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ZyXEL X-550 User’s Guide
3.2.3 ADVANCED - Applications
Figure 3-10 ADVANCED - Applications
APPLICATION LEVEL GATEWAY (ALG) CONFIGURATON
Here you can enable or disable ALGs. Some protocols and applications require special handling of the IP
payload to make them work with network address translation (NAT). Each ALG provides special handling
for a specific protocol or application. A number of ALGs for common applications are enabled by default.
PPTP:
Enabling this feature allows multiple machines on the LAN to connect to their corporate network using the
PPTP protocol.
IPSec VPN:
This feature allows multiple VPN clients to connect to their corporate network using IPSec protocol. Some
VPN clients support traversal of IPSec through NAT. This ALG may interfere with the operation of such
VPN clients. If you are having trouble connecting with your corporate network, try turning this ALG off.
Please check with the system administrator of your corporate network whether your VPN client supports
NAT traversal.
RTSP:
Enabling RTSP allows applications that use Real Time Streaming Protocol to receive streaming media
from the internet. QuickTime and Real Player are some of the common applications using this protocol.
Windows Messenger:
Enabling this feature supports the use of Microsoft Windows Messenger (the Internet messaging client that
ships with Microsoft Windows) on LAN computers. The SIP ALG must also be enabled when the
Windows Messenger ALG is enabled.
FTP:
Enabling this feature allows FTP clients and servers to transfer data across NAT. Refer to the
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