The TCP/IP Guide - IPv6 Address Space Allocation

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The TCP/IP Guide

The TCP/IP Guide
9 TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9 TCP/IP Internet Layer (OSI Network Layer) Protocols
           9 Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)
                9 Internet Protocol Version 6 (IPv6) / IP Next Generation (IPng)
                     9 IPv6 Addressing

IPv6 Address and Address Notation and Prefix Representation

IPv6 Global Unicast Address Format

IPv6 Address Space Allocation
(Page 2 of 3)

Current IPv6 Address Space Allocation Plans

The allocation of different parts of the address space still is done based on particular patterns of the first three to ten bits of the address, to allow certain categories to have more addresses than others. The elimination of the specific term denoting this is intended to convey that these bits should not be given “special attention”.

Table 60 shows the allocations of the IPv6 address space, and what fraction of the total address space each represents:

**Table 60: IPv6 Address Space Allocations**
Leading Bits	Fraction of Total IPv6 Address Space	Allocation
0000 0000	1/256	Unassigned (Includes special addresses such as the Unspecified and Loopback addresses)
0000 0001	1/256	Unassigned
0000 001	1/128	Reserved for NSAP Address Allocation
0000 01	1/64	Unassigned
0000 1	1/32	Unassigned
0001	1/16	Unassigned
001	1/8	Global Unicast Addresses
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	Unassigned
1111 1110 10	1/1024	Link-Local Unicast Addresses
1111 1110 11	1/1024	Site-Local Unicast Addresses
1111 1111	1/256	Multicast Addresses

This is more complicated than the IPv4 “classful” scheme because there are so many more categories and they range greatly in size, however, most of them are unassigned at the present time.

IPv6 Address and Address Notation and Prefix Representation

IPv6 Global Unicast Address Format

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Version 3.0 - Version Date: September 20, 2005

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