IP address assignment device

Abstract

To achieve decentralization appropriately and enable response to even dynamic changes in the case where a plurality of IP assignment devices are provided in the same network.SOLUTION: A permission list registration section 121 receives client identification information on a client device that is allowed to be given an IP addresses from its own device, and registers it to a permission list storage section 1032. The presence of other IP address assignment device is recognized through a series of message sending and receiving, such as sending a discovery message, receiving a proposal message, and then sending a declining message. To the other IP address assignment device of which presence is recognized, a permission MAC address that is stored in at least the permission list storage section 1032 is provided. The other IP address assignment device receives a permeation MAC address to be sent and stores it in an ignore list storage section 1033.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to, for example, an IP (Internet Protocol) addressing device that is connected to the same network and realizes decentralization.

Background Art

[0002] A DHCP (Dynamic Host Configuration Protocol) server realizes a function of automatically assigning setting information necessary for network use, such as an IP address, in response to requests from network devices on a LAN (Local Area Network). As a result, communication through the LAN and connection to the Internet become possible without detailed settings related to the network being made for each network device. Note that the DHCP server is often installed in a device that relays between networks, such as a device called a router. Further, network devices mean various communication terminal devices having a communication function, such as a PC (Personal Computer) or a tablet PC, and are also called client devices that receive services from a server device that means the providing side.

[0003] When constructing a LAN system, for example, a plurality of DHCP servers are provided in one LAN for redundancy. Redundancy related to a DHCP server means that, in case some failure occurs in the DHCP server, a backup DHCP server is arranged and operated as a backup from normal times so that the functions of the entire system can continue to be maintained even after the failure occurs. Patent Document 1 described later discloses an invention related to a multiplexed DHCP server that improves the reliability of a DHCP server and can dynamically switch the DHCP server by multiplexing the DHCP server in the same network.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-230788 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] When constructing a network, in addition to redundancy, there is a concept of decentralization. FIG. 10 is a diagram for explaining the decentralization of a DHCP server and problems that occur at that time. As shown in FIG. 10(A), in LAN2, a DHCP server SA for Group A and a DHCP server SB for Group B are provided, and each of them is connected to the Internet 4. In the case of the example shown in FIG. 10(A), the DHCP server SA and the DHCP server SB are, for example, those installed in a router. In FIG. 10(A), the DHCP server SA enables communication through LAN2 and connection to the Internet 4 for PCs 3A(1), 3A(2),... belonging to Group A. Also, in FIG. 10(A), the DHCP server SB enables communication through LAN2 and connection to the Internet 4 for PCs 3B(1), 3B(2),... belonging to Group B.

[0006] When requesting the assignment of an IP address to a DHCP server, a DHCP message is used. As shown in FIG. 10(B), the DHCP server SA has an IP address of "192.168.1.1" and realizes the function of assigning IP addresses in the network segment "192.168.1" to network devices. Also, as shown in FIG. 10(B), the DHCP server SB has an IP address of "192.168.2.1" and realizes the function of assigning IP addresses in the network segment "192.168.2". In this case, as shown in FIG. 10(B), an example of the case where PC 3A(1) in Group A requests the assignment of an IP address will be specifically described using the sequence diagram of FIG. 11.

[0007] FIG. 11 is a diagram for explaining DHCP messages. As shown in FIG. 11, when the PC3A(1) in Group A requests an IP address assignment, first, it broadcasts a DHCP Discover message (step M1). The DHCP Discover message has a destination IP address of "255.255.255.255", a source IP address of "0.0.0.0", and both the client IP address and the server IP address are "0.0.0.0". The DHCP Discover message is for discovering a DHCP server capable of assigning an IP address.

[0008] The DHCP server SA that has received the DHCP Discover message broadcasts a DHCP Offer message (step M2). The DHCP Offer message has a destination IP address of "255.255.255.255" and a source IP address of "196.168.1.1". Also, the DHCP Offer message has a client IP address of "192.168.1.10" and a server IP address of "192.168.1.1". In this example, the DHCP Offer message is for the DHCP server SA with an IP address of "192.168.1.1" to notify each client device that it can assign the IP address "192.168.1.10".

[0009] In response, PC3A(1) sends a DHCP request message to the DHCP server that provided the DHCP offer message earliest (step M3). The destination IP address of the DHCP request message is set to "255.255.255.255", and the source IP address is set to "0.0.0.0". Also, the client IP address in the DHCP request message is set to "0.0.0.0", and the server IP address is set to "192.168.1.1". Further, the DHCP request message requests the allocation of "192.168.1.10" proposed by the DHCP offer as the requested IP address. In this example, the DHCP request message requests the allocation of the IP address "192.168.1.10" from the DHCP server SA with the IP address "192.168.1.1".

[0010] In response, the DHCP server SA sends a DHCP ack (acknowledgment) message to the requesting PC3A(1) (step M4). The destination IP address of the DHCP ack message is set to "255.255.255.255", and the source IP address is set to "192.168.1.1". Also, the client IP address in the DHCP ack message is set to "192.168.1.10", and the server IP address is set to "192.168.1.1". In this example, the DHCP ack message is such that the DHCP server SA with the IP address "192.168.1.1" allocates the IP address "192.168.1.10" to PC3A(1) in response to the DHCP request.

[0011] According to the procedure described with reference to FIG. 11, clients such as PC3A(1) can obtain an IP address from a DHCP server and communicate through LAN2 or access the Internet 4. However, as shown in FIG. 10(B), assume that PC3A(1) in Group A sends a DHCP Discover message, and in response, DHCP server SB sends a DHCP Offer message to PC3A(1) in Group A earlier than DHCP server SA. In this case, PC3A(1) in Group A will receive an IP address from DHCP server SB, and it will not be possible to distribute the DHCP servers as originally intended.

[0012] Also, there may be cases where the networks to which multiple DHCP servers are connected are different. For example, the network to which DHCP server SA is connected may be a verification network where various servers used for product development are installed, and the network to which DHCP server SB is connected may be the Internet. In this case, if PC3A(1), 3A(2),... in Group A receive IP addresses from DHCP server SB, they will be able to connect only to the Internet when they actually want to connect to the verification network. Conversely, if PC3B(1), 3B(2),... in Group A receive IP addresses from DHCP server SA, they will be able to connect only to the verification network when they actually want to connect to the Internet.

[0013] Therefore, it is conceivable to register the MAC (Media Access Control) addresses of client devices such as PCs that are to be assigned IP addresses as permitted destinations for each of DHCP server SA and DHCP server SB. This is to assign IP addresses only to client devices with registered MAC addresses. However, in this case, when a DHCP server is removed or replaced from LAN2, it will be time-consuming and laborious to maintain the permitted destination MAC addresses. As a result, it will not be possible to construct a highly reliable LAN that operates normally even when a DHCP server is removed or replaced.

[0014] In view of the above, an object of the present invention is to appropriately achieve decentralization and be able to cope with dynamic changes when a plurality of IP address assignment devices are provided in the same network.

