The Alg Screen; The Address Mapping Screen - ZyXEL Communications VMG3312-T20A User Manual

11.6 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 VMG
registers with the SIP register server, the SIP ALG translates the VMG'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 VMG is
behind a SIP ALG.
Use this screen to enable and disable the ALGs in the VMG. To access this screen, click Network Setting
> NAT > ALG.
Figure 88 Network Setting > NAT > ALG
The following table describes the fields in this screen.
Table 63 Network Setting > NAT > ALG
LABEL
NAT ALG
SIP ALG
RTSP ALG
PPTP ALG
IPSEC ALG
Apply
Cancel

11.7 The Address Mapping Screen

Ordering your rules is important because the VMG applies the rules in the order that you specify. When a
rule matches the current packet, the VMG takes the corresponding action and the remaining rules are
ignored.
Click Network Setting > NAT > Address Mapping to display the following screen.
Chapter 11 Network Address Translation (NAT)
DESCRIPTION
Enable this to make sure applications such as FTP and file transfer in IM applications work
correctly with port-forwarding and address-mapping rules.
Enable this to make sure SIP (VoIP) works correctly with port-forwarding and address-mapping
rules.
Enable this to have the VMG detect RTSP traffic and help build RTSP sessions through its NAT. The
Real Time Streaming (media control) Protocol (RTSP) is a remote control for multimedia on the
Internet.
Enable this to turn on the PPTP ALG on the VMG to detect PPTP traffic and help build PPTP
sessions through the VMG's NAT.
Enable this to turn on the IPsec ALG on the VMG to detect IPsec traffic and help build IPsec
sessions through the VMG's NAT.
Click Apply to save your changes.
Click Cancel to restore your previously saved settings.
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