JP2005348145A - Inter-lan connection device and inter-lan connection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inter-LAN connection device and an inter-LAN connection method capable of eliminating restriction of the number of second routers, etc. arranged on the side of the second router when a first router which performs routing by terminating an IP packet and the second router connected with a communication path with which two or more routers and a communication terminal can be connected and performs routing of the IP packet are connected via a point-to-point network. <P>SOLUTION: The inter-LAN connection device 201 is arranged between a broadcast network 202 and the point-to-point network 203 and stores information about a set of IP address information of a PE router 207, a network address of a subnet to which first and second CE routers 204<SB>1</SB>, 204<SB>2</SB>belong and a net mask. Flow in of unnecessary packet to the first router side is blocked and control for setting courses of the packets to be transmitted to the first and second router sides based on these pieces of information. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inter-LAN connection device and an inter-LAN connection method via a point-to-point network, and more particularly to an inter-LAN connection device and an inter-LAN connection method that increase the degree of freedom of connection of various communication devices such as routers to the network. .

  With the development of communication networks, it has been proposed to connect LANs (Local Area Networks) via the Internet (see, for example, Patent Document 1). In addition, the introduction of WAN (Wide Area Network) such as IP-VPN (Virtual Private Network) that encapsulates and encrypts IP (Internet Protocol) packets and passes them through an IP network is accelerating. Under such circumstances, attention has been focused on a communication mode in which LANs are connected to each other via a point-to-point network including a dedicated line.

  By the way, in a service such as IP-VPN, a CE (Customer Edge) router as a base router that terminates an IP packet on a broadcast network, and a center router that terminates an IP packet on a point-to-point network. When connecting to a PE (Providor Edge) router via a point-to-point network, a signal conversion converter or terminal adapter is used.

In such a connection form, the number of CE routers that can be connected to the point-to-point network is limited to one. The reason is that when an ARP (Address Resolution Protocol) request is made to obtain the data link layer address of the communication partner in order to send an IP packet to the communication partner, a plurality of CE routers and communication terminals are connected to the broadcast network side. This is because the above-described converter for signal conversion and the like will return an ARP response unconditionally to all ARP requests from the host.
Japanese Patent Laying-Open No. 2003-273892 (paragraph 0012, FIG. 1)

  As a result, if servers or terminals other than CE routers or multiple CE routers are placed in the same subnet on the broadcast network side of these devices, ARP requests are not processed correctly and packet communication with the communication partner starts. There is a risk that it cannot be done. For this reason, a large-scale network cannot be constructed by arranging a plurality of CE routers and communication terminals.

  In addition, when a plurality of CE routers and communication terminals are arranged, an ARP response is returned unconditionally to all ARP requests from the host. Therefore, even unnecessary IP packets can be transmitted through the point-to-point network. There is also a problem that it is transferred to the router and increases the load on the network. Alternatively, in order to suppress this, the ARP entry is manually registered, and there is a problem that maintenance is difficult. For this reason, there are significant restrictions on the connection between LANs.

  Therefore, an object of the present invention is to connect a point-to-point network, terminate the IP packet, and route the IP packet by being connected to a communication path that can connect two or more routers and communication terminals. LAN capable of removing restrictions on the number of second routers arranged on the second router side and the arrangement of other communication terminals when connecting to the second router via the point-to-point network described above An object of the present invention is to provide an inter-connection device and an inter-LAN connection method.

  According to the first aspect of the present invention, (a) a first router that terminates and routes an IP packet as a packet that is connected to a predetermined local network and performs communication using the Internet protocol, is connected via a point-to-point network. And (b) a data link layer address corresponding to an IP address of a subordinate host connected to an independent local network different from the predetermined local network and routed IP packets. At least from two or more second routers or one second router as a router having an ARP response means for returning an ARP response when an ARP request for requesting a response comes from an external network and a predetermined communication terminal Composed An interface between communication devices for connecting to a network between communication devices as a network for communicating packets among a plurality of communication devices; (c) IP address information storage means for storing IP address information of the first router; (D) delivery destination information storage means for storing information on a set of network addresses and netmasks of IP subnets to which the second router belongs, as delivery destination information; and (e) in a local network connected to the first router. When an IP packet specifying the IP address of the communication partner is sent from the host of the host, when this is not a packet destined for itself, the sender protocol address is set as the IP address of the first router and the target protocol address is specified by the host Set the IP address of the communication partner and ARP request sending means for sending an ARP request incorporating the data link layer address of the interface, and (f) the data link layer address from the second router for the ARP request sent by this ARP request sending means as the target hardware address The IP address of the communication partner was specified based on the information of the next hop IP address indicating the second router and the data link layer address information that was found by the ARP response incorporated as A first sending means for sending a data link header to the IP packet and sending it to the network between the communication devices; and (g) an IP packet sent from the host of the IP address of the communication partner under the second router. Sent based on the data link layer address received by the second router The LAN connecting device is provided with a second sending means for sending this from the point-to-point interface to the first router.

  That is, according to the first aspect of the present invention, a point-to-point interface connected via a point-to-point network to a first router that terminates and routes an IP packet to an inter-LAN connection device that connects LANs, Two interfaces, that is, an interface between communication devices for connecting to a network between communication devices that communicate packets between communication devices are provided. In the present invention, the communication device refers to the second router and other communication terminals described above. Here, when an IP packet designating the IP address of the communication partner is sent from the host in the local network connected to the first router and sent to the inter-LAN connection device side, the ARP request sending means is connected between the LANs. When the packet is not addressed to the connection device itself, the sender protocol address is set to the IP address of the first router, the target protocol address is set to the IP address of the communication partner designated by the host, and the data link layer address of the interface between the communication devices is set. Send the embedded ARP request. Since this ARP request is sent to the second router side, if there is a host with the target protocol address, an ARP response is returned directly from that host or on behalf of the second router. When such an ARP response is returned to the LAN connecting device side, the LAN connecting device sends an IP packet to the network between communication devices connected to the second router, and the IP packet is sent to the LAN. When it is sent to the inter-connection device, it is sent to the first router that sent it first, thereby enabling communication between the host and the communication partner by IP packet. In this way, the inter-LAN connection device mediates between LANs, and communication with a plurality of CE routers becomes possible by utilizing the information stored in the delivery destination information storage means.

  According to the second aspect of the present invention, (a) a connection through a point-to-point network with a first router that terminates and routes an IP packet as a packet that is connected to a predetermined local network and performs communication using the Internet protocol. A point-to-point interface, and (b) two or more second routers or one second router that are connected to an independent local network different from the predetermined local network and route IP packets. An interface between communication devices for connecting to a network between communication devices that communicates IP packets among a plurality of communication devices including at least a terminal of (2), and (c) an IP address storing IP address information of the first router Information storage means, and (d) a second (D) a destination information storage means for storing information of a set of a network address and a netmask of each IP subnet to which the data belongs, and (e) a communication partner from a host in the local network connected to the second router An IP packet designating the IP address of the first router is sent to the second router, and the ARP request with the IP address of the first router as the target protocol address is generated because the IP address of the communication partner is not the IP address on the network side between the communication devices. ARP request receiving means for receiving an IP packet sent from the second router based on the IP packet, and (f) sent from the second router when an ARP request is received by the ARP request receiving means. The target protocol address in the received ARP request is its own IP address If not specified, an ARP response packet in which the data link layer address of the network between communication devices is set as the target hardware address, or the target protocol address in the ARP request sent from the second router is its own IP address ARP response packet sending means for generating an ARP response packet in which the data link layer address of the network between communication devices is set as the target hardware address and sending it from the interface between communication devices to the network between communication devices when the address is determined Are provided in the inter-LAN connection device.

