ZyXEL Communications Corporation P873HNUP51B Manuel D’Utilisation

Chapter 11 Network Address Translation (NAT)

P-873HNUP-51B User’s Guide

The following table describes the fields in this 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 Settings > NAT > ALG.

Figure 68   Network Settings > NAT > ALG

The following table describes the fields in this screen.

Table 49   Network Settings > NAT > DMZ

Default Server 
Address

Enter the IP address of the default server which receives packets from ports that 
are not specified in the NAT Port Forwarding screen. 

Note: If you do not assign a Default Server Address, the ZyXEL Device discards 

all packets received for ports that are not specified in the NAT Port 
Forwarding screen.

Apply

Click Apply to save your changes.

Cancel

Click Cancel to restore your previously saved settings.

Table 50   Network Settings > NAT > ALG

ALG

Enable this to make sure applications such as FTP and file transfer in IM 
applications work correctly with port-forwarding and address-mapping rules.

SIP ALG

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

Apply

Click Apply to save your changes.

Cancel

Click Cancel to restore your previously saved settings.