Network system, communication method, NAT device, and program

Abstract

To provide a network system capable of making IP address ranges usable in a plurality of subnets equal.SOLUTION: A network system comprises: a router device connected to a first subnet; a first NAT device connected to the first subnet; and a second NAT device connected to a second subnet having an address range equal to that of the first subnet. The router device performs routing of an IP packet addressed to a set first IP address to the first NAT device. The first NAT device performs routing after changing a destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address. The second NAT device performs routing after changing a destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a network system, a communication method, a NAT device, and a program. [Background technology]

[0002] Power system monitoring and control systems installed in control centers collect data from numerous on-site devices (TC, Tele-Control) installed over a wide geographical area. In recent years, some of the devices that make up the monitoring and control systems, such as data aggregation devices that collect the data and report-related devices that do not require real-time performance, have been migrated from on-premise locations in control centers to cloud environments such as data centers.

[0003] Patent Document 1 discloses a network system that enables the construction of a connection environment between on-premise and cloud environments while ensuring security. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-147233 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional on-premise and cloud environments, the subnets are different between the on-premise and cloud environments, and the ranges of available IP addresses are different, so the IP address of the migrated device needs to be changed, which can make the process of changing the IP addresses stored in other devices that communicate with the device complicated.

[0006] The present disclosure has been made in consideration of the above circumstances, and provides a network system, a communication method, an NAT device, and a program that can make the range of IP addresses available to multiple subnets the same. [Means for solving the problem]

[0007] This disclosure has been made to solve the above-mentioned problems, and one aspect of the present disclosure is a network system including a router device connected to a first subnet, a first NAT (Network Address Translation) device connected to the first subnet, and a second NAT device connected to a second subnet having the same address range as the first subnet, wherein the router device is configured to handle IP (Internet Protocol) addresses belonging to the address range. a NAT device configured to route IP packets addressed to a first IP address to the first NAT device, and upon receiving the IP packet addressed to the first IP address, the first NAT device changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the IP packet; the first NAT device is communicatively connected to the second NAT device via a network that routes IP packets addressed to the second IP address to the second NAT device, and upon receiving the IP packet addressed to the second IP address, the second NAT device changes the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address and routes the IP packet.

[0008] Another aspect of the present disclosure is the above-mentioned network system, wherein, when the first NAT device receives an IP packet having the second IP address set as its source, it changes the source address of the IP packet having the second IP address set as its source to the first IP address and routes the IP packet; and, when the second NAT device receives an IP packet having the first IP address set as its source, it changes the source address of the IP packet having the first IP address set as its source to the second IP address and routes the IP packet.

[0009] Another aspect of the present disclosure is the above-mentioned network system, wherein when the second NAT device receives an ARP (Address Resolution Protocol) request targeting a configured third IP address that is an IP address belonging to the address range, the second NAT device returns a MAC (Medium Access Control) address in the second subnet of the device, and when the second NAT device receives an IP packet addressed to the third IP address, the second NAT device changes the destination address of the IP packet addressed to the third IP address to a fourth IP address that has been stored in association with the third IP address and routes the packet, the network routes the IP packet addressed to the fourth IP address to the first NAT device, and when the first NAT device receives an IP packet addressed to the fourth IP address, the first NAT device changes the destination address of the IP packet addressed to the fourth IP address to the third IP address that has been stored in association with the fourth IP address and routes the packet.

[0010] Another aspect of the present disclosure is a communication method in a network system including a router device connected to a first subnet, a first NAT (Network Address Translation) device connected to the first subnet, and a second NAT device connected to a second subnet having the same address range as the first subnet, wherein the router device transmits an IP (Internet Protocol) address belonging to the address range. a step of, when the first NAT device receives the IP packet addressed to the first IP address, changing the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routing the IP packet; a step of, by a network that communicatively connects the first NAT device and the second NAT device, routing the IP packet addressed to the second IP address to the second NAT device; and a step of, when the second NAT device receives the IP packet addressed to the second IP address, changing the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address and routing the IP packet.

