JP2017038218A - Communication system and setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of equalizing the load among routers and reducing service stop time even when a router gets failed.SOLUTION: A DHCP (dynamic host configuration protocol) server 10 monitors the load on each router 20, and depending on the load on each router 20, sets, to a DHCP OFFER message, a piece of PRIO (priority) information relevant to the priority and transmits the same to each router 20. Each of the routers 20 extracts the PRIO information and exchanges the PRIO information with the other routers 20. When own value of the PRIO information is the highest, the router 20 operates as a master.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication system and a setting method.

  2. Description of the Related Art Conventionally, there has been known a communication system that allocates one VLAN (Virtual Local Area Network) to each terminal, suppresses the influence of packets from other users, and prevents unauthorized use. As a redundant configuration of such a communication system, for example, as illustrated in FIG. 13, it is known to extend a Y-shaped VLAN to an ACT (Active) router and an SBY (standby) router. .

  For example, in the example of FIG. 13, the terminal 30A is connected to the ACT router 200A and the SBY router 200C via “VLAN1”, and the terminal 30B is connected to the ACT router 200B and the SBY router 200C and “VLAN2”. Is connected via.

  In such a configuration, when the ACT router fails, the IP address of the SBY router is reassigned as the default gateway. For example, in the example of FIG. 13, when a failure occurs in the ACT router 200A, the DHCP (Dynamic Host Configuration Protocol) server 100 transmits a DHCP FORCERENEW which is a message for instructing the terminal 30A to perform reconfiguration. By redoing from the DHCP DISCOVER which is the search message of the DHCP server 100, the IP address of the SBY router 200C is re-assigned as the default gateway.

  In addition, even when the accommodation is changed for the purpose of correcting the router load or updating the file, the DHCP server 100 transmits DHCP FORCERENEW to the user terminal 30A and starts again from the DHCP DISCOVER to set the accommodation destination router. change.

"Dynamic Host Configuration Protocol", [online], [searched August 4, 2015], Internet <http://www.ietf.org/rfc/rfc2131.txt.pdf/>

  However, in the prior art, when the ACT router fails, the DHCP server 100 transmits DHCP FORCERENEW to the user terminal 30A in order to reissue the IP address of the SBY router as the default gateway, and DHCP DISCOVER. There was a problem that the service stop time was long.

  In order to solve the above-described problems and achieve the object, the communication system of the present invention includes a communication terminal having each terminal to which a different VLAN is assigned for each terminal and a plurality of routers connected to each terminal. A different VLAN is assigned to each terminal, and a plurality of terminals that are connected to all routers of the plurality of routers via the VLAN and that are assigned the same IP address on the same VLAN. A router that relays packets that have the connected terminal as a source or destination, and is connected to the terminal, and the master router In the case of a failure, another router is switched to a new master router.

  The communication system of the present invention is a communication system having a plurality of routers connected to each terminal to which a different VLAN is assigned for each terminal, and a server for controlling the plurality of routers, A monitoring unit that monitors the load of each router; and a transmission unit that transmits a packet including priority information about priority to each router according to the load of each router monitored by the monitoring unit at a predetermined opportunity. And each router assigned the same IP address on the same VLAN receives a packet including the Priority information from the server, and sets its own priority based on the Priority information. A reception unit that receives an address request for inquiring about a MAC address of a connection destination router from the terminal; and When the priority set by the fixed unit is the highest among the plurality of routers, as a master router, the self-priority is set to the transmission source terminal of the address request received by the receiving unit. A response unit that responds to the MAC address of the router; and a relay unit that relays a packet whose source or destination is the terminal to which the MAC address is responded by the response unit.

