Netopia Netopia ISDN Router, R310 - page 87

IP Setup and Network Address Translation 9-1
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The Netopia R310 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.
Netopia’s SmartIP features IP address serving and Network Address Translation. For a detailed discussion of
Network Address Translation, see Appendix E, “Understanding Netopia NAT Behavior.” This chapter describes
how to use the Network Address Translation feature of SmartIP.
Note: When you configured your Netopia R310 using SmartStart, Network Address Translation was enabled by
default. You have the option of disabling it, if you wish. This is done through the System Configuration screens
using Console-based Management.
This section covers the following topics:
■“Network Address Translation Overview” on page 9-1
■“MultiNAT Configuration” on page 9-6
■“IP setup” on page 9-7
■“MultiNAT Configuration Example” on page 9-24
■“IP subnets” on page 9-28
■“IP address serving” on page 9-34
Network Address Translation Overview
NAT (Network Address Translation) is a means of mapping one or more IP addresses and/or IP service ports
into different values. This mapping serves two functions:
■It allows the addresses of many computers on a LAN to be represented to the public Internet by only one or
a few addresses, saving you money.
■It can be used as a security feature by obscuring the true addresses of important machines from potential
hackers on the Internet.
To help you understand some of the concepts discussed here, it may be helpful to introduce some NAT
terminology.
The term mapping refers to rules that associate one or more private addresses on the Netopia R310’s LAN to
one or more public addresses on the Netopia R310’s WAN interface (typically the Internet).
The terms private and internal refer to addresses on the Netopia R310’s LAN. These addresses are considered
private because they are protected or obscured by NAT and cannot be directly accessed from the WAN (or
Internet) side of the Netopia R310 unless specifically configured otherwise.
The terms public and external refer to the WAN (or Internet) side of the Netopia R310.