As the mobile VPN users have recently increased, the mobile VPN services are diversifying so the service needs to support the communication between two mobile VPN users in foreign networks. However, it could degrade the performance of the service because of the triangular routing problem. Therefore, we propose route optimization mechanism based on the mobile VPN using an x-HA allocated by diameter MIP to provide an optimized path between the mobile VPN users in foreign networks. i-HA maintains VPN-TIA as a CoA with x-HoA to solve the security problem and support efficient route optimization in the proposed scheme. Also, we proposed revised IPsec tunnel configuration for reducing IPsec tunnel overheads to a MN when the MN communicates with several MNs at the same time. The VPN server, which is a security management entity in home network, notifies an additional IPsec tunnel establishment between two x-HAs that the communication peer registered to.