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TD-W8970B 300Mbps Wireless N Gigabit ADSL2+ Modem Router (Annex B) User Guide
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4.5.7 ALG Settings
Choose menu “Network”Æ“ALG Settings”, and then you can configure the basic security in the
screen as shown in Figure 4-23.
Figure 4-23
¾ Virtual Private Network (VPN): VPN Passthrough must be enabled if you want to allow VPN
tunnels using VPN protocols to pass through the modem router.
• PPTP Passthrough: Point-to-Point Tunneling Protocol (PPTP) allows the Point-to-Point
Protocol (PPP) to be tunneled through an IP network. To allow PPTP tunnels to pass
through the modem router, click Enable.
• L2TP Passthrough: Layer Two Tunneling Protocol (L2TP) is the method used to
enable Point-to-Point sessions via the Internet on the Layer Two level. To allow L2TP
tunnels to pass through the modem router, click Enable.
• IPSec Passthrough: Internet Protocol security (IPSec) is a suite of protocols for
ensuring private, secure communications over Internet Protocol (IP) networks, through
the use of cryptographic security services. To allow IPSec tunnels to pass through the
modem router, click Enable.
¾ Application Layer Gateway (ALG): It is recommended to enable Application Layer Gateway
(ALG) because ALG allows customized Network Address Translation (NAT) traversal filters to
be plugged into the gateway to support address and port translation for certain application
layer "control/data" protocols such as FTP, TFTP etc.
• FTP ALG: To allow FTP clients and servers to transfer data across NAT, click Enable.
• TFTP ALG: To allow TFTP clients and servers to transfer data across NAT, click
Enable.
• H323 ALG: To allow H323 clients and servers to transfer data across NAT, click
Enable.
• SIP ALG: To allow SIP clients and servers to transfer data across NAT, click Enable.
Click the Save button to save your settings.