The Alg Screen; The Sessions Screen - ZyXEL Communications P-660HN-51 User Manual

8.6 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 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 Settings > NAT > ALG.
Figure 51 Network Settings > NAT > ALG
The following table describes the fields in this screen.
Table 34 Network Settings > NAT > ALG
LABEL
Enable SIP ALG
Apply

8.7 The Sessions Screen

Use the Sessions screen to limit the number of concurrent NAT sessions all clients can use.
Click Network Settings > NAT > Sessions to display the following screen.
Figure 52 Network Settings > NAT > Sessions
Chapter 8 Network Address Translation (NAT)
DESCRIPTION
Select this to make sure SIP (VoIP) works correctly with port-forwarding and address-
mapping rules.
Click Apply to save your changes.
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