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INTERNET PROTOCOL VERSION 6 ADDRESS SPACE
[last updated 2003-07-09]
As defined in [RFC3513], the type of an IPv6 address is identified
by the high-order bits of the address. The current allocation of these prefixes
is as follows:
Allocation Prefix Fraction of
(binary) Address Space
----------------------------------- -------- -------------
Unassigned (see Note 1 below) 0000 0000 1/256
Unassigned 0000 0001 1/256
Reserved for NSAP Allocation 0000 001 1/128 [RFC1888]
Unassigned 0000 01 1/64
Unassigned 0000 1 1/32
Unassigned 0001 1/16
Global Unicast 001 1/8 [RFC2374]
Unassigned 010 1/8
Unassigned 011 1/8
Unassigned 100 1/8
Unassigned 101 1/8
Unassigned 110 1/8
Unassigned 1110 1/16
Unassigned 1111 0 1/32
Unassigned 1111 10 1/64
Unassigned 1111 110 1/128
Unassigned 1111 1110 0 1/512
Link-Local Unicast Addresses 1111 1110 10 1/1024
Site-Local Unicast Addresses 1111 1110 11 1/1024
Multicast Addresses 1111 1111 1/256
Notes:
1) The "unspecified address", the "loopback address", and the IPv6
Addresses with Embedded IPv4 Addresses are assigned out of the
0000 0000 binary prefix space.
2) For now, IANA should limit its allocation of IPv6 unicast
address space to the range of addresses that start with binary
value 001. The rest of the global unicast address space
(approximately 85% of the IPv6 address space) is reserved for
future definition and use, and is not to be assigned by IANA at
this time.
IPv6 Unicast addresses are distinguished from multicast addresses by the
value of the high-order octet of the addresses: a value of 0xFF (binary
11111111) identifies an address as a multicast address; any other value
identifies an address as a unicast address. Anycast addresses are taken
from the unicast address space, and are not syntactically distinguishable
from unicast addresses.
References
----------
[RFC2373] Hinden, R., and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, Nokia, Cisco Systems,
July 1998.
[RFC2374] Hinden, R., M. O'Dell, and S. Deering, "An Aggregatable Global
Unicast Address Format", RFC 2374, Nokia, UUNET, Cisco Systems,
July 1998.
[RFC3513] R. Hinden and S. Deering, "IP Version 6 Addressing Architecture",
RFC 3513, April 2003.
[]
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