Means for Solving the Problems

[0015] To solve the above problems, the IP address assignment device according to the invention described in claim 1 permission list registration means for receiving client identification information of a client device permitted as an IP address assignment destination from its own device and registering it in a permission list storage unit; discovery message transmission processing means for transmitting a discovery message used to discover other IP address assignment devices connected to the same network; proposal message reception processing means for receiving a proposal message including an available IP address from the other IP address assignment device that has received the discovery message and the assignment device identification information of the other IP address assignment device; rejection message transmission means for transmitting a rejection message notifying rejection of IP address assignment to the other IP address assignment device that is the transmission source of the proposal message; permission list providing means for transmitting its own device identification information and at least the client identification information stored in the permission list storage unit to the other IP address assignment device that is the transmission source of the proposal message; discovery message reception processing means for receiving the discovery message from the other IP address assignment device; proposal message transmission processing means for forming and transmitting the proposal message when the discovery message is received through the discovery message receiving means; identification information reception processing means for receiving the assignment device identification information and the client identification information from the other IP address assignment device; When the device identification information and the client identification information are received through the identification information receiving processing means, response message transmitting processing means for transmitting a response message to the other IP address assigning device of the transmission source; Ignore list registering means for registering the client identification information received through the identification information receiving processing means in an ignore list storage unit characterized by comprising.

[0016] According to the IP address assigning device of the invention described in claim 1, the permission list registering means receives the client identification information of the client device permitted as the assignment destination of the IP address from its own device and registers it in the permission list storage unit. Through the transmission and reception of a series of messages such as the transmission of a discovery message → the reception of a proposal message → the transmission of a rejection message, the existence of other IP address assigning devices is recognized. At least the client identification information stored in the permission list storage unit is provided to the recognized other IP address assigning device. In the other IP address assigning device, the transmitted client identification information is received and stored in the ignore list storage unit.

Effect of the Invention

[0017] According to the present invention, when a plurality of IP address assigning devices are provided in the same network, appropriate decentralization can be realized and dynamic changes can also be coped with.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the IP address assignment device according to the present invention will be described with reference to the drawings. The IP address assignment device according to the embodiments described below will be described by taking, as an example, a case where it is realized as a DHCP server mounted on a router, for example, in order to simplify the explanation. Also, hereinafter, regarding DHCP messages such as DHCP discover messages and DHCP offer messages, the word "message" will be omitted and described, for example, as DHCP discover and DHCP offer.

[0020] [Configuration Example of Network System] FIG. 1 is a diagram for explaining a configuration example of a network system configured by using an IP address assignment device according to an embodiment. As shown in FIG. 1, in LAN2, a DHCP server 1(1) for group A, a DHCP server 1(2) for group B, and a DHCP server 1(3) for group C are provided, and each of them is connected to the Internet 4. The DHCP server 1(1), the DHCP server 1(2), and the DHCP server 1(3) are those to which an embodiment of the IP address assignment device of the present invention is applied.

[0021] In FIG. 1, the DHCP server 1(1) assigns IP addresses to PCs 3A(1), 3A(2),... belonging to group A, enabling communication through LAN2 and connection to the Internet 4. Also, in FIG. 1, the DHCP server 1(2) assigns IP addresses to PCs 3B(1), 3B(2),... belonging to group B, enabling communication through LAN2 and connection to the Internet 4. Also, in FIG. 1, the DHCP server 1(3) assigns IP addresses to PCs 3C(1), 3C(2),... belonging to group C, enabling communication through LAN2 and connection to the Internet 4.

[0022] However, as described with reference to FIG. 11, when receiving an IP address assignment using a DHCP message, the existence of the DHCP server is confirmed, and the IP address is received from the DHCP server that first proposed (offered) the IP address. In this way, the DHCP servers cannot be dispersed for each group. Therefore, each of the DHCP servers 1(1), 1(2), and 1(3) receives the client identification information of the client device permitted as the IP address assignment destination from itself and registers it in the permission list storage unit. In this embodiment, the client identification information uses the MAC address of the client device.

[0023] However, just this alone may result in mistakes in registering MAC addresses. Therefore, each of the DHCP servers 1(1), 1(2), and 1(3) communicates with each other and receives the provision of the permission list each has. Since the received permission list is the permission list in other DHCP servers, it becomes a list of MAC addresses of client devices that should be ignored even if a request for IP address provision is made on the local device. For this reason, the permission list received from other DHCP servers is registered in the ignore list on the local device.

[0024] As a result, each of the DHCP servers 1(1), 1(2), and 1(3) can take actions such as assigning an IP address to a client device that has a MAC address registered in the permission list and not registered in the ignore list. Therefore, each of the DHCP servers 1(1), 1(2), and 1(3) can also take actions such as not assigning an IP address to a client device that has a MAC address registered in both the permission list and the ignore list.

[0025] Also, for each of the DHCP servers 1(1), 1(2), and 1(3), the MAC address of a newly connected client device may be added to the permission list, or the MAC address of a removed client device may be deleted. Also, the DHCP servers 1(1), 1(2), and 1(3) may be removed from or replaced in LAN2. For this reason, each of the DHCP servers 1(1), 1(2), and 1(3) periodically checks the connection (liveliness check) of other DHCP servers and updates the permission list and the ignore list. This enables appropriate decentralization of DHCP servers when multiple DHCP servers are provided in LAN2 and also enables handling of dynamic changes such as addition or deletion of client devices and deletion or replacement (exchange) of DHCP servers.

[0026] The configuration and operation of the DHCP servers 1(1), 1(2), and 1(3) of this embodiment will be described below. Since each of the DHCP servers 1(1), 1(2), and 1(3) basically has the same configuration, they are collectively referred to as the DHCP server 1 unless particularly distinguished. Also, in this embodiment, each of PC3A(1), 3(A(2), …, 3B(1), 3B(2), …, 3C(1), 3C(2), … also basically has the same configuration. Therefore, unless particularly distinguished, these are also abbreviated as PC3, and the PCs belonging to group A may be collectively referred to as PC3A, and the PCs belonging to group C may be collectively referred to as PC3C.

[0027] [Configuration Example of DHCP Server 1] FIG. 2 is a block diagram for explaining a configuration example of the DHCP server 1 which is an IP address assignment device of the embodiment. The connection terminal 101T constitutes a connection end to the Internet 4, and the communication I / F (Interface) 101 is a part that performs communication processing through the Internet 4. That is, the communication I / F 101 converts a signal addressed to itself transmitted via the Internet 4 into a signal in a form processable by itself and captures this signal. Also, the communication I / F 101 converts a signal to be transmitted from itself to a target destination into a signal in a transmission format and sends this signal to the Internet 4 for transmission to the destination.

[0028] The control unit 102 is a microprocessor equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), non-volatile memory, etc., which are not shown in the figure, and controls each part of the DHCP server 1. The storage device 103 is a device unit composed of a recording medium and its driver, such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and performs recording, reading, changing, deleting, etc. of various data to and from the recording medium. In addition to storing and holding necessary data and programs, the storage device 103 is also used as a working area for temporarily storing intermediate data generated in various processes.

[0029] In this embodiment, the storage device 103 is provided with a lease information list storage unit 1031, a permission list storage unit 1032, an ignore list storage unit 1033, a list of other servers storage unit 1034, and an assigned list storage unit 1035. FIGS. 3 and 4 are diagrams for explaining each storage unit formed in the storage device 103 of the DHCP server 1 of the embodiment. In the following, it is assumed that the DHCP server 1 has been updated with a network segment, a subnet mask, and a default gateway, and is in a state where an IP address can be assigned. That is, it is assumed that the client function unit 111 described later functions to collect necessary information by transmitting a predetermined message, and the server function unit 112 described later functions to complete the setting of necessary information and is in a state where an IP address can be assigned.

