8.6.20 PPTP Pass-throughDescriptionFor VPN packets that use PPTP and are sent and received from a specified device on the LAN, you canconfigure settings so that (1) the port number is not changed when these packets are sent and received and(2) these packets are allowed to cross the LAN–WAN boundary uninhibited.Only 1 device on the LAN can be designated as the PPTP pass-through device (acting as either a server or aclient).Setting DescriptionApplication PPTPProtocol/Protocol number GRE*1 / 47Port number TCP/1723: PPTPA VPN that uses PPTP is a tunnelling protocol, so the send/receive port number for packets additionallyindicates which tunnelling protocol the packets are using. If the port number is changed by the dynamic NAPT(IP masquerade) feature, the information that indicates the tunnelling protocol will be lost, and end-to-endcommunication will be impossible.To allow end-to-end communication, specified packets from a specified device are allowed to pass throughthe WAN–LAN boundary without having their port number changed.Conditions• Communication across the WAN–LAN boundary is subject to the following conditions:– One server–client pair is limited to 1 session.– A PPTP-controlled connection can be established from either the LAN side or the WAN side.– The GRE*1 tunnel’s first packet can be sent from either the LAN side or the WAN side.– You must set the LAN-side client’s IP address.*1 GRE: Generic Route EncapsulationPC Programming Manual References27.11 Router Configuration—VPN—[3-3] Pass Through8.6.21 L2TP Pass-throughDescriptionFor VPN packets that use L2TP (Layer 2 Tunnelling Protocol) and are sent and received from a specifieddevice on the LAN, you can configure settings so that (1) the port number is not changed when these packetsare sent and received and (2) these packets are allowed to cross the LAN–WAN boundary uninhibited.Only 1 device on the LAN can be designated as the L2TP pass-through device (LENS*1).Setting DescriptionApplication L2TPProtocol/Protocol number –Port number UDP/1701: L2TP392 Installation Manual8.6.21 L2TP Pass-through
