This format is referred to as a 'colon-hexadecimal' format rather than 'dotted-decimal.' The colon-hexadecimal format looks like this: 2001:0001:0000:0000:0000:0550:0000:0007 An IPv6 address is represented by 16 individual 16-bit blocks represented by a 4-digit hexadecimal number separated by colons. IPv4 relies on a dotted-decimal notation, where four blocks of 8-bits are represented with their decimal equivalent divided by periods, IPv6 addresses look much different. We will initially focus on how these massive numbers are formatted and simplified. This is not meant to imply that changing the total number of available addresses to an astonishingly huge number is the only improvement IPv6 brings us, but other improvements are not part of the scope of this discussion. This is accomplished by utilizing a 128-bit addressing scheme.

The IPv6 protocol stack changes the rules. The industry, relying on short term solutions has managed to delay the inevitable, with tools like Network Address Translation and Variable Length Subnet Masks (in the form of Classless Interdomain Routing), but the end of the road is coming. This situation was compounded by making poor decisions in issuing the address in the first place, and by the fact that many scopes of these addresses are or have been reserved for private or 'well known' use. Thus, we hit the first of the largest hurdles in internetworking in the history of the technology: 4,294,967,296 unique addresses are just not enough. The current IPv4 addressing model has served us well, but when it was initially being developed 40 or so years ago, none of the researchers could have possibly imagined a future where so many individuals, organizations, and devices would require an IP Address on a daily, almost hourly, basis. Most notably, we can point to the current IPv4 addressing issues we are facing on the internet today. In the networking field, things change so very quickly that it is hard to keep up. CompTIA Network+ N10-005 LiveLessons (Video Training)

Ipv6 compression rules