[0030] As shown in Fig. 3(A), the lease information list storage unit 1031 stores and holds information indicating the range of IP addresses that can be assigned to the own device. In the case of the lease information list storage unit 1031 shown in Fig. 3(A), it is managed that IP addresses can be assigned within the range from the start IP address "192.168.1.100" to the end IP address "192.168.1.120". Thus, the information consisting of the start IP address and the end IP address is the lease information list. In this embodiment, the number of assignable IP addresses is determined in advance according to the performance of the DHCP server 1 and the like.

[0031] As shown in Fig. 3(B), the permission list storage unit 1032 stores and holds the MAC address of the PC3 that is permitted as the destination for assigning an IP address from the own device. Therefore, the collection of the MAC addresses of the PC3 that are permitted as the destinations for assigning IP addresses from the own device (permitted MAC addresses) is the permission list. As shown in Fig. 3(C), the ignore list storage unit 1033 stores and holds the MAC address of the source DHCP server 1 and the MAC addresses of the PC3 that are not permitted (ignored) as the destinations for assigning IP addresses from the own device. Therefore, the ignore list is composed of the permission lists provided by other DHCP servers and is a collection of the MAC addresses of the PC3 that are not permitted (ignored) as the destinations for assigning IP addresses from the own device (ignored MAC addresses).

[0032] As shown in FIG. 4(A), the other server list storage unit 1034 consists of other server information, a MAC address, and an acquired permission list. The other server information is information indicating the existence of a DHCP server other than the own device, and can be represented by information different for each other DHCP server such as a sequence number, for example. The MAC address is the MAC address of a DHCP server other than the own device and corresponds to the assigned terminal identification information. The acquired permission list is a permission list provided by another DHCP server, and may be the permission list itself, or may be configured by information indicating the location such as the file name of the permission list stored as a separate file in a different storage area. In this embodiment, it is assumed that the permission list of the other server list is the permission list itself that has been provided. Thus, a collection of information consisting of other server information of another DHCP server, the MAC address of the other DHCP server, and the permission list from the other DHCP server is the other server list.

[0033] The allocated list storage unit 1035 is created when the DHCP server 1 actually assigns an IP address. As shown in FIG. 4(B), it consists of the MAC address of the PC 3 to which the IP address is assigned, the assigned IP address, and the lending time (h (hours)). In the case of the example shown in FIG. 4(B), it is shown that the IP address "192.168.1.102" was assigned to the PC 3 with the MAC address "aa:aa:aa:aa:aa:aa" for a lending time of 72 hours.

[0034] Also, in the case of the example shown in FIG. 4(B), it is shown that the IP address "192.168.1.103" has been assigned to the PC3 with the MAC address "bb:bb:bb:bb:bb:bb" for a lending period of 72 hours. Thus, a collection of information consisting of the MAC address of the PC3 which is the assignment destination of the IP address, the assigned IP address, and the lending time (h (hours)) is the assigned list. Note that the lending time is also notified to the client device which is the assignment destination of the IP address, and when the lending time has elapsed since the client device received the assignment of the IP address, the client device will receive a re-assignment of the IP address.

[0035] As described above, the DHCP server 1 of this embodiment is provided with a storage unit in which various lists are stored in the storage device 103. In particular, it is important that the DHCP server 1 has a permission list in the permission list storage unit 1032 and an ignore list in the ignore list storage unit 1033. By providing these lists, the decentralization of the DHCP server 1 can be appropriately realized, and the DHCP server 1 can flexibly respond to dynamic changes in the client device and the DHCP server 1.

[0036] The connection terminal 104T constitutes a connection end to LAN2, and the LAN I / F (Interface) 104 is a part that performs communication processing through LAN2. That is, the LAN I / F 104 converts a signal addressed to itself transmitted through LAN2 into a signal in a format that can be processed by the own device and captures this signal. Also, the LAN I / F 104 converts a signal to be transmitted from the own device to a target destination into a signal in a transmission format and sends this signal to LAN2 for transmission to the destination.

[0037] The DHCP function unit 110 includes a client function unit 111 and a server function unit 112, and is a part that realizes the basic functions of a DHCP server. As described above, the client function unit 111 collects necessary information by transmitting a predetermined message. The server function unit 112 updates the network segment, subnet mask, and default gateway based on the collected information so that an IP address can be assigned.

[0038] Also, the client function unit 111 is also a part that functions when the own device is a client device. Therefore, the client function unit 111 realizes a function of forming and transmitting DHCP messages such as DHCP Discover, DHCP Request, and DHCP Decline (rejection) under the control of the control unit 102 as described with reference to FIG. 11. Further, the client function unit 111 realizes a function of receiving and processing DHCP messages such as DHCP Offer, DHCP Ack, and DHCP Inform (information) transmitted from other DHCP servers.

[0039] On the other hand, the server function unit 112 is also a part that functions when the own device is a server device under the control of the control unit 102. Therefore, the server function unit 112 realizes a function of forming and transmitting DHCP messages such as DHCP Offer, DHCP Ack, and DHCP Inform as described with reference to FIG. 11. Further, the server function unit 112 realizes a function of receiving and processing DHCP messages such as DHCP Discover, DHCP Request, and DHCP Decline transmitted from other DHCP servers. In addition, when the server function unit 112 receives a DHCP Request from PC3 and returns a DHCP Ack to assign an IP address, it also performs a process of forming the allocation information shown in FIG. 4(B) and recording it in the allocated list storage unit 1035.

[0040] The share function unit 120 is a part that cooperates with the control unit 102 and the DHCP function unit 110 to enable appropriate decentralization of the own device and other DHCP servers and to respond to dynamic changes in client devices and DHCP servers. The share function unit 120 includes a permission list registration unit 121, a permission list providing unit 122, a ignore list registration unit 123, a other server list registration unit 124, a ignore list deletion unit 125, a other server list deletion unit 126, a ignore list update unit 127, and a other server list update unit 128.

[0041] The permission list registration unit 121 receives the MAC address of the client device permitted as the destination of the IP address from its own device and performs a process of registering it in the permission list storage unit 1032. The input of the MAC address is performed, for example, through the operation unit of the DHCP server 1 (not shown) or the PC3 connected to the DHCP server 1 via LAN. For each DHCP server 1, a port for receiving information from the PC3 may be determined in advance, and the MAC address of the PC3 that has transmitted information by designating the port may be automatically registered in the permission list storage unit 1032. In this case, for the PC3 that normally receives an IP address assignment from the DHCP server 1, the port of the DHCP server 1 needs to be designated, and the port needs to be designated in the transmission data to the DHCP server.

[0042] The permission list providing unit 122 performs a process of providing (transmitting) the MAC address stored in the permission list storage unit 1032 of the storage device 103 to other DHCP servers under the control of the control unit 102. In addition to the permission list in the permission list storage unit 1032, the permission list providing unit 122 can also provide the MAC addresses in the allocated list storage unit 1035 to other DHCP servers.

[0043] The ignore list registration unit 123 performs a process of registering (recording) the MAC address of the PC3 registered as the permission list transmitted from other DHCP servers in the ignore list storage unit 1033 of the storage device 103 under the control of the control unit 102. The other server list registration unit 124 forms an other server list based on the permission list transmitted from other DHCP servers under the control of the control unit 102 and performs a process of registering (recording) it in the other server list storage unit 1034 of the storage device 103. The permission list transmitted from other DHCP servers includes the source IP address and MAC address. Using the information for identifying the source and the permission list, an other server list to be registered in the other server list storage unit 1034 is formed.

