JP4516945B2 - Network system, access point, communication terminal, address determination method, and program - Google Patents

Description

  The present invention relates to an address determination method, and more particularly to an address determination method in an IP terminal.

  Conventionally, in order to realize access to an IP (Internet Protocol) terminal, the IP address of the terminal itself is set in advance. For this reason, the IP address may not match the subnet of the connected network. In such a case, it is a problem that it is necessary to disconnect the IP terminal from the network once and reset the IP address assigned to the terminal that accesses the IP terminal so as to match the IP address subnet configuration. It was.

A conventional technique will be described with reference to FIG.
In FIG. 1, a wireless LAN (Local Area Network) system includes a router 1, a wireless LAN access point terminal 2, and a wireless LAN terminal 3. The router 1 relays communication between the external network and the internal network. The router 1 also includes a DHCP (Dynamic Host Configuration Protocol) server 4. The DHCP server 4 automatically assigns an IP address to a computer connected to the external network. The wireless LAN access point terminal 2 is bridge-connected to the router 1 and the wireless LAN terminal 3. The router 1 relays between the external network and the wireless LAN terminal 3. The wireless LAN terminal 3 passes through the wireless LAN access point terminal 2 and communicates with an external network. The wireless LAN terminal 3 includes a DHCP client function unit 5. The DHCP client function unit 5 acquires an IP address from the DHCP server 4 and sets it in the wireless LAN terminal 3.

However, the conventional techniques have the following problems.
The wireless LAN terminal 3 obtains an IP address from the router 1 using the DHCP client function unit 5, whereas the wireless LAN access point terminal 2 has a fixed IP address.

  Therefore, the network addresses of the IP addresses of the wireless LAN terminal 3 and the wireless LAN access point terminal 2 may be different.

Japanese Patent Laid-Open No. 2004-112801 (Patent Document 1) discloses an IP address assignment apparatus and method.
This prior art includes an Internet access gateway that requests IP address assignment and an Internet service provider (ISP) that has a DHCP server that assigns IPA to a host, a DHCP client to which IPA is assigned through DHCP message communication, and a frame received from each host. A HAPT module that changes a source MAC address (Media Access Control address) and a port number of the frame, stores the change information in a HAPT table, and changes the destination MAC address and port number of the frame received from the ISP with reference to the HAPT table A local access point with a LIAT module for data collision prevention, and a DHCP server spoofer that assigns IPA to each host. .

Japanese Unexamined Patent Application Publication No. 2004-072453 (Patent Document 2) discloses a network management system and a network management method.
In this prior art, in a network management system having a DHCP server and dynamically distributing an IP address to a DHCP client by DHCP, a DHCP cooperation server for registering information of the DHCP client that distributes the IP address in the DHCP server And the host name, MAC address, and network segment of the client are set as DHCP setting information. In the DNS system, DNS information is generated in the DNS cooperation server so that it can be semi-automatically registered in the DNS server.

Japanese Patent Laid-Open No. 2003-087287 (Patent Document 3) discloses a network management device.
In this conventional technology, when a DHCP server and a DNS server are mounted on a network device, and the DHCP server assigns an IP address to a device connected to the network, the host name and MAC address of the device connected to the network on the DNS server. The DNS server notifies the external server of the MAC address, the external server has a correspondence table between the MAC address and the device type name, returns the device type name corresponding to the MAC address, and the DNS server responds. The registered device type name and IP address are registered in its own table. In addition, the DNS server has a table indicating correspondence between common names and device type names, and searches for a host name described by a common name from a common name column of the table indicating correspondence between the common name and the device type name when resolving the host name, and finds the common name Is converted to the device type name corresponding to.
However, in this prior art, when an IP address is set, there is a possibility that the IP address is duplicated, and a communication failure for an existing service may occur.

