Network Address Translation (Nat); Overview; What You Can Do In The Nat Screens; What You Need To Know About Nat - ZyXEL Communications P-660H-61 User Manual

Network Address Translation (NAT)

9.1 Overview

This chapter discusses how to configure NAT on the ZyXEL Device. 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 to a different IP address known
within another network.

9.1.1 What You Can Do in the NAT Screens

• Use the NAT General Setup screen
settings.
• Use the Port Forwarding screen
service requests to the server(s) on your local network.
• Use the Address Mapping screen
address mapping settings.
• Use the ALG screen
ZyXEL Device.

9.1.2 What You Need To Know About NAT

Inside/Outside
Inside/outside denotes where a host is located relative to the ZyXEL Device, for example, the
computers of your subscribers are the inside hosts, while the web servers on the Internet are the
outside hosts.
Global/Local
Global/local denotes the IP address of a host in a packet as the packet traverses a router, for
example, the local address refers to the IP address of a host when the packet is in the local
network, while the global address refers to the IP address of the host when the same packet is
traveling in the WAN side.
NAT
In the simplest form, NAT changes the source IP address in a packet received from a subscriber
(the inside local address) to another (the inside global address) before forwarding the packet to the
WAN side. When the response comes back, NAT translates the destination address (the inside
global address) back to the inside local address before forwarding it to the original inside host.
ADSL Router Series User's Guide
C
(Section 9.2 on page
(Section 9.3 on page
(Section 9.4 on page
(Section 9.5 on page 158) to enable and disable the SIP (VoIP) ALG in the
H A PT ER
152) to configure the NAT setup
153) to configure forward incoming
156) to change your ZyXEL Device's
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