[O/C]Network Security 103: Network Address Translation

Private and Public Addressing

Before we dive into NAT we must first discuss the difference between public and private IP addressing. Public IP addresses include the range 0.0.0.0 – 255.255.255.255, or over 4 billion unique addresses; this is of course with a few exceptions that we will not go into detail here.

Private IP networks are a special allocation of network addresses. They are typically used in networks where the total number of devices in a network exceed the amount of Public IP addresses that are available to the user. These ranges include the following networks:

*10.0.0.0/8 (IP Range 10.0.0.0 – 10.255.255.255, or 16,777,216 unique addresses)
*172.16.0.0/12 (IP Range 172.16.0.0 – 172.31.255.255, or 1,048,576 unique addresses)
*192.168.0.0/16 (IP Range 192.168.0.0 – 192.168.255.255, or 65,536 unique addresses)

Typically these private ranges are not routable across the public Internet, which is why you will only see them occur behind devices that support NAT.

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