The Alg Screen; The Sessions Screen - ZyXEL Communications P-660HN-51 - V1.10 Manual

Chapter 8 Network Address Translation (NAT)

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.
144
DESCRIPTION
Select this to make sure SIP (VoIP) works correctly with port-
forwarding and address-mapping rules.
Click Apply to save your changes.
P-660HN-51 User's Guide