ZyXEL Communications SBG5500-A, Руководство пользователя

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Chapter 8 Network Address Translation (NAT)
SBG5500 Series User’s Guide
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8.6 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 SBG
registers with the SIP register server, the SIP ALG translates the SBG’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 SBG is behind a
SIP ALG.
Use this screen to enable and disable the NAT, SIP (VoIP) and/or RTSP ALG in the SBG. To access this
screen, click
Configuration > NAT > ALG .
Figure 104 Configuration > NAT > ALG
The following table describes the fields in this screen.
Table 50 Configuration > 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.
FTP ALG Turn on the FTP ALG to detect FTP (File Transfer Program) traffic and help build FTP sessions
through the SBG’s NAT.
TFTP ALG Turn on the TFTP ALG to detect TFTP (Trivial File Transfer Protocol) traffic and help build TFTP
sessions through the SBG’s NAT.
RTSP ALG Enable this to have the SBG 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.
SIP ALG Enable this to make sure SIP (VoIP) works correctly with port-forwarding and address-mapping
rules.
H.323 ALG Turn on the H.323 ALG to detect H.323 traffic (used for audio communications) and help build
H.323 sessions through the SBG’s NAT.
PPTP ALG Turn on the PPTP ALG to detect PPTP (Point-to-point Tunneling Protocol) traffic and help build
PPTP sessions through the SBG’s NAT.
Apply Click Apply to save your changes.
Reset Click Reset to return the screen to its last-saved settings.