  That is, according to the second aspect of the present invention, a point-to-point interface connected via a point-to-point network to a first router that terminates and routes an IP packet to an inter-LAN connection device that connects LANs, Two interfaces, that is, an interface between communication devices for connecting to a network between communication devices that communicate packets between communication devices are provided. In the present invention, the communication device refers to the second router and other communication terminals described above. Here, it is assumed that an IP packet designating the IP address of the communication partner is transmitted from a host in the local network connected to the second router and received by the LAN connecting device. When the ARP request receiving means receives this in the inter-LAN connection device, or when it is not determined that the target protocol address in the ARP request sent from the second router is the IP address on the interface side between communication devices Then, an ARP response packet is created and sent to the network between communication devices on the side that has made the ARP request. Thereby, the load on the network related to the ARP request and the ARP response can be reduced by the inter-LAN connection device that grasps the information on the first router side.

  According to the seventh aspect of the present invention, (a) a host in the local network connected to a first router that is connected to a predetermined local network and terminates and routes an IP packet as a packet for communication using the Internet protocol. When an IP packet designating the IP address of the communication partner is sent from the destination, a destination determination step for determining whether or not this is a packet destined for itself, and (b) the destination determination step as a destination. The sender protocol address is set to the IP address of the first router, the target protocol address is set to the IP address of the communication partner designated by the host, and each is an independent local network different from the predetermined local network. IP packets connected to the network As a router having proxy ARP response means that returns an ARP response on behalf of an ARP request that arrives from an external network when an ARP request that requests a response of a data link layer address corresponding to the IP address of a subordinate host is received. Communication device for connecting to a network between communication devices as a network for communicating packets between a plurality of communication devices composed of at least two second routers or one second router and a predetermined communication terminal An ARP request sending step for sending an ARP request including the data link layer address of the inter-interface, and (c) data link layer addresses from two or more second routers in response to the ARP request sent in this ARP request sending step When there was a proxy ARP response incorporating The IP address of the communication partner is obtained from the host in the local network connected to the first router based on the information of the set of the next hop IP address indicating the second router and the data link layer address. A first sending step of adding a data link header to the designated IP packet and sending it to the network between the communication devices; and (d) a second IP packet from the host of the IP address of the communication partner under the second router. A second transmission step for transmitting the data link based on the data link layer address received by the router from the point-to-point interface toward the first router; and (e) being connected to a predetermined local network. Terminate IP packet as a packet to communicate using Internet protocol When an IP packet specifying the IP address of the communication partner is sent from a host in the local network connected to the second router to be routed, it is determined whether or not this is a packet destined for itself. And (f) receiving an ARP request sent from the second router based on an IP packet specifying the IP address of the communication partner from a host in the local network connected to the second router. The LAN connection method includes an ARP response sending step for sending an ARP response according to the request.

  That is, in the invention described in claim 7, the technical effect similar to that of the invention described in claim 1 is expressed as a method of connection between LANs, in a case where the second router can make a proxy response.

  As described above in detail, according to the present invention, the first router that is connected to a predetermined local network and terminates and routes an IP packet is passed through the point-to-point network and the LAN connecting device of the present invention. Since a plurality of second routers for routing packets can be connected, and these routers can be connected to other communication terminals, a large-scale network can be constructed.

  Moreover, when such a network is manually constructed by the user, in order to designate the second router to which the IP packet is to be delivered, a set of the IP address of the second router and the data link layer address is preliminarily set by the user. It must be registered in a storage means such as a table. For this reason, the user must manage all the data link layer addresses of the network devices, which makes it difficult to change and maintain the network. In the present invention, since it is not necessary to manually register the data link layer address for the IP address of the second router in advance in the LAN connecting device, it is possible to flexibly cope with network maintenance and changes.

  Further, when the present invention is used, it is possible not to explicitly assign an IP address. For example, since the IP address in the same subnet is not consumed, the present invention can be applied to a network such as 192.168.0.0/30 where only two host addresses can be given. Of course, the data link layer address of the second router can be resolved by the ARP protocol, but it is necessary to allocate one IP address in the same subnet to the apparatus.

  Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 shows an outline of a communication system using an inter-LAN connection apparatus in the first embodiment of the present invention. An inter-LAN connection device 201 of this embodiment connects one end of a broadcast network 202 and a point-to-point network 203. The broadcast network 202 is connected to a _first LAN (Local Area Network) 205 ₁ via a _first CE (Customer Edge) router 204 ₁ , and is connected to a second LAN 205 via a _second CE router 204 _2. Connected with ₂ . A communication terminal 206 such as a personal computer is also connected to the broadcast network 202. The other end of the point-to-point network 203, PE (Providor Edge) and router 207 is connected, a third LAN 205 ₃ are connected via this. The first LAN 205 ₁ is connected to the point-to-point network 203 via a _first CE router 204 ₁ as a base router that terminates IP packets on the broadcast network. Similarly, the second LAN 205 ₂ is connected to the point-to-point network 203 via the _second CE router 204 ₂ . The third LAN 205 ₃ is connected to a point-to-point network 203 via a PE router 207 as the center side of the router that terminates the IP packet.

Thus, the first LAN 205 ₁ and the third LAN 205 ₃ are connected via the point-to-point network 203. The same applies to the second LAN 205 ₂ and the third LAN 205 ₃ . Here, the first and second CE routers 204 ₁ and 204 ₂ and the PE router 207 are connected to different LANs 205 _{1 to} 205 ₃ , respectively. The IP address on the 201 side is arranged in the same subnet of IP (Internet Protocol).

FIG. 2 shows an outline of the configuration of the inter-LAN connection device of this embodiment. The inter-LAN connection device 201 includes two interfaces: a broadcast interface (I / F) 221 connected to the broadcast network 202 and a point-to-point interface 222 connected to the point-to-point network 203. The broadcast interface 221 transmits and receives data link layer frames between the first and second CE routers 204 ₁ and 204 ₂ and the communication terminal 206 shown in FIG. The point-to-point interface 222 transmits and receives IP packets to and from the PE router 207 shown in FIG. The point-to-point interface 222 itself is not assigned an IP address, and is connected to the broadcast interface 221 as a one-to-one connection.

A routing processing unit 223 that performs routing is provided between the broadcast interface 221 and the point-to-point interface 222, and is connected to the routing table 224. The routing processing unit 223 is connected to the host processing unit 229. Further, the inter-LAN connection device 201 is provided with an ARP processing unit 225 that performs ARP (Address Resolution Protocol) processing. The ARP processing unit 225 is used to obtain a data link layer address from an IP address in a TCP / IP (Transmission Control Protocol / Internet Protocol) protocol. For this reason, the ARP processing unit 225 is connected to the ARP table 226 having information on the combination of the IP address and the data link layer address, as well as the IP address information 227 of the PE router 207 shown in FIG. Alternatively, the delivery destination information 228 to the information of the combination of the IP network address and the netmask of the IP subnet to which the second CE routers 204 ₁ and 204 ₂ belong (hereinafter referred to as “the delivery destination information of the subnet to which the CE router belongs”). It has come to be referenced.

Such an inter-LAN connection device 201 includes a CPU (central processing unit) (not shown) and a storage medium storing a predetermined control program. The first to third LANs 205 _{1 to} LAN 205 shown in FIG. _It controls the routing of IP packets transferred between the _three .

  The user of the communication system shown in FIG. 1 sends the IP address information 227 of the PE router 207, the “delivery destination information to the subnet to which the CE router belongs” 228, and the IP address of the local station to the LAN connecting device 201. Are set in advance. Among these, the IP address of the local station is registered in the routing table 224 connected to the routing processing unit 223.

