DHCP Server and Network System

Abstract

To provide a DHCP server and a network system which enable efficient operation of a network during replacement of information terminals.SOLUTION: A fixed IP acquisition unit 26 refers to a fixed IP configuration table 16, determines whether or not a target terminal ID is a replacement source hit registered as a replacement source terminal ID, and acquires, when the target terminal ID is the replacement source hit, a corresponding fixed IP address. An IP address allocation unit 27 refers to a lease management table 17 to determine whether or not the acquired fixed IP address is in use, and allocates, when the address is not in use, the fixed IP address to the target terminal ID. A configuration table modification unit 28 replaces, when conditions are met, a registration content of the replacement source terminal ID by a registration content of a replacement destination terminal ID with respect to the fixed ID configuration table 16, and deletes the registration content of the replacement source terminal ID.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a DHCP server and a network system. [Background technology]

[0002] Patent Document 1 shows a server device capable of reducing the burden on a network administrator. The server device includes a DHCP reservation table in which a correspondence between a MAC address and an IP address is registered as first reservation information, and an account management table in which a correspondence between a MAC address and a fixed IP address is registered as the first registration information. When the first registration information is registered in the account management table, the server device registers the first reservation information in the DHCP reservation table based on the first registration information. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-007057 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when operating an in-house network, a DHCP (Dynamic Host Configuration Protocol) server may be used to assign fixed IP addresses to information terminals on the network. Also, there are cases where the same IP address is assigned to the same user. In the case where the same IP address is assigned to the same user, when the information terminal used by the user is replaced, the fixed IP address of the original information terminal must be handed over to the replacement information terminal.

[0005] In this case, the system administrator usually had to manually change the setting table of the fixed IP address stored in the DHCP server when it was time to replace the information terminal. This resulted in time constraints for the system administrator. Furthermore, when replacing many information terminals at once, in addition to the time constraints, the system administrator also had to bear a large workload associated with the change work. In addition, in this case, the change work sometimes required a period of time when the network was unavailable.

[0006] The present invention has been made in view of the above, and one of its objects is to provide a DHCP server and a network system that can improve the efficiency of network operation when information terminals are replaced.

[0007] The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] Among the inventions disclosed in this application, a brief outline of a representative embodiment will be described as follows.

[0009] A DHCP server according to an embodiment includes a memory, a terminal ID acquisition unit, a fixed IP acquisition unit, and an IP address allocation unit. The memory stores a source terminal ID for identifying a source information terminal, a destination terminal ID for identifying a destination information terminal, a fixed IP setting table for determining a correspondence relationship between a source terminal ID and a fixed IP address to be assigned to the source terminal ID or the destination terminal ID, and a lease management table for indicating an IP address in use. The terminal ID acquisition unit receives an IP address assignment request from an information terminal, and acquires the terminal ID included in the assignment request as a target terminal ID. The fixed IP acquisition unit refers to the fixed IP setting table, and determines whether the target terminal ID is a source hit registered as a source terminal ID, and acquires a corresponding fixed IP address if the target terminal ID is a source hit. The IP address allocation unit refers to the lease management table, and determines whether the acquired fixed IP address is in use, and assigns the fixed IP address to the target terminal ID if the target terminal ID is unused. Effect of the Invention

[0010] To briefly explain the effect obtained by a representative embodiment of the invention disclosed in this application, it becomes possible to improve the efficiency of network operation accompanying the replacement of information terminals. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a network system according to an embodiment; [Figure 2A] 2 is a schematic diagram showing an example of the configuration of a fixed IP setting table in FIG. 1; [Figure 2B] 2 is a schematic diagram showing an example of the configuration of a lease management table 17 in FIG. 1. [Figure 2C] 2 is a schematic diagram showing an example of the configuration of a dynamic IP setting table appearing in FIG. 1; [Figure 3A] 2 is a flow chart showing an example of processing contents of a DHCP server appearing in FIG. 1; [Figure 3B]2 is a flow chart showing an example of processing contents of a DHCP server appearing in FIG. 1; [Figure 4] 2 is a diagram for explaining a method of changing a fixed IP setting table, which is executed by the DHCP server appearing in FIG. 1; [Diagram 5] FIG. 2 is a diagram showing an example of a setting screen for the DHCP server appearing in FIG. [Figure 6] 1. FIG. 4 is a flowchart showing an example of another process performed by the DHCP server in FIG. [Figure 7] FIG. 2 is a diagram illustrating an example of an operation method in the network system illustrated in FIG. [Figure 8] 8 is a diagram showing an example of an operation method different from that shown in FIG. 7 in the network system shown in FIG. [Figure 9] 2 is a block diagram showing an example of the configuration of a main part of a DHCP server appearing in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiment, the same members are generally designated by the same reference numerals, and the repeated description will be omitted.

