Introduction to IPv6

Before getting into the technical details of this new version of IP, a simple question must be answered – why does the world need a new version of IP at all? There are many answers to this question, but the most basic reason involves the rapid depletion of the IPv4 address space. If you’ll recall from earlier in this chapter, IPv4 uses 32-bit addressing, and this limits the total number of IP addresses available for issue. When the Internet Protocol was first defined, nobody envisioned the phenomenal growth that defines the Internet we know today. As such, what was originally considered an almost endless supply of address space is now challenged as increasingly greater numbers of devices are connected to the Internet. Consider examples like cellular phones, PDAs, and other embedded systems, and it’s easy to see how the need for more IP address space is upon us.

Note: Talking about IPv6 begs a simple question – whatever happened to IPv5? The answer to that is that IPv5 is actually defined, although for a different purpose. IPv5 defines an experiment protocol that was originally developed to provide quality of service (QoS) features on IPv4 networks. You don’t need to know anything about IPv5 for the CCDA exam, but hopefully this helps to clear up what might have been a nagging thought. To that end, it’s also an interesting little piece of tech trivia!

A number of techniques have been developed and implemented to help slow down the need to deploy a new version of IP, and of these, network address translation (NAT) is clearly the most popular. Earlier in this chapter we also looked at the three ranges of IP addresses set aside for private addressing. While this technique has reduced the need for public IP addresses, it is still not a proper solution, and does little to address the foreseeable growth of the Internet in the longer term. Quite simply, a larger IP address space is required, and IPv6 addresses this issue with a 128-bit address space. At this time, a 128-bit address space would be capable of providing more than a thousand IPv6 addresses for each man, woman, and child on the planet.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.