Main Page | See live article | Alphabetical index


IPv6 is version 6 of the Internet Protocol. IPv6 is intended to replace the previous standard, IPv4, which only supports up to about 4 billion (4 109) addresses, whereas IPv6 supports up to about 3.4 1038 addresses.

IPv6 is the second version of the Internet Protocol to be widely deployed, and is expected (as of 2001) to form the basis for future expansion of the internet. In 2003, Nihon Keizai Shimbun (as cited in CNET Asia Staff, 2003) reported that Japan, China, and South Korea claimed to have made themselves determined to become the leading nations in internet technology, which would partially take the form of jointly developing IPv6, and completely adopting IPv6 starting in 2005.

The compelling reason behind the formation of IPv6 was lack of address space, especially in the heavily populated countries of Asia such as India and China.

Table of contents
1 IPv6 addressing
2 Notation for IPv6 addresses
3 IPv6 deployment
4 Related IETF working groups
5 External links
6 References

IPv6 addressing

The most dramatic change from IPv4 to IPv6 is the length of network addresses. IPv6 addresses, as defined by RFC 2373 and RFC 2374, are 128 bits long; this corresponds to 32 hexadecimal digits, which are normally used when writing IPv6 addresses, as described in the following section.

The number of possible addresses in IPv6 is 2128 ≈ 3.4 x 1038. The number of IPv6 addresses can also be thought of as 1632 as each of the 32 hexadecimal digits can take 16 values (see combinatorics).

In some situations, IPv6 addresses are composed of two logical parts: a 64-bit network prefix, and a 64-bit host-addressing part, which is often automatically generated from the interface MAC address.

Notation for IPv6 addresses

IPv6 addresses are 128 bits long but are normally written as eight groups of 4 hexadecimal digits each. For example,

is a valid IPv6 address.

If a 4 digit group is 0000, it may be omitted. For example,

is the same IPv6 address as

Following this rule, if more than two consecutive colons result from this omission, they may be reduced to two colons, as long as there is only one group of more than two consecutive colons. Thus
are all valid and mean the same thing, but
is invalid.

Also leading zeros in all groups can be omitted, thus

is the same thing as

If the address is an IPv4 address in disguise, the last 32 bits may be written in decimal; thus

::ffff: is the same as 
::ffff:c0a8:5909, but not the same as
:: or

The ::ffff: format is called an IPv4-mapped address, and is deprecated. The :: format is an IPv4-compatible address.

IPv4 addresses are easily convertible to IPv6 format. For instance, if the IPv4 address was, it could be converted to 0000:0000:0000:0000:0000:0000:874B:2B34 or ::874B:2B34. Then again, one could use the hybrid notation (IPv4 mapped addresses), in which case the address would be :: .

IPv6 deployment

To do:

Related IETF working groups

External links