What You Need to Know About IPv6 in Order to Pass a Microsoft Exam, Part 1
A Microsoft Technet article named “Microsoft’s objectives for IPv6” states that the conversion of IPv4 networks to IPv6 was a bigger and riskier task than “Year 2000”, and we all know what a big fuss that was. However, in reality, there is a lot more known about IPv6, and it began appearing within Microsoft operating systems in Windows 2000. With every continuing operating system release, IPv6 has become more and more prevalent, with the latest Windows 2008 series of exams including IPv6 as an accepted part of the course on the networking exam series. Like the rest of the world, there is no hiding from the fact that you will need to know about IPv6 for your networking exam series, including the key elements and what new features it brings with it in the Microsoft infrastructure course. So in order to break it down we will discuss the key facts you should know about IPv6 for your Microsoft exams, and then in part 2 we discuss IPv6 within the Microsoft operating system itself and where it appears throughout the course.
Understanding the IP address
The most obvious and daunting feature of IPv6 over IPv4 is the IP address itself. The concept of an IP address assigned to a device, and the device internetworking with other devices is still the same. However, in order to provide enough IP addresses for the rest of the universe forever and ever, there needed to be a significant change in the IP address structure. So from the traditional 32-bit IPv4 address there is now a 128-bit IP address, which is made up of 8 octets of sixteen bits. For example:
Already this looks completely different, and looks more like output from a Getmac command than an IPconfig (in fact, MAC addresses do play a partbut more on that later).
In order to make this a bit more manageable you can substitute (only once within an IPv6 IP) the zeros and represent them with a colon:
This can be shrunk down further by removing all of the leading zeros within the IPv6 address:
In order for you understand the address fully, you need to make sure you learn hexadecimal for your Microsoft exam studies; even before taking on the MTA networking exam, you should have an understanding of hexadecimal and what the letters A to F represent numerically.
In the same way that an IPv4 address divides up the IP address into the network bits and the host bits, the IPv6 network takes that a bit further. The main reason for this is the reduced amount of NAT required in IPv6 means that more information is required within the IP address itself.
When considering the subnet mask for IPv6, it also has to be approached differently, as only a portion of the address deals with the subnetting element.
So with the first 48 bits being taken for the global routing element, the next 16 bits are reserved for the subnet and the last 64 bits are defined for the interface range. As defined below, the red bits are representing the subnet range.
11111111111111111. 11111111111111111. 11111111111111111. 11111111111111111. 11111111111111111. 11111111111111111. 11111111111111111. 11111111111111111
However in order to display this subnet notation in a more manageable way you can represent the above address as
So you can use the same hexadecimal format as you can for the IPv6 address itself, although not all devices support this feature.
Different address types
As explained above, the first octet of the IPv6 is reserved as its global routing ID or prefix. This allows you to identify the IPv6 address as either a link-local, multicast, or global IP just by viewing its prefix.
One of the main aspects of Windows networking in the past has been the use of broadcasting. Broadcasting appears in all of the Microsoft networking series of exams right up to the current 2008 track. The main reason outside of networking is because of WINS (the Microsoft version of DNS), which uses NBT nodes to establish name resolution within a domain.
However, in the world of IPv6 broadcasting is a thing of the past, and they are now replaced by Unicast, Multicast and Anycast.
A unicast address is as it sounds in that it provides one-to-one communication between two devices at either a Local-link level, Unique-link level and the Global-link level. It is important you understand this for your exams, including the various levels that it works at as outlined below.
As it sounds this operates at layer 2 of the OSI model (it goes without saying you should know the OSI model inside out for any networking series of exams). So in short it operates in the local network only.
The Link local address starts with the global ID FE80::/10 with the second 64 bits reserved for the interface ID.
This level really exists to satisfy a network administrators need to have a subnet for their company. So this operates at the site level and always begin with FD00::/8 as its global ID, the second portion is its unique subnet ID and the last portion of bits is reserved for the interface ID.
This is the equivalent of a public IP address as it allows one-to-one communications between two external devices.
The global ID is called the “Global routing prefix” as it identifies what country it is representing. This always begins with a 2000::/3, so for example the UK could be 2002::/3
The remaining bits represent the subnet identifier and the interface identifier.
You may be familiar with multicasting addresses if you have covered any of the Microsoft networking exams in the past; however, this is likely to have been the IPv4 version, which has a much smaller IP range than IPv6. Multicasting is really the closest replacement for the broadcast as it identifies a network of devices as a single IP and so when data is received it sends it to all of the interfaces in that group.
The Global ID is FF00::/8 with additional 4 bit entries which establish what type of scope the multicast address is a member of. For the purpose of your Microsoft exams you won’t really need to know much more detail on multicasting than this.
Anycast addresses are a really great feature in IPv6 that is very similar to subnet prioritisation that in turn helps load balance network traffic based on the closest subnet available to handle a request. A good example would be Microsoft’s web servers. These are based all over the world handling web requests. With Anycast they can all be given the same IPv6 address and then the closest geographic interface answers the request.
Co-existence between IPv6 and IPv4
This is a guaranteed exam question area within any networking series exam that is focusing specifically on IPv6, as IPv4 still plays a major part.
Unlike the impending nature of the Y2K changeover, IPv6 is making a more gradual emergence into the networking world, which is down to a number of integrating features that are allowing IPv4 and IPv6 to work together.
Dual stack routers
This is fairly explanatory in that new routers are not only becoming IPv6 compliant but they allow both the IPv4 stack and the IPv6 stack to work together on the same device. For your Microsoft exams, you should understand what is meant by the term IP stack, as it will make understanding the dual stack methodology a bit clearer.
6to4 or 4to6
Imagine two IPv6 networks that wish to communicate with each other, but they must first traverse an IPv4 network; they can do this via 6to4 tunnelling. The process also works the other way round and in turn this allows the transport of data over the mixed stacks achievable.
This is really ongoing from the 6to4/4to6 method, where an ISP provides the Network Address TranslationPort Translation to occur in order for the two IP versions to communicate. For the purposes of your studies, understanding the purpose of NAT-PT is enough.
Within the Microsoft examination track, IPv6 is now fully embedded into the courses available from the MTA’s onwards, all of the way up to the most advanced Microsoft exams, which we will cover in Part Two of "What You Need to Know About IPv6 in Order to Pass a Microsoft Exam."