User`s guide

P-660HN-Fx User’s Guide
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CHAPTER 8
Network Address Translation
(NAT)
8.1 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.
8.1.1 What You Can Do in the NAT Screens
•Use the NAT General Setup screen (Section 8.2 on page 136) to configure the NAT setup
settings.
• Use the Port Forwarding screen (Section 8.3 on page 137) to configure forward
incoming service requests to the server(s) on your local network.
• Use the Address Mapping screen (Section 8.4 on page 140) to change your ZyXEL
Device’s address mapping settings.
• Use the SIP ALG screen (Section 8.5 on page 143) to enable and disable the SIP (VoIP)
ALG in the ZyXEL Device.
8.1.2 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.