  The setting method of the present invention is a setting method executed by a communication system having a plurality of routers connected to each terminal to which a different VLAN is assigned for each terminal and a server that controls the plurality of routers. A monitoring step in which the server monitors the load of each router, and a priority on the priority for each router according to the load of each router monitored by the monitoring step at a predetermined timing. A transmission step of transmitting a packet including information, and when each router assigned the same IP address on the same VLAN receives a packet including the Priority information from the server, based on the Priority information, A setting step for setting priority, and each router is connected to the MAC address of the router to which the terminal is connected A receiving step of receiving an address request to be inquired, and each router having the highest priority set by the setting step among the plurality of routers, as a master router, by the receiving step A response step of responding to the MAC address of the own router to the terminal of the transmission source of the received address request, and the master router sending or transmitting the terminal to which the MAC address is responded by the response step And a relaying step of relaying the previous packet.

  According to the present invention, it is possible to shorten the service stop time even when a router malfunctions.

FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to the first embodiment. FIG. 2 is a diagram illustrating each router in the communication system according to the first embodiment. FIG. 3 is a block diagram showing the configuration of the DHCP server according to the first embodiment. FIG. 4 is a diagram illustrating an example of information stored in the router load information storage unit according to the first embodiment. FIG. 5 is a diagram showing a packet configuration of the DHCP OFFER message. FIG. 6 is a block diagram illustrating a configuration of the router according to the first embodiment. FIG. 7 is a diagram illustrating an example of information stored in the PRIO information storage unit according to the first embodiment. FIG. 8 is a diagram illustrating an example of information stored in the address information storage unit according to the first embodiment. FIG. 9 is a diagram for explaining processing at the time of address delivery in the communication system according to the first embodiment. FIG. 10 is a flowchart showing a flow of PRIO information transmission processing of the DHCP server according to the first embodiment. FIG. 11 is a flowchart showing a flow of PRIO information setting processing of the router according to the first embodiment. FIG. 12 is a diagram illustrating a computer that executes a setting program. FIG. 13 is a diagram for explaining a conventional communication system.

  Embodiments of a communication system and a setting method according to the present application will be described below in detail with reference to the drawings. The communication system and the setting method according to the present application are not limited by this embodiment.

[First embodiment]
In the following embodiments, the configuration of the communication system according to the first embodiment, the configuration of the DHCP server, the configuration of the router, the processing flow of the DHCP server and the router will be described in order, and finally the first embodiment The effect of will be described.

[Configuration of communication system]
FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to the first embodiment. The communication system according to the first embodiment includes a DHCP server 10, a plurality of routers 20A to 20C, and a plurality of terminals 30A and 30B. Further, as shown in FIG. 1, in the communication system according to the first embodiment, a system is established in which VLANs are set up in a plurality of routers 20A to 20C. In addition, the number of each apparatus and function shown in FIG. 1 is an example to the last, and is not restricted to this. In addition, when a plurality of routers 20A to 20C and a plurality of terminals 30A and 30B are described without particular distinction, they are appropriately referred to as a router 20 and a terminal 30.

  The DHCP server 10 transmits network setting information to the terminals 30A and 30B in the same segment. This network setting information is setting information for the terminal 30 to perform data communication, and includes an IP address assigned to the terminal 30, an IP address of a default gateway used by the terminal 30, and the like.

  Further, the DHCP server 10 changes VRRP Priority (hereinafter referred to as PRIO as appropriate) information so that the router 20 with a small load becomes the master when receiving DHCP DISCOVER. Specifically, when receiving the DHCP DISCOVER, the DHCP server 10 sets PRIO information in option code 43 (Vender-Specific-Information) of the DHCP OFFER message and transmits it to the router 20.

  The router 20 relays communication of the terminal 30 connected by the VLAN. The terminal 30 is assigned a different VLAN for each terminal, and is connected to all the routers 20 among the plurality of routers 20 via the VLAN. The router 20 includes a real IP address, a real MAC address, a VRID (Virtual Router ID) that identifies a group of the router 20 to which the same virtual IP address is allocated in VRRP, a master (active), or a slave for each connected VLAN. PRIIO information, virtual IP address, and virtual MAC address, which are information for determining whether to enter (standby), are set.

