User's Guide Part 2

Chapter 8 Network Address Translation (NAT) Screens
P-660HW-Dx v2 User’s Guide
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The following table summarizes these types.
8.2 SUA (Single User Account) Versus NAT
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 Table 45 on page 132.
• 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.
8.3 SIP ALG
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
TYPE IP MAPPING
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