NAT functions
NAT enables private IP networks to connect to the Internet by replacing private IP addresses with public IP addresses. It conserves public addresses by advertising at minimum only one public address for the entire network to the outside world.
Private IP address ranges
Most devices within an IP network are assigned private IP addresses, which are not routable outside the company network due to the shortage of public IPv4 addresses. RFC 1918 defines the private IP address ranges that should not be advertised externally:
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10.0.0.0 through 10.255.255.255
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172.16.0.0 through 172.31.255.255
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192.168.0.0 through 192.168.255.255
One of the primary functions of NAT is to enable private IP networks to access the Internet by translating private IP addresses into legal, routable public addresses. This approach conserves public IP addresses since NAT can be configured to advertise only a single public address for the entire network.
Other functions of NAT include:
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Security: Hides internal IP addresses, discouraging direct attacks.
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IP routing solutions: Handles overlapping IP addresses without conflict.
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Flexibility: Allows internal IP addressing schemes to change without affecting externally visible public addresses.
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Translating between IPv4 and IPv6 (Routed mode only): Supports translating between IPv4 and IPv6, enabling interoperability between different network types.
Note | NAT is optional. If NAT is not configured for specific traffic, that traffic will not be translated but will still be subject to normal security policies. |