Japanese Patent Laid-Open No. 9-214533 (Patent Document 4) discloses an information processing apparatus, an IP address generation method thereof, a character processing apparatus, and an IP address generation method thereof.
In this prior art, the network system program inside the information processing apparatus or character processing apparatus causes the user to set the IP address of the host machine, extracts the network address of the host based on the IP address, and sets the terminal address of the own apparatus to the user. The IP address of the own device is generated based on the network address of the host and the terminal address input by the user. Thus, in this prior art, an IP address is set from each address set by the user.

JP 2004-112801 A JP 2004-072453 A JP 2003-087287 A JP 9-214533 A

An object of the present invention is to provide an address determination method in which a DHCP client user represented by a wireless LAN terminal has a DHCP client function represented by a wireless LAN access point terminal and can set an IP address in the terminal itself. It is to be.
Another object of the present invention is to provide a DHCP client function and set an IP address to the terminal itself. When accessing a terminal that can access the IP address from another terminal, an address suitable for the connected network is automatically set. It is to provide an address determination method that can be accessed without being disconnected from the network by generating and assigning it to the terminal.

  In the following, means for solving the problem will be described using the numbers used in [Best Mode for Carrying Out the Invention] in parentheses. These numbers are added to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers should not be used to interpret the technical scope of the invention described in [Claims].

  The network system of the present invention relays communication between a router (10) that automatically assigns IP addresses to subordinate terminals, the router (10), and a client terminal (30), and from the router (10). An access point terminal (20) that generates an IP address from the logical sum of the network address part of the acquired IP address and the host address part of a preset IP address, and sets the generated IP address as its own IP address ).

  When there is an IP address that conflicts with the generated IP address, the access point terminal (20) sets the preset IP address as its own IP address.

  The access point terminal (20) includes a network address portion of an IP address acquired from the router (10) based on a subnet mask acquired from the router (10) and a host address portion of the preset IP address. And an IP address is generated.

  The access point terminal (20) determines a network address part of the IP address acquired from the router (10) and a host address part of the preset IP address based on a preset subnet mask. , Generate an IP address.

  If the access point terminal (20) fails to obtain an IP address from the router (10), the access point terminal (20) checks whether there is an IP address that conflicts with the preset IP address, and if there is no conflicting IP address, The preset IP address is set as its own IP address.

  The access point terminal (20) transmits an ARP (Address Resolution Protocol) packet based on the IP address to be set, and determines that there is a conflicting IP address if there is a response to the ARP packet.

  The access point terminal (20) of the present invention includes a DHCP client function unit (22) that automatically acquires an IP address from a DHCP (Dynamic Host Configuration Protocol) server (11), and an IP acquired from the DHCP server (11). A subnet complement function unit (21) for generating an IP address from a logical sum of a network address part of an address and a host address part of a preset IP address, and setting the generated IP address as an IP address of the terminal itself It comprises.

  When the IP address cannot be obtained from the DHCP server (11), the subnet complementing function unit (21) sets a preset IP address as the IP address of the terminal itself.

  The subnet complement function unit (21), based on the subnet mask acquired from the DHCP server (11), when the acquired subnet address matches the preset subnet mask from the DHCP server (11), A network address part of the IP address acquired from the DHCP server (11) and a host address part of the preset IP address are determined, and an IP address is generated.

  When the subnet complement function unit (21) cannot acquire a subnet address from the DHCP server (11), based on the preset subnet mask, the network address part of the IP address acquired from the DHCP server (11) And a host address part of the preset IP address to generate an IP address.

  The subnet complementing function unit (21) transmits an ARP (Address Resolution Protocol) packet based on the IP address to be set, and determines that there is a conflicting IP address if there is a response to the ARP packet.

  The address determination method of the present invention includes (a1) a step of obtaining a distribution IP address and a distribution subnet mask from a DHCP server (11), and (a2) a network address from a logical product of the distribution IP address and the distribution subnet mask. (A3) generating a host address from the logical product of the default IP address given in the initial setting and the complement of the default subnet mask, and (a4) the network address and the host address Generating an IP address from the logical sum.