[0011] Another aspect of the present disclosure is a first NAT (Network Address Translation) device connected to a first subnet, which, when receiving an IP packet addressed to a first IP address belonging to the address range of the first subnet, changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the IP packet.

[0012] Another aspect of the present disclosure is a program for causing a computer to function as a first NAT (Network Address Translation) device connected to a first subnet, wherein the first NAT device, upon receiving an IP packet addressed to a first IP address belonging to the address range of the first subnet, changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the packet. [Effects of the Invention]

[0013] According to this disclosure, the network system, communication method, NAT device, and program can make the range of IP addresses available to multiple subnets the same. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic block diagram illustrating a configuration of a network system 100 for a power system monitoring and control system according to an embodiment of the present disclosure. [Figure 2] 2 is a schematic block diagram showing the configuration of an NAT device 23 in the embodiment. [Figure 3] 2 is a schematic block diagram showing the configuration of a NAT instance 32 in the embodiment. FIG. [Figure 4] 10 is a table showing an example of rules set in a conversion unit 231 of the NAT device 23 in the embodiment. [Figure 5] 10 is a table showing an example of rules set in a conversion unit 321 of a NAT instance 32 in the embodiment. [Figure 6] 10 is a flowchart illustrating the operation of the router device 21 in the embodiment. [Figure 7] 10 is a flowchart illustrating the operation of the NAT device 23 in the embodiment. [Figure 8] FIG. 2 is a sequence diagram illustrating the operation of the network system 100 according to the embodiment. [Figure 9] FIG. 2 is an explanatory diagram illustrating the hardware configuration of each device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic block diagram showing the configuration of a network system 100 for a power system monitoring and control system according to one embodiment of the present disclosure. In the power system monitoring and control system of this embodiment, devices installed at an on-premise site R and a cloud site C monitor and control the power system via local devices (TC, Tele-Control) 12 installed in various electric power stations and other locations distributed over a wide area. The devices installed at the cloud site C include devices that were originally installed at the on-premise site R and that were installed at the cloud site C in order to migrate their functions to a cloud environment.

[0016] Examples of devices to be migrated to a cloud environment include, but are not limited to, the data collection device 33 mentioned in this embodiment, as well as devices with low requirements for real-time performance, such as devices for creating reports. In the network system 100 of this embodiment, the subnet addresses of the subnet (first subnet) of the on-premise site R and the subnet (second subnet) of the cloud site C are the same, so that when a device at the on-premise site R is migrated to the cloud site C, it is not necessary to change the IP address of the device. As a result, other devices that communicate with the device migrated to the cloud site C store the IP address of the device migrated to the cloud site C, but there is no need to change the IP address.

[0017] The field device 12 stores data such as the status of each piece of equipment in the electric power station and measurements from each piece of equipment in an IP (Internet Protocol) packet addressed to the data collection device 33 and transmits the stored data. Note that an IP packet addressed to the data collection device 33 is an IP packet in which the IP address of the data collection device 33 is set as the destination address. The data collection device 33 is connected to the gateway 11 via a dedicated line N1.

[0018] The gateway 11 connects the leased line N1 and the leased line N2, and the IP address 11a on the leased line N1 side is "172.16.1.1" and the IP address 11b on the leased line N2 side is "172.16.2.1." The gateway 11 is also connected to the router device 21 via the leased line N2.

[0019] The router device 21 connects the leased line N2 and the subnet N3 (first subnet), and the IP address 21a on the leased line N2 side is "172.16.2.2" and the IP address 21b on the subnet N3 side is "172.168.0.1." A device (on-premises device) 22 at the on-premises site R of the power system monitoring and control system and a NAT (Network Address Translation) device 23 (first NAT device) are connected to the subnet N3. The subnet mask of the subnet N3 is 16, and the subnet address is "192.168.0.0 / 16." That is, the address range of the subnet N3 is from "192.168.0.0" to "192.168.255.255."

