ZyXEL Communications P-2612HW-F1 -, User Manual

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P-2612HW Series User’s Guide
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C
H A P T E R
9
Network Address Translation
(NAT)
9.1 Overview
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 ( Section 9.2 on page 170 ) to configure the
NAT setup settings.
• Use the Port Forwarding screen ( Section 9.3 on page 172 ) to configure
forward incoming service requests to the server(s) on your local network.
• Use the Address Mapping screen ( Section 9.4 on page 176 ) to change your
ZyXEL Device’s address mapping settings.
• Use the SIP ALG screen ( Section 9.4.2 on page 178 ) to enable and disable the
SIP (VoIP) ALG in the ZyXEL Device.
9.1.2 What You Need To Know About NAT
Inside/Outside and Global/Local
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 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.