Application Layer Gateway (ALG) allows customized NAT (Network Address Translation) traversal filters to be plugged into the gateway to support address and port translation for certain application layer "control/data" protocols: FTP, TFTP, H323, etc. Enabling ALG is recommended.
PPTP Pass-through - If selected, it allows Point-to-Point sessions to be tunneled through an IP network and passed through the router.
L2TP Pass-through - If selected, it allows Layer 2 Point-to-Point sessions to be tunneled through an IP network and passed through the router.
IPSec Pass-through - If selected, it allows IPSec (Internet Protocol security) to be tunneled through an IP network and passed through the router. IPSec uses cryptographic security services to ensure private and secure communications over IP networks.
FTP ALG - If selected, it allows FTP (File Transfer Protocol) clients and servers to transfer data via NAT.
TFTP ALG - If selected, it allows TFTP (Trivial File Transfer Protocol) clients and servers to transfer data via NAT.
H323 ALG - If selected, it allows Microsoft NetMeeting clients to communicate via NAT.
SIP ALG - If selected, it allows clients communicate with SIP (Session Initiation Protocol) servers via NAT.
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