[0044] The ignore list deletion unit 125 performs a process of deleting the ignore list added according to the permission list from other DHCP servers that have not returned a response after performing connection confirmation under the control of the control unit 102, which will be described in detail later, from the ignore list storage unit 1033. The other server list deletion unit 126 performs a process of deleting the other server list for other DHCP servers that have not returned a response after performing connection confirmation under the control of the control unit 102, which will be described in detail later, from the other server list storage unit 1034.

[0045] The ignore list update unit 127 performs a process of updating the ignore list in the ignore list storage unit 1033 based on the permission list provided by other DHCP servers under the control of the control unit 102. That is, as will be described in detail later, for connection confirmation, assuming that the other DHCP server has returned a response to the confirmation message sent by specifying the other DHCP server, and further, the MAC address registered in the permission list of the other DHCP server has been sent. In this case, it is the ignore list update unit 127 that updates the ignore list in the ignore list storage unit 1033 based on the sent MAC address. In addition, when, in addition to the MAC address of the permission list from other DHCP servers, the MAC address in the allocated list storage unit 1035 has been sent, the ignore list update unit 127 also considers this and updates the ignore list in the ignore list storage unit 1033.

[0046] The other server list update unit 128 performs a process of updating the permission list of the other server list in the other server list storage unit 1034 based on the permission list provided by another DHCP server under the control of the control unit 102. That is, although it will be described in detail later, for connection confirmation, in response to a confirmation message transmitted by designating another DHCP server, the other DHCP server returns a response, and further, it is assumed that the MAC address registered in the permission list of the other DHCP server is transmitted. In this case, based on the transmitted MAC address, the other server list update unit 128 updates the permission list of the other server list in the other server list storage unit 1034. In addition, it is assumed that, in addition to the MAC address of the permission list from another DHCP server, the MAC address in the allocated list storage unit 1035 is transmitted. In this case, the other server list update unit 128 also considers this and updates the permission list of the other server list in the other server list storage unit 1034.

[0047] With the share function unit 120 configured in this way, in the DHCP server 1, a permission list is formed in the permission list storage unit 1032 of the storage device 103, and a ignore list is formed in the ignore list storage unit 1033 of the storage device 103. With this information, the DHCP server can be made to assign an IP address only to the PC3 to which the IP address should be assigned from itself. Moreover, by appropriately updating the ignore list and the other server list, even if the deletion or addition of PC3 or the deletion or replacement of the DHCP server occurs, by appropriately updating the ignore list, the IP address assignment destination can be appropriately maintained.

[0048] [Explanation of the process performed by DHCP server 1] [Registration process of permission list] Next, the processing performed in the DHCP server 1 of this embodiment having the above-described configuration will be described. As described above, it is assumed that the DHCP server 1 is in a state where it is possible to assign IP addresses. In this case, the permission list registration unit 121 functions to accept the MAC address of the PC 3 permitted as the destination for IP address assignment from the own device, and registers it in the permission list storage unit 1032 of the storage device 103 to form a permission list.

[0049] In the DHCP server 1 of this embodiment, when a DHCP discover is received from a client device, if there is a registration in the permission list storage unit 1032, it follows that. Also, a DHCP discover from a client device whose MAC address exists in the ignore list is ignored. However, if there is no registration in the permission list and there is no corresponding MAC address in the ignore list, a DHCP offer is sent. As a result, it becomes possible to assign an IP address to a client device whose MAC address does not exist in the permission list.

[0050] If it is set like this, it becomes possible to register the permission list (permitted MAC address) in the permission list storage unit 1032 of the DHCP server 1 through the client device that has received the IP address assignment. In this case, it is preferable to register the MAC address of the client device in the permission list storage unit 1032 of the DHCP server 1 through the client device. However, even if it is not registered, as shown in FIG. 4(B), the destination for IP address assignment is managed in the assigned list storage unit 1035. For this reason, what is necessary is just to process so that the MAC address of the assigned list of the assigned list storage unit 1035 may be added to the permission list.

[0051] Therefore, when constructing a LAN system, first connect the DHCP server 1(1), send a DHCP discover from the PC3A(1), and have the PC3A(1) receive an IP address assignment and register it in the permission list. Next, connect the DHCP server 1(2), send a DHCP discover from the PC3B(1), and have the PC3B(1) receive an IP address assignment and register it in the permission list. Finally, connect the DHCP server 1(3), send a DHCP discover from the PC3C(1), and have the PC3C(1) receive an IP address assignment and register it in the permission list. By processing in this order, the permission list can be registered for the DHCP servers 1(1), 1(2), and 1(3) of each group through the client devices of each group.

[0052] As described with reference to FIG. 1, in this embodiment, the DHCP server 1(1) for group A, the DHCP server 1(2) for group B, and the DHCP server 1(3) for group C are connected to the LAN2. Also, as described with reference to FIG. 1, the DHCP server 1(1) for group A assigns IP addresses to the PC3A(1), 3A(2),..., and the DHCP server 1(2) for group B assigns IP addresses to the PC3B(1), 3B(2),.... Similarly, the DHCP server 1(3) for group C assigns IP addresses to the PC3C(1), 3C(2),.... In the following, for simplicity of explanation, initially, it is assumed that the client devices of group A are two devices, namely the PC3A(1) and 3A(2). Similarly, initially, it is assumed that the client devices of group B are two devices, namely the PC3B(1) and 3B(2), and the client devices of group C are two devices, namely the PC3C(1) and 3C(2).

[0053] FIG. 5 is a diagram for explaining the initial states of the permission list storage unit 1032 and the ignore list storage unit 1033 of the DHCP server according to the embodiment. In the case of this example, in the DHCP server 1(1) for Group A, as shown in FIG. 5(A), the MAC addresses A1 and A2 of the PCs 3A(1) and 3A(2) are recorded in the permission list storage unit 1032, and a permission list is formed. At this point, the ignore list storage unit 1033 has no information recorded. Similarly, in the DHCP server 1(2) for Group B, as shown in FIG. 5(B), the MAC addresses B1 and B2 of the PCs 3B(1) and 3B(2) are recorded in the permission list storage unit 1032, and a permission list is formed. However, at this point, the ignore list storage unit 1033 has no information recorded.

[0054] Similarly, in the DHCP server 1(3) for Group C, as shown in FIG. 5(C), the MAC addresses C1 and C2 of the PCs 3C(1) and 3C(2) are recorded in the permission list storage unit 1032, and a permission list is formed. However, at this point, the ignore list storage unit 1033 has no information recorded. The states shown in FIGS. 5(A), (B), and (C) are the initial states of the permission list storage unit 1032 and the ignore list storage unit 1033 of the DHCP servers 1(1), 1(2), and 1(3).

[0055] Thus, in the following description, for simplicity of explanation, the MAC addresses of the client devices PC3A(1), 3A(2),... belonging to Group A are represented as A1, A2,.... Similarly, the MAC addresses of the client devices PC3B(1), 3B(2),... belonging to Group B are represented as B1, B2,.... Further, the MAC address of the DHCP server 1(1) is X1, the MAC address of the DHCP server 1(2) is X2, and the MAC address of the DHCP server 1(3) is X3.