When there is an ARP request from _one of the first and second CE routers 204 ₁ and 204 ₂ , the ARP processing unit 225 receives the ARP request packet from the broadcast interface 221 and returns an ARP response. In this response processing, “delivery destination information to the subnet to which the CE router belongs”, IP address information of the PE router 207, routing information defined by the routing table 224, and data link layer address defined by the ARP table 226 Information is used to determine whether or not an ARP response can be made. If the ARP processing unit 225 determines that it can return an ARP response, it generates an ARP response packet and returns it to the broadcast interface 221. On the other hand, when it is determined that it is not possible to return an ARP response, the transmitted ARP request packet is discarded.

Contrary to the above, the case where the ARP processing unit 225 transmits ARP request packets in the directions of the first and second CE routers 204 ₁ and 204 ₂ and performs processing for receiving an ARP response from these ARP request packets will be described. In this case, in this embodiment, the data link layer address of the next hop IP address for delivering the IP packet transmitted from the routing processing unit 223 to the broadcast interface 221 is resolved using the same processing as that of normal ARP. I have to.

  In addition, when receiving an IP packet from the broadcast interface 221, the routing processing unit 223 checks routing information defined in the routing table 224. If the IP address as the destination of the IP packet is not the IP address of the local station, it is transmitted to the point-to-point interface 222. If the destination is the local station IP address, it is terminated by host processing.

  Further, when receiving an IP packet from the point-to-point interface 222, the routing processing unit 223 checks the routing information defined in the routing table 224. Then, the destination IP address of the IP packet is determined to be the next hop. If the IP address of the IP packet is other than the local station IP address, the IP packet is transmitted to the broadcast interface 221. When the destination IP address of the IP packet is the local station IP address, it is terminated by host processing.

In this embodiment, the first and second CE routers 204 ₁ and 204 ₂ function as a proxy ARP, that is, in response to an ARP request addressed to a predetermined host, the first and second CE routers. It is assumed that 204 ₁ and 204 ₂ have a function of returning the data link layer address of the router on behalf of the host.

Furthermore, in this embodiment, the following settings are made for each of the network systems.
(1) The user activates the proxy ARP of the first and second CE routers 204 ₁ and 204 ₂ .
(2) The user sets the IP address 192.168.0.1/24 in the _first CE router 204 ₁ .
(3) The user sets the IP address 192.168.0.3/24 in the _second CE router 2042.
(4) The user sets the IP address 192.168.0.4/24 to the communication terminal 206 shown in FIG. 1. (5) The user sets the second CE router 204 to the _first CE router 204 _1. Set the route information of the network under ₂ correctly.
(6) The user correctly sets the route information of the network under the control of the _first CE router 204 ₁ in the second CE router 204 ₂ .
(7) The user correctly sets the route information of the network under the control of the first CE router 204 ₁ and the route information of the network under the control of the second CE router 204 _{2 in} the communication terminal 206.
(8) The user sets 192.168.0.2 that is the IP address of the PE router 207 as a default route in the first and second CE routers 204 ₁ and 204 ₂ and the communication terminal 206.
(9) The user registers in advance the delivery destination information to the subnet to which the first and second CE routers 204 ₁ and 204 ₂ belong, in this LAN connecting device 201. The delivery destination information will be described later.
(10) The user registers in advance the IP address 192.168.0.2 of the PE router 207 in the LAN connecting device 201.
(11) The user previously sets 192.168.0.5/24 as the local station IP address in the LAN connecting device 201. As a result of this setting, the LAN connecting apparatus 201 sets 192.168.0.5/24 to the broadcast interface 221 and unpoints the point-to-point interface 222 to the broadcast interface 221.
(12) the user is in this LAN connecting unit 201, and route information of the first CE router 204 ₁ under the network, setting the route information of the second CE router 204 ₂ under the network correctly.

With such a series of settings by the user, the LAN connecting device 201, the PE router 207, the first and second CE routers 204 ₁ and 204 ₂ and the communication terminal 206 are 192.168.0.0/ It belongs to 24 same subnets.

  FIG. 3 shows a state in which the above settings have been made by the user.

  <First case>

Therefore, As a first case, in the state entry in the ARP table 226 of the LAN-to-LAN connecting device 201 is no, the host of the 3 IP address LAN205 ₃ of 20.0.0.1, the first of the IP address is 10.0.0.1 hosts LAN205 _1, ping (ping: Packet InterNet Groper) shall request is issued. Here, the ping request is a request for confirming whether the network is connected to the partner host.

The host with the IP address 20.0.0.1 in the third LAN 205 ₃ transmits the ping request packet to the host with the IP address 10.0.0.1 in the first LAN 205 ₁ . . The PE router 207 receives this IP packet from the host 20.0.0.0.1 in the _third LAN 2053 and transfers it to the LAN connecting device 201. The LAN connecting device 201 receives the IP packet transmitted from the PE router 207 at the point-to-point interface 222. The point-to-point interface 222 transmits this IP packet to the routing processing unit 223.

  FIG. 4 shows how the routing processing unit receives an IP packet as a ping request packet. The processing of the routing processing unit 223 is realized when the above-described CPU of the LAN connecting device 201 executes a control program stored in the above-described storage medium. When receiving the IP packet from the point-to-point interface 222 (step S301: Y), the routing processing unit 223 refers to the routing information defined in the routing table 224 (step S302). If the destination is the routing processing unit 223 itself (step S303: Y), it determines itself as the next hop and terminates at the host processing unit 229 (step S304).

  When the destination is other than the routing processing unit 223 (step S303: N), the destination IP address of the IP packet is determined as the next hop (step S305). Then, the IP packet is transmitted to the broadcast interface 221 (step S306).

  FIG. 5 shows the processing accompanying the ping request performed by the LAN connecting device after the processing shown in FIG. 4 with time. As a result of the processing shown in FIG. 4 being performed by the routing processing unit 223, ping request packets other than the ping request packet destined for the host processing unit 229 are sent to the broadcast interface 221. When receiving this IP packet, the broadcast interface 221 issues a request to the ARP processing unit 225 to resolve the data link layer address of the next hop (step S321).

  The ARP processing unit 225 resolves the data link layer address of the next hop using the same processing procedure as the normal ARP protocol (step S322). At this time, the ARP processing unit 225 sets the IP address of the next hop as the target protocol address (target protocol address) constituting the ARP request packet. Therefore, in this example, the destination IP address of the IP packet is set. Further, the ARP processing unit 225 sets the IP address of the PE router 207 instead of the local station IP address in the sender protocol address of the ARP request packet, and broadcast interface to the sender hardware address. A data link layer address 221 is set.

The ARP request packet issued by the ARP processing unit 225 is transmitted from the broadcast interface 221 to the broadcast network 202 to which the first and second CE routers 204 ₁ and 204 ₂ are connected (step S323).

Incidentally, the first CE router 204 ₁ has a route to the target protocol address of the sent ARP request packet, and the proxy ARP is set to be valid. Accordingly, the ARP request packet sent to realize the ping request for the host having the IP address 10.0.0.1 in the first LAN 205 ₁ is processed at the stage of the _first CE router 204 _1. Then, the ARP response packet is sent back to the inter-LAN connection apparatus 201 as a proxy for the original destination. Broadcast Interface 221 receives the ARP response packet sent from the CE router 204 ₁ of the first, and transmits to the ARP processing unit 225 (step S324).

  The ARP processing unit 225 analyzes the received ARP response packet, and stores information on a set of the next hop IP address and the data link layer address in the ARP table 226 (step S325).

Meanwhile, the broadcast interface 221, the data link layer address for the destination IP address of the IP packet is Nekisuto hop can be resolved as a first data link layer address of the CE router 204 _1, data link header in the IP packet to be transferred Is sent to the first CE router 204 ₁ (step S326). When receiving the IP packet from the LAN connecting device 201, the first CE router 204 ₁ transmits the IP packet to the host having the IP address in the first LAN 205 ₁ of 10.0.0.1. .

