User Manual
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Application Level Gateway (ALG) Configuration
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
Allows multiple machines on the LAN to connect to their corporate networks using PPTP protocol. When the PPTP ALG is enabled, LAN computers can
establish PPTP VPN connections either with the same or with different VPN servers. When the PPTP ALG is disabled, the router allows VPN operation in a
restricted way -- LAN computers are typically able to establish VPN tunnels to different VPN Internet servers but not to the same server. The advantage of
disabling the PPTP ALG is to increase VPN performance.
IPSec (VPN)
Allows multiple VPN clients to connect to their corporate networks using IPSec. Some VPN clients support traversal of IPSec through NAT. This option may
interfere with the operation of such VPN clients. If you are having trouble connecting with your corporate network, try disabling this option.
Check with the system adminstrator of your corporate network whether your VPN client supports NAT traversal.
Note that L2TP VPN connections typically use IPSec to secure the connection. To achieve multiple VPN pass-through in this case, the IPSec ALG must be
enabled.
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/MSN Messenger
Supports use on LAN computers of Microsoft Windows Messenger (the Internet messaging client that ships with Microsoft Windows) and MSN Messenger.
The SIP ALG must also be enabled when the Windows Messenger ALG is enabled.
FTP
Allows FTP clients and servers to transfer data across NAT. Refer to the Virtual Server page if you want to host an FTP server.
H.323 (Netmeeting)
Allows H.323 (specifically Microsoft Netmeeting) clients to communicate across NAT. Note that if you want your buddies to call you, you should also set
up a virtual server for NetMeeting.
SIP
Allows devices and applications using VoIP (Voice over IP) to communicate across NAT. Some VoIP applications and devices have the ability to discover
NAT devices and work around them. This ALG may interfere with the operation of such devices. If you are having trouble making VoIP calls, try turning
this ALG off.
Wake-On-LAN