[0056] In each of the DHCP servers 1(1), 1(2), and 1(3), the state is such that IP addresses can be assigned, and as described with reference to FIG. 5, it is assumed that a permission list is formed in the permission list storage unit 1032. In each of the DHCP servers 1(1), 1(2), and 1(3), a function for coping with the decentralization and dynamic changes of the DHCP servers (referred to as the DHCP sharing function) is enabled (turned on). As a result, the processes described below are performed. That is, the DHCP sharing function is a function realized in the DHCP server 1 to which the IP address assignment device according to the present invention is applied.

[0057] In the following, the case where the process is performed starting from the DHCP server 1(1) will be described as an example. However, the same process is performed starting from each of the DHCP servers 1(2) and 1(3). As a result, each of the DHCP servers 1(1), 1(2), and 1(3) can receive the provision of necessary information from each other and maintain the ignore list and the other server list.

[0058] <Distribution process of permission list> FIG. 6 is a sequence diagram for explaining the distribution process of the permission list performed in the DHCP server 1(1) of the embodiment. First, in the DHCP server 1(1), under the control of the control unit 102, the client function unit 111 of the DHCP function unit 110 functions, and a DHCP discover is transmitted by broadcast through the LAN2 (step S1). The DHCP discover is received by the DHCP servers 1(2) and 1(3) connected to the LAN2.

[0059] In response, the DHCP server 1(2) forms a DHCP offer and transmits it to the client (step S2). Similarly, the DHCP server 1(3) forms a DHCP offer and transmits it to the client (step S3). As described with reference to FIG. 11, the DHCP offer includes, in addition to the server IP address, information such as the MAC addresses of the DHCP servers 1(2) and 1(3), which are not shown in FIG. 11. Therefore, the DHCP server 1(1), which is the source of the DHCP discovery, can recognize that there are the DHCP servers 1(2) and 1(3) other than itself in LAN2, and can grasp their respective server IP addresses and MAC addresses.

[0060] The DHCP server 1(1) does not want to receive an IP address assignment; it only wants to know the existence of DHCP servers other than itself. Therefore, the client function unit 111 of the DHCP server 1(1) forms a DHCP decline and transmits it to the DHCP server 1(2) (step S4), and also transmits it to the DHCP server 1(3) (step S5). The DHCP decline is a DHCP message that notifies the rejection of an offer of an IP address by a DHCP offer message.

[0061] After that, under the control of the control unit 102, the permission list providing unit 122 of the DHCP server 1(1) functions, and the permission list (a list of MAC addresses) in the permission list storage unit 1032 is transmitted to the DHCP server 1(2), which is the source of the DHCP offer (step S6). Further, under the control of the control unit 102, the permission list providing unit 122 of the DHCP server 1(1) functions, and the permission list (a list of MAC addresses) in the permission list storage unit 1032 is transmitted to the DHCP server 1(3), which is the source of the DHCP offer (step S7).

[0062] In steps S6 and S7 of FIG. 6, the information to be provided is used as a permission list or the like. As described above, since there may be a client device to which an IP address has been assigned before the registration of the permission list, in addition to the permission list, it is intended to include the MAC address of the assigned list in the assigned list storage unit 1035. Further, the transmission of the permission list or the like in steps S6 and S7 is performed using the application layer (layer 7) of the OSI reference model network. This is because information regarding a specific system or service is transmitted and received.

[0063] The DHCP server 1(2) that has received the permission list or the like from the DHCP server 1(1) returns a response (step S8). Similarly, the DHCP server 1(3) that has received the permission list or the like from the DHCP server 1(1) returns a response (step S9). Thereby, the DHCP server 1(1) that is the transmission source of the permission list can grasp that the permission list or the like has been appropriately received by the DHCP servers 1(2) and 1(3) that are the transmission destinations.

[0064] After that, the DHCP server 1(2) that has received the permission list or the like functions the ignore list registration unit 123 under the control of the control unit 102, and registers (records) the permission list or the like received from the DHCP server 1(1) in the ignore list storage unit 1033 (step S10). That is, the permitted MAC address provided as the permission list and the MAC address of the assigned list are registered in the ignore list storage unit 1033. In this case, if the permitted MAC address provided as the permission list and the MAC address of the assigned list overlap, only one of them will be registered and there will be no overlap. As described above with reference to FIG. 3(C), the ignore list is composed of the MAC address of the DHCP server 1 that is the provider of the permission list and the ignore MAC address corresponding to the permission list. Thereby, in the DHCP server 1(2), the PC3A recognized as the destination for IP address assignment in the DHCP server 1(1) can be recognized as a client device that ignores it without recognizing it as the destination for IP address assignment.

[0065] Furthermore, the DHCP server 1(2) that has received the permission list, under the control of the control unit 102, functions the other server list registration unit 124 to create an other server list and register (record) it in the other server list storage unit 1034 (step S11). Specifically, the process of step S11 identifies other server information for distinguishing each DHCP server. This other server information may be, for example, a sequence number in the registration order. Next, the MAC address of the DHCP server 1(1) which is the transmission source added to the permission list received from the DHCP server 1(1), and the permission list, etc. are extracted. Since it is the permission list, etc., it includes the permitted MAC address provided as the permission list and the MAC address of the allocated list, but is made non-duplicative. After this, as shown in FIG. 4(A), an other server list consisting of the other server information, the MAC address of the transmission source of the permission list, and the permission list is formed and additionally recorded in the other server list storage unit 1034.

[0066] Similarly, the DHCP server 1(3) that has received the permission list, etc., under the control of the control unit 102, functions the ignore list registration unit 123 to register (record) the permission list, etc. received from the DHCP server 1(1) in the ignore list storage unit 1033 (step S12). The process of this step S12 is the same as the process performed in step S10. As described above with reference to FIG. 3(C), the ignore list is composed of the MAC address of the DHCP server 1 which is the provider of the permission list and the ignore MAC address corresponding to the permission list. Thereby, in the DHCP server 1(3), the PC3A recognized as the destination for IP address assignment in the DHCP server 1(1) can be recognized as a client device that ignores it without recognizing it as the destination for IP address assignment.

[0067] Furthermore, upon receiving the permission list, the DHCP server 1(3) causes the other server list registration unit 124 to function under the control of the control unit 102 to create an other server list and register (record) it in the other server list storage unit 1034 (step S13). The process of step S13 is the same as the process performed in step S11. Specifically, the process of step S13 is the same as the process of step S11 described above. That is, other server information for distinguishing each DHCP server is specified. Next, the MAC address of the DHCP server 1(1) which is the transmission source added to the permission list received from the DHCP server 1(1) and the permission list are extracted. After that, as shown in FIG. 4(A), an other server list composed of the other server information, the MAC address of the transmission source of the permission list, and the permission list is formed and additionally recorded in the other server list storage unit 1034.

[0068] Through the process shown in this FIG. 6, the DHCP server 1(1) can provide the permission list and the like (the MAC address of the client device to which the IP address is assigned from itself) in itself to the other DHCP servers 1(2) and 1(3) connected to the LAN2. The DHCP servers 1(2) and 1(3) can register the provided permission list and the like in their own ignore list storage unit 1033. Also, in the other DHCP servers 1(2) and 1(3), the MAC address of the destination that has received the permission list and the permission list can be grasped in association with each other by the other server list in the other server list storage unit 1034.

