Nat; Chapter 10 Nat; Overview; What You Can Do - ZyXEL Communications LTE3301 Series User Manual

10.1 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 LTE3301. 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 LTE3301, which is
192.168.1.1.
Figure 54 NAT Example
A: 192.168.1.33
FTP, Telnet, SNMP
Ports 21 to 25
B: 192.168.1.34
Port 80
C: 192.168.1.35
Note: You must create a firewall rule in addition to setting up NAT, to allow traffic from
the WAN to be forwarded through the LTE3301.

10.1.1 What You Can Do

• Use the General screen to enable NAT
• Use the Port Forwarding screen to set a default server and change your LTE3301's port
forwarding settings to forward incoming service requests to the server(s) on your local network
(Section 10.3 on page
C
HAPTER
LAN
192.168.1.1
(Section 10.2 on page
89).
LTE3301 Series User's Guide
88
WAN
IP address
assigned by ISP
89).
1 0

NAT