ZyXEL Communications Corporation AMG1302 Manuel D’Utilisation

AMG1302-T10A User’s Guide

This chapter discusses how to configure NAT on the 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.

• Use  the NAT General Setup screen (

) to configure the NAT setup 

settings.

• Use  the Port Forwarding screen (

) to configure forward incoming 

service requests to the server(s) on your local network. 

• Use  the Address Mapping screen (

) to change your Device’s address 

mapping settings.

• Use  the ALG screen (

) to enable and disable the SIP (VoIP) ALG in the 

Device.

Inside/outside denotes where a host is located relative to the 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 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. 

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.