  For example, as illustrated in FIG. 2, for the VLAN 1, the router 20 </ b> A has an actual IP address “10.1.1.1”, an actual MAC address “70: 58: 12: 27: B7: 17”, and a VRID “1”. ”, PRIO“ 200 → 50 ”, virtual IP address“ 10.1.1.5 ”, and virtual MAC address“ 00: 00: 5E: 00: 00: 01 ”are set.

  Further, when receiving the PRIO information from the DHCP server 10, the router 20A sets the PRIO information from the PRIO information. Specifically, the router 20A receives the DHCP OFFER message, and sets PRIO information set in option code 43 (Vender-Specific-Information) of the DHCP OFFER message. For example, in the example of FIG. 2, the PRIOR information “200” is set in the router 20A. However, the router 20A receives the DHCP OFFER message, and the PRIO set in option code 43 (Vender-Specific-Information) of the DHCP OFFER message. Since the information is “50”, the PRIO information is updated from 200 to 50 (described as “200 → 50” in FIG. 2).

  Thus, the DHCP server 10 changes PRIO information according to the load of each router 20. The router having the largest PRIO information value among the routers becomes the master. For example, in the example of FIG. 2, the PRIO information of the router 20A is changed from “200” to “50”, the PRIO information of the router 20B is changed from “100” to “200”, and the PRIO information of the router 20C is “50”. ”To“ 100 ”, the master is changed from the router 20A to the router 20B.

  After becoming the master router 20 </ b> B, the terminal 30 transmits a DHCP REQUEST to the DHCP server 10. Then, the DHCP server 10 responds to the terminal 30 with a DHCP ACK.

  Thereafter, when each of the routers 20A to 20C receives an ARP (Address Resolution Protocol) request from the terminal 30, only the router 20B responds with the virtual MAC address of the router 20B as an ARP response. A switch (not shown) learns from the ARP response, and transfers a packet destined for the terminal 30 or a packet destined for the terminal 30 to the router 20B when receiving the packet destined for the terminal 30. As a result, the router 20B operates as a master.

  Here, in the communication system, since the virtual IP addresses of the routers 20A to 20C on the same VLAN are the same, when the master router 20B fails, it is not necessary to start over from the DHCP DISCOVER, and the new master router By sending a (Gratuitous ARP) message, the switch learns and the master router switches immediately.

[Configuration of DHCP server]
Next, the configuration of the DHCP server 10 shown in FIG. 1 will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration of the DHCP server 10 according to the first embodiment. As illustrated in FIG. 3, the DHCP server 10 includes a communication processing unit 11, a control unit 12, and a storage unit 13. The processing of each of these units will be described below.

  The communication processing unit 11 controls communication related to various information exchanged with the router 20. For example, the communication processing unit 11 transmits a DHCP OFFER message in which PRIO information is set to the router 20.

  The storage unit 13 stores data and programs necessary for various types of processing by the control unit 12, and has a router load information storage unit 13a particularly closely related to the present invention. For example, the storage unit 13 is a semiconductor memory device such as a RAM (Random Access Memory) or a flash memory, or a storage device such as a hard disk or an optical disk.

  The router load information storage unit 13a stores information related to the load of each connected router 20. For example, the router load information storage unit 13a stores the number of subscribers accommodated in each router 20 as information related to the load. Referring to the example of FIG. 4, the router load information storage unit 13 a stores a “router name” that identifies the router 20 and a “load” that indicates the number of accommodated routers 20 in association with each other. In the example of FIG. 4, the router load information storage unit 13a stores, for example, the router name “Router 1” and the load “2000” in association with each other. This means that the accommodation number of “router 1” is “2000”. Note that the information regarding the load is not limited to the accommodation number, and for example, information regarding the CPU and memory of each router 20 may be stored.

  The control unit 12 has an internal memory for storing a program that defines various processing procedures and necessary data, and performs various processes using them, and particularly as closely related to the present invention, It has a monitoring unit 12a and a transmission unit 12b.

  The monitoring unit 12a monitors the load on each router 20. For example, the monitoring unit 12a requests the current accommodation number information from each router 20 at a predetermined time interval, and stores the acquired accommodation number information in the router load information storage unit 13a. In addition, you may make it the monitoring part 12a acquire the information regarding the load of each router 20 from an external apparatus.

