ZyXEL Communications 1001H manual NAT Mapping Types, How NAT Works

P100IH ISDN Router

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.

Figure 4-1 How NAT Works

4.1.3NAT 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 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).

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.

4-2 NAT