Communicating apparatus and controlling method of thereof

A method of controlling a communicating apparatus for relaying a data communication between a first network and a second network, comprising the steps of:

• receiving a packet from a terminal connected to the first network;
• acquiring an IP address of the terminal from the received packet, obtaining a range of a subnet mask value which can be taken by the terminal based on the IP address, and acquiring a candidate for a host address corresponding to each subnet mask value;
• setting the host address candidate accessibly from the terminal and determining an estimated value of the subnet mask value of the terminal based on a state of the packet transmitted to the host address candidate sent from the terminal;
• and
• setting the estimated value as a subnet mask value corresponding to an interface for a first network connection.

A method of controlling a communication apparatus for relaying a data communication between a first network and a second network, the method comprising the steps of:

• receiving a packet from a terminal connected to the first network;
• acquiring an IP address of the terminal from the packet;
• obtaining a candidate for a host address based on the IP address;
• setting a candidate accessibly from the terminal;
• determining an estimated subnet mask value of the terminal based on a state of another packet caused to be sent from the terminal in response to the terminal executing access to a set host address;
• and
• setting the estimated value as a subnet mask value of the terminal corresponding to an interface for the first network connection.

A communication apparatus for relaying a data communication between a first network and a second network, the communication apparatus comprising:

• a receiving unit having an interface providing a first network connection and serving to receive a packet from a terminal connected to the interface;
• and
• a control processor that:
• (1) checks a packet from a terminal,
• (2) determines a default gateway IP address of the terminal based on the packet,
• (3) sets the default gateway IP address as an IP address corresponding to the interface for the first network connection if the packet received by the receiving unit is transmitted from the terminal,
• (4) obtains a candidate for a host address based on the IP address,
• (5) sets a candidate accessibly from the terminal,
• (6) determines an estimated subnet mask value of the terminal based on an arrival state of another packet caused to be sent from the terminal in response to the terminal executing access to a set host address, and
• (7) sets the estimated value as a subnet mask value of the terminal corresponding to the interface for the first network connection.