[0020] The NAT device 23 connects the subnet N3 and the gateway 24, and its IP address 23a on the subnet N3 side is "192.168.0.2" and its IP address 23b on the gateway 24 side is "10.0.0.2". The gateway 24 connects the NAT device 23 to the leased line N4, and its IP address 24a is "10.0.0.3." The gateway 24 is also connected to the gateway 31 via the leased line N4. The gateway 31 connects the leased line N4 with the NAT instance 32 (second NAT device), and its IP address 31a is "10.0.0.4."

[0021] The NAT instance 32 connects the gateway 31 and the subnet N5 (second subnet), and its IP address 32a on the gateway 31 side is "10.0.0.1" and its IP address 32b on the subnet N5 side is "192.168.0.1".

[0022] A cloud device 34, a data collection device 33, and a NAT instance 32 that have been migrated to a cloud site C of the power system monitoring and control system are connected to subnet N5. The subnet mask of subnet N5 is 16, and its subnet address is "192.168.0.0 / 16." That is, the address range of subnet N5 is the same as that of subnet N3, ranging from "192.168.0.0" to "192.168.255.255." Each of the cloud device 34, the data collection device 33, and the NAT instance 32 may be an instance on the cloud, or may be realized by one or more computers that are not on the cloud reading and executing a program.

[0023] The data collection device 33 is a device that collects data transmitted by the local devices 12, and is an instance in which the functions of a device installed at the on-premise site R have been migrated to the cloud at the cloud site C. The IP address of the data collection device 33 is "192.168.0.50", which is the same as the IP address of the device installed at the on-premise site R before the migration.

[0024] The network system 100 includes gateways 11, 24, and 31, a router device 21, a NAT device 23, and a NAT instance 32. The router device 21 routes IP packets addressed to a first IP address that belongs to the address range of the subnet N3 and that is set at the time of installation or maintenance of the router device 21 to the NAT device 23. The router device 21 may be configured to perform this routing using static routing. Alternatively, the NAT device 23 may be configured at the time of installation or maintenance of the router device 21 so as to respond to an ARP (Address Resolution Protocol) request for the first IP address with its own MAC address on the subnet N3 side, and the router device 21 may route IP packets addressed to the first IP address to the NAT device 23 based on this response. Note that static routing refers to routing performed according to a routing table that is preset in the router device 21, rather than a routing table that changes dynamically as in dynamic routing. The first IP address is, for example, the IP address “192.168.0.50” of the data collecting device 33, and the IP packet addressed to the first IP address is an IP packet sent from the on-site device 12 and addressed to the data collecting device 33.

[0025] When the NAT device 23 receives an IP packet addressed to a first IP address, it changes the destination address of the IP packet addressed to the first IP address to a second IP address that has been previously stored in association with the first IP address, and routes the IP packet. The second IP address is, for example, IP address "10.0.0.50" outside the address range of subnets N3 and N5. Alternatively, the second IP address may be IP address "10.0.0.1" on the gateway 31 side of the NAT instance 32. The NAT device 23 is communicatively connected to the NAT instance 32 via a network (gateways 24, 31, and leased line N4) that routes IP packets addressed to the second IP address to the NAT instance 32.

[0026] When the NAT instance 32 receives an IP packet addressed to the second IP address, it changes the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address, and routes the IP packet. As a result, for example, if the first IP address is the IP address of the data collection device 33, the IP packet is sent to the data collection device 33. In this way, the subnet addresses of the subnet N3 of the on-premises site R and the subnet N5 of the cloud site C are made the same, and the functions of the devices installed at the on-premises site R can be migrated to the cloud at the cloud site C without changing settings such as the IP address of the destination of data from the local device 12. Note that the above-mentioned IP address and subnet mask values ​​are merely examples, and other values ​​may be used.

[0027] Furthermore, when the NAT device 23 receives an IP packet with the second IP address set as its source, it may change the source address of the IP packet with the second IP address set as its source to the first IP address and route the IP packet.Furthermore, when the NAT instance 32 receives an IP packet with the first IP address set as its source, it may change the source address of the IP packet with the first IP address set as its source to the second IP address and route the IP packet.

[0028] 2 is a schematic block diagram showing the configuration of the NAT device 23 in this embodiment. The NAT device 23 includes a conversion unit 231 and a transmission unit 232. The conversion unit 231 converts the destination address, the source address, or both of a received IP packet in accordance with set and stored rules.

