It’s IPv4 expressed through IPv6 so that the application only needs to support one IP stack. Being able to reference IPv4 addresses through IPv6 notation means I can work on getting IPv6 support really solid in my application, and not have to worry about duplicating effort. These days some distributions disable IPv4 compatibility by default … Read more
I looked through the older IPv6 RFCs in order to find a clue about the history, but I think the answer lies in RFC 4291 section 2.2.3: 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 … Read more
http://en.wikipedia.org/wiki/Hexspeak http://www.urbandictionary.com/define.php?term=dead%3Abeef “Dead beef” is a very popular sentence in programming, because it is built only from letters a-f, which are used in hexadecimal notation. Colons in the beginning and in the middle of the sentence make this sentence a (theoretically) valid IPv6 address.