ZyXEL Communications AX Series User Manual

AX/DX/EX/PX Series User’s Guide
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CHAPTER 13
Network Address Translation
(NAT)
13.1 NAT 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.
13.1.1 What You Can Do in this Chapter
• Use the Port Forwarding screen to configure forward incoming service requests to the servers on your
local network (Section 13.2 on page 332).
• Use the Port Triggering screen to add and configure the Zyxel Device’s trigger port settings (Section
13.3 on page 335).
• Use the DMZ screen to configure a default server (Section 13.4 on page 338).
• Use the ALG screen to enable or disable the SIP ALG (Section 13.5 on page 339).
• Use the Address Mapping screen to enable and disable the NAT Address Mapping in the Zyxel Device
(Section 13.6 on page 340).
• Use the Sessions screen to limit the number of concurrent NAT sessions each client can use (Section
13.7 on page 343).
• Use the Port Control Protocol screen to configure incoming traffic for devices behind the Zyxel Device
(Section 13.8 on page 343).
13.1.2 What You Need To Know
The following terms and concepts may help as you read this chapter.
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.
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

ZyXEL Communications AX Series Specifications

General

Brand	ZyXEL Communications
Model	AX Series
Category	Network Router
Language	English