So how big is an IPv4 address compared to IPv6 - let's talk in bits for a moment. We'll think back to the roots of IPv4, how big is that address in terms of bits. Well, we represent it as four, dotted decimal octets, and octet being 8 bits. So we put 4 of those together, we get 32 bits. And think about the impact of adding just a single bit onto the length of an address, you're doubling the space in which you can represent values. So when we leap towards 128 bits which is the size of an IPv6 address, we aren't quadrupling the space, we're quadrupling the bit space but that geometrically increases the amount of addresses that we are capable of uniquely identifying, and that is one of the strengths – not the only strengths – but one of the big strengths of IPv6, the fact that we have the scalability inborn in the address. You see, they didn't really anticipate IPv4 needing to support all of the devices that we do presently. They didn't anticipate things like our dishwashers, our refrigerators, our cell phones, our gaming consoles – all consuming addresses. They were thinking – maybe a little bit more narrow minded than they should've, but IPv6 is almost overcompensating for that in some regards. The designers do say though that they're not committing to ever having to deal with an exhaustion of IPv6 addresses. They think that it is possible that even IPv6 address spaces will be exhausted sometime in the distant future.
Greater demand for public IP addresses
We need a larger address space because of several reasons. For example, the Internet population was approximately two billion users in 2011, which is a 480% growth rate in 2000-2011. In February 2011, the Internet Assigned Numbers Authority (IANA) announced the allocation of the last five/8 IPv4 address blocks. The peer-to-peer communications are pervasive. There are mobile users using devices such as smart phones, PDA, pen tablet, notepad, gaming, and so on. Internet-connected mobile devices exceeded one billion by 2013. There is consumerization of IT; enterprise workforce is increasingly using consumer devices to connect to corporate environments. There are a variety of consumer devices such as E-book readers, TVs and cable set-top boxes, photo cameras, and so on in addition to the billions of home and industrial appliances. The next wave is machine-to-machine (M2M) communications, smart grids, networked security cameras and sensors, connected to home appliances and HVAC equipments, and so on. There were 1.1 billion automobiles in 2010.
When we think about why IPv6 is the future, it is not all about the size of the address. It is now built with all of the knowledge and the lessons learned from IPv4. We had a lot of lessons learned in IPv4. I will say that we're still continuing to learn lessons inside of the IPv4 protocol suite and the IPv6 protocol suite. IPv6 right now is not exactly what it was six years ago. Things are still evolving with that protocol suite, but there are some things we know that IPv6 is really built for.
It takes IPsec and makes it more of a staple technology as opposed to an augmentation. It supports things like roaming IP addresses with mobile IP. Basically, that allows you to keep your IP address and preserve that despite the fact that you might be in a different subnet that is not your native subnet, so think things like wireless and the ability to roam with wireless. Quality of service is no longer an afterthought. We are going to work with our addresses quite a bit differently. We'll still see things like DHCP, Network Address Translation though is very, very different here. The way that we do partitioning of address spaces is also very different. So when they say CIDR and VLSM, don't think that we're going to be subnetting our class A, B, and C spaces. Subnetting is very different and actually it's a lot more straightforward assuming you're good with powers of two and hexadecimal numbering. Another thing that I'd add here is also native support for multicast communication. Multicast is one of those things that we did as an afterthought in IPv4, we're paying the price for that, and we still haven't really come to terms with the full utilization of multicast communication, but at least it is not one of those things that's jammed in after the fact. They are trying to be forward thinking in that regard.
IPv6 Addressing and Routing
There are different types of IPv6 addressing but we are not going to repeat everything which is quite well explained under the ICND1 class. The same is valid for the IPv6 routing where you are going to see basically the same routing protocols but with some differences in order to match the IPv6 specifics.
Please read carefully the following topics:
After completing this topic, you should be able to describe the features of IPv6 that make it an improvement on IPv4; recognize the shorthand notations for IPv6 addresses.
Describe the types of addresses supported by IPv6. Match the basic types of IPv6 unicast addresses with their descriptions.
Recognize the different ways IPv6 addresses can be allocated. Recognize the configuration commands for enabling IPv6.
Match the IPv6 header fields with their correct descriptions. Recognize the different ICMPv6 message types. Describe the functions of neighbor discovery in IPv6.
After completing this topic, you should be able to describe the IPv6 stateless address autoconfiguration.
After completing this topic, you should be able to identify the command to configure IPv6 static routing.
After completing this topic, you should be able to describe the OSPF features that have been updated for IPv6 and to configure OSPFv3.