Nat configuration, Overview, Introduction to nat – H3C Technologies H3C SecBlade FW Cards User Manual
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NAT configuration
This chapter includes these sections:
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Configuring a NAT policy in the web interface
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Overview
Introduction to NAT
Network Address Translation (NAT) provides a way of translating the IP address in an IP packet header
to another IP address. In practice, NAT is primarily used to allow users using private IP addresses to
access public networks. With NAT, a smaller number of public IP addresses are used to meet public
network access requirements from a larger number of private hosts, and thus NAT effectively alleviating
the depletion of IP addresses.
NOTE:
A private IP address is used only in an internal network, whereas a public or external IP address is used
on the Internet and is globally unique.
According to RFC 1918, three blocks of IP addresses are reserved for private networks:
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Class A: 10.0.0.0 through 10.255.255.255,
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Class B: 172.16.0.0 through 172.31.255.255,
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Class C: 192.168.0.0 through 192.168.255.255.
No host with an IP address in the above three ranges exists on the Internet. You can use those IP addresses
in an enterprise network freely without requesting them from an ISP or registration center.
depicts the operation of NAT.