ZyXEL Communications VMG1312-B10C, User Manual

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VMG1312-B10C User’s Guide
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Network Address Translation (NAT)
10.1 Overview
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.
10.1.1 What You Can Do in this Chapter
• Use the Port Forwarding screen to configure forward incoming service requests to the server(s)
on your local network ( Section 10.2 on page 150 ).
• Use the Applications screen to forward incoming service requests to the server(s) on your local
network ( Section 10.3 on page 153 ).
• Use the Port Triggering screen to add and configure the Device’s trigger port settings ( Section
10.4 on page 155 ).
• Use the DMZ screen to configure a default server ( Section 10.5 on page 158 ).
• Use the ALG screen to enable and disable the NAT and SIP (VoIP) ALG in the Device ( Section
10.6 on page 158 ).
• Use the Address Mapping screen to configure the Device's address mapping settings ( Section
10.7 on page 159 ).
10.1.2 What You Need To Know
Inside/Outside
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
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