The world is running out of IPv4 Addresses like 18.104.22.168, depending on where you are and your requirements – it could be 6 to 18 months before it directly affects you. People who need one or more fixed IP addresses are already being affected.
The World IPv6 Day has been organized to flush out problems with moving to IPv6 so they can be fixed. A number of big sites like Google are enabling IPv6 for their main URL's for 24 hours.
Fortunately, about 10 years ago IPv6 was developed to replace IPv4 with vastly more addresses and improved functionality. However, the improved functionality mostly directly affects the infrastructure providers and people with non-trivial networks.
An IPv6 address comprises 128 bits, 4 times the number available for IPv4. An example of an IPv6 address is 2001:470:1:18::114 - but note that the letters a, .., f can also be used, as the numbers are hexadecimal. Most people will simply use a fully qualified domain name like slashdot.org, linuxtoday.com, or www.archidevsys.co.nz. DNS servers (Domain Name Service servers) convert the fully qualified domain name into an actual internet address - now most of the IPv4 form, but increasingly the IPv6 form.
Unfortunately most ISP's and equipment manufacturers have been somewhat tardy in getting up to speed in IPv6. ISP's need to provide IPv6 capable DNS servers and to allocate people IPv6 prefixes (so people can construct their IPv6 addresses). If you want to know more, there is a lot of detailed information available on the Internet - use your favourite search engine.
To test your IPv6 readiness click on: http://test-ipv6.com/#
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