  The transmission unit 12b transmits a packet including PRIO information regarding priority to each router 20 according to the load of each router 20 monitored by the monitoring unit 12a at a predetermined opportunity. For example, when receiving the DHCP DISCOVER from the terminal 30, the transmitting unit 12b sets the larger value as PRIO information in option code 43 (Vender-Specific-Information) of the DHCP OFFER message as the load on each router 20 decreases. To do.

  Further, when sending the DHCP FORCERENEW message, the transmitting unit 12b may set PRIO information in the DHCP FORCERENEW message. Specifically, the transmission unit 12b sets PRIO information to Vender-Specific-Information in an option field (Option field) of the DHCP FORCERENE message according to the load of each router monitored by the monitoring unit 12a. Send FORCERENEW message.

  Here, as shown in FIG. 5, the packet structure of the DHCP OFFER message will be described. FIG. 5 is a diagram showing a packet configuration of the DHCP OFFER message. As shown in FIG. 5, in the DHCP OFFER message, PRIO information is set in option code 43 (Vender-Specific-Information), which is a field for setting vendor-specific information in an option field.

[Router configuration]
Next, the configuration of the router 20 shown in FIG. 1 will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of the router 20 according to the first embodiment. As illustrated in FIG. 6, the router 20 includes a communication processing unit 21, a control unit 22, and a storage unit 23. The processing of each of these units will be described below.

  The communication processing unit 21 controls communication related to various information exchanged with the DHCP server 10, the terminal 30, and the like. For example, the communication processing unit 21 receives a DHCP OFFER message from the DHCP server 10.

  The storage unit 23 stores data and programs necessary for various types of processing by the control unit 22. The storage unit 23 includes a PRIO information storage unit 23 a and an address information storage unit 23 b that are particularly closely related to the present invention.

  The PRIO information storage unit 23a stores the value of PRIO information set in the own device. For example, as illustrated in FIG. 7, the PRIO information storage unit 23 a stores “VRID” and “PRIO” in association with each other. In the example of FIG. 7, for example, VRID “VRID1” and PRIO information “200” are stored in association with each other.

  The address information storage unit 23b stores information related to the address of the own device. For example, as illustrated in FIG. 8, “real IP address”, “real MAC address”, “virtual IP address”, and “virtual MAC address” are stored in association with VRID. In the example of FIG. 8, for example, the address information storage unit 23 b associates with “VRID 1” and associates the real IP address “10.1.1.1” and the real MAC address “70: 58: 12: 27: B7: 17 ”, virtual IP address“ 10.1.1.5 ”, and virtual MAC address“ 00: 00: 5E: 0: 01: 01 ”are stored.

  The control unit 22 has an internal memory for storing a program that defines various processing procedures and the necessary data, and executes various processes using these programs. Particularly, as closely related to the present invention, A setting unit 22a, a receiving unit 22b, a response unit 22c, and a relay unit 22d are included.

  When the setting unit 22a receives a packet including PRIO information from the DHCP server 10, the setting unit 22a sets its own priority based on the PRIO information. For example, when receiving a DHCP OFFER message including PRIO information from the DHCP server 10, the setting unit 22a extracts PRIO information set in option code 43 (Vender-Specific-Information) of the DHCP OFFER message and stores the PRIO information. Stored in the unit 23a. Then, the setting unit 22a exchanges PRIIO information with other routers 20 based on the VRRP procedure, and sets the own device as a master when the value of the PRIIO information of the own device is the highest.

  The receiving unit 22b receives an ARP request for inquiring about the MAC address of the connection destination router 20 from the terminal 30. Specifically, when receiving the ARP request from the terminal 30, the receiving unit 22b notifies the response unit 22c that the ARP request has been received.