[0069] The process executed starting from the DHCP server 1(1) described with reference to FIG. 6 is also executed starting from the DHCP server 1(2), and also starting from the DHCP server 1(3). Thereby, the permission list exchange process is performed among each of the DHCP servers 1(1), 1(2), and 1(3), and the permission lists of the other DHCP servers can be registered as the ignore list of the local device.

[0070] FIG. 7 is a diagram for explaining the states of the permission list and the ignore list after the exchange process of the ignore list of the DHCP server according to the embodiment. As shown in FIG. 7(A), the MAC addresses A1 and A2 of PC3A(1) and 3A(2) are registered in the permission list storage unit 1032 of the DHCP server 1(1). Similarly, as shown in FIG. 7(B), the MAC addresses B1 and B2 of PC3B(1) and 3B(2) are registered in the permission list storage unit 1032 of the DHCP server 1(2). Similarly, as shown in FIG. 7(C), the MAC addresses B1 and B2 of PC3B(1) and 3B(2) are registered in the permission list storage unit 1032 of the DHCP server 1(3).

[0071] In this case, by performing the distribution process of the permission list and the like described with reference to FIG. 6 starting from each of the DHCP servers 1(1), 1(2), and 1(3), the ignore list can be organized in the ignore list storage unit 1033 of the DHCP server 1(1). In the case of this example, as shown in the ignore list storage unit 1033 of FIG. 7(A), the ignore MAC addresses B1 and B2 corresponding to the permission list of the DHCP server 1(2) whose MAC address is X2 are registered. Further, as shown in the ignore list storage unit 1033 of FIG. 7(A), the ignore MAC addresses C1 and C2 corresponding to the permission list of the DHCP server 1(3) whose MAC address is X3 are registered.

[0072] Similarly, the ignore list can be organized in the ignore list storage unit 1033 of the DHCP server 1(2). In the case of this example, as shown in the ignore list storage unit 1033 of FIG. 7(B), the ignore MAC addresses A1 and A2 corresponding to the permission list of the DHCP server 1(1) whose MAC address is X1 are registered. Further, as shown in the ignore list storage unit 1033 of FIG. 7(B), the ignore MAC addresses C1 and C2 corresponding to the permission list of the DHCP server 1(3) whose MAC address is X3 are registered.

[0073] Similarly, the ignore list storage unit 1033 of the DHCP server 1(3) can maintain the ignore list. In this example, as shown in the ignore list storage unit 1033 of FIG. 7(C), the ignore MAC addresses A1 and A2 corresponding to the permission list of the DHCP server 1(1) with the MAC address X1 are registered. Further, as shown in the ignore list storage unit 1033 of FIG. 7(C), the ignore MAC addresses B1 and B2 corresponding to the permission list of the DHCP server 1(2) with the MAC address X2 are registered.

[0074] As described above, through the distribution process of the permission list and the like explained with reference to FIG. 6, the DHCP server 1(1) can distribute its own permission list to the DHCP servers 1(2) and 1(3) and register it in their respective ignore lists. Similarly, starting from the DHCP server 1(2), by performing the same process as in FIG. 6, the DHCP server 1(2) can distribute its own permission list to the DHCP servers 1(1) and 1(3) and register it in their respective ignore lists. Similarly, starting from the DHCP server 1(3), by performing the same process as in FIG. 6, the DHCP server 1(2) can distribute its own permission list to the DHCP servers 1(1) and 1(3) and register it in their respective ignore lists.

[0075] Therefore, as shown in FIG. 7(A), according to the permission list in the permission list storage unit 1032, the DHCP server 1(1) can assign IP addresses in response to requests from the PCs 3A(1) and 3A(2) with the MAC addresses A1 and A2. However, according to the ignore list in the ignore list storage unit 1033, requests from the PCs 3B(1) and 3B(2) with the MAC addresses B1 and B2 and the PCs 3C(1) and 3C(2) with the MAC addresses C1 and C2 will be ignored.

[0076] Similarly, as shown in FIG. 7(B), according to the permission list in the permission list storage unit 1032, the DHCP server 1(2) can assign IP addresses in response to requests from the PCs 3B(1) and 3B(2) with MAC addresses B1 and B2. However, according to the ignore list in the ignore list storage unit 1033, requests from the PCs 3A(1) and 3A(2) with MAC addresses A1 and A2 and the PCs 3C(1) and 3C(2) with MAC addresses C1 and C2 will be ignored.

[0077] Similarly, as shown in FIG. 7(C), according to the permission list in the permission list storage unit 1032, the DHCP server 1(3) can assign IP addresses in response to requests from the PCs 3C(1) and 3C(2) with MAC addresses C1 and C2. However, according to the ignore list in the ignore list storage unit 1033, requests from the PCs 3A(1) and 3A(2) with MAC addresses A1 and A2 and the PCs 3B(1) and 3B(2) with MAC addresses B1 and B2 will be ignored.

[0078] <Connection Confirmation Process> FIG. 8 is a sequence diagram for explaining the connection confirmation process of the DHCP server according to the embodiment. In the example shown in FIG. 8, the DHCP server 1(1) and the DHCP server 1(2) remain connected to the LAN2, but the case where the DHCP server 1(3) is removed (deleted) from the LAN2 will be described as an example. For each of the DHCP servers 1(1), 1(2), and 1(3) in this embodiment, the transmission interval of the DHCP inform used when requesting information other than the IP address is predetermined. This transmission interval is stored (set) in advance, for example, in a non-volatile memory of the control unit 102 or a predetermined storage area of the storage device 103. The transmission interval of the DHCP inform can be set at an appropriate interval. For example, it can be set to every 180 minutes, every 300 minutes, or it can also be set, for example, at 9:00 am on Monday every week.

[0079] When the transmission timing of the DHCP inform arrives, the control unit 102 of the DHCP server 1(1) controls the client function unit 111 of the DHCP function unit 110 to form and transmit a DHCP inform that requests the provision of a permission list or the like. In the case of this example, the client function unit 111 of the DHCP function unit 110 identifies the destination based on the other server list managed by the other server list storage unit 1034. Therefore, in the case of this example, the client function unit 111 of the DHCP function unit 110 of the DHCP server 1(1) transmits the formed DHCP inform to the DHCP server 1(2) (step S21), and further transmits it to the DHCP server 1(3) as well (step S22).

[0080] As described above, in the case of this example, the DHCP server 1(2) is in a state of being connected to the LAN2. For this reason, the control unit 102 of the DHCP server 1(2) controls the server function unit 112 to form a DHCP ack and reply to the DHCP server 1(1) that is the transmission source of the DHCP inform (step S23). Further, the control unit 102 of the DHCP server 1(2) controls the permission list providing unit 122 to transmit the permission list or the like in the permission list storage unit 1032 to the DHCP server 1(1) according to the DHCP inform from the DHCP server 1(1) (step S24).

[0081] The reason for using the permission list, etc. here is that, similar to the processing of steps S6 and S7 described with reference to FIG. 6, it includes the MAC address of the destination (recipient) of the IP address in the allocated list storage unit 1035. Therefore, if there is an overlap between the permission list and the MAC address of the destination (recipient) of the IP address in the allocated list storage unit 1035, one of them will be deleted. Also, the transmission of the permission list, etc. in step S24 is performed using the application layer (layer 7) of the OSI reference model network. This is because information regarding specific systems and services is to be transmitted and received. Through the processing of this step S24, the DHCP server 1(1), which is the source of the DHCP inform, acquires a new permission list, etc. from the DHCP server 1(2). For this reason, the control unit 102 of the DHCP server 1(1) controls the ignore list update unit 127 and the other server list update unit 128 to update the ignore list and the other server list (step S25).

