Chapter 8 Network Address Translation (NAT)
P-792H v2 User’s Guide
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8.5 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 P-792H v2 registers with the SIP register
server, the SIP ALG translates the P-792H v2’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 P-792H v2 is behind a SIP ALG.
Use this screen to enable and disable the SIP (VoIP) ALG in the P-792H v2. To
access this screen, click Network > NAT > ALG.
Figure 46 Network > NAT > ALG
The following table describes the fields in this screen.
8.6 NAT Technical Reference
This chapter contains more information regarding NAT.
8.6.1 NAT Definitions
Inside/outside denotes where a host is located relative to the P-792H v2, for
example, the computers of your subscribers are the inside hosts, while the web
servers on the Internet are the outside hosts.
Global/local denotes the IP address of a host in a packet as the packet traverses a
router, for example, the local address refers to the IP address of a host when the
Table 28 Network > NAT > ALG
LABEL DESCRIPTION
Enable SIP ALG Select this to change the private ports or IP in SIP messages so that the
VoIP client behind the P-792H v2 can be found in RTP traffic.
Apply Click this to save your changes.
Reset Click this to restore your previously saved settings.
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