[0013] <Network system overview> Fig. 1 is a schematic diagram showing an example of the configuration of a network system according to an embodiment. The network system shown in Fig. 1 includes a network 10, information terminals TM1 and TM2, and a DHCP server 11 connected to the information terminals TM1 and TM2 via the network 10. The network 10 is, for example, an in-house network, and includes, for example, an L2 switch that handles relay processing of Layer 2 (L2) of the OSI reference model, an L3 switch that handles relay processing of Layer 3 (L3), and the like.

[0014] The information terminals TM1 and TM2 are used by a user 12 and are, for example, computer systems such as a PC (Personal Computer) or a tablet terminal. In the embodiment, as shown in Fig. 1, it is assumed that the user 12 replaces the information terminal TM1 with the information terminal TM2. The information terminal TM1, which is the source terminal, has a MAC address MA1, and the information terminal TM2, which is the destination terminal, has a MAC address MA2. In the specification, the information terminals TM1 and TM2 are collectively referred to as information terminals TM.

[0015] The DHCP server 11 is managed by a system administrator 13, and assigns an IP address to the information terminal TM. The DHCP server 11 is realized, for example, by a computer system having a processor and memory 15 (not shown). However, the DHCP server 11 is not limited to a computer system, and may be realized by hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0016] The memory 15 is configured, for example, by a combination of a volatile memory such as a DRAM or an SRAM, and a non-volatile memory such as a flash memory, an SSD (Solid State Drive), or an HDD (Hard Disk Drive). The memory 15 stores a fixed IP setting table 16, a lease management table 17, and a dynamic IP setting table 18. The memory 15 also stores programs executed by the processor, etc.

[0017] Fig. 2A is a schematic diagram showing an example of the configuration of the fixed IP setting table in Fig. 1. The fixed IP setting table 16 shown in Fig. 2A is set by the system administrator 13. Specifically, the system administrator 13 registers predetermined contents in the fixed IP setting table 16 via the user interface of the DHCP server 11 or a management terminal connected to the DHCP server 11, such as a display or a keyboard.

[0018] The fixed IP setting table 16 defines a correspondence relationship between a source terminal ID that identifies the source information terminal TM, a destination terminal ID that identifies the destination information terminal TM, and a fixed IP address to be assigned to the source terminal ID or the destination terminal ID. The terminal ID, i.e., the terminal identifier, is, for example, a MAC address. Thus, the fixed IP setting table 16 is different from a general setting table that defines a one-to-one correspondence relationship between a terminal ID and a fixed IP address, and allows two terminal IDs to be registered as the terminal ID.

[0019] In this example, the system administrator 13 registers the MAC address MA1 of the information terminal TM1 in the source terminal ID, and registers the MAC address MA2 of the information terminal TM2 in the destination terminal ID. The system administrator 13 also registers a fixed IP address IPAs1, for example, "10.10.10.123", in correspondence with the MAC addresses MA1 and MA2.

[0020] Furthermore, in the fixed IP setting table 16, manual switching can be selected to be on or off in association with the above-mentioned correspondence. In this example, the system administrator 13 selects manual switching to be off. Although details will be described later, the DHCP server 11 automatically changes the registered contents of the fixed IP setting table 16 when a specific condition is met, regardless of whether manual switching is on or off. However, the time when the specific condition is met is determined automatically when manual switching is off and is determined manually when manual switching is on.

[0021] In addition, the fixed IP setting table 16 also displays the remaining valid period associated with the lease valid period, for example, in association with the above-mentioned correspondence. When the DHCP server 11 assigns an IP address to the information terminal TM, the DHCP server 11 generally manages the period during which the IP address can be used as the lease valid period. The lease valid period is usually set to a length of 24 hours or less.

[0022] For example, when the fixed IP address IPAs1 is being assigned to the MAC address MA1, which is the original terminal ID, the DHCP server 11 calculates and displays the remaining lease validity period when displaying the fixed IP setting table 16. This allows the system administrator 13 to perform various registrations after confirming whether the original terminal is in operation or not, and if so, how long it will take for the validity period to expire.

[0023] Incidentally, the information terminal TM normally transmits a DHCP request message including the assigned IP address to the DHCP server 11 when half the lease validity period has elapsed. In response, the DHCP server 11 extends the lease validity period for that IP address. Furthermore, the information terminal TM normally transmits a DHCP release message including the assigned IP address to the DHCP server 11 when it is shut down. In response, the DHCP server 11 changes the IP address from a used state to an unused state.

[0024] Fig. 2B is a schematic diagram showing an example of the configuration of the lease management table 17 in Fig. 1. The lease management table 17 shown in Fig. 2B shows IP addresses in use, and is registered by the DHCP server 11. In this example, the lease management table 17 shows the correspondence between IP addresses in use, the terminal IDs to which the IP addresses are assigned, and the remaining lease validity periods.