[0082] In step S25, the ignore list update unit 127 updates the ignore MAC address (ignore list) associated with the MAC address of the DHCP server 1(2) in the ignore list storage unit 1033 based on the newly provided permission list, etc. from the DHCP server 1(2). Specifically, the MAC addresses that exist in both the new permission list, etc. and the ignore list are left as they are. Also, the MAC addresses that exist in the new permission list, etc. but do not exist in the ignore list are added to the ignore list, and the MAC addresses that do not exist in the new permission list, etc. but exist in the ignore list are deleted from the ignore list. Briefly, all the ignore MAC addresses associated with the MAC address of the DHCP server 1(2) in the ignore list storage unit 1033 may be deleted and the newly provided permission list, etc. from the DHCP server 1(2) may be added instead.

[0083] Also, in step S25, the other server list update unit 128 updates the acquired permission list having the MAC address of the DHCP server 1(2) in the other server list storage unit 1034 based on the permission list and the like newly provided from the DHCP server 1(2). Specifically, the MAC addresses existing in both the new permission list and the like and the acquired permission list of the other server list are left as they are. Also, the MAC addresses existing in the new permission list and the like but not existing in the acquired permission list of the other server list are added to the acquired permission list. Further, the MAC addresses not existing in the new permission list and the like but existing in the acquired permission list of the other server list are deleted from the acquired permission list. Briefly, all of the acquired permission lists of the other server list associated with the MAC address of the DHCP server 1(2) in the other server list storage unit 1034 are deleted. After that, the permission list and the like newly provided from the DHCP server 1(2) may be added to the acquired permission list of the other server list.

[0084] Also, as shown in FIG. 8, the DHCP server 1(3) has been removed from the LAN2 and is in a deleted state. For this reason, as indicated by the dotted arrow, no DHCP ack is returned from the DHCP server 1(3). As described above, the DHCP server 1(1) also transmits a DHCP inform to the DHCP server 1(3) by unicast. Therefore, when no DHCP ack is returned from the DHCP server 1(3), the fact that no DHCP ack is returned from the DHCP server 1(3) and the MAC address of the DHCP server 1(3) can be grasped. This is because the other server list of the DHCP server 1(3) exists in the other server list storage unit 1034.

[0085] Therefore, in the DHCP server 1(1) which is the source of the DHCP inform, the ignore list and the other server list corresponding to the DHCP server 1(3) are deleted (step S26). That is, in step S26, under the control of the control unit 102, the ignore list deletion unit 125 functions to delete the ignore MAC address (ignore list) having the MAC address of the DHCP server 1(3) that no longer exists. Also, in step S26, under the control of the control unit 102, the other server list deletion unit 126 functions to delete the other server list consisting of the other server information, the MAC address, and the permission list obtained with the MAC address of the DHCP server 1(3) that no longer exists. Thereby, the stored information in the ignore list storage unit 1033 and the other server list storage unit 1034 of the DHCP server 1(1) which is the source of the DHCP inform is updated to the latest appropriate content.

[0086] The process shown in this FIG. 8 is shown for the case where it is performed starting from the DHCP server 1(1), but the same process is also performed starting from the DHCP server 1(2) connected to the LAN2. Thereby, also in the DHCP server 1(2), the stored information in the ignore list storage unit 1033 and the other server list storage unit 1034 is updated to the latest appropriate content.

[0087] FIG. 9 is a diagram for explaining the states of the permission list and the ignore list after the connection confirmation process of the DHCP server according to the embodiment. Here, as shown in FIG. 9(A), in the permission list storage unit 1032 of the DHCP server 1(1), the client device of group A has one more PC3A(3), and the MAC addresses A1, A2, and A3 for the three units of PC3A(1), 3A(2), and 3A(3) are registered. Similarly, as shown in FIG. 9(B), in the permission list storage unit 1032 of the DHCP server 1(2), the client device of group B has one more PC3B(3), and the MAC addresses B1, B2, and B3 for the three units of PC3B(1), 3B(2), and 3B(3) are registered. The DHCP server 1(3) has been deleted and thus does not exist.

[0088] In this case, by performing the connection confirmation process described with reference to FIG. 8 starting from each of the DHCP servers 1(1) and 1(2), the ignore list storage unit 1033 of the DHCP server 1(1) can be equipped with an ignore list that matches the current situation. In the case of this example, as shown in the ignore list storage unit 1033 of FIG. 9(A), the ignore MAC addresses B1, B2, and B3 corresponding to the permission list of the DHCP server 1(2) with the MAC address X2 are registered in the ignore list storage unit 1033. Since the DHCP server 1(3) has been deleted, there is no ignore list corresponding to the permission list of the DHCP server 1(3) or the like.

[0089] Similarly, the ignore list storage unit 1033 of the DHCP server 1(2) can be equipped with an ignore list that matches the current situation. In the case of this example, as shown in the ignore list storage unit 1033 of FIG. 9(B), the ignore MAC addresses A1 and A2 corresponding to the permission list of the DHCP server 1(1) with the MAC address X1 are registered in the ignore list storage unit 1033. Since the DHCP server 1(3) has been deleted, there is no ignore list corresponding to the permission list of the DHCP server 1(3) or the like.

[0090] As described above, by the connection confirmation process described with reference to FIG. 8, both the ignore list of the ignore list storage unit 1033 of the DHCP server 1 connected to the LAN2 and the other server list of the other server list storage unit 1034 can be appropriately managed according to the connection state. That is, by appropriately maintaining the permission list according to the increase or decrease of the client devices under the DHCP server 1, the ignore list of the ignore list storage unit 1033 can be appropriately updated according to the connection state of the clients. Further, even when the DHCP server 1 is deleted or replaced, both the ignore list of the ignore list storage unit 1033 of each DHCP server 1 and the other server list of the other server list storage unit 1034 can be appropriately managed according to the connection state.

[0091] [Summary of Connection Control Using Permission List and Ignore List] As described above, when a DHCP Discover arrives, the server function unit 112 of the DHCP function unit 110 of the DHCP server 1 assigns an IP address to a client device having a MAC address that exists in the permission list and does not exist in the ignore list. Therefore, an IP address is not assigned to a client device having a MAC address that does not exist in the permission list and exists in the ignore list.

[0092] However, for a client device having a MAC address that exists in both the permission list and the ignore list, the ignore list is given priority and control is performed so that an IP address is not assigned. This is because when it exists in the ignore list, it may be under the control of IP address allocation by another DHCP server. Therefore, for the MAC address that the user assumes is permitted, even if it is explicitly registered in the permission list, if it also exists in the ignore list at the same time, it is handled so that an IP address is not assigned without responding.

[0093] Note that an IP address may be assigned to a client device having a MAC address that is not registered in either the permission list or the ignore list. This is the same as the handling in the case where nothing is registered in the permission list and nothing is registered in the ignore list as described above.