[0029] If the IP packet received by the NAT device 23 has not been converted by the conversion unit 231, the transmission unit 232 routes the received IP packet, and if it has been converted, the transmission unit 232 routes the converted IP packet. Note that routing may mean, for example, determining a destination MAC (Medium Access Control) address based on the destination address of the IP packet, setting the determined MAC address as the destination of an Ethernet packet storing the IP packet, and transmitting the packet.

[0030] 3 is a schematic block diagram showing the configuration of NAT instance 32 in this embodiment. NAT instance 32 includes a conversion unit 321 and a transmission unit 322. Conversion unit 321 and transmission unit 322 are similar to conversion unit 231 and transmission unit 232 in FIG. 2, respectively, but conversion unit 321 has different rules set therein from conversion unit 231.

[0031] 4 is a table showing an example of a rule set in the conversion unit 231 of the NAT device 23 in this embodiment. The rule is a rule by which the conversion unit 231 converts the destination address, the source address, or both of an IP packet, and is set when the NAT device 23 is installed or during maintenance. In the first row of the table shown in FIG. 4, the source address (Source Address) "Any" (arbitrary) and the destination address (Destination Address) "192.168.0.50" (the IP address of the data collection device 33) before conversion are associated with the source address "Any" (arbitrary) and the destination address "10.0.0.50" after conversion. This indicates that when the source address of a received IP packet is any and the destination address is "192.168.0.50," the conversion unit 231 leaves the source address of the IP packet as is and sets the destination address to "10.0.0.50."

[0032] Also, in the second line, the source address "10.0.0.50" and destination address "Any" before conversion are associated with the source address "192.168.0.50" and destination address "10.0.0.50" after conversion. This indicates that when the source address of a received IP packet is "10.0.0.50" and the destination address is any address, the conversion unit 231 sets the source address of the IP packet to "192.168.0.50" and leaves the destination address unchanged.

[0033] In the third line, the source address "Any" and destination address "10.0.0.80" before conversion are associated with the source address "Any" and destination address "192.168.0.80" after conversion. In the fourth line, the source address "192.168.0.80" and destination address "Any" before conversion are associated with the source address "10.0.0.80" and destination address "Any" after conversion.

[0034] The first and second lines are settings for enabling communication between the data collection device 33 connected to the subnet N5 of the cloud site C and a device connected outside the subnet N5. The third and fourth lines are settings for enabling communication between the device (on-premise device 22) with the IP address "192.168.0.80" connected to the subnet N3 of the on-premise site R and a device connected to the subnet N5 of the cloud site C.

[0035] For example, an IP packet with a source address of "192.168.0.80" and a destination address of "192.168.0.50" corresponds to lines 1 and 4. Therefore, the source address of "10.0.0.80" and the destination address of "10.0.0.50" are set in the IP packet.

[0036] 5 is a table showing an example of rules set in the conversion unit 321 of the NAT instance 32 in this embodiment. These rules are the same as those in FIG. 4, and are rules by which the conversion unit 321 converts the destination address, the source address, or both of an IP packet, and are set when the NAT instance 32 is installed or during maintenance.

[0037] In the first line, the source address "Any" and destination address "10.0.0.50" before conversion are associated with the source address "Any" and destination address "192.168.0.50" after conversion. In the second line, the source address "192.168.0.50" and destination address "Any" before conversion are associated with the source address "10.0.0.50" and destination address "Any" after conversion.

[0038] In the third line, the source address "Any" and destination address "192.168.0.80" before conversion are associated with the source address "Any" and destination address "10.0.0.80" after conversion. In the fourth line, the source address "10.0.0.80" and destination address "Any" before conversion are associated with the source address "192.168.0.80" and destination address "Any" after conversion.

