When Do I Need Nat; What Ip/Port Mapping Does Nat Support - ZyXEL Communications P-2612HNU-Fx Support Notes

firewall protection. In such case, all incoming connections to your network will be
filtered out by the device, thus preventing intruders from probing your network.
The SUA feature that the device supports previously operates by mapping the
private IP addresses to a global IP address. It is only one subset of the NAT. The
device supports most of the features of the NAT based on RFC 1631. For more
information on IP address translation, please refer to RFC 1631, The IP Network
Address Translator (NAT).

When do I need NAT?

a. Make local server accessible from outside Internet
When NAT is enabled the local computers are not accessible from outside. You can
use Multi-NAT to make an internal server accessible from outside.
a. Support Non-NAT Friendly Applications
Some servers providing Internet applications such as some mIRC servers do not allow
users to login using the same IP address. Thus, users on the same network can not
login to the same server simultaneously. In this case it is better to use Many-to-Many
No Overload or One-to-One NAT mapping types, thus each user login to the server
using a unique global IP address.

What IP/Port mapping does NAT support?

NAT supports five types of IP/port mapping. They are: One to One, Many to One,
Many to Many Overload, Many to Many No Overload and Server. The details of the
mapping between ILA and IGA are described as below. Here we define the local IP
addresses as the Internal Local Addresses (ILA) and the global IP addresses as the
Inside Global Address (IGA),
1. One to One
In One-to-One mode, the device maps one ILA to one IGA.
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