Chapter 10 NAT
LTE3302-M432 & LTE3312-M432 User’s Guide
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10.5 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 LTE
Device registers with the SIP register server, the SIP ALG translates the LTE 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 LTE Device is behind a SIP ALG
To enable and disable the SIP ALG in the LTE Device, click Configuration > Network > NAT > ALG. The
screen appears as shown.
Figure 67 Configuration > Network > NAT > ALG
The following table describes the labels in this screen.
10.6 Technical Reference
The following section contains additional technical information about the LTE Device features described
in this chapter.
10.6.1 NATPort Forwarding: Services and Port Numbers
A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or FTP, that you
can make accessible to the outside world even though NAT makes your whole inside network appear
as a single machine to the outside world.
Use the Port Forwarding screen to forward incoming service requests to the server(s) on your local
network. You may enter a single port number or a range of port numbers to be forwarded, and the local
IP address of the desired server. The port number identifies a service; for example, web service is on port
80 and FTP on port 21. In some cases, such as for unknown services or where one server can support
more than one service (for example both FTP and web service), it might be better to specify a range of
port numbers.
Table 43 Configuration > Network > NAT > ALG
LABEL DESCRIPTION
ALG-SIP Select Enable to make sure SIP (VoIP) works correctly with port-forwarding and address-
mapping rules. Otherwise, select Disable to turn off the SIP ALG.
Cancel Click Cancel to begin configuring this screen afresh.
Apply Click Apply to save your changes back to the LTE Device.
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