Chapter 1 Nat Configuration; Nat Overview - H3C S7500 Series Operation Manual

Operation Manual – NAT, Netstream, Policy Routing
H3C S7500 Series Ethernet Switches

Chapter 1 NAT Configuration

When configuring NAT, go to these sections for information you are interested in:

NAT Overview

NAT Features
Configuring NAT
Displaying NAT Configuration
NAT Configuration Example
Note:
Currently, the LS81VSNP boards installed in S7500 series switches support the NAT
feature. In this manual, the LS81VSNP board is called LPU (line processing unit).
1.1 NAT Overview
As described in RFC1631, network address translation (NAT) is a procedure to
translate the private IP address in packet header into a public IP address. With NAT, a
private network that provides a great number of private addresses for its internal users
to communicate with each other can use relatively smaller quantity of public addresses
for its internal users to access the Internet. This allows private network users to access
public networks and saves public IP address resources.
Note:
Private IP addresses refer to the addresses used by the hosts in a private network to
communicate to each other instead of to external networks. Public IP addresses refer
to the globally unique, registered IP addresses that can be used on the Internet.
RFC1918 reserves the following three blocks of IP addresses for private networks:
Class A: from 10.0.0.0 to 10.255.255.255
Class B: from 172.16.0.0 to 172.31.255.255
Class C: from 192.168.0.0 to 192.168.255.255
The above three blocks of IP addresses are not for use on the Internet, and users can
use them freely within their enterprises without the necessary to apply to the ISP or NIC
for them.
The following figure depicts a basic NAT application.
1-1
Chapter 1 NAT Configuration