Such IP address of the first LAN205 ₁ in the the host of 10.0.0.1 receives a ping request. Then, it generates a ping response packet, IP address, the third LAN205 ₃ is to be transmitted to the host of 20.0.0.1.

When the first CE router 204 ₁ receives an IP packet from the host with the IP address 10.0.0.1 in the first LAN 205 ₁ , the first CE router 204 ₁ sends the IP packet to the PE router 207 set as the default route. Send. When the first CE router 204 ₁ receives the ARP request packet sent in step S323 of FIG. 5, the data link layer address corresponding to the IP address of the PE router 207 is used as the data link layer address of the LAN connecting device 201. It has been solved. Therefore, the first CE router 204 ₁ transmits an IP packet to the LAN connecting device 201.

FIG. 6 shows how the LAN connecting device controls the ping response packet sent from the first CE router. The inter-LAN connection apparatus 201 receives a ping response packet that is an IP packet sent from the host having the IP address 10.0.0.1 in the first LAN 205 ₁ via the first CE router 204 _1. It is received by the broadcast interface 221 and transmitted to the routing processing unit 223 (step S341). The routing processing unit 223 receives this IP packet (step S342), and determines whether or not the destination is its own IP address (step S343). As a result, if it is an IP packet addressed to itself (Y), it is terminated at the host processing unit 229 (step S344).

If it is not an IP packet addressed to itself (step S343: N), this IP packet is transmitted to the point-to-point interface 222 (step S345). The point-to-point interface 222 transmits the received IP packet to the PE router 207 (step S346). The PE router 207 transmits the received IP packet to the host having the IP address 20.0.0.1 in the _third LAN 2053. The host processes the ping response packet.

As described above, the host IP address of the third LAN205 ₃ is 20.0.0.1, the IP address of the first LAN205 within ₁ to communicate with hosts 10.0.0.1 It turns out that it is possible.

Then, IP address, from a host of the 3 IP address LAN205 ₃ of 20.0.0.1 second LAN205 within ₂ issues a ping request to the host 172.16.0.1 The case will be described. Also in this case, the second CE router 204 ₂ knows the route to the IP address 172.16.0.1 and has a proxy ARP as in the case of the first CE router 204 ₁ described above. The second CE router 204 ₂ will return an ARP response. As a result, LAN connecting unit 201 of the present embodiment can transmit an IP packet to the second CE router 204 _2, IP address of the third LAN205 ₃ is 20.0.0.1 host host and IP address of the second LAN205 within ₂ 172.16.0.1 is enabled to communicate.

Next, from the host having the IP address 200.0.0.1 in the _third LAN 2053 to the terminal having the IP address 192.168.0.4 arranged in the same subnet as the first CE router 204 _1. A case where a ping request is issued will be described. In this case, the difference is that the terminal having the IP address of 192.168.0.4 returns an ARP response directly in the above description. As a result, LAN connecting unit 201 of this embodiment can be an IP address to send an IP packet to the terminal of 192.168.0.4, the IP address of the third LAN205 within ₃ 20.0.0 .1 and a terminal having an IP address of 192.168.0.4 can communicate with each other.

  <Second case>

As a second case, in the state where there is no entry in the ARP table 226 of the inter-LAN connection device 201, a host with the IP address in the first LAN 205 ₁ of 10.0.0.1 is sent to the third LAN 205 _3. A case where a ping request is issued to a host whose IP address is 20.0.0.1 will be described. The difference between the first case, there issuing packet performing ping request to the broadcast interface 221 side, the first CE router 204 ₁ issues an ARP request packet in order to resolve the IP address of the PE router 207 The LAN connection device 201 terminates this. This will be described in detail.

First, the host having the IP address 10.0.0.1 in the first LAN 205 ₁ transmits a ping request packet to the host having the IP address 200.0.0.1 in the _third LAN 205 ₃ . .

The first CE router 204 ₁ receives the ping request packet from the host with the IP address 10.0.0.1 in the first LAN 205 ₁ and forwards this packet to the PE router 207 set as the default route. try to. At this time, the first CE router 204 ₁ transmits an ARP request packet to the subnet to which the _first CE router 204 ₁ belongs in order to resolve the data link layer address of the PE router 207 using the ARP protocol.

FIG. 7 shows processing until the LAN connecting apparatus receives an ARP request packet from the first CE router and transmits an ARP response packet in the second case. Broadcast Interface 221 receives the ARP request packet from the first CE router 204 ₁ transmits the ARP processing unit 225 (step S361). The ARP processing unit 225 includes IP address information about the PE router 207 included in the ARP processing unit 225, data link layer address information defined by the ARP table 226 included in the ARP processing unit 225, and “delivery destination information to the subnet to which the CE router belongs”. From the routing information defined in the routing table 224 of the routing processing unit 223, whether or not an ARP response is possible is determined according to a predetermined algorithm. This will be specifically described.

  The ARP processing unit 225 receives the ARP request packet (step S362), and determines whether or not the target protocol address (target protocol address) is its own IP address (step S363). If it is the own IP address (Y), an ARP response packet is generated and transmitted to the broadcast interface 221 (step S364).

If the target protocol address is not its own IP address (step S363: N), it is checked whether this target protocol address is the same as the IP address of the PE router 207, 192.168.0.2 (step S365). ). If so (Y), the process proceeds to step S364. Otherwise (step S365: N), it is checked whether the target protocol address belongs to the subnet to which the first and second CE routers 204 ₁ and 204 ₂ belong (step S366). If they belong to the same subnet (Y), the ARP request packet is discarded (step S367).

When it is determined that it does not belong to the subnet to which the first and second CE routers 204 ₁ and 204 ₂ belong (step S366: N), it is checked whether the target protocol address is included in the ARP table 226 ( Step S368). When the target protocol address is included in the ARP table 226 (Y), that is, when the data link layer address corresponding to the target protocol address exists in the ARP table 226, the host having the target protocol address is assigned to the CE routers 204 ₁ and 204 _2. That belongs to the subnet on the other side, or belongs to a subnet beyond the CE router. For this reason, in this case, the IP packet should not be transferred to the PE router 207. In step S367, the ARP request packet is discarded and no ARP response is made.

If it is determined in step S368 that the target protocol address is not included in the ARP table 226 (N), it is determined whether or not the target protocol address is included in the routing table 224 (step S369). If it is included in the routing table 224 (Y), it is determined whether the target protocol address is on the first or second CE router 204 ₁ , 204 ₂ side (step S 370). If a route to the target protocol address exists in the routing table 224 and the route is in the same direction as the first or second CE router 204 ₁ , 204 ₂ , the IP packet should be transferred to the PE router 207. Not. In this case (Y), the process proceeds to step S367, where the ARP request packet is discarded and no ARP response is made.

When it is determined in step S369 that the target protocol address is not included in the routing table 224 (N), and in step S370, it is determined that the target protocol address is not on the first or second CE router 204 ₁ , 204 ₂ side. If (N), the process proceeds to step S364, where an ARP response packet is generated and transmitted to the broadcast interface 221.

  In the above processing, the ARP processing unit 225 sets the IP address of the PE router 207 instead of setting the IP address of the local station in the sender protocol address of the ARP response packet, and sends the sender hardware. The data link layer address of the broadcast interface 221 is set in the address (sender hardware address).

Broadcast Interface 221, upon receiving an ARP response packet been sent, in step S364, it transmits the first to the CE router 204 ₁ (step S371), ARP from the reception of the ARP request packet LAN connecting unit 201 A series of processing up to the transmission of the response packet is terminated (end).

