ZyXEL Communications Corporation IX253P Manuel D’Utilisation
Chapter 8 The NAT Configuration Screens
Users Guide
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8.5 ALG
Some applications, such as SIP, cannot operate through NAT (are NAT un-friendly)
because they embed IP addresses and port numbers in their packets’ data
payload.
because they embed IP addresses and port numbers in their packets’ data
payload.
Some NAT routers may include a SIP Application Layer Gateway (ALG). An
Application Layer Gateway (ALG) manages a specific protocol (such as SIP, H.323
or FTP) at the application layer.
Application Layer Gateway (ALG) manages a specific protocol (such as SIP, H.323
or FTP) at the application layer.
A SIP ALG allows SIP calls to pass through NAT by examining and translating IP
addresses embedded in the data stream.
addresses embedded in the data stream.
Click ADVANCED > NAT Configuration > ALG to enable and disable SIP (VoIP),
FTP (file transfer), and H.323 (audio-visual) ALG in the WiMAX Modem.
FTP (file transfer), and H.323 (audio-visual) ALG in the WiMAX Modem.
Figure 38 ADVANCED > NAT Configuration > ALG
The following table describes the labels in this screen.
Table 29 ADVANCED > NAT Configuration > ALG
LABEL
DESCRIPTION
Enable SIP ALG
Select this to make sure SIP (VoIP) works correctly with port-
forwarding and port-triggering rules.
Enable FTP ALG Select this to make sure FTP (file transfer) works correctly with port-
forwarding and port-triggering rules.
Enable H.323
ALG
ALG
Select this to make sure H.323 (audio-visual programs, such as
NetMeeting) works correctly with port-forwarding and port-triggering
rules.
NetMeeting) works correctly with port-forwarding and port-triggering
rules.
Apply
Click to save your changes.
Cancel
Click to return to the previous screen without saving your changes.