  The (a1) step includes (a11) a step of transmitting a DHCP DISCOVER packet on the network and waiting for a reply from the DHCP server (11), and (a12) receiving a DHCP OFFER packet from the DHCP server (11). Extracting the distribution IP address and the distribution subnet mask included in the DHCP OFFER packet.

  The address determination method of the present invention includes (b1) a step of determining whether or not the IP address generation is successful, and (b2) an IP address that conflicts with the generated IP address when it is determined that the IP address generation is successful. (B3) if there is no conflicting IP address, setting the generated IP address as its own IP address; and (b4) if there is a conflicting IP address, the default IP Checking if there is a conflicting IP address in the address; (b5) if there is no IP address conflicting with the default IP address, setting the default IP address as its own IP address; and (b6) IP If it is determined that the address generation has failed, the default IP address is conflicted. A step to check the IP address is not there to, when there is no (b7) conflict IP address further comprises the step of setting the default IP address as its own IP address.

  The (b1) step includes (b11) a step of determining that the generation fails when the distribution IP address or the distribution subnet mask cannot be acquired, and (b12) a case where the distribution subnet mask and the default subnet mask are different values. And a step of determining that the generation has failed.

  The program of the present invention causes a computer to execute the above address determination method.

The first effect is that the same network as the network to which the DHCP server and other DHCP client terminals belong has to have the DHCP client function, the IP address can be set to the terminal itself, and the IP address can be accessed from other terminals. Since the address is set, the user of another DHCP client terminal can realize access to the IP terminal without changing the IP address assigned to the DHCP client terminal.
The second effect is that since the IP terminal checks whether the address to be set already exists before setting the IP address, the IP address is duplicated, thereby preventing a communication failure for the existing service. Be able to.

  In the present invention, a terminal that has a DHCP client function, can set an IP address in the terminal itself, and can access the IP address from another terminal is provided with a function for a user to access the terminal without reconfiguring the network.

A first embodiment of the present invention will be described below with reference to the accompanying drawings.
Referring to FIG. 2, there is shown a network connection configuration as one embodiment of the present invention. The wireless LAN system of the present invention includes a router 10, a wireless LAN access point terminal 20, and a wireless LAN terminal 30.

  The router 10 relays between the external network 40 and the wireless LAN terminal 30. The router 10 includes a DHCP server 11. The router 10 assigns IP addresses to the wireless LAN access point terminal 20 and the wireless LAN terminal 30 by the DHCP server 11. Note that the DHCP server 11 may be connected to the router 10.

  In FIG. 2, a wireless LAN access point terminal 20 is a terminal having the function of the present invention. In the wireless LAN access point terminal 20, the wireless LAN access point terminal 20 bridges the router 10 connected to the wired LAN 50 and the wireless LAN terminal 30 connected to the wireless LAN 60. The wireless LAN access point terminal 20 is an IP terminal that can set an IP address in itself and can access the IP address from other terminals. Here, the wireless LAN access point terminal 20 includes a subnet complementing function unit 21 and a DHCP client function unit 22. The wireless LAN access point terminal 20 acquires a new IP address by the subnet complementing function unit 21.

  More specifically, the subnet complementing function unit 21 extracts the network address part from the IP address issued by the DHCP server 11 to the subordinate apparatus terminal, that is, the IP address acquired by the DHCP client function part 22, and preliminarily extracts the apparatus terminal (wireless LAN). By combining with the host address part of the IP address determined for the access point terminal 20), an IP address suitable for the subnet form of the connected network is generated. The network address portion indicates a portion where the subnet mask bit is 1, and the host address portion indicates the portion where the subnet mask bit is 0. The function of the subnet supplement function unit 21 is a subnet supplement function.

  The wireless LAN terminal 30 (30-i, i = 1 to n: n is the number of terminals) is at least one terminal. The wireless LAN terminal 30 communicates with the external network 40 through the wireless LAN access point terminal 20. Each wireless LAN terminal 30 includes a DHCP client function unit 31. The wireless LAN terminal 30 acquires an IP address from the DHCP server 11 by the DHCP client function unit 31.