  When the value of its own PRIO information set by the setting unit 22a is the highest among the plurality of routers 20, the response unit 22c responds to the terminal 30 that is the transmission source of the ARP request received by the reception unit 22b. To respond with its own virtual MAC address. Specifically, when the response unit 22c notifies that the ARP request has been received from the reception unit 22b, if the own device is a master, the response unit 22c stores address information in the terminal 30 that is the transmission source of the ARP request. Refers to the unit 23b, and responds with the virtual MAC address of its own device. If the device itself is not the master, the received ARP request is discarded.

  The relay unit 22d relays a packet whose source or destination is the terminal 30 to which the response unit 22c responds the MAC address. For example, the relay unit 22d performs NAT (Network Address Translation) conversion or the like when receiving a packet whose destination is the terminal 30 to be connected or a packet whose source is the terminal 30 to be connected. And send the packet to the destination.

  As shown in FIG. 9, the process at the time of address payout of the communication system according to the first embodiment will be described. FIG. 9 is a diagram for explaining processing at the time of address delivery in the communication system according to the first embodiment. As shown in FIG. 9, the terminal 30 transmits DHCP DISCOVER to the DHCP server 10 via the routers 20A to 20C via the switch (SW) 40 (see (1) in FIG. 9). Then, the DHCP server 10 sets PRIO information in option code 43 (Vender-Specific-Information) of the DHCP OFFER message, and transmits a DHCP OFFER message to each of the routers 20A to 20C (see (2) in FIG. 9).

  When each of the routers 20A to 20C receives the DHCP OFFER message including PRIO information from the DHCP server 10, the routers 20A to 20C extract the PRIO information set in option code 43 (Vender-Specific-Information) of the DHCP OFFER message. The information is stored in the information storage unit 23a. Then, the setting unit 22a exchanges PRIIO information with other routers 20 based on the VRRP procedure, and sets the own device as a master when the value of the PRIIO information of the own device is the highest. In the example of FIG. 9, the PRIO of the router 20A is changed from “200” to “50”, the PRIO of the router 20B is changed from “100” to “200”, and the PRIO of the router 20C is changed from “50” to “100”. Therefore, the master is changed from the router 20A to the router 20B.

  Then, only the router 20B which is the new master relays the DHCP OFFER message and transmits it to the terminal 30, and the other routers 20A and 20C do not relay the DHCP OFFER message. In this way, since the router 20B having a small load is made the master by using the change of the VRRP PRIO information, it is possible to realize not only the redundancy of the VRRP but also the load leveling.

  Further, in the above description, the processing at the time of address delivery when the terminal 20 determines the accommodation destination router has been described as an example. However, the master is assigned in the same procedure when the accommodation router is changed when the accommodation destination router is changed. It is possible to change. For example, the DHCP 10 sets PRIO information in option code 43 (Vender-Specific-Information) of the DHCP FORCERENEW message, which is a message for instructing the terminal 30A to perform reconfiguration, and transmits a DHCP FORCERENEW message to each of the routers 20A to 20C. .

  When each of the routers 20A to 20C receives a DHCP FORCERENEW message including PRIO information from the DHCP server 10, the routers 20A to 20C extract PRIIO information set in option code 43 (Vender-Specific-Information) of the DHCP FORCERENEW message. The information is stored in the information storage unit 23a. Then, the setting unit 22a exchanges PRIIO information with other routers 20 based on the VRRP procedure, and sets the own device as a master when the value of the PRIIO information of the own device is the highest.

  Then, only the router 20B as the new master relays the DHCP FORCERENE message and transmits it to the terminal 30, and the other routers 20A and 20C do not relay the DHCP FORCERENEW message.

  Thereafter, the terminal 30 transmits DHCP REQUEST to the DHCP server 10. Then, the DHCP server 10 responds to the terminal 30 with a DHCP ACK.

[Processing flow of DHCP server]
Next, a processing flow of the DHCP server 10 according to the first embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing a flow of PRIO information transmission processing of the DHCP server according to the first embodiment.

  As shown in FIG. 10, when the DHCP server 10 receives the DHCP DISCOVER from the terminal 30 (Yes in step S101), the DHCP server 10 sets the option code 43 (Vender-Specific-Information) of the DHCP OFFER message based on the load of each router 20. PRIO information is set (step S102). Then, the DHCP server 10 transmits a DHCP OFFER message to each router 20 (step S103).

