ZyXEL Communications P-660RU-T1 v3, User Manual, Page: 88 / 230

Chapter 10 Network Address Translation (NAT)
P-660RU-Tx v3 User’s Guide
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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 side. When the response comes back, NAT translates the destination
address (the inside global address) back to the inside local address before forwarding it to the
original inside host.
Port Forwarding
A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or
FTP, that you can make visible to the outside world even though NAT makes your whole
inside network appear as a single computer to the outside world.
Single IP Versus NAT
Single IP is a ZyNOS implementation of a subset of NAT that supports two types of mapping,
Many-to-One and Server . The ZyXEL Device also supports multiple IPs to map multiple
public IP addresses to multiple private LAN IP addresses of clients or servers using mapping
types.
• Choose Single IP if you have just one public WAN IP address for your ZyXEL Device.
• Choose Multiple IPs if you have multiple public WAN IP addresses for your ZyXEL
Device.
Finding Out More
See Section 10.6 on page 95 for advanced technical information on NAT.
10.2 The NAT Screen
Use this screen to configure NAT for each PVC. Click Advanced Setup > NAT to open the
following screen.
Figure 34 Advanced Setup > NAT