Netopia R5000 User Reference Manual page 102

9-2 User's Reference Guide
NAT works by remapping the source IP address of traffic from the LAN to a single static or dynamically assigned
IP address shown to the remote side of the router.
The feature can be implemented on a per–connection profile basis. The network router can use two or more
connection profiles simultaneously to connect to two or more networks. Each profile can have NAT enabled.
When NAT is enabled, the Netopia R5000 Series Router can use either a statically assigned IP address or one
dynamically assigned each time the router connects to the ISP. While a dynamically assigned IP address offers
the ISP more flexibility, it does have an important limitation: the router requires a static IP address to support
Web, FTP, or other services available to the WAN. To support these services with NAT enabled, a service can be
associated with only one machine on the LAN.
When connected to the Internet or some other large network using NAT, the individual machines on your LAN are
not directly accessible from the WAN. NAT provides an inherently secure method of connection to the outside
world.