[0039] Furthermore, the NAT instance 32 may be configured, for example, when the NAT instance 32 is installed or during maintenance, so as to respond to an ARP request for the IP address of the on-premises device 22 with the MAC address of the on-premises device 22 on the subnet N5 side, such as the IP address "192.168.0.80." As a result, an IP packet addressed to the on-premises device 22 and transmitted by the cloud device 34 connected to the subnet N5 or the data collection device 33 is subjected to address conversion by the NAT instance 32 and routed to the NAT device 23. Furthermore, based on the settings such as those in the third and fourth lines of FIG. 4 , the NAT device 23 converts the address of the IP packet and routes it to the on-premises device 22.

[0040] In this way, each line in Figure 4 and Figure 5 is paired. The source address and destination address converted by the rules in Figure 4 are set to be restored by the rules in Figure 5. Similarly, the source address and destination address converted by the rules in Figure 5 are set to be restored by the rules in Figure 4.

[0041] 6 is a flowchart illustrating the operation of the router device 21 in this embodiment. When the router device 21 receives data (IP packet) (step Sa1), it determines whether the destination address of the IP packet is addressed to a static routing target (for example, to the data collection device 33) (step Sa2). If it determines that the IP packet is addressed to a static routing target (step Sa2-Yes), the router device 21 routes the received data to the NAT device 23 based on the static routing settings (step Sa3). If it is determined in step Sa2 that the data is not addressed to a static routing target (step Sa2-No), the router device 21 routes the received data according to the normal routing rules (step Sa4).

[0042] 7 is a flowchart illustrating the operation of the NAT device 23 in this embodiment. When the NAT device 23 receives data (IP packet) (step Sb1), it determines whether the combination of the source address and destination address of the IP packet is an address to be translated (step Sb2). The column before translation in FIG. 4 corresponds to the address to be translated.

[0043] If it is determined that the address is to be translated (step Sb2-Yes), the NAT device 23 translates the source address and destination address of the IP packet according to the set rules (step Sb3), and then routes the translated IP packet (step Sb4).

[0044] If it is determined in step Sb2 that the address is not a target for translation (step Sb2-No), the NAT device 23 routes the IP packet (step Sb4).

[0045] 8 is a sequence diagram illustrating the operation of the network system 100 in this embodiment. Sequences SE1 to SE7 are an example of a sequence when the on-site device 12 transmits data to the data collecting device 33. Sequences SE8 to SE14 are an example of a sequence when the data collecting device 33 transmits data to the on-premise device 22.

[0046] First, an example of a sequence in which the on-site device 12 transmits data to the data collecting device 33 will be described. The on-site device 12 transmits data addressed to the data collecting device 33 using an IP packet in which the IP address of the data collecting device 33, "192.168.0.50," is set as the destination address. The IP packet is transmitted to the router device 21 via the leased line N1, the gateway 11, and the leased line N2 (sequence SE1). The router device 21 references the destination address of the IP packet, determines that the IP packet is subject to static routing (sequence SE2), and routes the IP packet to the NAT device 23 in accordance with the set static routing rules (sequence SE3).

[0047] Upon receiving the IP packet, the NAT device 23 performs address conversion on the IP packet in accordance with the set and stored rules (sequence SE4) and routes the IP packet. In this address conversion, the IP address "10.0.0.50" is set as the destination address of the IP packet in accordance with the rule in the first line of Fig. 4. The converted IP packet is routed to the NAT instance 32 via the gateway 24, leased line N4, and gateway 31 (sequence SE5). Note that the routing by the NAT device 23 and gateways 24 and 31 may be static routing.

[0048] When the NAT instance 32 receives the IP packet routed by sequence SE5, it performs address conversion on the IP packet in accordance with the set and stored rules (sequence SE6). In this address conversion, the destination address of the IP packet is set to IP address "192.168.0.50," i.e., the IP address of the data collection device 33, in accordance with the rule in the first line of Figure 5. The NAT instance 32 transmits the address-converted IP packet to the data collection device 33 in accordance with the destination address (sequence SE7).

