User Manual

NBG-418N v2 User’s Guide
103
C HAPTER 10
Ne twork Addre ss Tra nslation
10.1 Ove rvie w
This chapter discusses how to configure NAT on the NBG-418N v2.
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-418N v2 keeps track of the original addresses and port numbers so incoming reply
packets can have their original values restored. The following figure illustrates this.
Fig ure 74 NAT Example
For more information on IP address translation, refer to RFC 1631, The IP Ne two rk Addre ss Transla to r
(NAT).
Note: You must create a firewall rule in addition to setting up NAT, to allow traffic from the
WAN to be forwarded through the NBG-418N v2.
10.2 Wha t You Ca n Do
• Use the Ge nera l screen to enable NAT and set a default server (
Section 10.3 on page 105).
A: 192.168.1.33
B: 192.168.1.34
C: 192.168.1.35
IP address
192.168.1.1
WANLAN
assigned by ISP
FTP, Telnet, SNMP
Port 80
Ports 21 to 25