Nat Overview; Introduction To Nat - 3Com MSR 50 Series Configuration Manual

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NAT Overview

Introduction to NAT

NAT C
When configuring NAT, go to these sections for information you are interested in:
"NAT Overview" on page 1811
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"NAT Configuration Task List" on page 1815
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"Configuring Address Translation" on page 1816
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"Configuring Internal Server" on page 1818
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"Configuring NAT Log" on page 1818
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"Configuring Connection-limit" on page 1820
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"Displaying and Maintaining NAT" on page 1822
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"NAT Configuration Example" on page 1823
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"Troubleshooting NAT" on page 1827
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Network Address Translation (NAT for short) provides a way of translating the IP
address in an IP packet header to another IP address. In practice, NAT is primarily
designed for private network users to access public networks. This way of using a
smaller number of public IP addresses to represent a larger number of private IP
addresses can effectively alleviate the depletion of IP addresses.
n
Private or internal IP addresses refer to IP addresses used in an internal network
whereas public or external IP addresses refer to the globally unique IP addresses
used on the Internet.
According to RFC 1918, three blocks of IP addresses are reserved for private
networks
In Class A: 10.0.0.0 to 10.255.255.255;
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In Class B: 172.16.0.0 to 172.31.255.255;
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In Class C: 192.168.0.0 to 192.168.255.255;
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The above three ranges of IP addresses are not assigned over the Internet. You can
use these IP addresses in enterprises freely without the need for applying them
from the ISPs or the registration center.
Figure 526 depicts a basic NAT operation:
ONFIGURATION