[0025] In the example of Fig. 2B, when the DHCP server 11 assigns the fixed IP address IPAs1 to the MAC address MA1, it registers the correspondence and the remaining lease valid period in the lease management table 17. Also, when the DHCP server 11 assigns the dynamic IP address IPAd1 to the MAC address MA2, it registers the correspondence and the remaining lease valid period in the lease management table 17. Note that when the remaining lease valid period has elapsed or when the DHCP server 11 receives a DHCP release message, it deletes the entry of the corresponding IP address from the lease management table 17 and manages the IP address as being in an unused state.

[0026] Figure 2C is a schematic diagram showing a configuration example of the dynamic IP setting table in FIG. 1. The dynamic IP setting table 18 shown in FIG. 2C is set by the system administrator 13 in the same manner as the fixed IP setting table 16. The system administrator 13 registers, for the dynamic IP setting table 18, the lease range of the dynamic IP address using the minimum value IPAd(min), for example, "10.20.10.10", and the maximum value IPAd(max), for example, "10.20.10.100". When assigning a dynamic IP address to the information terminal TM, the DHCP server 11 selects an unused dynamic IP address based on the lease management table 17 from within the lease range based on the dynamic IP setting table 18.

[0027] <Operation of DHCP Server> FIGS. 3A and 3B are flowcharts showing an example of the processing content of the DHCP server in FIG. 1. In FIG. 3A, the DHCP server 11 receives a request for assignment of an IP address from the information terminal TM, and acquires, as the target terminal ID, the terminal ID included in the assignment request, for example, the MAC address (step S101). Subsequently, the DHCP server 11 refers to the fixed IP setting table 16 using the acquired target terminal ID as a key (step S102), and determines whether or not the target terminal ID is a replacement hit registered as the replacement source terminal ID (step S103).

[0028] If it is a replacement hit in step S103 ("Yes"), the DHCP server 11 acquires the corresponding fixed IP address (step S104a). Next, the DHCP server 11 refers to the lease management table 17 using the acquired fixed IP address as a key (step S105a), and determines whether the acquired fixed IP address is in a used state or an unused state (step S106a).

[0029] If the address is in an unused state in step S106a (if "Yes"), the DHCP server 11 assigns the acquired fixed IP address to the target terminal ID, i.e., the original terminal ID (step S107a). Then, the DHCP server 11 registers the correspondence between the target terminal ID, i.e., the original terminal ID, and the assigned fixed IP address, for example, the correspondence between the MAC address MA1 and the fixed IP address IPAs1 in FIG. 2B, together with the remaining lease valid period in the lease management table 17 (step S108a).

[0030] On the other hand, if the terminal is in use in step S106a (if "No"), the DHCP server 11 extends the lease valid period or performs error processing (step S109a). Specifically, if the DHCP server 11 receives an allocation request from the source terminal ID in step S101 in a state where the correspondence between the source terminal ID and the fixed IP address has already been registered in the lease management table 17, the DHCP server 11 extends the lease valid period. On the other hand, if the DHCP server 11 receives an allocation request from the source terminal ID in step S101 in a state where the correspondence between the terminal ID and the fixed IP address different from the source terminal ID is registered in the lease management table 17, the DHCP server 11 performs error processing.

[0031] Also, if the replacement source is not hit in step S103 (if "No"), as shown in Fig. 3B, the DHCP server 11 judges whether or not manual switching OFF is selected (step S201). If manual switching ON is selected in step S201 (if "No"), the DHCP server 11 assigns a dynamic IP address to the target terminal ID (step S204). That is, if manual switching ON is selected, the DHCP server 11 assigns a dynamic IP address if the replacement source is not hit in step S103, in other words, if the assignment request is from a terminal ID different from the replacement source terminal ID.

[0032] Then, the DHCP server 11 registers the correspondence between the target terminal ID, i.e., the terminal ID different from the original terminal ID, and the assigned dynamic IP address together with the remaining lease validity period in the lease management table 17 (step S205). In this way, when manual switching is selected to be on, the DHCP server 11 performs substantially the same processing as the assignment processing based on a general setting table in which the one-to-one correspondence between the fixed IP address and the original terminal ID is registered.

[0033] On the other hand, when the manual switching OFF is selected in step S201 ("Yes"), the DHCP server 11 judges whether the target terminal ID is a replacement destination hit registered as a replacement destination terminal ID (step S202). If it is not a replacement destination hit in step S202 ("No"), that is, if it is a miss hit that is neither a replacement source hit nor a replacement destination hit, the DHCP server 11 assigns a dynamic IP address to the target terminal ID in steps S204 and S205, and registers the assignment details in the lease management table 17.

