ZyWALL 5/35/70 Series User’s Guide
435
CHAPTER 22
Network Address Translation
(NAT)
22.1 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 is changed to a different IP address known within another network.
22.1.1 What You Can Do Using the NAT Screens
• Use the NAT Overview screen (Section 22.2 on page 436) to configure global NAT
settings and enable NAT on a WAN interface.
•Use the Address Mapping screens (Section 22.3 on page 438) to change your ZyWALL’s
address mapping settings. Not all fields are available on all models.
• Click Port Forwarding screens (Section 22.4 on page 441) to make servers with private
IP addresses on your network (behind NAT) visible to the outside world.
• Click Port Triggering screens (Section 22.5 on page 445) to change your ZyWALL’s
trigger port settings.
22.1.2 What You Need To Know About NAT
NAT Mapping Types
NAT supports five types of IP/port mapping. They are:
• One to One: In One-to-One mode, the ZyWALL maps one local IP address to one global
IP address.
• Many to One: In Many-to-One mode, the ZyWALL maps multiple local IP addresses to
one global IP address. This is equivalent to SUA (i.e., PAT, port address translation),
ZyXEL's Single User Account feature (the SUA option).
• Many to Many Overload: In Many-to-Many Overload mode, the ZyWALL maps the
multiple local IP addresses to shared global IP addresses.
• Many One to One: In Many-One-to-One mode, the ZyWALL maps each local IP address
to a unique global IP address.
• Server: This type allows you to specify inside servers of different services behind the
NAT to be accessible to the outside world although, it is highly recommended that you use
the DMZ port for these servers instead.
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