Networks IX

Using IPv6


Earlier in this chapter, I mentioned that the world’s supply of
registered IP addresses is nearly exhausted. To address this issue,
most organizations reduce the number of registered IP addresses that
they need by implementing a NAT router. However, using a NAT router is
a short-term solution. To fully address this issue, a new version of
the IP protocol is needed that can handle the number of IP addresses
the modern computing world needs.




To accomplish this, IP version 6 (IPv6) is being rolled out throughout
the world. IPv6 is expected to completely replace IPv4 over the next
decade. Instead of 32 bits, IPv6 defines 128-bit IP addresses. This
allows for a maximum of 3.4 × 1038 total unique IP addresses.
(Hopefully, this will be enough!) Most Linux distributions support
both IPv4 and IPv6.




IPv6 addresses are composed of eight four-character hexadecimal
numbers (called quartets), separated by colons instead of periods.
Each quartet is represented as a hexadecimal number between 0 and
FFFF. For example, a valid IPv6 address could be
35BC:FA77:4898:DAFC:200C :FBBC:A007:8973.


This 128-bit address contains two parts:



• Prefix 

The prefix is the first 64 bits. The prefix includes the
network and subnet addresses. This is equivalent to an IPv4 network
address. In fact, we reference the prefix in IPv6 using CIDR notation,
just we did for IPv4 addresses. Because IPv6 prefixes are 64-bits
long, we specify /64.



• Interface ID

The interface ID is the last 64 bits. This is the
unique address assigned to a network host. This is equivalent to an
IPv4 host address.





NOTE Because IPv6 addresses are so long, you will frequently see them
abbreviated. If the address contains a long string of multiple zeros,
we can omit them by specifying ::.


For example, if you had an IPv6 address of 2001:1db8:3a4c:1115:0000:0000:1a2f:1a2b,
you could omit all the extra zeros using a shorthand notation of
2001:1db8:3a4c:1115::1a2f:1a2b.




There are three major types of IPv6 addresses you need to be familiar with:

• Global unicast
• Unique local
• Link local







LX0-104 Exam Objectives (R)