Communication Between Remote LANs Based on L2TP

L2TP (Layer 2 Tunneling Protocol)is a type of VPDN(Virtual Private Dial-up Network)tunneling protocol. It extends the application of PPP (Point-to-Point Protocol). L2TP establishes a tunnel from the enterprise branch user to the enterprise headquarters through the dial-up network and PPP based negotiation, so that remote users can access the enterprise headquarters. In order to ensure the security and the convenience of operation, this paper describes how to communicate between the remote LAN devices through the L2TP protocol. The transparent bridging function between the LAC (L2TP Access Concentrator)and the tunnel entry and Ethernet port is implemented in the embedded Linux device. The bridging function enables the PCs connected to the lower end of the LAC device to communicate with the devices connected to the lower end of the LNS (L2TP Network Server).