ZyXEL Communications 1001H User Manual
P100IH ISDN Router
4-2
NAT
and Many-to-Many Overload NAT mapping) and then forwards each packet to the Internet ISP, thus making
them appear as if they had come from the NAT system itself (e.g., the Prestige). The Prestige keeps track of
the original addresses and port numbers so incoming reply packets can have their original values restored.
The following diagram illustrates this.
them appear as if they had come from the NAT system itself (e.g., the Prestige). The Prestige keeps track of
the original addresses and port numbers so incoming reply packets can have their original values restored.
The following diagram illustrates this.
Figure 4-1 How NAT Works
4.1.3
NAT Mapping Types
NAT supports five types of IP/port mapping. They are:
1. One to One: In One-to-One mode, the Prestige maps one local IP address to one global IP address.
2. Many to One: In Many-to-One mode, the Prestige maps multiple local IP addresses to one global IP
2. Many to One: In Many-to-One mode, the Prestige maps multiple local IP addresses to one global IP
address. This is equivalent to SUA (i.e., PAT, port address translation), ZyXEL’s Single User Account
feature that previous ZyXEL routers supported (the SUA Only option in today’s routers).
feature that previous ZyXEL routers supported (the SUA Only option in today’s routers).
3. Many to Many Overload: In Many-to-Many Overload mode, the Prestige maps the multiple local IP
addresses to shared global IP addresses.
4. Many to Many No Overload: In Many-to-Many No Overload mode, the Prestige maps the each local IP
addresses to unique global IP addresses.
5. Server: This type allows us to specify multiple inside servers of different types behind the NAT.
Port numbers do not change for One-to-One and Many-to-Many-No Overload NAT
mapping types.
The following table summarizes these types.