ZyXEL Communications EMG5324-D10A ユーザーズマニュアル

Chapter 10 Network Address Translation (NAT)

EMG5324-D10A User’s Guide

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 Device registers with the SIP register server, the SIP ALG translates the 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 Device is behind a SIP ALG.

Use this screen to enable or disable the SIP (VoIP) ALG in the Device. To access this screen, click 
Network Setting > NAT > ALG.

Network Setting > NAT > ALG

The following table describes the fields in this screen.

This section provides some technical background information about the topics covered in this 
chapter.

Inside/outside denotes where a host is located relative to the Device, for example, the computers 
of your subscribers are the inside hosts, while the web servers on the Internet are the outside 
hosts. 

Global Start IP

Enter the starting Inside Global IP Address (IGA). Enter 0.0.0.0 here if you have a dynamic 
IP address from your ISP. You can only do this for the Many-to-One mapping type. 

Global End IP

Enter the ending Inside Global IP Address (IGA). This field is blank for One-to-One and 
Many-to-One mapping types.

MAP Set

Select the number of the mapping set for which you want to configure.

OK

Click OK to save your changes.

Cancel

Click Cancel to exit this screen without saving.

Address Mapping: Add/Edit (continued)

Network Setting > NAT > ALG

ALG

Enable this to make sure SIP (VoIP) works correctly with port-forwarding and address-
mapping rules.

Apply

Click Apply to save your changes.