[0034] Also, if the replacement destination is hit in step S202 (if "Yes"), the DHCP server 11 performs the process of steps S104b to S108b in the same manner as in steps S104a to S108a shown in Fig. 3A. That is, the DHCP server 11 refers to the fixed IP setting table 16 and acquires a corresponding fixed IP address (step S104b). Then, the DHCP server 11 refers to the lease management table 17, and if the acquired fixed IP address is in an unused state, assigns the fixed IP address to the target terminal ID, i.e., the replacement source terminal ID (steps S105b to S107b).

[0035] In this way, as shown in steps S107a and S107b, if the fixed IP address acquired in response to the replacement source hit or replacement destination hit is in an unused state, the DHCP server 11 assigns the fixed IP address to the target terminal ID, i.e., the replacement source terminal ID or the replacement destination terminal ID. Then, the DHCP server 11 registers the assignment details in the lease management table 17 (steps S108a and S108b).

[0036] However, the processing contents when the acquired fixed IP address is in use differ between the replacement source hit and the replacement destination hit, as shown in step S109 and steps S204 and 205. Specifically, in step S106b, if the acquired fixed IP address is in use (if "No"), that is, if it is in use and is a replacement destination hit, the DHCP server 11 assigns a dynamic IP address to the target terminal ID (step S204). Then, the DHCP server 11 registers the correspondence between the replacement destination terminal ID and the assigned dynamic IP address, for example, the correspondence between the MAC address MA2 and the dynamic IP address IPAd1 in FIG. 2B, in the lease management table 17 (step S205).

[0037] Furthermore, in the case of a replacement destination hit, unlike the case of a replacement source hit, the process of step S203 is performed after step S108b. In step S203, the DHCP server 11 changes the fixed IP setting table 16. That is, in the case of a replacement destination hit (step S202: Yes) and in the case of assigning a fixed IP address to the replacement destination terminal ID, which is the target terminal ID (step S107b), the DHCP server 11 changes the fixed IP setting table 16.

[0038] Fig. 4 is a diagram for explaining a method of changing the fixed IP setting table executed by the DHCP server in Fig. 1. In step S203 in Fig. 3B, the DHCP server 11 replaces the registered contents of the replacement source terminal ID, here MAC address MA1, with the registered contents of the replacement destination terminal ID, here MAC address MA2, in the fixed IP setting table 16, as shown in Fig. 4. Then, the DHCP server 11 deletes the registered contents of the replacement destination terminal ID, here MAC address MA2.

[0039] As a result, the DHCP server 11 thereafter treats the information terminal TM2 having the MAC address MA2 as the terminal to be replaced. Then, the DHCP server 11 executes the flow shown in FIG. 3A in response to subsequent allocation requests from the information terminal TM2.

[0040] Fig. 5 is a diagram showing an example of a setting screen for the DHCP server in Fig. 1. The setting screen 20 shown in Fig. 5 is displayed on the display of the DHCP server 11 or its management terminal. In addition to the fixed IP setting table 16, the setting screen 20 displays a switch trigger button 21. Also, in the fixed IP setting table 16, unlike the case of Fig. 2A, on is selected as the manual switch for the entry of the fixed IP address IPAs1.

[0041] Fig. 6 is a flow diagram showing an example of another process of the DHCP server in Fig. 1. In Fig. 6, the DHCP server 11 judges whether or not there is an entry in the fixed IP setting table 16 for which manual switching is selected to be on (step S301). If there is no entry for which manual switching is selected to be on in step S301 (in the case of "No"), the DHCP server 11 ends the process.

[0042] On the other hand, if there is an entry in which manual switching is selected to be on in step S301 (if "Yes"), the DHCP server 11 monitors the switching trigger (step S302) and waits for the switching trigger to be detected (step S303). In the example of Fig. 5, the DHCP server 11 monitors whether the switching trigger button 21 has been pressed. Note that the switching trigger is not limited to the button 21, and may be generated based on a manual input by the system administrator 13. Specifically, the switching trigger may be generated based on, for example, a timer time or an occurrence time manually set by the system administrator 13.

[0043] When a switching trigger is detected in step S303 (if "Yes"), the DHCP server 11 changes the entry in which manual switching is selected to ON in the fixed IP setting table 16 (step S304). Specifically, as shown in Fig. 4, the DHCP server 11 replaces the registered content of the replacement source terminal ID with the registered content of the replacement destination terminal ID in the fixed IP setting table 16, and deletes the registered content of the replacement destination terminal ID.

[0044] When there are multiple entries for which manual switching is selected to on, the DHCP server 11 changes the multiple entries at once, for example, in response to one button 21. However, this is not limiting, and for example, a switching trigger button may be provided for each entry, or a switching trigger may be applied for each entry by selecting an entry and then pressing the switching trigger button.

