Introduction

The IPv6 address format, at first, can look long and complex. As you learn more about them, you’ll see that they are easy to work with.

For an example, even though an IPv6 address has 128 bits it would be easy to call an engineer at another location on the phone to correct a mistyped character.

Other examples of IPv6 addresses being easier to work with than legacy IPv4 addresses, such as subnetting, will present themselves in future lessons.

In this lesson we’ll cover:

  • Hexadecimal Characters
  • IPv6 address structure
  • Nibbles and Hextets
  • Counting of bit values

Hexadecimal Characters

  • IPv6 addresses use hexadecimal characters.
  • Hex = 6. This refers to the six letters A-F.
  • Decimal = 10. Remember we use the numbers 0-9 inclusive for a total of 10.
  • 6 + 10 = 16. Every character can have one of 16 different values.

Decimal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F
Decimal to Hexadecimal

To work with these values we do simple addition:
05AF = 0+5+A+F = 30

Structure

Hexadecimal characters are arranged in 8 groups of four. These groups are separated by colons:
2001:0123:CAFE:0001:0000:0000:0000:0001

Names

To make it easier for us to talk about an address we describe a single character as a nibble and a group of 4 nibbles as a hextet.

Nibble

A nibble has four bits. Each bit may have a value of 0 or 1. A 0 means that the bit is unused, while a 1 means that we “turn it on”.

  • The value of the bits are:
  • 1st bit = 8
  • 2nd bit = 4
  • 3rd bit = 2
  • 4th bit = 1

Decimal Hex
Bit Value 8 4 2 1
0 0
Binary 0 0 0 0 1 1
0 0 0 1 2 2
0 0 1 0 3 3
0 0 1 1 4 4
0 1 0 0 5 5
0 1 0 1 6 6
0 1 1 0 7 7
0 1 1 1 8 8
1 0 0 0 9 9
1 0 0 1 10 A
1 0 1 0 11 B
1 0 1 1 12 C
1 1 0 0 13 D
1 1 0 1 14 E
1 1 1 0 15 F
1 1 1 1 16 G
Binary to Decimal to Hex

Let's use the row with 1110 as an example. Remember a bit with a 1 is an "on" bit...on bits are added together:
8+4+2+0 = 14 = E

Not too difficult!

Hextet

Note: Sometimes those with a Windows background may refer to a hextet as a quartet.

One nibble = 4 bits
One hextet = 4 nibbles = 16 bits

Hextet Explained

One address = 8 hextets = 128 bits

address hex bits explained

Conclusion

If we were to notice a mistyped character, we could quickly and easily call on the phone:

2001:CAFE:0000:0000:FEED:0000:0000:0123
2001:CAFE:0000:0000:DEED:0000:0000:0123

"Please change the character in the 5th hextet, 1st nibble, from an F to a D."

In the next lesson, you'll learn the three simple rules for shortening these 128-bit addresses to make them even easier to read and work with.

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