In this way, the first CE router 204 ₁ receives the ARP response packet. Since the first CE router 204 ₁ was able to resolve the data link layer address of the PE router 207 as the data link layer address of the broadcast interface 221 of the LAN connection device 201, the first CE router 204 ₁ sends an IP packet to the LAN connection device 201. Will do.

  In the inter-LAN connection apparatus 201, the broadcast interface 221 receives this IP packet and transmits it to the routing processing unit 223 in accordance with the algorithm described in FIG. 6 (step S341). The routing processing unit 223 refers to the routing information defined in the routing table 224, and transmits the packet to the point-to-point interface 222 (step S345) if it is not an IP packet addressed to itself (step S343). If it is an IP packet addressed to itself, it is terminated by host processing (step S344). The point-to-point interface 222 transmits the received IP packet to the PE router 207 (step S346).

PE router 207, IP address, the third LAN205 ₃ transmits the IP packet to host 20.0.0.1. Host IP address of the third LAN205 ₃ is 20.0.0.1 processes the ping request packet, generates a ping response packet, and transmits the PE router 207.

  The LAN connecting device 201 receives the IP packet transmitted from the PE router 207 according to the algorithm described in FIG. 4 from the point-to-point interface 222, and the point-to-point interface 222 transmits this to the routing processing unit 223. . The routing processing unit 223 refers to the routing information defined in the routing table 224 (step S302). As a result, if it is not an IP packet addressed to itself (step S303: N), the routing processing unit 223 determines the next hop according to the algorithm described in FIG. It is determined (step S305) and transmitted to the broadcast interface 221 (step S306). If it is an IP packet addressed to itself, it terminates at the host processing unit 229 (step S304).

  The broadcast interface 221 receives an IP packet from the routing processing unit 223 according to the algorithm described in FIG. 5, and then issues a request to the ARP processing unit 225 to resolve the link layer address of the next hop (step S321). The ARP processing unit 225 resolves the data link layer address of the next hop using the same procedure as in the normal ARP protocol (step S322). At this time, since the next hop IP address is set as the target protocol address of the ARP request packet, the destination IP address of the IP packet is set in this case. In addition, the IP address of the PE router 207 is set in the sender protocol address of the ARP request packet instead of the IP address of the local station, and the data link layer address of the broadcast interface 221 of the LAN connecting device 201 is set in the sender hardware address. The points are the same as in FIG.

The ARP request packet issued by the ARP processing unit 225 is transmitted from the broadcast interface 221 to the broadcast network 202 to which the first and second CE routers 204 ₁ and 204 ₂ are connected (step S323).

The first CE router 204 ₁ has a route to the target protocol address of the ARP request packet, and has a proxy ARP function. For this reason, in response to this ARP request packet, an ARP response packet is generated and transmitted to the LAN connecting device 201.

The LAN connecting device 201 receives the ARP response packet from the _first CE router 2041 from the broadcast interface 221 and transmits it to the ARP processing unit 225. The ARP processing unit 225 analyzes the ARP response packet and stores the next hop IP address and its data link layer address in the ARP table 226. Broadcast Interface 221, since not solve the data link layer address of Nekisuto hop as the first data link layer address of the CE router 204 _1, imparts a data link header in the IP packet to be transferred. Then, this IP packet is transmitted to the _first CE router 204 ₁ .

The first CE router 204 ₁ receives the IP packet from the LAN connecting device 201 and further transmits the packet to the host having the IP address 10.0.0.1 in the first LAN 205 ₁ . The host with the IP address 10.0.0.1 in the first LAN 205 ₁ receives and processes the ping response packet.

The above description, the host IP address of the first LAN205 ₁ is 10.0.0.1, the IP address of the third LAN205 ₃ can communicate with the host 20.0.0.1 It is shown again.

When a ping request is issued from a host whose IP address in the second LAN 205 ₂ is 172.16.0.1 to a host whose IP address in the third LAN 205 ₃ is 20.0.0.1, The first CE router 204 _{1 described} as “has a route to the target protocol address of the ARP request packet and has a function of proxy ARP” is described as “the second CE router 204 ₂ has the function of proxy ARP”. It is sufficient to replace the content with “We know the route to IP address 172.16.0.1 and have proxy ARP”. Therefore, in this case, the second CE router 204 ₂ returns an ARP response, but the processing is different. As a result, LAN connecting unit 201 of this embodiment can transmit the IP packet to the second CE router 204 _2. Thus, IP address, the second LAN205 the ₂ and the host 172.16.0.1 host IP address of the third LAN205 ₃ is 20.0.0.1 allowing communication.

The 3 IP address LAN205 ₃ from the communication terminal 206 of the first CE router 204 ₁ and arranged IP address on the same subnet 192.168.0.4 Whereas host 20.0.0.1 When the ping request is issued, the communication terminal 206 having the IP address of 192.168.0.4 returns the ARP response packet directly in the process of returning the ARP response. As a result, LAN connecting unit 201 may be an IP address to send an IP packet to the communication terminal 206 of 192.168.0.4, the IP address of the third LAN205 ₃ is 20.0.0. 1 and the communication terminal 206 having an IP address of 192.168.0.4 can communicate with each other.

  <Third case>

The operation when a ping request is issued from a host having an IP address of 10.0.0.1 in the first LAN 205 ₁ to a host having an IP address of 172.16.0.1 in the second LAN 205 ₂ is as follows. Explained. In this case, unlike the first and second cases, local communication between hosts or routers belonging to the same subnet as the broadcast interface 221 occurs, not communication between hosts across the LAN connecting device 201. doing.

First, a host having an IP address of 10.0.0.1 in the first LAN 205 ₁ transmits a ping request packet to a host having an IP address of 172.16.0.1 in the second LAN 205 ₂ . . The first CE router 204 ₁ receives this ping request packet from the host having the IP address 10.0.0.1 in the first LAN 205 ₁ , and follows the next hop in accordance with the routing information of the _first CE router 204 _1. An IP packet is to be transmitted to the second CE router 204 ₂ . At this time, in order to resolve the data link layer address for the IP address of the second CE router 204 ₂ using the ARP protocol, the first CE router 204 ₁ generates an ARP request packet and generates the first CE router 204 ₁ . Transmit to the subnet to which the router 204 ₁ belongs.

The broadcast interface 221 in the LAN connecting device 201 receives the ARP request packet from the _first CE router 2041, and transmits it to the ARP processing unit 225. The ARP processing unit 225 includes IP address information of the PE router 207, data link layer address information defined by the ARP table 226 of the ARP processing unit 225, “delivery destination information to the subnet to which the CE router belongs”, routing Whether or not an ARP response is possible is determined according to the algorithm described with reference to the routing information defined in the routing table 224 of the processing unit 223 according to the algorithm described with reference to FIG.

Accordingly, only the second CE router 204 ₂ responds to the ARP request packet transmitted to the subnet to which the first CE router 204 ₁ belongs. Since the first CE router 204 ₁ was able to resolve the data link layer address for the IP address of the second CE router 204 ₂ that is the next hop, a data link header is added to the IP packet to provide the second CE router 204 _2. Send to.

The second CE router 204 ₂ receives the IP packet and transmits it to the host whose IP address in the second LAN 205 ₂ is 172.16.0.1. The host with the IP address 172.16.0.1 in the second LAN 205 ₂ receives the ping request packet, generates a ping response packet, and the IP address in the first LAN 205 ₁ is 10.0. Send to 0.1 host.

The second CE router 204 ₂ receives an IP packet from the host having the IP address 172.16.0.1 in the second LAN 205 ₂ and transmits it to the first CE router 204 ₁ . The first CE router 204 ₁ receives the IP packet from the first CE router 204 ₁ and transmits it to the host having the IP address in the first LAN 205 ₁ of 10.0.0.1. The host with the IP address 10.0.0.1 in the first LAN 205 ₁ receives and processes the ping response packet.

