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Introduction to Network Address Translation
Similar to Classless Inter-Domain Routing (CIDR), the original intention for NAT was to slow
the depletion of available IP address space by allowing many private IP addresses to be represented
by some smaller number of public IP addresses.
Since then, it’s been discovered that NAT is also a useful tool for network migrations and
mergers, server load sharing, and creating "virtual servers." So in this section, I’m going to
describe the basics of NAT functionality and the terminology common to NAT.
At times, NAT really decreases the overwhelming amount of public IP addresses required
in your networking environment. And NAT comes in really handy when two companies that
have duplicate internal addressing schemes merge. NAT is also great to have around when an
organization changes its Internet service provider (ISP) and the networking manager doesn’t
want the hassle of changing the internal address scheme.
Here’s a list of situations when it’s best to have NAT on your side:
- You need to connect to the Internet and your hosts don’t have globally unique IP
addresses.
- You change to a new ISP that requires you to renumber your network.
- You need to merge two intranets with duplicate addresses.
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