[0045] <Network operation method> [Manual Switching Off] Fig. 7 is a diagram showing an example of an operation method in the network system shown in Fig. 1. Here, it is assumed that manual switching is off in the fixed IP setting table 16. In Fig. 7, first, the system administrator 13 registers the contents shown in Fig. 2A in the fixed IP setting table 16 of the DHCP server 11, for example, on or before the day before the information terminal TM is replaced (step S401). In this case, the replacement source terminal ID is the MAC address MA1 of the information terminal TM1, and the replacement destination terminal ID is the MAC address MA2 of the information terminal TM2.

[0046] Next, the user 12 starts up the information terminal TM1 on the replacement date (step S402). In response to this, the DHCP server 11 receives an IP address allocation request, such as a DHCP discover message, from the information terminal TM1 (step S403), and acquires the MAC address MA1 of the information terminal TM1 included in the allocation request (step S404).

[0047] Next, the DHCP server 11 refers to the fixed IP setting table 16 using the acquired MAC address MA1 as a key, and refers to the lease management table 17 using the acquired fixed IP address IPAs1 as a key (step S405). As a result, the DHCP server 11 recognizes that the fixed IP address IPAs1 is in an unused state, and assigns the fixed IP address IPAs1 to the information terminal TM1 (step S406). In addition, the DHCP server 11 registers the assignment details in the lease management table 17.

[0048] After that, the user 12 starts up the information terminal TM2 (step S407). In response to this, the DHCP server 11 receives an IP address allocation request, such as a DHCP discover message, from the information terminal TM2 (step S408), and acquires the MAC address MA2 of the information terminal TM2 included in the allocation request (step S409).

[0049] Next, the DHCP server 11 refers to various tables (step S410). Specifically, the DHCP server 11 refers to the fixed IP setting table 16 using the acquired MAC address MA2 as a key, and acquires the fixed IP address IPAs1. However, the fixed IP address IPAs1 is in use in the lease management table 17. Therefore, the DHCP server 11 selects an unused working IP address IPAd1 based on the dynamic IP setting table 18 and the lease management table 17.

[0050] Then, the DHCP server 11 assigns the selected operating IP address IPAd1 to the information terminal TM2 (step S411). In addition, the DHCP server 11 registers the assignment details in the lease management table 17. In this state, the user 12 performs, for example, a transfer operation of business data, setting data, and the like from the information terminal TM1 to the information terminal TM2 (step S412).

[0051] Furthermore, when the migration work is completed, the user 12 shuts down the information terminal TM1 (step S413). When the information terminal TM1 shuts down, it transmits a DHCP release message to the DHCP server 11 (step S414). In response to this, the DHCP server 11 updates the lease management table 17 and changes the fixed IP address IPAs1 to an unused state.

[0052] After that, the user 12 reboots, for example, the information terminal TM2 (step S415). In response to this, the DHCP server 11 receives an IP address allocation request from the information terminal TM2 (step S416) and acquires the MAC address MA2 of the information terminal TM2 contained in the IP address allocation request (step S417). Note that, in response to the reboot of the information terminal TM2, the dynamic IP address IPAd1 becomes unused.

[0053] Next, the DHCP server 11 refers to various tables (step S418). Specifically, the DHCP server 11 refers to the fixed IP setting table 16 using the acquired MAC address MA2 as a key, and acquires the fixed IP address IPAs1. The fixed IP address IPAs1 is in an unused state in the lease management table 17 following step S414.

[0054] Therefore, the DHCP server 11 assigns the fixed IP address IPAs1 to the information terminal TM2 (step S419). In addition, the DHCP server 11 registers the assignment details in the lease management table 17. Furthermore, the DHCP server 11 changes the fixed IP setting table 16 as shown in FIG. 4 (step S420).

[0055] This makes it possible to improve the efficiency of network operation accompanying replacement of the user's information terminal TM in an operation in which the same IP address is assigned to the same user. In particular, it makes it possible to reduce the workload of the system administrator 13. As a comparative example, a case is assumed in which a general setting table that defines a one-to-one correspondence between terminal IDs and fixed IP addresses is used. In this case, the system administrator 13 had to manually change the setting table, for example, at the timing when the migration work of the information terminal TM in step S412 is completed. As a result, time constraints were imposed on the system administrator 13.

[0056] Furthermore, when the number of information terminals TM to be replaced increases, it is necessary to have each user 12 perform migration work within a certain period of time, and then set a period during which the network 10 is unavailable, during which the system administrator 13 collectively changes the registered contents of the setting table. In this case, the utilization efficiency of the network 10 decreases, and in order to shorten the period during which the network 10 is unavailable, a large workload must be imposed on the system administrator 13.