  For example, when receiving the DHCP DISCOVER from the terminal 30, the transmitting unit 12b sets the larger value as PRIO information in option code 43 (Vender-Specific-Information) of the DHCP OFFER message as the load on each router 20 decreases. To do.

[Router processing flow]
Next, a processing flow of the router 20 according to the first embodiment will be described with reference to FIG. FIG. 11 is a flowchart showing a flow of PRIO information setting processing of the router according to the first embodiment.

  As shown in FIG. 11, when the router 20 receives a DHCP OFFER message including PRIO information from the DHCP server 10 (Yes in step S201), the router 20 is set to option code 43 (Vender-Specific-Information) of the DHCP OFFER message. PRIO information is extracted (step S202).

  Then, the router 20 exchanges PRIIO information with the other routers 20 based on the VRRP procedure (step S203), and determines whether the value of the PRIIO information of its own device is the highest (step S204). As a result, when the value of the PRIIO information of the own device is the highest (Yes at Step S204), the router 20 sets the own device as a master (Step S205).

[Effect of the first embodiment]
Thus, in the communication system according to the first embodiment, since the virtual IP address on the same VLAN is the same for each router 20, it is not necessary to redo from DHCP DISCOVER when the master router fails, and the new master The switch learns from the issued GARP and can immediately switch the master router. In addition, since the router 20 having a small load is made a master by using the change of the PRIRP information of the VRRP, it is possible not only to make the VRRP redundant, but also to equalize the load on the router. For this reason, the load on the router can be leveled and the service stop time can be shortened even when the router 20 fails.

  In addition, the load leveling can be realized by changing the PRIIO information using DHCP OFFER and switching the master by using DHCP DISCOVER, etc., and also during the DHCP FORCERENE Alternatively, the service stop time is short because only the SW learning table is changed by GARP from the new master without changing the virtual IP address of the default GW by changing the PRIIO information using DHCP ACK. Furthermore, since each router is used as an ACT, there is an effect that resource waste is small and there is a small risk that the switching destination at the time of switching at the time of router failure is broken.

[System configuration, etc.]
Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  In addition, among the processes described in the present embodiment, all or part of the processes described as being automatically performed can be manually performed, or the processes described as being manually performed can be performed. All or a part can be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above-described document and drawings can be arbitrarily changed unless otherwise specified.

[program]
FIG. 12 is a diagram illustrating a computer that executes a setting program. The computer 1000 includes, for example, a memory 1010 and a CPU (Central Processing Unit) 1020. The computer 1000 also includes a hard disk drive interface 1030, a disk drive interface 1040, a serial port interface 1050, a video adapter 1060, and a network interface 1070. These units are connected by a bus 1080.

  The memory 1010 includes a ROM (Read Only Memory) 1011 and a RAM (Random Access Memory) 1012. The ROM 1011 stores a boot program such as BIOS (Basic Input Output System). The hard disk drive interface 1030 is connected to the hard disk drive 1031. The disk drive interface 1040 is connected to the disk drive 1041. For example, a removable storage medium such as a magnetic disk or an optical disk is inserted into the disk drive 1041. The serial port interface 1050 is connected to a mouse 1051 and a keyboard 1052, for example. The video adapter 1060 is connected to the display 1061, for example.

  The hard disk drive 1031 stores, for example, an OS 1091, an application program 1092, a program module 1093, and program data 1094. That is, a program that defines each process of the DHCP server 10 and the router 20 is implemented as a program module 1093 in which a code executable by a computer is described. The program module 1093 is stored in the hard disk drive 1031, for example. For example, a program module 1093 for executing processing similar to the functional configuration in the apparatus is stored in the hard disk drive 1031. The hard disk drive 1031 may be replaced by an SSD (Solid State Drive).

