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Chapter 7 NAT
FSG1100HN User’s Guide
64
7.3 NAT General Screen
The NAT window General tab allows users to configure NAT settings. 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 FSG1100HN
keeps track of the original addresses and port numbers so incoming reply packets can
have their original values restored.
Click Networking > NAT > General to open the NAT General screen.
Networking > NAT > General
The following table describes the NAT general labels in this screen.
Networking > NAT > General
LABEL
DESCRIPTION
NAT Setup
Network
Address
Translation
Enable or Disable Network Address Translation (NAT). NAT allows
the translation of an Internet protocol address used within one network
(for example a private IP address used in a local network) to a
different IP address known within another network (for example a
public IP address used on the Internet).
NAT
Loopback
Enable or Disable NAT Loopback. NAT Loopback allows users on the
LAN side to access a pubic server located on the LAN side by a public
IP address or domain name.
SIP ALG
Enable or Disable SIP ALG. SIP Application Level Gateway (ALG)
allows VoIP calls to pass through NAT by examining and translating IP
addresses embedded in the data stream. When a VoIP device behind
the FSG1100HN registers with the SIP register server, the
FSG1100HN translates the device’s private IP address inside the SIP
data stream to a public IP address.
RTSP ALG
Enable or Disable RTSP ALG. Application Level Gateway (ALG).
This is designed to dynamically open pinholes for media streaming.
When disabled, you are limited to static NAT only.