Describe IPV6 addresses
Exam: Cisco 640-816 - Interconnecting Cisco Networking Devices Part 2
We all know that IPV4 address had some issues and because they were running out of numbers so we had to come up with a broader IP addressing scheme which we now call as IPV6 addresses. IPV4 was launched in 1981 and contains around 4.2 billion addresses but because of the rising number of internet users, mobile devices and equipment, IPV4 will not be able to satisfy the increasing demands. IPV6 on the other hand will allow much larger number of devices to be able to connect to the internet. In 2015, 7.1 billion mobile internet users are expected to exist.
IPV6 addresses are 128 bits long. A very simple representation of the IPV6 addresses is shown below:
0010 0000 0000 0001 0000 1101 1011 1000 1100 1010 1111 1110 0000 0000 0000 0001 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0001
This is not what we are going to see on a daily basis. We now will group the bits shown above into groups of 16 bits each.
So, for example, we pick the first 16 bits:
0010 0000 0000 0001
We will now convert these into equivalent hexadecimal number i.e. the above mention bits will be: 2001 This is one part of the complete address. Now we will place a colon to concatenate next set of four and then we convert the next 16 bits. So after converting next 16 bits: 0000 1101 1011 1000, the address becomes 2001:0DB8.
We keep on doing this for 8 times to get the complete address.
The final address will be: 2001:0DB8:cafe:0001:0000:0000:0000:0001
This address looks a bit long, so to make it short there are some rules that have been made.
- Omit the leading Zeroes, i.e. If there is a zero exactly after the colon, then those zeroes can be omitted. After omitting the leading zeroes, the above address will become: 2001:DB8:cafe:1:0:0:0:1.
- To make it more short, we can remove continuous set of zeroes with a special operator "::".
After applying this rule, the above address will become:
2001:db8:cafe:1::1. In a simpler terms, we can say that this operator indicates us to fill in as many number of zeroes to make it 128 bits.