[0057] On the other hand, in the case of Fig. 7, the system administrator 13 simply registers the replacement destination terminal ID in the fixed IP setting table 16 at a convenient timing, for example, up to the day before the replacement date, in step S401. Also, the system administrator 13 does not need to do anything in particular on the replacement date. Furthermore, there is no need to provide a period during which the network 10 is not in use. As a result, it is possible to make the operation of the network more efficient.

[0058] [Manual Switching On] Figure 8 is a diagram showing an example of an operation method different from that shown in Figure 7 in the network system shown in Figure 1. Here, it is assumed that manual switching is set to ON in the fixed IP setting table 16. In Figure 8, first, the system administrator 13, as in the case of Figure 7, registers the contents shown in Figure 5 in the fixed IP setting table 16 of the DHCP server 11, for example, on or before the day before the information terminal TM is replaced (step S501).

[0059] Next, in steps S502 to S511, the same processes as in steps S402 to S411 shown in Fig. 7 are sequentially performed. However, in step S510, unlike in step S410, the DHCP server 11 does not acquire a fixed IP address, but selects a dynamic IP address IPAd1 based on the fact that the MAC address MA2 is not registered as the source terminal ID. Then, the DHCP server 11 assigns the selected dynamic IP address IPAd1 to the information terminal TM2 (step S511), similar to the case of step S411 in Fig. 7.

[0060] Thereafter, the user 12 performs a migration operation from the information terminal TM1 to the information terminal TM2 (step S512) in the same manner as in step S412 in Fig. 7. After the migration operation is completed, unlike the case in Fig. 7, a switching trigger is generated based on an input from the system administrator 13 (step S513). In response to this, the DHCP server 11 changes the fixed IP setting table 16 as shown in Fig. 4 (step S514).

[0061] This also enables the efficient operation of the network associated with the replacement of the information terminal TM. That is, the system administrator 13 only needs to register the replacement destination terminal ID in the fixed IP setting table 16 at a convenient timing until the day before the replacement date in step S501. Also, on the replacement date, the system administrator 13 only needs to press the switching trigger button 21 shown in FIG. 5, for example, and this does not impose a significant workload on the system administrator 13.

[0062] Note that turning on the manual switching is beneficial when it is desired to reliably prevent a situation where the fixed IP setting table 16 is unintentionally changed. Specifically, for example, after the user 12 finishes the migration work, if the actual application date of the replacement destination information terminal TM2 is postponed, and during that time, the user wants to use the replacement source information terminal TM1. Also, in FIG. 7, for example, during the migration work, if the user 12 starts the information terminal TM2 while the information terminal TM1 is in the shutdown state, the fixed IP setting table 16 may be unintentionally changed. Such a situation is an example where it is desired to prevent it.

[0063] <Configuration of the DHCP Server> FIG. 9 is a block diagram showing a configuration example of the main part of the DHCP server in FIG. 1. The DHCP server 11 shown in FIG. 9 includes, in addition to the memory 15, a terminal ID acquisition unit 25, a fixed IP acquisition unit 26, an IP address allocation unit 27, and a setting table change unit 28. Each of these units is realized, for example, when a processor executes a program in the memory 15. However, as described in FIG. 1, some or all of these units may be realized by hardware such as an FPGA or an ASIC.

[0064] As described above, the memory 15 stores the fixed IP setting table 16, the lease management table 17, and the dynamic IP setting table 18. First, the operation of each unit will be described assuming that the manual switching is set to off. As shown in step S101 in Fig. 3A, the terminal ID acquisition unit 25 receives an IP address allocation request from the information terminal TM, and acquires the terminal ID included in the allocation request as the target terminal ID.

[0065] As shown in steps S102 and S103, the fixed IP acquisition unit 26 refers to the fixed IP setting table 16 and judges whether the target terminal ID is a replacement source hit registered as a replacement source terminal ID. If it is a replacement source hit, the fixed IP acquisition unit 26 acquires a corresponding fixed IP address as shown in step S104a. If it is not a replacement source hit, the fixed IP acquisition unit 26 judges whether the target terminal ID is a replacement destination hit registered as a replacement destination terminal ID as shown in step S202 in FIG. 3B. If it is a replacement destination hit, the fixed IP acquisition unit 26 acquires a corresponding fixed IP address as shown in step S104b.

[0066] In this way, the fixed IP acquisition unit 26 refers to the fixed IP setting table 16 and judges whether it is a replacement source hit, a replacement destination hit, or other, i.e., a miss hit. If it is a replacement source hit or a replacement destination hit, the fixed IP acquisition unit 26 acquires the corresponding fixed IP address.