[0049] Next, an example of a sequence in which the data collection device 33 transmits data to the on-premise device 22 with the IP address "192.168.0.80" will be described. When data (IP packets) addressed to the on-premise device 22 is generated, the data collection device 33 broadcasts an ARP request for the IP address (third IP address) of the on-premise device 22 because the IP address of the on-premise device 22 is within the address range of the subnet N5 (sequence SE8). In response to the ARP request in sequence SE8, the NAT instance 32 replies with the MAC address of its own device on the subnet N5 side (sequence SE9). In this way, when the NAT instance 32 receives an ARP request targeted at the set third IP address, which is an IP address belonging to the address ranges of the subnets N3 and N5, it returns the MAC address of its own device in the subnet N5.

[0050] The data collection device 33 stores an IP packet addressed to the on-premise device 22 in an Ethernet packet with the MAC address obtained from the response set as the destination address, and transmits the packet (sequence SE10). Since the MAC address set as the destination address belongs to the NAT instance 32, the Ethernet packet is received by the NAT instance 32.

[0051] The NAT instance 32 extracts an IP packet addressed to the on-premises device 22 from the received Ethernet packet and performs address translation in accordance with the set and stored rules (sequence SE11). In this address translation, the IP address "10.0.0.50" is set as the source address of the IP packet and the IP address "10.0.0.80" (fourth IP address) is set as the destination address in accordance with the rules in the second and third lines of FIG. 5. The translated IP packet is routed to the NAT device 23 via the gateway 31, the leased line N4, and the gateway 24 (sequence SE12). In this way, when the NAT instance 32 receives an IP packet addressed to the third IP address, it changes the destination address of the IP packet addressed to the third IP address to the fourth IP address stored in association with the third IP address, and routes the IP packet. Note that the routing by the NAT instance 32 and the gateways 24 and 31 may be static routing, as in sequence SE5. Furthermore, the fourth IP address set as the destination address may be the IP address "10.0.0.2" of the NAT device 23 on the gateway 24 side.

[0052] When the NAT device 23 receives the IP packet routed in sequence SE12, it performs address conversion on the IP packet in accordance with the set and stored rule (sequence SE13). In this address conversion, the destination address of the IP packet is set to the IP address "192.168.0.80," i.e., the IP address of the on-premise device 22, in accordance with the rule in the third line of FIG. 4. The NAT device 23 transmits the address-converted IP packet to the on-premise device 22 in accordance with the destination address (sequence SE14). In this way, when the NAT device 23 receives an IP packet addressed to the fourth IP address, it changes the destination address of the IP packet addressed to the fourth IP address to the third IP address that has been stored in association with the fourth IP address, and routes the IP packet.

[0053] Although the above embodiment has been described as an example in which the network system 100 uses IPv4, the network system 100 may also use IPv6.

[0054] FIG. 9 is an explanatory diagram illustrating the hardware configuration of each device according to this embodiment. The devices are gateways 11, 24, and 31, a router device 21, a NAT device 23, a NAT instance 32, an on-premise device 22, a data collection device 33, and a cloud device 34. Each device includes an input / output module I, a storage module M, and a control module P. The input / output module I is implemented by including some or all of the communication module H11, the connection module H12, the pointing device H21, the keyboard H22, the display H23, the button H3, the microphone H41, the speaker H42, the camera H51, and the sensor H52. The storage module M is implemented by including a drive H7. The storage module M may further be configured by including some or all of a memory H8. The control module P is implemented by including a memory H8 and a processor H9. These hardware components are connected to each other so as to be able to communicate with each other via a bus, and are supplied with power from a power supply H6.

[0055] The connection module H12 is a digital input / output port such as a USB (Universal Serial Bus). The pointing device H21, keyboard H22, and display H23 may be touch panels. The sensor H52 may be an acceleration sensor, a gyro sensor, a GPS receiver module, a proximity sensor, or the like. The power supply H6 is a power supply unit that supplies the electricity necessary to operate each device. The power supply H6 may be a battery. The drive H7 is an auxiliary storage medium such as a hard disk drive or a solid-state drive. The drive H7 may be a non-volatile memory such as an EEPROM or a flash memory, or a magneto-optical disk drive or a flexible disk drive. The drive H7 is not limited to being built into each device, but may also be an external storage device connected to the connector of the connection module H12. The memory H8 is a main storage medium such as a random access memory. The memory H8 may be a cache memory. The memory H8 stores instructions when executed by one or more processors H9. The processor H9 is a CPU (Central Processing Unit). The processor H9 may be an MPU (microprocessing unit) or a GPU (graphics processing unit). The processor H9 reads programs and various data from the drive H7 via the memory H8 and performs calculations to execute instructions stored in one or more memories H8.

