Network Address Translation; Ne Two Rk Addre Ss T Ra Nsla Tio N; Overview; What You Can Do - ZyXEL Communications NBG-418N v2 User Manual

Ne two rk Addre ss T ra nsla tio n

10.1 O ve 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
A: 192.168.1.33
FTP, Telnet, SNMP
Ports 21 to 25
B: 192.168.1.34
Port 80
C: 192.168.1.35
For more information on IP address translation, refer to RFC 1631 , T he IP Ne two rk Addre ss T ra nsla 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 Yo u C a n Do
G e ne ra l
• Use the
192.168.1.1
screen to enable NAT and set a default server
NBG-418N v2 User's Guide
103
C
HA PTER
LAN WAN
IP address
assigned by ISP
(Section 10.3 on page
1 0
105).