[0067] 3A and 3B, the IP address allocation unit 27 judges whether the fixed IP address acquired in response to the replacement source hit or replacement destination hit is in use or unused state by referring to the lease management table 17. If the acquired fixed IP address is in unused state, the IP address allocation unit 27 assigns the fixed IP address to the information terminal TM having the target terminal ID, as shown in steps S107a and S107b.

[0068] On the other hand, if the acquired fixed IP address is in use and is a replacement hit, the IP address allocation unit 27 allocates a dynamic IP address to the information terminal TM having the target terminal ID, as shown in step S204 in Fig. 3B. At this time, the IP address allocation unit 27 selects the dynamic IP address based on the lease management table 17 and the dynamic IP setting table 18.

[0069] When the condition is satisfied, the setting table change unit 28 replaces the registered contents of the replacement source terminal ID with the registered contents of the replacement destination terminal ID in the fixed IP setting table 16, and deletes the registered contents of the replacement destination terminal ID. In detail, as shown in step S203 in FIG. 3B, when a fixed IP address is assigned to the target terminal ID and when a replacement destination hit occurs, the setting table change unit 28 changes the fixed IP setting table 16.

[0070] Next, assume that manual switching is ON. In this case, the IP address allocation unit 27 assigns a dynamic IP address to the target terminal ID when the replacement source is not hit, as shown in steps S103, S201, and S204 in Fig. 3A and Fig. 3B. Also, the setting table change unit 28 changes the fixed IP setting table 16 when a switching trigger based on a manual input occurs, as shown in steps S303 and S304 in Fig. 6.

[0071] <Major Effects of the Embodiment> As described above, in the method of the embodiment, a fixed IP setting table 16 is provided in which a replacement source terminal ID and a replacement destination terminal ID can be registered. Then, the DHCP server 11 can automatically change the registered contents of the fixed IP setting table 16 when a certain condition is satisfied. This typically makes it possible to improve the efficiency of network operation accompanying the replacement of the information terminal TM. Specifically, it makes it possible to reduce the workload of the system administrator 13 or to improve the utilization efficiency of the network.

[0072] The invention made by the present inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above-mentioned embodiments and can be modified in various ways without departing from the gist of the invention. For example, the above-mentioned embodiments have been described in detail to easily explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0073] For example, the above-mentioned program may be stored in a non-transitory tangible computer-readable recording medium and then supplied to a computer. Examples of such a recording medium include magnetic recording media such as hard disk drives, optical recording media such as DVDs (Digital Versatile Discs) and Blu-ray Discs, and semiconductor memories such as flash memories. [Explanation of symbols]

[0074] 10: network, 11: DHCP server, 15: memory, 16: fixed IP setting table, 17: lease management table, 18: dynamic IP setting table, 21: switch trigger button, 25: terminal ID acquisition unit, 26: fixed IP acquisition unit, 27: IP address allocation unit, 28: setting table change unit, TM: information terminal

Claims

1. A DHCP server that assigns an IP address to an information terminal, a memory for storing a source terminal ID for identifying a source information terminal, a destination terminal ID for identifying a destination information terminal, a fixed IP setting table for determining a correspondence relationship between the source terminal ID and the fixed IP address to be assigned to the source terminal ID or the destination terminal ID, and a lease management table for indicating IP addresses in use; a terminal ID acquisition unit that receives an IP address allocation request from an information terminal and acquires a terminal ID included in the IP address allocation request as a target terminal ID; a fixed IP acquisition unit that refers to the fixed IP setting table, determines whether the target terminal ID is a replacement source hit registered as the replacement source terminal ID, and acquires the corresponding fixed IP address if the target terminal ID is a replacement source hit; an IP address allocation unit that determines whether the fixed IP address acquired by the fixed IP acquisition unit is in the used state or the unused state by referring to the lease management table, and assigns the fixed IP address to the target terminal ID if the fixed IP address is in the unused state; Equipped with DHCP server.

2. 2. The DHCP server according to claim 1, When the target terminal ID is not the replacement source hit, the fixed IP acquisition unit determines whether the target terminal ID is a replacement destination hit registered as the replacement destination terminal ID, and when the target terminal ID is the replacement destination hit, acquires the corresponding fixed IP address; the IP address allocation unit, when the fixed IP address acquired in response to the replacement source hit or the replacement destination hit is in the unused state, assigns the fixed IP address to the target terminal ID, and when the acquired fixed IP address is in the used state and is the replacement destination hit, assigns a dynamic IP address to the target terminal ID. DHCP server.

3. 3. The DHCP server according to claim 2, a setting table change unit that, when the fixed IP address acquired in response to the replacement destination hit is assigned to the target terminal ID, changes the fixed IP setting table by replacing the registered contents of the replacement source terminal ID with the registered contents of the replacement destination terminal ID and deleting the registered contents of the replacement destination terminal ID; DHCP server.

