Chapter 9 - Ip Setup And Network Address Translation; Network Address Translation Features; Using Network Address Translation; Connection Profiles - Netopia R5100 User Reference Manual

The Netopia R5000 Series Router uses Internet Protocol (IP) to communicate both locally and with remote
networks. This chapter shows you how to configure the router to route IP traffic. You also learn how to configure
the router to serve IP addresses to hosts on your local network and to configure Network Address Translation.
This section covers the following topics:
"Network Address Translation features" on page 9-1
"Using Network Address Translation" on page 9-3
"Connection Profiles" on page 9-8
"IP setup" on page 9-12
"IP address serving" on page 9-22
Network Address Translation allows communication between the LAN connected to the Netopia R5000 Series
Router and the Internet using a single IP address instead of an routed with individual IP addresses for each
computer on the network.
Network Address Translation also provides increased security by hiding the local IP addresses of the LAN
connected to the Netopia R5000 Series from the outside world.
For a detailed discussion of Network Address Translation, see
Behavior."
Network Address Translation (NAT) offers users the following features:
NAT is selectable on a per connection basis, optionally allowing real addresses to be used for intranet
connections and proxied addresses to be used for Internet connections.
You can use any combination of NAT (proxied) and non-NAT (unproxied) addresses simultaneously on the
available connection channels. For instance, one non-NAT connection profile can be used to connect to
corporate headquarters, while another NAT connection profile can simultaneously connect your Netopia
R5000 Series Router and LAN to the Internet.
In a one-to-many NAT connection the single address on the WAN side may be acquired at connection time
from the remote side. The address can be assigned by the remote router from either a dynamic pool of
addresses or a fixed, static address.
Static NAT security is simpler and more reliable because only one IP address needs a firewall, and because
the internal network structure is not visible from the Internet.
Netopia's NAT implementation allows for multiple servers (mail, web, ftp, etc.) to be accessible from the
WAN or Internet. However, only one server of each application type (or TCP port) can be accessed from the
WAN or Internet. Making a LAN server available to the WAN is called exporting a service.
IP Setup and Network Address Translation 9-1
Appendix C, "Understanding Netopia NAT