Network Address Translation (Nat); Overview; What You Can Do - ZyXEL Communications NBG-419N User Manual

Network Address Translation (NAT)

15.1 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 NBG-419N 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 93 NAT Example
For more information on IP address translation, refer to RFC 1631, The IP Network Address
Translator (NAT).

15.2 What You Can Do

• Use the General screen
• Use the Application screen
the server(s) on your local network.
• Use the Advanced screen
settings.
NBG-419N User's Guide
C
HAPTER
(Section 15.3 on page 126) to enable NAT and set a default server.
(Section 15.4 on page
(Section 15.5 on page 128) to change your NBG-419N's trigger port
126) o forward incoming service requests to
1 5
125