ZyXEL Communications EMG6765-Q10A, Руководство пользователя

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EMG6765-Q10A User’s Guide
109
C
HAPTER
13
NAT
13.1 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 EMG6765-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 EMG6765-Q10A, which is 192.168.1.1.
Figure 58 NAT Example
This chapter discusses how to configure NAT on the EMG6765-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 EMG6765-Q10A.
13.1.1 What You Can Do
• Use the General screen to enable NAT ( Section 13.2 on page 111 ).
• Use the Port Forwarding screen to set a default server and change your EMG6765-Q10A’s port
forwarding settings to forward incoming service requests to the server(s) on your local network
( Section 13.3 on page 112 ).