Welcome IPv4 user

Time for some audience participation

I have added a new feature to the blog template. You'll notice a thin coloured bar right at the top of the page.

If you see a red bar then you are using a legacy IPv4 connection. If - however - you see a green at the top of the page then you are visiting this site over IPv6. If you're sure that you've setup IPv6 but you still see a red bar then your IPv6 is most likely broken.

Now I'm interested in getting some feedback from you. If you reach this site over IPv6 then please post a comment about the service provider that you are using or the tunnelling mechanism that you are using.

Looking forward to some feedback.


Where does that IP come from?

Due to the size of the IPv6 address space it has been possible to reserve large blocks of addresses for specific purposes and reduce the fragmentation of IP blocks considerably. This leads us to be able to quite easily identify the IPv6 addresses which appear in log files and connection lists:

  • 2001:0:* - This block of addresses is assigned to the Teredo protocol. This tunneling protocol is installed by default on Windows Vista and Windows7 operating systems. It is used by hosts behind NAT gateways to reach IPv6 hosts. Teredo is NOT preferred over IPv4 and will only generally be used when a suitable IPv4 connection can't be made. Teredo is quite popular with torrent clients to reach hosts behind a NAT.
  • 2001:200-A000:* - The first global address allocations were made out of this range of prefixes. Typically these are early adopter networks and many of the major tunnel brokers have prefixes in this range.
  • 2002:* - The 6to4 protocol was assigned this prefix. The 8 digits following the initial sequence are a hexadecimal representation of the public IPv4 address that defines the end of the tunnel. 6to4 thus only functions if the tunnel endpoint is a public IP. In the past 6to4 has been popular for providing IPv6 along side IPv4 on residential gateway/router devices.
  • 240*: - Range that was issued to APNIC for users in the Asia and Pacific regions.
  • 260*: - Range that was issued to ARIN for users in the North American region.
  • 280*: - Range that was issued to LACNIC for user in the Latin American region.
  • 2A0*: - Range that was issued to RIPE NCC for user in the European region.
  • 2C0*: - Range that was issued to AfriNIC for user in the African region.

Getting Connected to IPv6

The first logical step to beginning your IPv6 journey is getting connected. No South African ISPs yet provide end user connectivity that is natively IPv6 enabled but IPv6 was designed to handle this very problem. There are a wide variety of standards that have been developed to allow you to create tunnels over the current IPv4 network of your service provider to get you to the next generation IPv6 Internet.

These IPv6-over-IPv4 tunnels have to terminate on a tunnel server or router that is connected to both the IPv4 and IPv6 Internet so that they can route traffic between the networks. There are many freely available tunnel services but none of these are currently provided in South Africa. This means that all your IPv6 traffic has to go via a tunnel server located usually in Europe or the US. This will add an additional 200-300ms latency to all your connections but it is usually not of concern when you are accessing international websites or Internet services.


This innovative tunneling protocol is potentially the easiest to get working on any host that has a public IPv4 address. The four octets (the bits between the dots) of the IPv4 address are converted into hex and then used to automatically calculate your new IPv6 address. Your ISP then automatically connects you with your closest 6to4 gateway server through a technique called anycast. 6to4 addresses are easy to identify since they all begin with:


The values of ww, xx, yy and zz are calculated as follows:

IPv4 Address:                192.0  .2  .12
Hex Equivalent of octets:    C0  00  02  0C

IPv6 Prefix:              2002:C000:020C::/48

Note that each IPv4 address maps to an entire prefix (or subnet) of IPv6 addresses - many thousands of IPv6 addresses in fact. This means that you could use 6to4 on your ADSL router and then assign globally unique IPv6 addresses to each device connected to that router even though they only have private IPv4 addresses.

A number of short scripts are availble for many common types of systems that will automatically configure a 6to4 connection on your host.


If you have a single PC that you want to connect to IPv6 and you are behind a NAT gateway (like a typical cheap ADSL router) then 6to4 will not work since you do not have a public IPv4 address on your PC. You need to tunnel your IPv6 traffic in a way that will pass freely through your NAT gateway. This is typically done through UDP tunneling.

A number of so-called tunnel brokers exist that can provide this service. You load their software onto your PC and then it creates a connection to the tunnel broker to provide you with IPv6 connectivity. This is doneĀ  in a similar way to VPN software.

SixXS is one popular provider of this tunnel broker service. The easiest service to get connected with is however Go6. You simply install their tunnel setup software and you can be connected to the IPv6 Internet in a matter of minutes. You can then register on their website and obtain a fixed IP. This means that no matter where you connect from you will always have the same IPv6 address.


The best option to choose if you want to connect a server with a fixed IP to the IPv6 Internet is 6in4. This provides you with a statically configured tunnel with a known endpoint that you can reliably control. The best provider of 6in4 connections is the Hurricane Electric Tunnelbroker service. They can provide you with a fixed IPv6 over IPv4 tunnel to one of their many tunnel servers around the world. You are free to choose the server that has the least latency and they will assign you a large prefix of IPv6 addresses on request via their web interface.

Other options

If you are still looking for options then why don't you look at how Vista automatically tunnels IPv6 traffic over Teredo.

Better still - phone up your ISP and ask them when they are going to provide you with IPv6 connectivity directly!