Next, the operation of the address determination method of the wireless LAN access point terminal of FIG. 2 will be described using the flowchart shown in FIG. Referring to FIG. 3, there is shown a flowchart from when the wireless LAN access point terminal shown in FIG. 2 is activated until an IP address is set. FIG. 3 shows operations after the wireless LAN access point terminal power supply is activated.
(1) Step S101
The wireless LAN access point terminal 20 is turned on and the wireless LAN access point terminal 20 is activated.
(2) Step S102
When the wireless LAN access point terminal 20 is activated, the address determination module is activated. The address determination module performs processing from the generation of an IP address by the subnet complement function to the setting of the IP address. In FIG. 3, it is assumed that the address determination module is included in the subnet complementing function unit 21.
(3) Step S103
The address determination module generates an IP address with a subnet complement function. Here, the IP address and subnet mask are acquired from the DHCP server 11, and based on the acquired subnet mask, the network address part of the IP address acquired from the DHCP server 11 and the host address part of the IP address set in advance And decide. Then, an IP address is generated by the logical sum of the network address part of the IP address acquired from the DHCP server 11 and the host address part of the IP address set in advance.
(4) Step S104
Thereafter, it is determined whether or not the IP address generation is successful. When the IP address or the subnet mask cannot be acquired from the DHCP server 11, the generation has failed. Further, if the subnet mask acquired from the DHCP server 11 and the subnet mask set in advance do not match, it may be determined that the generation has failed.
(5) Step S105
If the IP address is successfully generated, it is checked whether there is an IP address that conflicts with the IP address generated by the subnet complementing function unit 21. The conflicting IP address is called a conflicting IP address. Whether there is a conflicting IP address is checked by using an ARP (Address Resolution Protocol) packet that resolves the MAC address from the IP address. In the ARP packet, if a specific IP address is set for a terminal in the same network, an ARP request that requests to teach the MAC address, and an ARP that actually answers the request for the ARP request and teaches the MAC address. There is a reply packet. Therefore, when the wireless LAN access point terminal 20 sends an ARP request to teach the MAC address to the same IP address as the generated IP address, if the ARP reply is received, the same IP address is on the same network. , IP addresses are in conflict. Therefore, the wireless LAN access point terminal 20 sends this ARP request to the generated IP address and checks whether there is a competing IP address depending on whether or not an ARP reply has been received.
(6) Step S106
If there is no conflicting IP address, the IP address generated by the subnet complement function is set. Since the IP address generated by this subnet complementing function uses the network address of the IP address distributed from the DHCP server 11, it becomes the same network as the DHCP server 11. As shown in FIG. 2, the DHCP server 11 is one of the functions of the router 10 and therefore has the same network as the router 10.
(7) Step S107
On the other hand, if there is a competing IP address, it is checked whether there is a competing IP address in the default IP address stored in the wireless LAN access point terminal 20. The default IP address here is an IP address that is given by the wireless LAN access point terminal 20 as an initial setting and that is also used when using the subnet complement function. It can also be changed by the user.
(8) Step S108
If there is no IP address that conflicts with the default IP address, the set IP address becomes the default IP address.
(9) Step S109
If there is an IP address that conflicts with the default IP address, the IP address is not set.
(10) Step S110
If it is determined that IP address generation has failed, it is checked whether there is a conflicting IP address in the default IP address.
(11) Step S111
If there is no conflicting IP address, a default IP address is set.
(12) Step S112
If there is a conflicting IP address, the IP address is not set.

  Next, a method for generating an IP address in the subnet complementing function unit 21 will be described with reference to FIG. Referring to FIG. 4, details of the subnet complement function unit 21 are shown. The subnet complementing function unit 21 includes a DHCP acquisition IP address 211, a DHCP acquisition subnet mask 212, a network address 213, a device setting default IP address 214, a device setting subnet mask 215, a host address 216, and a generated IP address 217. Hold. In FIG. 4, the generated IP address 217 indicates an IP address generated when the subnet complementing function unit 21 shown in FIG. 3 generates an IP address.

