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11
Scaling IP Addresses with NAT
It is imperative for a CCNP candidate to understand the use of NAT. This information is
needed in today's network environment as well; NAT is a standard deployment for almost
all enterprise networks.
In the last few years, much ado has been given to IP Version 6 as a way to alleviate the
current IP Version 4 address limitations. IP Version 6 proposes the use of 128 bits for
address space compared to the current IP Version 4 space of 32 bits.
The prolific use of NAT has ameliorated the necessity of transitioning to this larger address
space. Most companies now embrace the idea of using the private address space, defined in
RFC 1918, and using NAT to access the Internet.
The use of NAT enables a large corporation to utilize their own selected address space and
still gain access to the Internet. Whatever address space is used on the inside of a private
network, NAT can provide the necessary numbering for Internet access in a much more
efficient manner.
Overloading an IP address enables a private company to use a single legitimate address as
a proxy for hundreds and thousands of private addresses. This feature is discussed in the
"Foundation Topics" section of this chapter, along with the other features of NAT. This
topic is not only germane to obtaining a CCNP or CCDP, but also relevant in a real-world
sense.
How to Best Use This Chapter
By taking the following steps, you can make better use of your study time:
·
Keep your notes and answers for all your work with this book in one place for easy
reference.
·
Take the "Do I Know This Already?" quiz and write down your answers. Studies show
retention is significantly increased through writing facts and concepts down, even if
you never look at the information again.
·
Use the diagram in Figure 11-1 to guide you to the next step.