ZyXEL Communications P-660HW-DX User Manual

Chapter 8 Network Address Translation (NAT) Screens

P-660HW-Dx User’s Guide

The following table summarizes these types.

SUA (Single User Account) 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 Full 
Feature NAT to map multiple global IP addresses to multiple private LAN IP addresses of 
clients or servers using mapping types as outlined in 

. 

• Choose SUA Only if you have just one public WAN IP address for your ZyXEL Device.
• Choose Full Feature if you have multiple public WAN IP addresses for your ZyXEL 

Device.

Some applications, such as SIP, cannot operate through NAT (are NAT un-friendly) because 
they embed IP addresses and port numbers in their packets’ data payload. 
Some NAT routers may include a SIP Application Layer Gateway (ALG). An Application 
Layer Gateway (ALG) manages a specific protocol (such as SIP, H.323 or FTP) at the 
application layer. 
A SIP ALG allows SIP calls to pass through NAT by examining and translating IP addresses 
embedded in the data stream. 
When the ZyXEL Device registers with the SIP register server, the SIP ALG translates the 
ZyXEL Device’s private IP address inside the SIP data stream to a public IP address. You do 
not need to use STUN or an outbound proxy if your ZyXEL Device is behind a SIP ALG. 

Table 45   NAT Mapping Types

One-to-One

ILA1ÅÆ IGA1

Many-to-One (SUA/PAT)

ILA1ÅÆ IGA1
ILA2ÅÆ IGA1
…

Many-to-Many Overload

ILA1ÅÆ IGA1
ILA2ÅÆ IGA2
ILA3ÅÆ IGA1
ILA4ÅÆ IGA2
…

Many-to-Many No Overload

ILA1ÅÆ IGA1
ILA2ÅÆ IGA2
ILA3ÅÆ IGA3
…

Server

Server 1 IPÅÆ IGA1
Server 2 IPÅÆ IGA1
Server 3 IPÅÆ IGA1