  First, it is confirmed whether there is a DHCP acquisition IP address 211 and a DHCP acquisition subnet mask 212. The acquisition method of the DHCP acquisition IP address 211 and the DHCP acquisition subnet mask 212 transmits a DHCP DISCOVER packet on the network and waits for a reply from the DHCP server. When the DHCP OFFER packet is received from the DHCP server, it is obtained by extracting the candidate IP address and subnet mask included in the DHCP OFFER packet. If the IP address cannot be acquired by DHCP, the DHCP acquisition IP address 211 is 0.0.0.0, resulting in generation failure. If the subnet mask cannot be acquired by DHCP, the DHCP acquisition subnet mask 212 is 0.0.0.0, which also fails to generate. In this embodiment, if there is no DHCP acquisition subnet mask 212, the generation fails. However, even if the device setting subnet mask 215 is set instead of the DHCP acquisition subnet mask 212 without generating failure, the operation of the present invention can be performed. It is valid. When there is the DHCP acquisition IP address 211, the logical product of the bits of the DHCP acquisition IP address 211 and the DHCP acquisition subnet mask 212 is obtained, and the network address 213 is generated.

  Next, the host address 216 is generated from the logical product of the device setting default IP address 214 and the complement of the device setting subnet mask 215. The device setting default IP address 214 is the same as the default IP address 214 described in FIG. 3, and is given by the initial setting of the wireless LAN access point terminal, and can be changed by the user. Similarly, the device setting subnet mask 215 is given by the initial setting of the wireless LAN access point terminal and can be changed by the user. Here, if the DHCP acquisition subnet mask 212 and the device setting subnet mask 215 have different values, an error occurs, and the IP address is not generated, resulting in generation failure. At this time, it is confirmed whether or not the DHCP acquisition subnet mask 212 matches the device setting subnet mask 215.

  The generated IP address 217 is obtained by taking the logical sum of the network address 213 and the host address 216 generated as described above. When the generated IP address 217 is created, the generation is successful. The process until generating the above IP address is the subnet complementing function in the present invention. By setting this generated IP address 217 in the wireless LAN access point terminal, the user of the wireless LAN terminal can access the wireless LAN access point terminal without changing the IP address.

The second embodiment of the present invention will be described below.
In the second embodiment of the present invention, the basic configuration is the same as in the first embodiment. However, even when the router is not a DHCP server, it is further prevented from having the same IP address as that of the router or the wireless LAN terminal. I am devised. FIG. 5 shows a configuration when the router is not a DHCP server.

  Referring to FIG. 5, another wireless LAN system of the present invention includes a router 10, a wireless LAN access point terminal 20, and a wireless LAN terminal 30. In the present embodiment, there is no DHCP-related function, and the wireless LAN access point terminal 20 only includes the subnet complementing function unit 21 for the function of setting the IP address.

  In FIG. 5, the wireless LAN access point terminal 20 is bridge-connected with the router 10 connected to the wired LAN and the wireless LAN terminal 30. The router 10 relays between the external network 40 and the wireless LAN terminal 30. The wireless LAN terminal 30 communicates with the external network 40 through the wireless LAN access point terminal 20. Further, the address of the wireless LAN terminal 30 is directly input so that the user checks the router 10 and becomes the address of the same network. That is, the address of the wireless LAN terminal 30 is a fixed IP address.

  Therefore, when the router 10 does not use a function such as a DHCP server, the wireless LAN access point terminal 20 cannot generate an address by the subnet complementing function unit 21 that is an address determination module at the time of activation.

  However, the subnet complementing function unit 21 checks whether there is an IP address that conflicts with the default IP address set in the device, and sets the default IP address set in the device if there is no conflicting IP address. By this processing, the same IP address as that of the router 10 or the wireless LAN terminal 30 is not obtained.

