User's Manual

NBG6503 User’s Guide 117
CHAPTER 14
Network Address Translation (NAT)
14.1 Overview
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in
a packet. For example, the source address of an outgoing packet, used within one network is
changed to a different IP address known within another network.
Each packet has two addresses – a source address and a destination address. For outgoing packets,
NAT maps private (local) IP addresses to globally unique ones required for communication with
hosts on other networks. It replaces the original IP source address in each packet and then
forwards it to the Internet. The Router keeps track of the original addresses and port numbers so
incoming reply packets can have their original values restored. The following figure illustrates this.
Figure 83 NAT Example
For more information on IP address translation, refer to RFC 1631, The IP Network Address
Translator (NAT).
14.2 What You Can Do
•Use the General screen (Section 14.3 on page 118) to enable NAT and set a default server.
•Use the Application screen (Section 14.4 on page 118) o forward incoming service requests to
the server(s) on your local network.
•Use the Advanced screen (Section 14.5 on page 120) to change your Router’s trigger port
settings.