In the early 1990s, huge number of users come across the Internet and the use of IP addresses also increased. Soon the IETF realized, the existing IPv4 addresses will not be sufficient in the upcoming time. Then the new protocol was introduced as ‘IPv6’.
IPv6 is 128-bits protocol, in the comparison of 32-bits of IPv4.
IPv6 has more than enough IP addresses for the growing Internet even today.
We discussed in detail about history and the need of IPv6 in our previous article “Out of IPv4, It is time to reintroduce IPv6 now” .
Here in this article, we wish to introduce you to the various type of addresses in IPv6, as the whole addressing scheme of IPv6 is fundamentally very different from previous IPv4. Having a fair grasp over the types of addresses available in IPv6, you will find yourself in a relatively better position to understand the nuances of higher concepts pertaining to IPv6 implementation. Many of those we will share with you in our subsequent articles.
However, before I start the discussion on the different types of IPv6 addresses, I wish to bring your attention to 2-important aspects:
- What does this 128-bits of IPv6 mean?
- How can we change the prefix value in IPv6, as per the number of IP addresses we require?
Understanding the concept of 128-bits
As we all know that IPv6 is a 128-bits addressing scheme, but do we really know what does these mean within the context?
8 Sets x 4 Hexadecimal Numbers x 4 bits = 128 bits
It means —
- 128-bits of IPv6 addresses, have 8 sets, where each set can have a maximum of 4 hexadecimal numbers, and each number is the combination of 4-bits.
- Each of these 8 sets is separated by a colon (:)
Let us dig a little deeper.
The conversion from hexadecimal to binary, or vice-versa, is very easy. If you want to practice the conversion, with the help of below-given table you can do it easily, it depicts the decimal, binary, and hexadecimal numbers.
I took one IPv6 address and convert into binary in the example given below:
Here we have clearly plotted all the 128-bits of an IPv6 address. Right?
Well, regardless of the IP version of the address we use, it essentially contains two sections: network portion, and host portion.
In IPv4, you can use either the subnet mask or prefix, to represent the number of bits used for the network portion. But in case of IPv6, we can use only the prefix, to show the number of bits used for network portion.
Since various network designs places varying network size requirements, we practically need to choose among the prefix-length(s) available to us, w.r.t., the IP in question. Because the selection of right prefix-lengths is imperative to minimize the wastage of IP Addresses.
Prefix Length of IPv6 vs IPv4
For IPv4, the bits used for the network portion can be shown either in prefix or subnet mask. But for IPv6, we always represent it in the ‘prefix’ only.
According to the number of IP addresses we require for our devices on the network, we need to know– how many bits should we use for the network portion, and how any bits we need for the host portion. Also to minimize the wastage of IP addresses, we have to accomplish the process of subnetting.
The two charts exhibit the IPv4 and IPv6 for– how we can change the prefix value as per the number of IP addresses we require.
For the better clarity about the prefix, you can see how to calculate the number of bits used for the network portion.
When we are using 4-sets out of 8-sets the IPv6 address, the prefix will be /64, and how that comes?
Each set is having 16-bits and 4-sets having 64-bits.
In the same manner, when we will consider 3-sets for network portion, then the prefix will be /48 and in 2-sets, it will be /32.
The above demonstration was to establish that it is very easy to calculate the prefix value for an IPv6 address.
IPv6 Address Types
IPv6 addresses lies in mainly any of the three categories:
- Unicast
- Multicast
- Anycast
It all depends upon how the source wants to communicate with the destination. e.g.
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http://luminisindia.com/it-networking-blog/161-a-visual-explanation-of-ipv6-address-types
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