  As described above, in this embodiment, the same IP address as that of the router or the wireless LAN terminal is not used, so that it is possible to prevent a communication failure with respect to an existing service.

  Further, in addition to when the wireless LAN access point terminal is activated, the subnet supplementary function unit 21 is used to set an IP address.

  In FIG. 2, when the DHCP server is not operating normally at the time of activation, the subnet complementing function unit 21 does not generate an IP address. Even in such a case, after the supplementary function unit 21 periodically monitors the DHCP server, detects activation of the DHCP server, and confirms that the IP address and the subnet mask can be extracted from the DHCP server, the subnet supplementary function unit 21 By generating the IP address in step S1, it is possible to generate an IP address that matches the subnet configuration of the connected network.

  As described above, in this embodiment, since the IP address can be generated by subnet complementation, the user of the wireless LAN terminal can communicate with the wireless LAN access point terminal to change the wireless LAN setting. The effect that it can do without a change is acquired.

  As described above, in the present invention, a terminal that has a DHCP client function, can set an IP address in the terminal itself, and can access the IP address from another terminal, a terminal having a DHCP client function separately from the present terminal In the network environment to which the DHCP server is connected, the network address part is extracted from the IP address issued by the DHCP server to the terminal and combined with the host address part of the IP address determined in advance for the terminal. An IP address suitable for the subnet configuration of the selected network can be generated. Then, by assigning the generated IP address to the terminal, it is possible for a user of a terminal having a DHCP client function different from the terminal to access the terminal without reconfiguring the network. Yes.

  Here, a terminal that has a DHCP client function, can set an IP address in the terminal itself, and can access the IP address from another terminal is an IP terminal.

  Also, by extracting the network address part from the IP address issued by the DHCP server to this terminal and combining it with the host address part of the IP address determined in advance for this terminal, an IP suitable for the subnet form of the connected network Generating an address is called a subnet complement function.

  The IP terminal can generate an IP address by the subnet complement function, and set the IP address in the IP terminal after confirming that the same IP address is not used on the same network.

  In this way, in the present invention, an IP address suitable for the same network as the network to which the terminal is connected is set in the terminal. A user of a terminal having a DHCP client function different from that of this terminal changes the IP address of the terminal having a DHCP client function different from that of the terminal to access the terminal when changing the setting of the terminal. Can be done without. When a user of a terminal having a DHCP client function different from the terminal accesses the terminal, the host address part of the IP address of the terminal is fixed and preset, and the address of the network address part is Since the network address is the same as that of the terminal, it is possible to prevent the IP address set for the terminal from being unknown.

FIG. 1 is a diagram showing a conventional network connection configuration. FIG. 2 is a diagram showing a network connection configuration of the present invention. FIG. 3 is a flowchart showing the operation of the present invention. FIG. 4 is a diagram illustrating a method for generating an IP address by the subnet complement function. FIG. 5 is a diagram showing a network connection configuration according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Router 2 ... Wireless LAN access point terminal 3 ... Wireless LAN terminal 4 ... DHCP (Dynamic Host Configuration Protocol) server 5 ... DHCP client function part 10 ... Router 11 ... DHCP server 20 ... Wireless LAN access point terminal 21 ... Subnet complement function Unit 211 ... DHCP acquisition IP address 212 ... DHCP acquisition subnet mask 213 ... network address 214 ... device setting default IP address 215 ... device setting subnet mask 216 ... host address 217 ... generated IP address 22 ... DHCP client function unit 30 (-i, i = 1 to n) Wireless LAN terminal 31 (-i, i = 1 to n) DHCP client function unit 40 External network 50 Line LAN
60 ... Wireless LAN

Claims (14)

