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AMG1312-T Series User’s Guide 147
CHAPTER 11
Network Address Translation (NAT)
11.1 Overview
This chapter discusses how to configure NAT on the AMG1312-T Series. 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.
11.1.1 What You Can Do in the NAT Screens
•Use the General screen (Section 11.2 on page 148) to activate/deactivate NAT for the default
WAN connection (PVC0).
•Use the Port Forwarding screen (Section 11.3 on page 149) to configure forward incoming
service requests to the server(s) on your local network.
•Use the DMZ screen to configure a default server (Section 11.4 on page 152).
•Use the ALG screen to enable and disable the NAT and SIP (VoIP) ALG in the AMG1312-T Series
Section 11.5 on page 152).
11.1.2 What You Need To Know About NAT
Inside/Outside
Inside/outside denotes where a host is located relative to the AMG1312-T Series, 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.