Patent ID: 7266119

Claim:
A method for supporting mobile Internet protocol (IP) in private networks, wherein a mobile node moves from its home network to a foreign private network and obtains a care of address (CoA) from the private network, and the private network has a network address translation (NAT) device, the method comprising: a registration packet sending step, in which the mobile node sends a registration packet to a home agent in the home network, and the registration packet has a header with a source address field containing the CoA, a destination address field containing an address of the home agent and a swap address option field; a first NAT translating step, in which a NAT device swaps contents of the source and the swap address fields of the registration packet and translates the content of the source address field into a public address of the NAT device according to NAT regulations, thereby sending the registration packet to the home agent; a registration reply packet sending step, in which, after receiving the registration packet, the home agent responds a registration reply packet with a header having a source address field containing the address of the home agent, a destination address field containing the public address of the NAT device and a swap address option field filled therein the CoA; and a second NAT translating step, in which a NAT device swaps contents of the destination and the swap address fields of the registration reply packet, thereby sending the registration reply packet to the mobile node and completing registration.