  A router having a DHCP server function;
  An access point connected to the router and having a DHCP client function;
  A communication terminal connected to the access point and having a DHCP client function;
Including
  The router, the access point, and the communication terminal exist on the same network,
  The access point is
  Means for extracting a network part from an IP address assigned to the access point by the router;
  Means for combining the extracted network part with a host address part determined in advance as the access point, and generating an IP address suitable for a subnet form of the network;
  Means for setting the generated IP address in the access point;
Comprising
  The communication terminal is
  Means for fixing and presetting the host address part of the access point;
  Means for using the same network unit as the access point for the network unit of the communication terminal;
  Means for specifying an IP address of the access point based on a network part of the communication terminal and a host address part of the access point and accessing the access point;
With
  Network system.   The network system according to claim 1,
  The access point is
  Means for retaining an initial default IP address;
  Means for confirming the presence or absence of an IP address that conflicts with the generated IP address;
  Means for setting the generated IP address in the access point if there is no IP address competing with the generated IP address;
  When there is an IP address that conflicts with the generated IP address, when an IP address is not allocated from the router, or when an IP address that conforms to the subnet configuration of the network cannot be generated, Means for confirming the presence or absence of an IP address that conflicts with the default IP address;
  Means for setting the default IP address in the access point if there is no IP address conflicting with the default IP address;
Further comprising
  Network system.   The network system according to claim 1 or 2,
  A specific communication terminal connected from the communication terminal and having a DHCP client function
Further including
  The router, the access point, the communication terminal, and the specific communication terminal exist on the same network,
  The specific communication terminal is
  Means for extracting a network part from an IP address assigned to the specific communication terminal by the router;
  Means for combining the extracted network unit with a host address unit determined in advance for the specific communication terminal, and generating an IP address suitable for the subnet form of the network;
  Means for setting the generated IP address in the specific communication terminal;
Comprising
  The communication terminal is
  Means for presetting a fixed host address part of the specific communication terminal;
  Means for using the same network unit as the specific communication terminal for the network unit of the communication terminal;
  Means for specifying an IP address of the specific communication terminal based on a network part of the communication terminal and a host address part of the specific communication terminal and accessing the specific communication terminal;
Further comprising
  Network system.   An access point that exists on the same network as a router having a DHCP server function and a communication terminal having a DHCP client function, and that has a DHCP client function,
  Means for extracting a network part from an IP address assigned by the router;
  Means for generating an IP address adapted to a subnet form of the network by combining the extracted network unit with a fixed host address unit that is determined in advance and also holding the communication terminal;
  Means for setting the generated IP address;
With
  access point.   The access point according to claim 4,
  Means for retaining an initial default IP address;
  Means for confirming the presence or absence of an IP address that conflicts with the generated IP address;
  Means for setting the generated IP address if no IP address conflicts with the generated IP address;
  When there is an IP address that conflicts with the generated IP address, when an IP address is not allocated from the router, or when an IP address that conforms to the subnet configuration of the network cannot be generated, Means for confirming the presence or absence of an IP address that conflicts with the default IP address;
  Means for setting the default IP address if no IP address conflicts with the default IP address;
Further comprising
  access point.   A communication terminal that exists on the same network as a router having a DHCP server function, is connected to an access point having a DHCP client function, and has a DHCP client function,
  Means for fixing and presetting the host address part of the access point;
  Means for using the same network unit as the access point for the network unit of the communication terminal;
  Means for specifying an IP address of the access point based on a network part of the communication terminal and a host address part of the access point and accessing the access point;
With
  Communication terminal.   The communication terminal according to claim 6, wherein
  Means for extracting a network part from an IP address assigned by the router;
  Means for combining the extracted network part with a predetermined host address part to generate an IP address suitable for the subnet form of the network;
  Means for setting the generated IP address;
  Means for fixing and presetting the host address part of a specific communication terminal on the same network;
  Means for using the same network unit as the specific communication terminal for the network unit of the communication terminal;
  Means for specifying and accessing an IP address of the specific communication terminal based on a network part of the communication terminal and a host address part of the specific communication terminal;
