D-Link DSR-250N - VPN Passthrough for Firewall; Figure 64: Available ALG Support on the Router

Unified Services Router User Manual
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Figure 64: Available ALG support on the router.
5.7 VPN Passthrough for Firewall
Advanced > Firewall Settings > VPN Passthrough
This router’s firewall settings can be configured to allow encrypted VPN traffic for
IPsec, PPTP, and L2TP VPN tunnel connections between the LAN and internet. A
specific firewall rule or service is not appropriate to introduce this passthrough
support; instead the appropriate check boxes in the VPN Passthrough page must be
enabled.