Guy’s Ezine 136 – IPv6 Overview

Guy’s Ezine 136 – IPv6 Overview

IPv6 – Overview

Do the numbers mean anything to you?  If you see an IP address of do you think hmm… private network?  Could 169.254.x.y indicate no DHCP server available?  If any of the foregoing dot decimal numbers ring a bell then clearly you have a working knowledge of IP4.  What I would like to do is give you a similar basic understanding of IPv6.

The good news is that IPv6 principles are very similar to those of IPv4.  Moreover, networks and applications can make the transition to IPv6 easily.  The biggest stumbling block is that we humans struggle to see patterns within these new large hexadecimal numbers.  My objective in this ezine is to give meaning to IPv6 addresses such as: 2001:0618:71A3:0801:1319:0211:FEC2:82DC

Topics for IPv6

US Government steps into the IPv6 arena

Before we get to know the new IPv6 hexadecimal numbers, I would like to say a few words about why you need a working knowledge of IPv6.  What made me suddenly sit up and take notice was when I read that the USA government has decreed that all federal agencies must be IPv6 compliant by June 2008.  Previously, I pigeon-holed IPv6 in the category of having more false dawns than teams like the Arizona Cardinals (NFL), or Newcastle United (Soccer).

Insufficient IPv4 addresses

China and India will want a lot more IP addresses to become a presence on the internet.  Moreover, developed countries need additional IP addresses for cell phones and other mobile devices.  Cisco have analysed the data, and conclude that IANA’s allocation pool of IPv4 addresses will probably run out in between 3 and 10 years. 

This assessment of the available IPv4 pool takes into account American universities such as Stanford and MIT who have handed over their Class A addresses so that the rest of the world can benefit.  Although techniques such as NAT and Supernetting (CIDR) have served their purpose in extending the useful life of IPv4 on the internet; however, in 2008 they are seen as limited, and are choking internet communication. 

At their heart, both IPv4 and IPv6 are level 3 routing protocols.  However IPv6 is just that bit quicker, smarter and lot more scaleable.  Nevertheless, it is the realization that the 32bit IPv4 just cannot deliver sufficient unique address which has been the driving force to upgrade to a 128bit IPng (new generation), or IPv6 as it’s better known.

IPv6 – Theory Behind the Numbers

It is well-known that there are lies, damn lies and statistics.  In the case of IP numbers, your best friends are estimation, approximation and the big picture.  My point is that in the case of IPv4 mathematicians told us with a 32bit number there would be 4,294,967,296 possible IP addresses, in practice this turned out there were only about 17 million useful addresses.  What springs to mind is Oscar Wilde’s adage ‘A cynic (mathematician) is a man who knows the price of everything but the value of nothing’.

With the 128bit IPv6, the same mathematicians say there will be 340,300,000,000,000,000,000,000,000,000,000,000,000,000 IP addresses.  Guy guestimates that there may be as few as: 18,000,000,000,000 useful IPv6 address.  This is partly due to reserved and unassigned bits in the 128bit address.  Even with my extremely low estimate, no worries, it means that everybody on the planet could be given 3,000 IP addresses.  In my mind’s eye I see: one for their computer, one for their phone, car, fridge, cooker and every other appliance – then some.

IPv6 – Getting to Know the Numbers

IPv6 numbers will be in hexadecimal.  Therefore you will see IP addresses containing not only numbers but also the letters ABCDEF, for example: 2001:0618:71A3:08D3:1319:8A2E:0370:7017.  As you can see, 128bit numbers are split into 8 groups of 16bit.  Observe how each group is separated by a colon rather than a dot.  It is also apparent that this scheme dramatically expands on IPv4s 4 groups of 8bit numbers.  Surprisingly, the hex letters are not case sensitive.

Many private networks won’t need to use the full range of IPv6 numbering capabilities; hence many of the values will be zero.  In this circumstance, thanks to compressing zeros, you will see simpler notation, for example, instead of FD01:0000:0000:0000:0000:0000:0000:0002, you will see FD01::2.  Note the double colon :: indicating suppression of the intervening zeros.  Thus the term ‘compression’ in IPv6 refers to the notation and not to the protocol packets themselves.

The biggest reason that there will be fewer IPv6 addresses than the theoretical maximum is that each 64bit number will include the MAC address of the host.  While incorporating the hardware address cuts down the available numbers, it makes this protocol more efficient, secure and useful than IPv4.

IPv6 Examples

0:0:0:0:0:0:0:1 The classic loopback address. Compressed format ::1

FF01:0:0:0:0:0:0:42 A multicast address.  Compressed to FF01::42

0:0:0:0:0:0:  An IPv4 address.  Note triple colon in the compressed form :::

FE80::23a1:b131 A local-link address.  An address for use in the internal organisation, but not on the internet.

