Chapter 9 Network Address Translation (NAT)
9.5 The SIP 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 > NAT > ALG.
Figure 73 Network > NAT > ALG
The following table describes the fields in this screen.
Table 49 Network > NAT > ALG
LABEL | DESCRIPTION |
Enable SIP ALG | Select this to make sure SIP (VoIP) works correctly with port- |
| forwarding and |
|
|
Apply | Click this to save your changes. |
|
|
Reset | Click this to restore your previously saved settings. |
|
|
9.6 NAT Technical Reference
This chapter contains more information regarding NAT.
9.6.1 NAT Definitions
Inside/outside denotes where a host is located relative to the ZyXEL Device, 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
| 181 |
|
|