Draytek Vigor2500V Manual page 46

Vigor2500V series
Chapter 5
NAT (Network Address Translation)
5.1 Introduction
NAT (Network Address Translation) provides you with a method of mapping
one or more IP addresses and/or service ports into different specified
applications. The Vigor router takes a single public IP address, allocated by
your ISP and automatically forwards data between the Vigor router and the
local computer or laptop on your local network. For the outside world, the
public IP address of the router is visible by external users. However, the
external users cannot address the internal private IP address of every
computer / laptop. Any "unsolicited" TCP/IP packet to your public IP
address will arrive at your router but the router can not send the packet to any
computer or laptop on the LAN. The NAT plays an important guard for your
network clients because the internal private IP address of every computer or
laptop is hidden from the outside world, unless you open up ports/protocols to
allow contact.
Through a single public IP address, several computers of your internal local
network can share the broadband access of an ADSL line. For cost concern,
you do not need to subscribe more than one public IP address for every
computer or laptop because the NAT facility of Vigor router can transform a
single public IP address to many internal private IP addresses.
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