In the above description, the host of the first 205 ₁ within LAN, can communicate with the host in the second LAN205 _2, unnecessary packets are understood not be transferred to the PE router 207.

The IP address in the first LAN 205 ₁ is set to 10.0.0 from the communication terminal 206 having the IP address 192.168.0.4 arranged in the same subnet as the first and second CE routers 204 ₁ and 204 _2. when issuing a ping request to .1 host, and the host of the first 205 ₁ within LAN, creating compared with processing with the host of the second LAN205 within _2, LAN connecting device 201 an ARP reply that the first CE router 204 ₁ not return returns an ARP response directly is different. That is, also in this case, the communication terminal 206 arranged in the same subnet as the first and second CE routers 204 ₁ and 204 ₂ and the IP address in the first LAN 205 ₁ are 10.0.0.1. It can be seen that communication with the host is possible and unnecessary packets are not transferred to the PE router 207.

  <Fourth case>

Next, consider a fourth case that does not occur much. In the fourth case, further fourth IP address LAN205 ₄ of not shown preceding the IP address of the first LAN205 ₁ from host 10.0.0.1 second LAN is 172.16. This is a case where a ping request is issued to the 10.1 host. In the case of this example, it is assumed that the user has correctly set the route to the _fourth LAN 2054 in advance in the inter-LAN connection device 201. However, the first CE router 204 ₁ shall route information of the fourth LAN is not set correctly. A case where the first CE router 204 ₁ tries to transmit a ping request packet to the PE router 207 which is the default route of the first CE router 204 ₁ in such a situation will be described.

In the fourth case, the host of the IP address of the first LAN205 within ₁ 10.0.0.1 is, IP addresses in the fourth LAN is ping the host of 172.16.10.1 Send a request packet. The first CE router 204 ₁ receives an IP packet from a host having an IP address of 10.0.0.1 in the first LAN 205 ₁ and is a default route according to the routing information of the _first CE router 204 _1. An attempt is made to send an IP packet to the PE router 207. At this time, the first CE router 204 ₁ generates an ARP request packet in order to resolve the data link layer address for the IP address of the PE router 207 using the ARP protocol, and the first CE router 204 ₁ Send to the subnet to which it belongs.

The broadcast interface 221 receives the ARP request packet from the first CE router 204 ₁ and transmits it to the ARP processing unit 225. The ARP processing unit 225 in the LAN-to-LAN connection device 201 includes the IP address information of the PE router 207, the data link layer address information defined by the ARP table 226 of the ARP processing unit 225, and “to the subnet to which the CE router belongs. Based on the “delivery destination information” and the routing information defined by the routing table 224 of the routing processing unit 223, whether or not an ARP response is possible is determined according to the algorithm shown in FIG. As a result, since the route information to the fourth LAN is preset in the LAN connecting device 201, the LAN connecting device 201 does not return an ARP response.

Since the first CE router 204 ₁ does not receive the ARP response packet, it cannot transmit the IP packet. Therefore, the first CE router 204 ₁ transmits an ICMP (Internet Control Message Protocol) error packet that cannot be delivered to the host having the IP address 10.0.0.1 in the first LAN 205 ₁ . . Here, ICMP is a protocol for controlling a protocol error in IPv4 (Internet Protocol version 4). Therefore, the host of the ping request for an IP address of the first LAN205 ₁ is 10.0.0.1 will fail.

The above description, even if there is insufficient in the first CE router 204 ₁ of route information, if properly route set to the LAN connecting unit 201, unwanted IP packets to a network under the PE router 207 It indicates that it will not be transferred.

  <Fifth case>

Next, as a fifth case, the case where the IP address of the first LAN205 ₁ by the host processing of the LAN-to-LAN connecting device 201 issues a ping request to the host of 10.0.0.1. The host processing LAN connecting apparatus 201, IP address of the first LAN205 ₁ is to sent the ping request packet to the host 10.0.0.1. Routing processing unit 223 knows the IP address of the host in the first LAN205 within ₁ 10.0.0.1 is the broadcast interface 221 side. Therefore, according to the algorithm shown in FIG. 4, the destination IP address of the IP packet is determined as the next hop, and the IP packet is transmitted to the broadcast interface 221. A transmission packet from the host processing unit 229 to the broadcast interface 221 is the same as that received from the point-to-point interface 222.

  After receiving the IP packet from the routing processing unit 223, the broadcast interface 221 issues a request to the ARP processing unit 225 to resolve the data link layer address of the next hop. The ARP processing unit 225 resolves the data link layer address of the next hop using the same procedure as the normal ARP protocol. At this time, the ARP processing unit 225 sets the IP address of the next hop as the target protocol address of the ARP request packet. In this case, the destination IP address of the IP packet is set. Further, the ARP processing unit 225 sets the IP address of the local station as the sender protocol address of the ARP request packet, and sets the data link layer address of the broadcast interface 221 as the sender hardware address.

The ARP request packet issued by the ARP processing unit 225 is transmitted from the broadcast interface 221 to the network to which the first and second CE routers 204 ₁ and 204 ₂ are connected. The first CE router 204 ₁ has a route to the target protocol address of the ARP request packet, and has a proxy ARP function. Therefore, this ARP request packet is processed, and an ARP response packet is transmitted to the LAN connecting device 201. The broadcast interface 221 receives the ARP response packet from the _first CE router 2041, and further transmits it to the ARP processing unit 225.

The ARP processing unit 225 analyzes the ARP response packet and stores in the ARP table 226 information on a set of the next hop IP address and the data link layer address. Broadcast Interface 221, the data link layer address for the destination IP address of the IP packet is Nekisuto hop can be resolved as a first data link layer address of the CE router 204 _1, applying a data link header in the IP packet to be transferred Then, the IP packet is transmitted to the first CE router 204 ₁ . The first CE router 204 ₁ receives the packet from the LAN connecting device 201 and further transmits the IP packet to the host whose IP address of the first LAN is 10.0.0.1.

The host with the IP address 10.0.0.1 in the first LAN 205 ₁ receives the ping request packet, generates a ping response packet, and the IP address 192.168.0.5 of the LAN connecting device 201. Send to. The first CE router 204 ₁ receives an IP packet from the host having the IP address 10.0.0.1 in the first LAN 205 ₁ and transmits the packet to the LAN connecting device 201. At this time, since the first CE router 204 ₁ has already stored the sender protocol address and the sender hardware address when receiving the ARP request packet, the data link layer address corresponding to the IP address of the LAN connecting device 201 Has been resolved. Therefore, the first CE router 204 ₁ transmits an IP packet to the LAN connecting device 201.

  The LAN connecting device 201 receives the IP packet from the broadcast interface 221 and transmits it to the routing processing unit 223. The routing processing unit 223 recognizes that the IP packet is addressed to itself and terminates at the host processing unit 229.

From the above description, it can be seen that communication between the LAN connecting device 201 and 10.0.0.1 in the first LAN is possible. The communication between the LAN connecting device 201 and the host having the IP address in the second LAN 205 ₂ of 172.16.0.1, or the IP address in the LAN connecting device 201 and the third LAN 205 ₃ is 20.0. Communication with a host of 0.1, or communication between a LAN connection device 201 and a host with an IP address of 172.168.0.1 in the fourth LAN is also possible.

  <Sixth case>

Finally, as a sixth case, a case where an IP address is not explicitly assigned to the LAN connecting device 201 will be described. For example, it is assumed that a provider and a user who provide IP-VPN make a contract with an available subnet as 192.168.0.0/30. In this case, there are only two host addresses that can be assigned, 192.168.0.1 and 192.168.0.2, and the first and second CE routers 204 ₁ and 204 ₂ and the PE router, respectively. Set to 207. Therefore, there is no IP address that can be assigned to the LAN connecting device 201. In such a case, the LAN connecting device 201 automatically sets 127.0.0.1/32 which is a loopback address as a virtual address as the IP address of the broadcast interface 221 for itself.