  The setting data used in the processing of the above-described embodiment is stored as program data 1094 in, for example, the memory 1010 or the hard disk drive 1031. Then, the CPU 1020 reads the program module 1093 and the program data 1094 stored in the memory 1010 and the hard disk drive 1031 to the RAM 1012 as necessary, and executes them.

  Note that the program module 1093 and the program data 1094 are not limited to being stored in the hard disk drive 1031, but may be stored in, for example, a removable storage medium and read by the CPU 1020 via the disk drive 1041 or the like. Alternatively, the program module 1093 and the program data 1094 may be stored in another computer connected via a network (LAN (Local Area Network), WAN (Wide Area Network), etc.). Then, the program module 1093 and the program data 1094 may be read by the CPU 1020 from another computer via the network interface 1070.

DESCRIPTION OF SYMBOLS 10 DHCP server 11, 21 Communication processing part 12, 22 Control part 12a Monitoring part 12b Transmission part 13, 23 Storage part 13a Router load information storage part 20, 20A-20C Router 22a Setting part 22b Receiving part 22c Response part 22d Relay part 23a PRIO information storage unit 23b Address information storage unit 30, 30A, 30B Terminal 40 Switch

Claims (6)

A communication system having each terminal to which a different VLAN is assigned for each terminal, and a plurality of routers respectively connected to each terminal,
A different VLAN is assigned to each terminal, and a terminal connected to all of the plurality of routers via the VLAN;
A plurality of routers assigned the same IP address on the same VLAN;
Have
Of all the routers connected to the terminal, one router acts as the master router, relays the packet with the connected terminal as the source or destination, and if the master router fails, the other A communication system, characterized in that a router of a new one is switched to a new master router. A communication system having a plurality of routers connected to each terminal to which a different VLAN is assigned for each terminal, and a server for controlling the plurality of routers,
The server
A monitoring unit that monitors the load on each router;
A transmission unit that transmits a packet including priority information about priority to each router according to a load of each router monitored by the monitoring unit at a predetermined opportunity;
Have
Each router assigned the same IP address on the same VLAN
When receiving a packet including the Priority information from the server, a setting unit for setting its own priority based on the Priority information;
A receiving unit for receiving an address request for inquiring about a MAC address of a connection destination router from the terminal;
When the priority set by the setting unit is the highest among the plurality of routers, as a master router, for the terminal of the source of the address request received by the receiving unit, A response unit that responds to the MAC address of its own router;
A relay unit that relays a packet whose source or destination is a terminal to which the MAC address is responded by the response unit;
A communication system comprising:   3. The communication system according to claim 2, wherein the transmission unit sets a larger value in the packet as priority information for a router having a smaller load monitored by the monitoring unit, and transmits the packet.   When the transmission unit receives a DHCP DISCOVER message from the terminal, the transmission unit sets the priority information in the option field of the DHCP OFFER message according to the load of each router monitored by the monitoring unit. The communication system according to claim 2, wherein the DHCP OFFER message is transmitted.   The transmission unit sets the Priority information in a field for setting vendor-specific information in an option field of a DHCP FORCERENE message according to the load of each router monitored by the monitoring unit, and transmits the DHCP FORCERENEW message. The communication system according to claim 2 or 3, characterized by: A setting method executed by a communication system having a plurality of routers connected to each terminal to which a different VLAN is assigned for each terminal, and a server that controls the plurality of routers,
A monitoring step in which the server monitors the load of each router;
A transmission step in which the server transmits a packet including priority information about priority to each router according to a load of each router monitored by the monitoring step at a predetermined opportunity;
When each router to which the same IP address is assigned on the same VLAN receives a packet including the Priority information from the server, a setting step of setting its own priority based on the Priority information;
A receiving step in which each router receives an address request for inquiring about a MAC address of a connection destination router from the terminal;
When each of the routers has the highest priority set in the setting step among the plurality of routers, as a master router, the source of the address request received in the receiving step A response step of responding to the terminal with the MAC address of the own router;
A relay step in which the master router relays a packet whose source or destination is the terminal to which the MAC address is responded in the response step;
The setting method characterized by including.

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