:0:0:101        a multicast address
         0:0:0:0:0:0:0:1             the loopback address
         0:0:0:0:0:0:0:0             the unspecified addresses

      may be represented as:

         1080::8:800:200C:417A       a unicast address
         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

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 [CIDR].  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.





 
RFC 3513              IPv6 Addressing Architecture            April 2003


      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,