A series of procedures are completely the same as the first to fourth cases described above. Since the IP address of the LAN connecting device 201 is 127.0.0.1/32 and the host process does not operate, the fifth case is not applied. In this case, ARP processing unit 225, ARP response packet to be transmitted to the ARP request packet or the first or second CE router 204 _1, 204 ₂ to be transmitted to the first or second CE router 204 _1, 204 ₂ The IP address of the PE router 207 specified in advance is used instead of the IP address 127.0.0.1, which is internally set in the broadcast interface 221 as the sender protocol address, and broadcast to the sender hardware address. The data link layer address of the interface 221 is used.

  The advantage of setting 127.0.0.1/32 as the IP address of the inter-LAN connection device 201 is that security is also taken into consideration. There are infinitely few hosts and routers that send packets to the loopback address. Furthermore, even if there is a host or router that can send packets to the LAN connection device 201 having a loopback address, the subnet mask is “32”, so that the host function of the LAN connection device 201 does not operate at all. No response is returned. For this reason, it is also considered in terms of security.

<< Variation of Invention >>

In the embodiment described above, the first and second CE routers 204 ₁ and 204 ₂ shown in FIG. 1 have been described as having the proxy ARP function. However, even in other cases, a plurality of CE routers can be connected to the PE router via a point-to-point network. For example, when the routing processing unit 223 transmits a packet from the point-to-point interface 222 to the broadcast interface 221, when all the routes of the network can be registered in the routing table 224 of the inter-LAN connection device 201, all the routes A similar effect can be obtained by examining the information in the routing table 224 in which is registered.

  FIG. 8 corresponds to FIG. 4 of the previous embodiment, and shows a process of the routing processing unit that receives an IP packet as a ping request packet as a modification. The same steps as those in FIG. 4 are denoted by the same step numbers. When the destination is not the routing processing unit 223 itself (step S303: N), it is checked whether or not the route of the received IP packet exists on the broadcast interface 221 side (step S401). If it does not exist (N), the process proceeds to step S305 as in the case of FIG. 4, and the destination IP address of the IP packet is determined as the next hop, and the IP packet is transmitted to the broadcast interface 221 (step S306).

  When the route of the received IP packet exists on the broadcast interface 221 side (step S401: Y), the next hop indicated by the routing table 224 is acquired (step S402). Based on this, the IP packet is transmitted to the broadcast interface 221 in step S306.

That is, usually, the user sets the route to the network to the first LAN 205 ₁ and the second LAN 205 ₂ on the broadcast interface 221 side in the routing table 224 of the LAN connecting device 201, and the first and second CE routers 204. register _1, 204 ₂ as Nekisuto hop. Therefore, if the route of the destination address of the IP packet is in the routing table 224, the next hop is the IP address of the first or second CE router 204 ₁ , 204 ₂ . This indicates that the ARP request packet from the LAN connecting device 201 is issued to resolve the IP addresses of the first and second CE routers 204 ₁ and 204 ₂ . In the case of this example, the first and second CE routers 204 ₁ and 204 ₂ do not need the proxy ARP function and need only have a general ARP function.

If the process shown in FIG. 8 is performed, the data link layer address is resolved by the ARP protocol for each destination IP address of the IP packet to be transferred. For this reason, it is possible to compensate for the disadvantage that the entry of the ARP table 226 is consumed for each destination IP address of the IP packet to be transferred. That is, by performing the process shown in FIG. 8 of this modification, only one entry in the ARP table 226 is consumed by the first and second CE routers 204 ₁ and 204 ₂ .

However, in this modification, all the routes of the network are registered in the routing table 224 of the LAN connecting device 201. Therefore, when such registration cannot be performed, the IP address of the IP packet that cannot be searched by the routing processing unit 223 is determined as the next hop and transmitted to the broadcast interface 221. Become. In order to prevent the occurrence of such a situation, the first and second CE routers 204 ₁ and 204 ₂ need to have a proxy ARP function. For destination IP addresses that are not registered in the routing table 224, An entry in the ARP table 226 is consumed for each destination IP.

  By the way, when a plurality of CE routers do not have a proxy ARP function, the plurality of CE routers cannot be automatically connected. However, if the user pre-sets information on a set of all destination IP addresses and corresponding data link layer addresses in the ARP table 226 of the LAN connecting device 201, a plurality of CE routers can be connected manually. Is possible. In this case, unnecessary packets are not transmitted to the PE router even in local communication between hosts or routers arranged in the subnet to which the CE router belongs.

  If a plurality of CE routers do not have proxy ARP, these CE routers cannot be automatically connected. However, instead of “delivery destination information to the subnet to which the CE router belongs”, information on the combination of the IP address and netmask of only one CE router (hereinafter referred to as “delivery information to the CE router”) When the user sets the inter-connection device 201 in advance, it is possible to automatically connect only one CE router.

  FIG. 9 corresponds to FIG. 2 and shows an outline of the configuration of the inter-LAN connection device according to this modification. 9, the same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The inter-LAN connection device 201A of this modification differs from the inter-LAN connection device 201 of the embodiment shown in FIG. 2 in that the routing processing unit 223A refers to the “delivery information to CE router” 411 and the ARP table 226. To do.

  FIG. 10 shows an IP packet reception process in a routing processing unit in which the algorithm shown in FIG. 4 is modified in this modification of the present invention. In FIG. 10, the same parts as those in FIG. 4 are denoted by the same step numbers, and description thereof will be omitted as appropriate. In the case of the modification, if it is determined in step S303 that the destination of the IP packet is not the routing processing unit 223A itself (N), it is determined whether or not the IP address of the destination is included in the ARP table 226. (Step S421). If it is included (Y), it means that the data link layer address of the next hop to which the IP packet is to be transmitted has already been resolved. Accordingly, the destination IP address of the IP packet to be transferred is determined as the next hop (step S422), and the IP packet is transmitted to the broadcast interface 221 (step S306). As a result, the next hop IP address is not resolved by the ARP protocol in the ARP processing unit 225, and the broadcast interface 221 transmits the IP packet directly to a device having a data link layer address corresponding to the next hop IP address. Can do. If the device having the data link layer address for the next hop IP address is a host, the IP packet is terminated at that host. If the device having the data link layer address for the next hop IP address is a CE router, the CE router delivers the received IP packet to the subordinate network.

  If it is determined in step S421 that the destination IP address is not included in the ARP table 226 (N), it means that the next hop to which the IP packet is to be transmitted has not been determined. Therefore, the IP address of the CE router included in the “delivery information to the CE router” is determined as the next hop (step S423). Then, this IP packet is transmitted to the broadcast interface 221. The data link layer address corresponding to the IP address of the CE router is resolved by the ARP processing unit 225 using the ARP protocol, and the broadcast interface 221 transmits the IP packet to the CE router. The CE router delivers the received IP packet to the network under the router.

  In the LAN connecting device and the LAN connecting method according to the embodiment and the modification described above, all types of data links can be used if the network between the PE router 207 and the LAN connecting devices 201 and 201A is a point-to-point link. The present invention is applicable to. For example, the present invention is applied to a protocol for mapping an IP packet on a point-to-point data link layer, such as IP over ATM by ATM (Asynchronous Transfer Mode), IP over FR by frame relay (FR), etc. can do.