[0094] [Utilization of Other Server Lists] The other server list in the other server list storage unit 1034 has the same content as the ignore list in the ignore list storage unit 1033. For this reason, the ignore list in the ignore list storage unit 1033 can also be configured as a list consisting of ignore MAC addresses that do not have a source MAC address. However, assume that the ignore list is configured as a list consisting of ignore MAC addresses that do not have a source MAC address. In this case, since it is not possible to determine which permission list of which DHCP server 1 each ignore MAC address corresponds to, for the update and deletion of the ignore list, after deleting the entire ignore list, it may be recreated according to the permission list obtained from the other server list.

[0095] In addition, in the above-described embodiment, for the sake of simplicity of explanation, it has been described that the ignore list is configured in the ignore list storage unit 1033. However, it is also possible to use the other server list in the other server list storage unit 1034 as the ignore list.

[0096] [Effects of the Embodiment] According to the DHCP server 1 of the above-described embodiment to which one embodiment of the IP address assignment device of the present invention is applied, when a plurality of DHCP servers are provided in the same network, appropriate decentralization can be realized and dynamic changes can also be coped with. As a result, the load on the DHCP server can be dispersed, and the execution environment of the process using each client device can be kept good.

[0097] In addition, even when the network of the connection destination is different for each DHCP server, it becomes possible to appropriately control the DHCP server that assigns an IP address for each client device, and the client device can surely be connected to the target network.

[0098] [Modification Example] In the above-described embodiment, each of the DHCP servers 1(1), 1(2), and 1(3) has been described as being mounted on the router. However, the present invention is not limited to this. It is also possible to mount on various devices having a function of connecting a client device to a network, such as a so-called gateway device and a SIP (Session Initiation Protocol) server. Further, it is also possible to provide a single DHCP server directly below a device having a function of connecting different networks such as a router, a gateway device, and a SIP server.

[0099] Also, the above-described embodiment described the case where initially three DHCP servers 1(1), 1(2), and 1(3) were connected to LAN2 and then DHCP server 1(3) was deleted, but it is not limited to this. The number of DHCP servers 1 connected to LAN2 may be any number as long as it is two or more. Also, even when the number of DHCP servers 1 to be deleted or replaced is not one by one but multiple servers are deleted or replaced simultaneously, the IP address assignment device of the present invention can function.

[0100] In the above-described embodiment, if a DHCP server without the DHCP sharing function provided in DHCP servers 1(1), 1(2), and 1(3) is connected to LAN2, it will be treated as non-compatible with the DHCP sharing function. In this case, since it may hinder the proper decentralization of the DHCP servers, it is preferable to use only the DHCP servers equipped with the DHCP sharing function.

[0101] In addition, when there is a DHCP server without the DHCP sharing function, it is conceivable to set the response priority of the DHCP servers. That is, each DHCP server may be set so that the DHCP server with the DHCP sharing function responds preferentially, and the DHCP server without the DHCP sharing function may be configured to send a DHCP offer in response to a DHCP discover.

[0102] Also, when there is a DHCP server without the DHCP sharing function, one parent server is provided, and the others are child servers. The parent server manages the status of each child server, that is, whether it has the DHCP sharing function or not. For a child server without the DHCP sharing function, the parent server controls it to send a DHCP offer after another DHCP server has sent a DHCP offer. Thereby, the DHCP offer from the DHCP server with the DHCP sharing function can be preferentially provided to the client device. Thereby, for a client device whose MAC address is not registered in the permission list or ignore list of any DHCP server, it can receive an IP address assignment from a child server without the DHCP sharing function.

Description of Signs

[0103] 1…DHCP server, 1(1), 1(2), 1(3)…DHCP servers, 101T…connection terminal, 101…communication I / F, 102…control unit, 103…storage device, 1031…lease information list storage unit, 1032…permission list storage unit, 1033…ignore list storage unit, 1034…other server list storage unit, 1035…assigned list storage unit, 104T…connection terminal, 104…LAN I / F, 110…DHCP function unit, 111…client function unit, 112…server function unit, 120…sharing function unit, 121…permission list registration unit, 122…permission list providing unit, 123…ignore list registration unit, 124…other server list registration unit, 125…ignore list deletion unit, 126…other server list deletion unit, 127…ignore list update unit, 128…other server list update unit, 2…LAN, 3…PC, 3A, 3A(1), 3A(2), 3A(3)…PCs, 3B, 3B(1), 3B(2), 3B(3)…PCs, 3C, 3C(1), 3C(2), 3C(3)…PCs, 4…Internet

Claims

1. Permission list registration means for receiving client identification information of a client device permitted as an IP address assignment destination from the own device and registering it in the permission list storage unit; Discovery message transmission processing means for transmitting a discovery message used to discover other IP address assignment devices connected to the same network; Proposal message reception processing means for receiving a proposal message including an available IP address from the other IP address assignment device that has received the discovery message and the assignment device identification information of the other IP address assignment device; Rejection message transmission means for transmitting a rejection message notifying rejection of IP address assignment to the other IP address assignment device that is the source of the proposal message; Permission list providing means for transmitting the device identification information of the own device and at least the client identification information stored in the permission list storage unit to the other IP address assignment device that is the source of the proposal message; Discovery message reception processing means for receiving the discovery message from the other IP address assignment device; Proposal message transmission processing means for forming and transmitting the proposal message when the discovery message is received through the discovery message reception processing means; Identification information reception processing means for receiving the assignment device identification information and the client identification information from the other IP address assignment device; Response message transmission processing means for transmitting a response message to the other IP address assignment device that is the source when the assignment device identification information and the client identification information are received through the identification information reception processing means; Ignore list registration means for registering the client identification information received through the identification information reception processing means in the ignore list storage unit An IP address assignment device characterized by comprising.

2. The IP address assignment device according to claim 1, Confirmation message transmission processing means for periodically transmitting a confirmation message for confirming the existence of each of the IP address assignment devices specified by the device identification information of the other server list storage unit that stores and holds the device identification information of other IP address assignment devices connected to the same network; Confirmation response message reception processing means for receiving a confirmation response message from the IP address assignment device that is the destination of the confirmation message transmitted; When the confirmation response message is received through the confirmation response message receiving processing means, second permission list providing means for providing at least the client identification information of the permission list storage unit to the IP address assigning device of the destination of the confirmation response message; When the confirmation response message has not been transmitted from the IP address assigning device of the destination of the confirmation message through the confirmation message transmitting processing means, the one or more pieces of client identification information in the other server list storage unit specified by the assigning device identification information of the IP address assigning device of the destination are deleted from the ignore list storage unit; Confirmation message receiving processing means for receiving the confirmation message from the other IP address assigning device; Confirmation message transmitting means for forming and transmitting the confirmation response message when the confirmation message is received through the confirmation message receiving processing means; Ignore list updating means for updating the client identification information in the ignore list storage unit using the client identification information to be transmitted when the confirmation response message is transmitted through the confirmation message transmitting means An IP address assigning device characterized by comprising:

3. The IP address assigning device according to claim 1, Comprising assigned list holding means for holding an assigned list including client identification information of the destination when an IP address is assigned to a client device; The permission list providing means transmits the client identification information of the assigned list holding means in addition to the client identification information of the permission list storage unit. An IP address assigning device characterized by:

4. The IP address assigning device according to claim 2, Comprising assigned list holding means for holding an assigned list including client identification information of the destination when an IP address is assigned to a client device; The second permission list providing means transmits the client identification information of the assigned list holding means in addition to the client identification information of the permission list storage unit. An IP address assigning device characterized by:

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