LOCAL AREA NETWORK CORRESPONDENCE NETWORK ADDRESS CONVERSION GATE WAY USING LOCAL IP ADDRESS AND CONVERSION IMPOSSIBLE PORT ADDRESS

摘要

PROBLEM TO BE SOLVED: To set a safe VPN by using an NAT gate way. SOLUTION: A gate way 20 provides normal network conversion to an IP data gram which moves from a local area network 10 to an external network. When a port is reserved for a specified protocol such as an ISAKMP 'handshaking' protocol being a part of an IPSec protocol model, source service address (port) conversion is interrupted. A network interface without port conversion is provided. Then transmission with sure enciphering is started by the gate way between the local area network 10 using a local IP address and a server on the Internet 50 through the use of the IPSec protocol and also is kept.