Operation Manual

Chapter 9 Network Address Translation (NAT)
eircom F1000 Modem User’s Guide
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The following table describes the fields in this screen.
9.6 The ALG Screen
Some NAT routers may include a SIP Application Layer Gateway (ALG). A SIP ALG allows SIP calls
to pass through NAT by examining and translating IP addresses embedded in the data stream.
When the Device registers with the SIP register server, the SIP ALG translates the Device’s private
IP address inside the SIP data stream to a public IP address. You do not need to use STUN or an
outbound proxy if your Device is behind a SIP ALG.
Use this screen to enable and disable the NAT and SIP (VoIP) ALG in the Device. To access this
screen, click Network Setting > NAT > ALG.
Figure 90 Network Setting > NAT > ALG
The following table describes the fields in this screen.
Table 60 Network Setting > NAT > DMZ
LABEL DESCRIPTION
Default Server
Address
Enter the IP address of the default server which receives packets from ports that are not
specified in the NAT Port Forwarding screen.
Note: If you do not assign a Default Server Address, the Device discards all packets
received for ports that are not specified in the NAT Port Forwarding screen.
Apply Click Apply to save your changes.
Cancel Click Cancel to restore your previously saved settings.
Table 61 Network Setting > NAT > ALG
LABEL DESCRIPTION
NAT ALG Enable this to make sure applications such as FTP and file transfer in IM applications work
correctly with port-forwarding and address-mapping rules.
SIP ALG
Enable this to make sure SIP (VoIP) works correctly with port-forwarding and address-
mapping rules.
RTSP ALG
Enable this to have the Device detect RTSP traffic and help build RTSP sessions through its
NAT. The Real Time Streaming (media control) Protocol (RTSP) is a remote control for
multimedia on the Internet.
Apply Click Apply to save your changes.
Cancel Click Cancel to restore your previously saved settings.