1 is a system configuration diagram of a communication system using an inter-LAN connection device according to a first embodiment of the present invention. It is explanatory drawing which showed the outline | summary of the structure of the connection apparatus between LAN in a 1st Example. It is explanatory drawing which showed the example of a setting of each part of the connection apparatus between LAN in a 1st Example. It is a flowchart showing the reception process of the IP packet in a routing process part in a present Example. FIG. 5 is a flowchart illustrating a process associated with a ping request performed by an inter-LAN connection device after the process illustrated in FIG. 4 in the present embodiment. It is a flowchart showing the mode of control of the connection apparatus between LAN with respect to the ping response packet sent from the 1st CE router in a present Example. It is the flowchart which showed the process until the LAN connection apparatus receives an ARP request packet from the first CE router and transmits an ARP response packet in this embodiment. It is a flowchart showing the reception process of the IP packet in the routing process part in the modification of this invention. It is explanatory drawing which shows the outline | summary of the connection apparatus between LAN by the modification of this invention. It is a flowchart showing the reception process of the IP packet in the routing process part in the modification of this invention.

Explanation of symbols

201 Inter-LAN connection device 202 Broadcast network 203 Point-to-point network 204 ₁ First CE router (second router)
204 ₂ Second CE router (second router)
205 ₁ First LAN
205 ₂ Second LAN
205 ₃ Third LAN
206 Communication terminal 207 PE router (first router)
221 Broadcast interface 222 Point-to-point interface 223 Routing processor 224 Routing table 225 ARP processor 226 ARP table 227 IP address information 228 Delivery destination information

Claims (9)

A point-to-point interface for connecting via a point-to-point network with a first router that terminates and routes an IP packet as a packet that is connected to a predetermined local network and communicates using the Internet protocol;
An ARP request has arrived from an external network, each of which is connected to an independent local network different from the predetermined local network, routes an IP packet, and requests a response of a data link layer address corresponding to the IP address of a subordinate host. Packets are communicated between a plurality of communication devices composed of at least two second routers or one second router and a predetermined communication terminal as routers having an ARP response means that sometimes returns an ARP response. An interface between communication devices for connecting to a network between communication devices as a network to be connected;
IP address information storage means for storing IP address information of the first router;
Delivery destination information storage means for storing information on a set of a network address and a netmask of an IP subnet to which each of the second routers belongs as delivery destination information;
When an IP packet designating the IP address of the communication partner is sent from a host in the local network connected to the first router, the sender protocol address is set to the first protocol address when the packet is not addressed to itself. ARP request sending means for setting the target protocol address as the IP address of the communication partner designated by the host as the IP address of the router and sending the ARP request in which the data link layer address of the interface between the communication devices is incorporated in the sender hardware address When,
In response to the ARP request sent by the ARP request sending means, when there is an ARP response in which the data link layer address of the second router is incorporated in the target hardware address from the second router, the second A data link header is added to the IP packet designating the IP address of the communication partner on the basis of the information of the pair of the next hop IP address indicating the router 2 and the data link layer address thereof, and is directed to the network between the communication devices. First sending means for sending
When an IP packet sent from the host of the IP address of the communication partner under the second router is sent based on the data link layer address received by the second router, this is pointed to the point-to-point. A LAN-to-LAN connection device, comprising: a second sending means for sending the data from a point interface toward the first router. A point-to-point interface for connecting via a point-to-point network with a first router that terminates and routes an IP packet as a packet that is connected to a predetermined local network and communicates using the Internet protocol;
Between a plurality of communication devices including at least two or more second routers or one second router and a predetermined terminal that are connected to an independent local network different from the predetermined local network and route IP packets. An interface between communication devices for connecting to a network between communication devices that communicate IP packets in
IP address information storage means for storing IP address information of the first router;
Delivery destination information storage means for storing information on a set of a network address and a netmask of an IP subnet to which each of the second routers belongs as delivery destination information;
An IP packet designating the IP address of the communication partner is sent from the host in the local network connected to the second router to the second router, and the IP address of the communication partner is the IP address on the network side between the communication devices. An ARP request receiving means for receiving an ARP request having the IP address of the first router as a target protocol address because it is not an address, based on an IP packet from the second router;
When the ARP request is received by the ARP request receiving means, when it is not determined that the target protocol address in the ARP request sent from the second router is its own IP address, the target hardware address is set. When generating an ARP response packet in which the data link layer address of the network between communication devices is set, or when it is determined that the target protocol address in the ARP request sent from the second router is its own IP address, ARP response packet sending means for generating an ARP response packet in which the data link layer address of the network between communication devices is set as a target hardware address and sending it to the network between communication devices from the interface between communication devices LAN connecting unit, characterized in that. ARP request receiving means for receiving an ARP request from the second router when it is sent;
ARP response availability determining means for determining whether or not an ARP response can be made to the ARP request based on the target protocol address of the ARP request received by the ARP request receiving means;
2. The inter-LAN connection according to claim 1, further comprising: an ARP response rejection unit that discards the ARP request and does not return an ARP response when the ARP response availability determination unit determines that the ARP response should not be performed. apparatus.   Remote route information storage means for storing route information of another network via a local network connected to the second router, and the ARP response availability determination means uses the remote route information storage means as a search target. The inter-LAN connection device according to claim 3, wherein:   3. The inter-LAN connection device according to claim 1, wherein a loopback address is set as an IP address for itself.   2. The inter-LAN connection device according to claim 1, wherein the second router performs the ARP response to the ARP request on behalf of a host in the local network connected thereto. An IP packet in which an IP address of a communication partner is specified from a host in a local network connected to a first router that terminates and routes an IP packet that is connected to a predetermined local network and performs communication using the Internet protocol. Destination determination step for determining whether or not this is a packet destined for itself,
When it is determined in this destination determination step that the packet is not addressed to itself, the sender protocol address is set to the IP address of the first router and the target protocol address is set to the IP address of the communication partner designated by the host. Is connected to an independent local network different from the predetermined local network and routes an IP packet, and an ARP request for requesting a reply of a data link layer address corresponding to the IP address of a subordinate host arrives from an external network Packets between two or more second routers as routers having proxy ARP response means for returning an ARP response as a proxy, or a plurality of communication devices comprising at least one second router and a predetermined communication terminal Network to communicate And ARP request sending step of sending an ARP request incorporating data link layer address as the sender target address of the communication device between the interface for connecting to a communication device between networks as,
In response to the ARP request sent in this ARP request sending step, when there is a proxy ARP response in which the data link layer address of the second router is incorporated into the target hardware address from the two or more second routers. The IP address of the communication partner from the host in the local network connected to the first router based on the information of the set of the next hop IP address indicating the second router and the data link layer address determined by A first sending step of attaching a data link header to the IP packet designating the packet and sending it to the network between the communication devices;
When an IP packet is sent based on the data link layer address received by the second router from a host of the IP address of the communication partner under the second router, this is sent from the point-to-point interface. A second sending step for sending to the first router;
An IP packet in which an IP address of a communication partner is specified from a host in a local network connected to a second router that terminates and routes an IP packet that is connected to a predetermined local network and performs communication using the Internet protocol. A destination determination step for determining whether this is a packet destined for itself,
When receiving an ARP request transmitted from the second router based on an IP packet designating an IP address of a communication partner from a host in the local network connected to the second router, an ARP according to the ARP request is received. An ARP response sending step for sending a response.   3. The inter-LAN connection apparatus according to claim 1, further comprising a delivery destination information storage unit that stores information on a set of a host address and a netmask of the second router as delivery destination information.   An IP packet in which an IP address of a communication partner is specified from a host in a local network connected to a first router that terminates and routes an IP packet that is connected to a predetermined local network and performs communication using the Internet protocol. 3. The LAN according to claim 1, further comprising search target setting means for searching for the next hop as an ARP table, delivery information to the CE router, and route information as a search target. Inter-connection device.

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