ZyXEL VMG4825 User Guide - Page 161
The ALG Screen, The Address Mapping Screen
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Chapter 11 Network Address Translation (NAT) 11.6 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 VMG registers with the SIP register server, the SIP ALG translates the VMG'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 VMG is behind a SIP ALG. Use this screen to enable and disable the ALGs in the VMG. To access this screen, click Network Setting > NAT > ALG. Figure 83 Network Setting > NAT > ALG The following table describes the fields in this screen. Table 61 Network Setting > NAT > ALG LABEL DESCRIPTION NAT 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 addressmapping rules. RTSP ALG Enable this to have the VMG detect RTSP traffic and help build RTSP sessions through its NAT. The Real Time Streaming (media control) Protocol (RTSP) is a remote control for multimedia on the Internet. PPTP ALG Enable this to turn on the PPTP ALG on the VMG to detect PPTP traffic and help build PPTP sessions through the VMG's NAT. IPSEC ALG Apply Enable this to turn on the IPsec ALG on the VMG to detect IPsec traffic and help build IPsec sessions through the VMG's NAT. Click Apply to save your changes. Cancel Click Cancel to restore your previously saved settings. 11.7 The Address Mapping Screen Ordering your rules is important because the VMG applies the rules in the order that you specify. When a rule matches the current packet, the VMG takes the corresponding action and the remaining rules are ignored. Click Network Setting > NAT > Address Mapping to display the following screen. Figure 84 Network Setting > NAT > Address Mapping VMG4825-B10A User's Guide 161