Internet Security Appliance User's Guide

Chapter 22 Network Address Translation (NAT)
ZyWALL 5/35/70 Series User’s Guide
447
22.6 Technical Reference
This technical reference contains the following sections:
• Inside/outside and Global/local
• What NAT Does
• How NAT Works
• NAT Application
• Port Restricted Cone NAT
Inside/outside and Global/local
Inside/outside denotes where a host is located relative to the ZyWALL. 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.
Note that inside/outside refers to the location of a host, while global/local refers to the IP
address of a host used in a packet. Thus, an inside local address (ILA) is the IP address of an
inside host in a packet when the packet is still in the local network, while an inside global
address (IGA) is the IP address of the same inside host when the packet is on the WAN side.
Incoming Incoming is a port (or a range of ports) that a server on the WAN uses when it sends
out a particular service. The ZyWALL forwards the traffic with this port (or range of
ports) to the client computer on the LAN that requested the service.
Start Port Type a port number or the starting port number in a range of port numbers.
End Port Type a port number or the ending port number in a range of port numbers.
Trigger The trigger port is a port (or a range of ports) that causes (or triggers) the ZyWALL to
record the IP address of the LAN computer that sent the traffic to a server on the WAN.
Start Port Type a port number or the starting port number in a range of port numbers.
End Port Type a port number or the ending port number in a range of port numbers.
Apply Click Apply to save your changes back to the ZyWALL.
Reset Click Reset to begin configuring this screen afresh.
Table 134 ADVANCED > NAT > Port Triggering
LABEL DESCRIPTION