Further comprising
  Communication terminal.   A router having a DHCP server function, an access point connected to the router and having a DHCP client function, and a communication terminal connected to the access point and having a DHCP client function are disposed on the same network;
  In the access point,
  Extracting the network part from the IP address assigned to the access point by the router;
  Combining the extracted network part with a host address part determined in advance as the access point, and generating an IP address suitable for the subnet form of the network;
  Setting the generated IP address to the access point;
  In the communication terminal,
  The host address part of the access point is fixed and set in advance;
  Using the same network part as the access point for the network part of the communication terminal;
  Specifying the IP address of the access point based on the network part of the communication terminal and the host address part of the access point, and accessing the access point;
including
  Address determination method.   The address determination method according to claim 8, comprising:
  In the access point,
  Keep the default IP address of the initial settings,
  Checking for the presence of an IP address in conflict with the generated IP address;
  If no IP address conflicts with the generated IP address, setting the generated IP address to the access point;
  When there is an IP address that conflicts with the generated IP address, when an IP address is not allocated from the router, or when an IP address that conforms to the subnet configuration of the network cannot be generated, Checking for an IP address that conflicts with the default IP address;
  If there is no IP address that conflicts with the default IP address, setting the default IP address to the access point;
Further includes
  Address determination method.   The address determination method according to claim 8 or 9, wherein
  Placing the router, the access point, the communication terminal, and a specific communication terminal connected from the communication terminal and having a DHCP client function on the same network;
  In the specific communication terminal,
  Extracting a network part from an IP address assigned to the specific communication terminal by the router;
  Combining the extracted network part with a host address part determined in advance for the specific communication terminal, and generating an IP address suitable for the subnet form of the network;
  Setting the generated IP address in the specific communication terminal;
  In the communication terminal,
  Setting a fixed host address part of the specific communication terminal in advance;
  Using the same network unit as the specific communication terminal for the network unit of the communication terminal;
  Specifying the IP address of the specific communication terminal based on the network part of the communication terminal and the host address part of the specific communication terminal, and accessing the specific communication terminal;
Further includes
  Address determination method.   A program for an access point having a DHCP client function that exists on the same network as a router having a DHCP server function and a communication terminal having a DHCP client function,
  Extracting a network part from an IP address assigned by the router;
  Combining the extracted network part with a fixed host address part that is predetermined and also held by the communication terminal, and generating an IP address suitable for the subnet form of the network;
  Setting the generated IP address;
For the access point to execute
  A program for access points.   A program for an access point according to claim 11,
  Holding an initial default IP address; and
  Checking for the presence or absence of an IP address that conflicts with the generated IP address;
  If no IP address conflicts with the generated IP address, setting the generated IP address;
  When there is an IP address that conflicts with the generated IP address, when an IP address is not assigned from the router, or when an IP address that conforms to the subnet configuration of the network cannot be generated, Checking whether there is an IP address conflicting with the default IP address;
  If there is no IP address conflicting with the default IP address, setting the default IP address;
For further access point execution
  A program for access points.   A program for a communication terminal that exists on the same network as a router having a DHCP server function, is connected to an access point having a DHCP client function, and has a DHCP client function,
  A fixed and preset host address portion of the access point;
  Using the same network unit as the access point for the network unit of the communication terminal;
  Specifying an IP address of the access point based on a network part of the communication terminal and a host address part of the access point, and accessing the access point;
To run the communication terminal
  A program for communication terminals.   A communication terminal program according to claim 13,
  Extracting a network part from an IP address assigned by the router;
  Combining the extracted network part with a predetermined host address part to generate an IP address suitable for the subnet form of the network;
  Setting the generated IP address;
  A step of presetting a fixed host address part of a specific communication terminal on the same network;
  Using the same network unit as the specific communication terminal for the network unit of the communication terminal;
  Identifying and accessing the IP address of the specific communication terminal based on the network part of the communication terminal and the host address part of the specific communication terminal;
To further execute the communication terminal
  A program for communication terminals.

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