ZyXEL Communications Corporation NBG5615 Manuel D’Utilisation
NBG5615 User’s Guide
139
C
H A P T E R
1 5
NAT
15.1 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.
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 (
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 NBG5615. The ISP
assigns the WAN IP address. The NAT network appears as a single host on the Internet. All traffic
coming from
coming from
A
to
D
going out to the Internet use the IP address of the NBG5615, which is
192.168.1.1.
Figure 81
NAT Example
This chapter discusses how to configure NAT on the NBG5615.
Note: You must create a firewall rule in addition to setting up NAT, to allow traffic from
the WAN to be forwarded through the NBG5615.
15.1.1 What You Can Do
• Use the
Ge n e r a l
screen to enable NAT (
).
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