System and method for supporting inter-NAT-domain handoff in a VPN by associating L2TP and mobile IP

摘要

The present invention relates to a system and method for supporting inter-NAT-domain handoff in a VPN by associating L2TP and mobile IP. A mobile node is able to roam from an Intranet to a foreign network, and implement a VPN by L2TP. The Intranet has a VPN gateway and a home agent corresponding to the mobile node. The foreign network has a NAT gateway. An L2TP (PPP) tunnel passing the NAT gateway is established between the mobile node in the foreign network and the VPN gateway. The L2TP (PPP) tunnel has a first terminal on the VPN gateway, with an address set to the home agent's IP address, and a second terminal on the mobile node, with an address set to the mobile node's CoA.