| 摘要 |
PROBLEM TO BE SOLVED: To prevent a terminal connected to an internal LAN from being specified from the outside without complicated ciphering and to easily provide a fire wall effect. SOLUTION: At the time of transmitting a packet from a terminal 1 to the terminal 2, an address conversion circuit 30 converts the originating side IP address of the packet delivered from an internal LAN controller 10 from an intrinsic IP address to a pseudo IP address by referring to an address memory 40 and records the set of the pseudo IP address and the intrinsic IP address in a main memory 50. Also, at the time of returning the packet from the terminal 2 to the terminal 1, the address conversion circuit 30 converts the transmission destination IP address of the packet delivered from an external LAN controller 20 from the pseudo IP address to the intrinsic IP address by referring to the main memory 50 and eliminats the set of the pseudo IP address and the intrinsic IP address from the main memory 50.
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