[0056] The input / output module I is used in the gateways 11, 24, and 31, the router device 21, the NAT device 23, the NAT instance 32, the on-premise device 22, the data collection device 33, and the cloud device 34. The control module P is used to implement each of the gateways 11, 24, and 31, the router device 21, the NAT device 23, the NAT instance 32, the on-premise device 22, the data collection device 33, and the cloud device 34. In this specification and the like, the terms gateways 11, 24, and 31, the router device 21, the NAT device 23, the NAT instance 32, the on-premise device 22, the data collection device 33, and the cloud device 34 may be replaced with the term control module P.

[0057] The present disclosure may be embodied as follows. (1) One embodiment of the present disclosure is a network system including a router device connected to a first subnet, a first NAT (Network Address Translation) device connected to the first subnet, and a second NAT device connected to a second subnet having the same address range as the first subnet, wherein the router device is configured to handle IP (Internet Protocol) addresses belonging to the address range. a NAT device configured to route IP packets addressed to a first IP address to the first NAT device, and upon receiving the IP packet addressed to the first IP address, the first NAT device changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the IP packet; the first NAT device is communicatively connected to the second NAT device via a network that routes IP packets addressed to the second IP address to the second NAT device, and upon receiving the IP packet addressed to the second IP address, the second NAT device changes the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address and routes the IP packet.

[0058] (2) Another embodiment of the present disclosure is the network system described in (1), wherein, when the second NAT device receives an IP packet having the second IP address set as its source, it changes the source address of the IP packet having the second IP address set as its source to the first IP address and routes the IP packet; and when the first NAT device receives an IP packet having the first IP address set as its source, it changes the source address of the IP packet having the first IP address set as its source to the second IP address and routes the IP packet.

[0059] (3) Another embodiment of the present disclosure is a network system according to (1) or (2), wherein, when the second NAT device receives an Address Resolution Protocol (ARP) request for a set third IP address that is an IP address belonging to the address range, the second NAT device returns a Medium Access Control (MAC) address in the second subnet of the device; when the second NAT device receives an IP packet addressed to the third IP address, the second NAT device changes the destination address of the IP packet addressed to the third IP address to a fourth IP address that has been stored in association with the third IP address and routes the IP packet; the network routes the IP packet addressed to the fourth IP address to the first NAT device; and when the first NAT device receives an IP packet addressed to the fourth IP address, the first NAT device changes the destination address of the IP packet addressed to the fourth IP address to the third IP address that has been stored in association with the fourth IP address and routes the IP packet.

[0060] (4) Another embodiment of the present disclosure is a communication method in a network system including a router device connected to a first subnet, a first NAT (Network Address Translation) device connected to the first subnet, and a second NAT device connected to a second subnet having the same address range as the first subnet, wherein the router device transmits an IP (Internet Protocol) address belonging to the address range. a step of, when the first NAT device receives the IP packet addressed to the first IP address, changing the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routing the IP packet; a step of, by a network that communicatively connects the first NAT device and the second NAT device, routing the IP packet addressed to the second IP address to the second NAT device; and a step of, when the second NAT device receives the IP packet addressed to the second IP address, changing the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address and routing the IP packet.

[0061] (5) Another embodiment of the present disclosure is a first NAT (Network Address Translation) device connected to a first subnet, which, upon receiving an IP packet addressed to a first IP address belonging to the address range of the first subnet, changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the IP packet.

[0062] (6) Another embodiment of the present disclosure is a program for causing a computer to function as a first NAT (Network Address Translation) device connected to a first subnet, wherein the first NAT device, upon receiving an IP packet addressed to a first IP address belonging to the address range of the first subnet, changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address and routes the IP packet.

