User's Manual

Chapter 19 ALG
ZyWALL USG 20/20W User’s Guide
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• See Section 19.3 on page 357 for ALG background/technical information.
19.1.3 Before You Begin
You must also configure the firewall and enable NAT in the ZyWALL to allow
sessions initiated from the WAN.
19.2 The ALG Screen
Click Configuration > Network > ALG to open the ALG screen. Use this screen
to turn ALGs off or on, configure the port numbers to which they apply, and
configure SIP ALG time outs.
Figure 215 Configuration > Network > ALG
The following table describes the labels in this screen.
Table 98 Configuration > Network > ALG
LABEL DESCRIPTION
Enable SIP ALG Turn on the SIP ALG to detect SIP traffic and help build SIP sessions
through the ZyWALL’s NAT.
Enable SIP
Transformations
Select this to have the ZyWALL modify IP addresses and port numbers
embedded in the SIP data payload.
You do not need to use this if you have a SIP device or server that will
modify IP addresses and port numbers embedded in the SIP data
payload.