ZyXEL Communications P-660HN-T1H User Manual

Chapter 9 Network Address Translation (NAT)

P-660HN-T1H User’s Guide

The following figure illustrates a possible NAT application, where three inside LANs 
(logical LANs using IP alias) behind the ZyXEL Device can communicate with three 
distinct WAN networks.

Figure 71   NAT Application With IP Alias

NAT supports five types of IP/port mapping. They are:

• One to One: In One-to-One mode, the ZyXEL Device maps one local IP address 

to one global IP address.

• Many to One: In Many-to-One mode, the ZyXEL Device maps multiple local IP 

addresses to one global IP address. This is equivalent to SUA (for instance, PAT, 

port address translation), ZyXEL’s Single User Account feature that previous 

ZyXEL routers supported (the SUA Only option in today’s routers). 

• Many to Many Overload: In Many-to-Many Overload mode, the ZyXEL Device 

maps the multiple local IP addresses to shared global IP addresses.

• Many-to-Many No Overload: In Many-to-Many No Overload mode, the ZyXEL 

Device 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.