[0063] 1 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to realize the gateways 11, 24, 31, router 21, NAT device 23, and NAT instance 32. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0064] "Computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" also includes devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or over communication lines like telephone lines, and devices that store programs for a fixed period of time, such as volatile memory within computer systems that serve as servers or clients. The programs may also be programs that implement some of the aforementioned functions, or may be programs that can realize the aforementioned functions in combination with programs already stored in the computer system.

[0065] The embodiments of this disclosure have been described in detail above with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of this disclosure. [Explanation of symbols]

[0066] 11, 24, 31 Gateway 12 Local equipment 21 Router device 22 On-premise equipment 23 NAT device 32 NAT instances 33 Data Collection Equipment 34 Cloud Devices 100 Network Systems N1, N2, N4 leased lines N3, N5 subnets R On-premise location C Cloud base

Claims

1. A network system comprising: a router device connected to a first subnet; a first NAT (Network Address Translation) device connected to the first subnet; and a second NAT device connected to a second subnet having the same address range as the first subnet, the router device routes IP packets destined for a set first IP address, which is an IP (Internet Protocol) address belonging to the address range, to the first NAT device; when the first NAT device receives an IP packet addressed to the first IP address, it changes the destination address of the IP packet addressed to the first IP address to a second IP address that has been stored in association with the first IP address, and routes the IP packet; the first NAT device is communicatively connected to the second NAT device by a network that routes IP packets destined for the second IP address to the second NAT device; When the second NAT device receives an IP packet addressed to the second IP address, it changes the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address, and routes the IP packet. Network system.

2. when the first NAT device receives an IP packet having the second IP address set as its source address, it changes the source address of the IP packet having the second IP address set as its source address to the first IP address and routes the IP packet; When the second NAT device receives an IP packet having the first IP address set as its source address, it changes the source address of the IP packet having the first IP address set as its source address to the second IP address and routes the IP packet. The network system according to claim 1 .

3. the second NAT device, upon receiving an ARP (Address Resolution Protocol) request targeted at a set third IP address that is an IP address belonging to the address range, returns a MAC (Medium Access Control) address in the second subnet of the second NAT device; when the second NAT device receives an IP packet addressed to the third IP address, it changes the destination address of the IP packet addressed to the third IP address to a fourth IP address that has been stored in association with the third IP address, and routes the IP packet; the network routes IP packets destined for the fourth IP address to the first NAT device; when the first NAT device receives an IP packet addressed to the fourth IP address, it changes the destination address of the IP packet addressed to the fourth IP address to the third IP address stored in association with the fourth IP address, and routes the IP packet.

3. The network system according to claim 1.

4. A communication method in a network system including a router device connected to a first subnet, a first NAT (Network Address Translation) device connected to the first subnet, and a second NAT device connected to a second subnet having the same address range as the first subnet, the method comprising: a step of routing, by the router device, an IP packet destined for a set first IP address, which is an IP (Internet Protocol) address belonging to the address range, to the first NAT device; when the first NAT device receives an IP packet addressed to the first IP address, it changes the destination address of the IP packet addressed to the first IP address to the second IP address stored in association with the first IP address and routes the IP packet; a network communicatively connecting the first NAT device and the second NAT device to route IP packets destined for the second IP address to the second NAT device; when the second NAT device receives an IP packet addressed to the second IP address, changing the destination address of the IP packet addressed to the second IP address to the first IP address stored in association with the second IP address and routing the IP packet; A communication method comprising:

5. a first Network Address Translation (NAT) device connected to a first subnet, When receiving an IP packet addressed to a first IP address belonging to the address range of the first subnet, the destination address of the IP packet addressed to the first IP address is changed to a second IP address stored in association with the first IP address, and the IP packet is routed. NAT device.

6. Computer, A program for functioning as a first NAT (Network Address Translation) device connected to a first subnet, When the first NAT device receives an IP packet addressed to a first IP address belonging to the address range of the first subnet, the first NAT device changes the destination address of the IP packet addressed to the first IP address to a second IP address stored in association with the first IP address, and routes the IP packet. program.

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