ZyXEL Communications EMG3425-Q10A, Руководство пользователя

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EMG3425-Q10A User’s Guide
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H A P T E R
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NAT
12.1 Overview
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in
a packet. For example, the source address of an outgoing packet, used within one network is
changed to a different IP address known within another network.
The figure below is a simple illustration of a NAT network. You want to assign ports 21-25 to one
FTP, Telnet and SMTP server (
A in the example), port 80 to another ( B in the example) and assign
a default server IP address of 192.168.1.35 to a third ( C in the example).
You assign the LAN IP addresses to the devices ( A to D ) connected to your EMG3425-Q10A. The
ISP assigns the WAN IP address. The NAT network appears as a single host on the Internet. All
traffic coming from
A to D going out to the Internet use the IP address of the EMG3425-Q10A,
which is 192.168.1.1.
Figure 55
NAT Example
This chapter discusses how to configure NAT on the EMG3425-Q10A.
Note: You must create a firewall rule in addition to setting up NAT, to allow traffic from
the WAN to be forwarded through the EMG3425-Q10A.
12.1.1 What You Can Do
• Use the General screen to enable NAT ( Section 12.2 on page 101 ).
A: 192.168.1.33
B: 192.168.1.34
C: 192.168.1.35
IP address
192.168.1.1
WAN LAN
assigned by ISP
FTP, Telnet, SNMP
Port 80
Ports 21 to 25