ZyXEL Communications P-660HN-TxA - Manual (Page 145)

Chapter 9 Network Address Translation (NAT)
P-660HN-TxA User’s Guide
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9.5 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 ZyXEL Device registers with the SIP
register server, the SIP ALG translates the ZyXEL 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 ZyXEL Device is behind a SIP ALG.
Use this screen to enable and disable the SIP (VoIP) ALG in the ZyXEL Device. To
access this screen, click Network > NAT > ALG.
Figure 70 Network > NAT > ALG
The following table describes the fields in this screen.
Global End IP This is the ending global IP address (IGA). This field is N/A for One-to-
One, Many-to-One and Server mapping types.
Server
Mapping Set
Edit Details
Click this link to go to the Port Forwarding screen to edit a port
forwarding set that you have selected in the Server Mapping Set field.
Back Click this to return to the previous screen without saving.
Apply Click this to save your changes.
Cancel Click this to restore your previously saved settings.
Table 45 Network > NAT > Address Mapping: Edit (continued)
LABEL DESCRIPTION
Table 46 Network > NAT > ALG
LABEL DESCRIPTION
Enable SIP ALG Select this to make sure SIP (VoIP) works correctly with port-
forwarding and address-mapping rules.
Apply Click this to save your changes.
Reset Click this to restore your previously saved settings.