IPv6 Address Format (RFC 3587 and 2374)

Here are 3 or 4 slightly different ways of describing the IPv6 address format.

Global Routing Prefix    |    Subnet ID      | Interface ID
Subscriber ID             |
(Top Level Routing ID) | (Organise Sites) | (MAC Address)

Slightly more information of first 4 bytes:

  3     |    13                                   |     32                            |          16          | (64-bit Interface ID)

 001  | Top Level Aggregate Identifier  | Next-level Aggregate ID    | Site-level Aggregate Identifier
 001  | TLA ID                                 | NLA ID                           | SLA ID

Each IP address can be divided into sections.  The first part contains routing information, while in the middle holds the site identifier and subnetting information.  The last part of the hex address has the interface ID which is the 48-bit link-layer (MAC) address plus a 16-bit global identifier.

If you want to know the bit-by-bit significance of each number in IPv6, the ultimate fountain of knowledge is held in ‘Refer For Comments’ documents such as RFC 3587 and RFC 2374, also 3315 for DHCP.  These articles are freely available on the internet.

Guy Recommends: The Free IP Address Tracker (IPAT) IP Tracker

Calculating IP Address ranges is a black art, which many network managers solve by creating custom Excel spreadsheets.  IPAT cracks this problem of allocating IP addresses in networks in two ways:

For Mr Organized there is a nifty subnet calculator, you enter the network address and the subnet mask, then IPAT works out the usable addresses and their ranges. 

For Mr Lazy IPAT discovers and then displays the IP addresses of existing computers. Download the Free IP Address Tracker


To implement IPv6 you will need new DHCP and DNS services.  As expected, Windows Server 2008 is ready and aware of IPv6, and can supply and register these New Generation IP addresses. 

With IPv6, hosts can obtain their own IP address using information from routers, thus DHCP is not essential.  However, I would recommend implementing DHCP to supply extra information and to keep central control of IP addresses on the network, for example, auditing IP addresses.


Security is built in to IPv6; whereas IPSec is an add-on to IPv4.

Speed of IPv6

IPv6 will be faster in several ways.  Physically, because IPv6 does not fragment the packets as IPv4 does.  Logically, because IPv6 will be hierarchical, thus internet routers won’t need such large routing tables.  In addition, IPv6 headers have been redesigned to speed their path through a router and to create true ‘end to end’ capability, the result is more efficient network traffic on the internet backbone

The underlying improvement for IP allocation is that IPv6 addresses will be leased based on geographic region, rather than first come first served basis seen with IPv4.  Take Europe for example, RIPE (Reseaux IP Europeans) has allocated the UK-BT IPv6 addresses beginning with 2001:0618

QOS (Quality of Service)

IPv6 has better scalability and an improved ability to prioritise packets.  As with many of the benefits of IPv6, Quality of Service builds on features that IPv4 only partially delivers.

Mobile Support

I don’t want to get bogged down with technical details, but I do want to emphasis is that IPv6’s support for mobile devices illustrates the thought that has gone into designing the new protocol, for example, the ‘Mobile Node’ (MN) is identified by its home address (HoA) and its care of address (CoA), which is the mobile’s current location.

IPv6 Public Root

ICANN/IANA distribute network blocks to Regional Internet Registries (RIR)

RIPE (Europe, Middle-east)
ARIN (North America)
LACNIC (Latin America)
APNIC (Asia Pacific)
AfriNIC (Africa)

In turn, these RIR hand out blocks Local Internet Registries (LIR) who are mainly Internet Providers (ISP)

LIR hand out IP blocks to End Users

Only IPv6 address beginning with 2000: and 3000: will be distributed to start with.

See IPv6 in Windows 8 ยป

Guy Recommends: Tools4ever’s UMRAUMRA The User Management Resource Administrator

Tired of writing scripts? The User Management Resource Administrator solution by Tools4ever offers an alternative to time-consuming manual processes.

It features 100% auto provisioning, Helpdesk Delegation, Connectors to more than 130 systems/applications, Workflow Management, Self Service and many other benefits. Click on the link for more information onUMRA.

Will and Guy’s Humour

This week Will and Guy are flying high, we have just added to our collection of plane & pilot, jokes, funny pictures, and videos.  Check out our latest addition which features a Typhoon pilot asking:‘How much closer do you want me?’

See more interesting DNS, DHCP and IP articles

E 194 Delete Accounts  •E 136 IPv6  •E 93 Ipconfig  • E 52 Wins  • E 51 WINS  • Ezines

E 44 DHCP  • E 42 DNS  • E 33 DHCP  • E 32 Tools  •Free CSV Import Utility  • E 10 Tools

E 9Tools  • E 8 Security Permissions  • Free IP Tracker  •Review of Permissions Monitor