4. 2. The DHCP server according to claim 1, In the fixed IP setting table, the manual switching can be selected to be on or off in association with the correspondence relationship. When the manual switch is turned on, the IP address allocation unit, when the replacement source hit is not found, allocates a dynamic IP address to the target terminal ID; a setting table change unit that, when a switching trigger based on a manual input occurs, changes the fixed IP setting table by replacing the registered contents of the replacement source terminal ID with the registered contents of the replacement destination terminal ID and deleting the registered contents of the replacement destination terminal ID; DHCP server.

5. 5. The DHCP server according to claim 4, When the manual switch is set to off, When the target terminal ID is not the replacement source hit, the fixed IP acquisition unit determines whether the target terminal ID is a replacement destination hit registered as the replacement destination terminal ID, and when the target terminal ID is the replacement destination hit, acquires the corresponding fixed IP address; the IP address allocation unit, when the fixed IP address acquired in response to the replacement source hit or the replacement destination hit is in the unused state, assigns the fixed IP address to the target terminal ID, and when the acquired fixed IP address is in the used state and is the replacement destination hit, assigns a dynamic IP address to the target terminal ID; the setting table change unit, when allocating the fixed IP address acquired in response to the replacement destination hit to the target terminal ID, performs the change to the fixed IP setting table. DHCP server.

6. An information terminal; a DHCP server connected to the information terminal via a network and for assigning an IP address to the information terminal; A network system having: The DHCP server includes: a memory for storing a source terminal ID for identifying a source information terminal, a destination terminal ID for identifying a destination information terminal, a fixed IP setting table for determining a correspondence relationship between the source terminal ID and the fixed IP address to be assigned to the source terminal ID or the destination terminal ID, and a lease management table for indicating IP addresses in use; a terminal ID acquisition unit that receives an IP address allocation request from an information terminal and acquires a terminal ID included in the IP address allocation request as a target terminal ID; a fixed IP acquisition unit that refers to the fixed IP setting table, determines whether the target terminal ID is a replacement source hit registered as the replacement source terminal ID, and acquires the corresponding fixed IP address if the target terminal ID is a replacement source hit; an IP address allocation unit that determines whether the fixed IP address acquired by the fixed IP acquisition unit is in the used state or the unused state by referring to the lease management table, and assigns the fixed IP address to the target terminal ID if the fixed IP address is in the unused state; Equipped with Network system.

7. 7. The network system according to claim 6, When the target terminal ID is not the replacement source hit, the fixed IP acquisition unit determines whether the target terminal ID is a replacement destination hit registered as the replacement destination terminal ID, and when the target terminal ID is the replacement destination hit, acquires the corresponding fixed IP address; the IP address allocation unit, when the fixed IP address acquired in response to the replacement source hit or the replacement destination hit is in the unused state, assigns the fixed IP address to the target terminal ID, and when the acquired fixed IP address is in the used state and is the replacement destination hit, assigns a dynamic IP address to the target terminal ID; Network system.

8. 8. The network system according to claim 7, The DHCP server includes a setting table change unit that, when the fixed IP address acquired in response to the replacement destination hit is assigned to the target terminal ID, changes the fixed IP setting table by replacing the registered contents of the replacement source terminal ID with the registered contents of the replacement destination terminal ID and deleting the registered contents of the replacement destination terminal ID. Network system.

9. 7. The network system according to claim 6, In the fixed IP setting table, the manual switching can be selected to be on or off in association with the correspondence relationship. When the manual switch is turned on, the IP address allocation unit, when the replacement source hit is not found, allocates a dynamic IP address to the target terminal ID; The DHCP server includes a setting table change unit that, when a switching trigger based on a manual input occurs, changes the fixed IP setting table by replacing the registered contents of the replacement source terminal ID with the registered contents of the replacement destination terminal ID and deleting the registered contents of the replacement destination terminal ID. Network system.

10. 10. The network system according to claim 9, When the manual switch is set to off, When the target terminal ID is not the replacement source hit, the fixed IP acquisition unit determines whether the target terminal ID is a replacement destination hit registered as the replacement destination terminal ID, and when the target terminal ID is the replacement destination hit, acquires the corresponding fixed IP address; the IP address allocation unit, when the fixed IP address acquired in response to the replacement source hit or the replacement destination hit is in the unused state, assigns the fixed IP address to the target terminal ID, and when the acquired fixed IP address is in the used state and is the replacement destination hit, assigns a dynamic IP address to the target terminal ID; the setting table change unit, when allocating the fixed IP address acquired in response to the replacement destination hit to the target terminal ID, performs the change to the fixed IP setting table. Network system.

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