Introduction to IPv6

While the need for a larger address space was the primary consideration in defining a new version of IP, it was far from the only one. Over time, many lessons has been learned about how IP could be improved in terms of providing better performance and security features, as well as methods to simplify host configuration. Some of the major advantages that IPv6 provides over IPv4 include:

Larger address space. By using a 128-bit address space, the total number of IPv6 addresses available is approximately 3.4 x 1038, or more than one thousand addresses for every person on the planet. In case you care, that’s 340,282,366,920,938,463,374,607,432,768,211,456 (340 undecillion) IP addresses!

Simplified header format. IPv6 removes many of header fields previously found in the IPv4 header, including those associated with packet fragmentation, which is no longer supported. This helps to make packet processing on routers easier, and ultimately faster. Header extensions are also supported, allow for a range of options to be included in packets both now and in the future.

Hierarchical addressing format. IPv6 uses hierarchical addressing techniques that associates networks and allows them to be aggregated in a manner much more efficient than with IPv4. Ultimately, this will help to reduce the size of Internet routing tables.

Address autoconfiguration techniques. IPv6 introduces different autoconfiguration techniques to simplify the configuration of IPv6 interface addresses.

Mandatory support for IPSec. Unlike in IPv4 where IPSec support in the IP protocol is optional, IPSec support is mandatory in IPv6.

Elimination of the need for NAT. Based on the size of its address space, IPv6 eliminates the need for network address translation (NAT) devices. Outside of being a potential single point of failure, NAT devices break the end-to-end connectivity goal of IP.

Increased multicast address space. IPv6 provides a much larger multicast address space than IPv4, and improves network efficiency as a protocol by not supporting broadcast transmissions.

So when will IPv6 finally be used on the worldwide Internet? The answer is that it already is! A portion of the today’s Internet, known as the 6bone, has been running IPv6 since 1996. Both companies and service providers already connect to this network as part of planning the eventual but inevitable migration to IPv6. To find out more about the 6bone, visit

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.