IPv6 Explained for Beginners

ipv6-iconIPV6 has been developed to replace IPV4 which is running out of addresses.

Although it has been around almost 10 years it is still not widely deployed and supported.

However adoption rates are increasing rapidly and IPv6 traffic crossed the 10% threshold in February 2016 (wiki) .





For small business/home and home office networks it is likely to be many years before IPV6 becomes an issue.

All modern computers and mobile phones support both IPv4 and IPv6, and if you look at your device IP addresses you will probably see both.

In this tutorial I want to take a quick look at IPv6 addresses, and how they relate to IPv4 addresses.

Therefore it will help if you are already familiar with IPv4 -See IPv4 Addressing and classes for Beginners

IPv6 addresses

An Ipv6 address uses 128 bits as opposed to 32 bits in IPv4.

IPv6 addresses are written using hexadecimal, as opposed to dotted decimal in IPv4. See Binary numbers explained

Because an hexadecimal number uses 4 bits this means that an IPv6 address consists of 32 hexadecimal numbers.

These numbers are grouped in 4’s giving 8 groups or blocks. The groups are written with a : (colon) as a separator.

group1:group2: ……etc…. :group8

Here is an IPv6 address example:

IPv6-Address-Example

Note: Because of the length of IPv6 addresses various shortening techniques are employed.

The main technique being to omit repetitive 0’s as shown in the example above.

Network And Node Addresses

In IPv4 an address is split into two components a network component and a node component.

This was done initially using Address classes and later using subnet masking.

In IPv6 we do the same. The first step is to split the address into two parts.

The address is split into 2 64 bit segments the top 64 bits is the network part and the lower 64 bits the node part:

ipv6-address-network-node

The upper 64 bits are used for routing.

The lower 64 bits identify the address of the interface or node, and is derived from the actual physical or MAC address using IEEE’s Extended Unique Identifier (EUI-64) format. See this Wiki description for exact details.

If we look at the upper 64 bits in more detail we can see that it is split into 2 blocks of 48 and 16 bits respectively the lower 16 bits are used for subnets on an internal networks, and are controlled by a network administrator.

The upper 48 bits are used for the global network addresses and are for routing over the internet.

ipv6-address-structure

 Address Types and Scope

IPv6 addresses have three types:

  • Global Unicast Address –Scope Internet- routed on Internet
  • Unique Local — Scope Internal Network or VPN internally routable, but Not routed on Internet
  • Link Local – Scope network link- Not Routed internally or externally.

 

ipv6-address-types

Global and Public Addresses

Global addresses are routable on the internet and start with 2001:

These addresses are known as global Unicast addresses and are the equivalent of the public addresses of IPv4 networks.

The Internet authorities allocate address blocks to ISPs who in turn allocate them to their customers. See Global Address assignments

Internal Addresses- Link Local and Unique Local

In IPv4 internal addresses use the reserved number ranges 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 and 169.254.0.0/16.

These addresses are not routed on the Internet and are reserved for internal networks.

IPv6 also has two Internal address types.

  • Link Local
  • Unique Local

Link Local

These are meant to be used inside an internal network, and again they are not routed on the Internet.

It is equivalent to the IPv4 address 169.254.0.0/16 which is allocated on an IPv4 network when no DHCP server is found.

Link local addresses start with fe80

They are restricted to a link and are not routed on the Internal network or the Internet.

Link Local addresses are self assigned i.e. they do not require a DHCP server.

A link local address is required on every IP6 interface even if no routing is present.

Unique Local

Unique Local are meant to be used inside an internal network.

They are routed on the Internal network but not routed on the Internet.

They are equivalent to the IPv4 addresses are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16

The address space is divided into two /8 spaces: fc00::/8 for globally assigned addressing, and fd00::/8 for locally assigned addressing.

For manually assignment by an organisation use the fd00 prefix.

Using IPv6 Addresses in URLs

On IPv4 networks you can access a network rsource e.g. a web page using the format

http://192.168.1.21/webpage

However IPv6 addresses contain a colon as separator and so must be enclosed in square brackets.

http:[IPv6 address]/webpage.

IPv6 Loop Back

The IPv6 loopback address is ::1. You can ping it as follows:

ping ::1

Ping-Loopback-IPv6

Video

Here is a good video that cover the above

Related Articles and Resources:

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21 comments

  1. This is a great article. You simplified without over explanation, and your graphic examples were perfect — I now understand, in under 5 minutes —
    Why IPV6
    That IPV6 is 128 bits, 16 bits per section – with the front 64 being for routing
    That IPV6 addresses 2001:…. are public/global, fe80:… are local only with no DHCP , fc00::/8 – fd00::/8 are for Internal networks (but if assigning them manually, to use fd00::/8
    You have a lot of extra’s in here too, like how to ping loop back, and access an IPV6 address through a browser.
    I really enjoyed this read – it’s not every day I find an article that is packed with so much information, in an easy to absorb layout – I will be re-reading this a couple more times to make sure I have it all — and I would love to see a follow up article for people who want to dive deeper into it, but this is enough for my everyday understanding, and was written great.
    I’ve Favorited — and will share the page with others.

    Thank you

  2. Hey Steve, great article! Thanks for creating. One question I have, if there are so many available IP Addresses in v6, would it be possible just to hard code each device OOTB with a unique IP address? Why even bother with DHCP and instead just pre-configure. So, your cable modem would get a unique ipv6 address at the factory and when it connected to your ISP, it would just tell it what IP address it had. Is that possible? Especially at IoT levels, it would seem to be nice to have a known address to reach. I realize that there are security risks that might make this a bad idea, but is it possible?

    1. Hi
      IPv6 doesn’t require DHCP but using it does give you more control over the devices as the information is in one place. You can also use set prefixes see this article
      https://docs.infoblox.com/display/NAG8/Configuring+IPv6+Fixed+Addresses
      You can also assign static addresses like on IPv4.
      I think if you want to know the IP address of each device then DHCP is probably better.
      Currently on my home IPv4 network the only network map I have is from the home router which has the DHCP server.
      Rgds
      Steve

  3. Thanks for the article. You say: “For small business/home and home office networks it is likely to be many years before IPV6 becomes an issue. All modern computers and mobile phones support both IPv4 and IPv6, and if you look at your device IP addresses you will probably see both.” I believe, though, that their ISP will need to support both IPv4 through Carrier Grade NAT (CGNAT) or dual stack so their customers can access remaining content that is IPv4 only. For example, if the ISP migrates their network to IPv6, their customers will not be able to access IPv4 content unless there is something like CGNAT translating between v6 and v4.

  4. I must be really stupid. I don’t get it.
    If I want to assign a bunch of IP’s how do I know what they are? How are they numbered?
    For example, if I have a /64 – what are the actual IP’s? how do they end? like 01234567ABCDEF? Can you give me a simple example of say the first 20 IP’s? How do I calculate them? I’ve been looking online for a way to simply list a bunch of them from a range so they can be added as static IP’s to a few computers, but how do I know what they are? This is supposed to be a basic guide, but it went way over my head 🙁

  5. Thank you!
    So far all explanations about IPv6 where so cloudy, this one I totally get and it now all makes sense what I see on my interfaces.
    JWR

  6. Great Article! I am newbie / dumbo to his IPv6. My personal requirement is, I need a way to directly connect / communicate (say via HTTP/S) between 2 mobile phones that are geographically separated and under 2 different Mobile Service Providers. Presuming that the 2 Service Providers provide IPv6 addressing, would it be possible that I could browse to a URL served from one device, through a browser in the second device?

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