JP2527275B2 - LAN interconnection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN interconnection device for interconnecting local area networks in a data communication system.

2. Description of the Related Art Conventionally, Japanese Patent Publication No. 2-28941 discloses a dual address check method as a method for detecting duplicate addresses in a network in which various stations are connected to a trunk LAN. This conventional method is a ring type main line
It consists of a plurality of slave stations connected on the LAN and a master station that manages and controls them. The master station enters the slave station's address in the address field in the frame,
The control information for duplicate address check is put in the control field and transmitted. The target slave station receives the frame because it is addressed to itself, and changes the control information field to duplicate address check response information to form a response frame, which is sent back to the master station.

In this case, since the trunk LAN is a ring type, the response frame is checked by each slave station from the received slave station to the master station. When there is a second slave station having the same address as the slave station, the response frame is also received by the second slave station having the same station address.

Here, also in the second slave station, the master station expects a frame containing duplicate address check control information. However, the frame received by the second slave station is a response frame, and since the control field stores duplicate address check response information, it is determined that it is a frame transmitted by another slave station. It can be seen that the same address is set for multiple slave stations.

However, according to the above-described conventional method, there is a drawback that the detection of the duplicate address is limited to the slave station connected to the trunk LAN.

In view of the above circumstances, the present invention is a network in which a branch LAN is connected to a trunk LAN via an inter-LAN interconnection device, and includes not only stations connected on the trunk but also stations connected on the branch. The purpose is to provide a LAN interconnection device that can exhibit the address detection function.

Means for Solving the Problems In order to solve the above problems, a LAN interconnection device according to the present invention has a main line L that enables access to a main line LAN.
Main LAN and branch line with AN access control means and branch line LAN access control means to enable access to branch line LAN
An inter-LAN interconnection device that relays frames between LANs, and records and updates the source address and the port number of the receiving side of a frame received from a trunk LAN or branch LAN every time the frame is received. A learning table is provided, and if the port number previously learned for the same source address and the port number learned this time are different, a connection confirmation frame with the source address as the destination address is sent to each port. However, when there are a plurality of responses to this, a duplicate address detecting means for determining that a duplicate address is set is provided.

Operation According to the above configuration, every time a frame is received, the source address of the frame and the port number indicating the position of the transmitting station are learned, and the learning at the time of receiving a frame with the same source address is performed previously. If the learned port number is different from the learned port number this time, it is determined that either the station has been relocated or there is a station with duplicated addresses.

In this case, when the LAN-to-LAN interconnection device sends a connection confirmation frame to each port and receives a plurality of responses to this, it is possible to confirm that the duplicate address is set.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows a LAN interconnection device and each L in the present invention.
It shows the connection relationship with AN. In Figure 1, the main line LA
The N1 and the branch line LAN2 are connected via a LAN interconnection device 52. The trunk line LAN1 and the branch line LAN3 are connected via a LAN interconnection device 53. The trunk line LAN1 and the branch line LAN4 are connected via a LAN interconnection device 54. Station 21 is connected to branch line LAN2, stations 31 and 32 are connected to branch line LAN3, branch line LAN4
A station 41 is connected to.

In the LAN interconnection device 52, the branch LAN2 side has a port number 522, and the trunk LAN1 side has a port number 521. LAN
Port number 53 on the branch LAN3 side in the inter-connection device 53
2 and port number 531 on the trunk LAN1 side. In the LAN interconnection device 54, the branch LAN 4 side has a port number 542, and the trunk LAN 1 side has a port number 541.

FIG. 2 shows the internal configuration of the LAN interconnection device 53 and the connection relationship between the trunk line LAN1 and the branch line LAN3.
The inter-connection device 53 includes a trunk LAN access management means 534 that enables access to the trunk LAN 1, a branch LAN access management means 535 that allows access to the branch LAN 3, and a trunk LA.
Relay means for relaying frames between N1 and branch line LAN3 536
Is provided. Further, a learning table 20 for recording / updating the source address of the frame received from the trunk LAN 1 or the branch LAN 3 and the port number of the receiving side each time the frame is received is provided, and the port number for the same source address is set. When the previously learned port number and the currently learned port number are different, a connection confirmation frame destined to the source address is sent to each port 531 and 532, and when there are multiple responses, a duplicate address The duplicate address detecting means 537 for determining that is set.

FIG. 3 shows a learning table 20 provided in the LAN interconnection device according to the present invention. The learning table 20 includes a station address field 201, a port number field 202, and a survival time field 203.

FIG. 4 shows a format of a frame exchanged between stations. The frame 30 includes a destination address 301, a source address 302, a control field 303, and an information field 304.
And an FCS (frame check sequence) field 305.

Next, a method of registering and updating the station address and port number in the learning table will be described. When the LAN interconnection device receives a frame 30 from either the main LAN or branch LAN, the source address field of that frame
It is searched whether the address set in 302 is already stored in the learning table 20. If it is not stored, the received source address is registered in the station address field 201 of the learning table 20, and the port number of the receiving side at that time is registered in the port number field 202. That is, the port number means to which port side the registered station is connected to the LAN interconnection device. A specified initial value is set in the survival time field 203. The value set in the survival time field 203 is decremented at regular time intervals, and when the value becomes 0, the entry consisting of the station address field, port number field, and survival time field is deleted. this is,
This is a process that is useful for always reflecting the latest information in the learning table 20.

When the transmission source address is stored in the learning table 20, the port number field 202 is reset to the received port number, and the survival time field 203 is updated to the specified initial value.

A frame relay system in the LAN interconnection device using the learning table created by the above procedure will be described.
It is assumed that the learning tables in the LAN interconnection devices 52, 53 and 54 have already registered the addresses of the station 21, station 31, station 32 and station 41 and the corresponding port numbers. When a frame is transmitted from the station 31 to the station 41, the address of the station 41 is stored in the destination address field 301 of this frame, and the address of the station 31 is stored in the source address field 302 of this frame. The LAN interconnection device 53 searches the learning table 20 for the address set in the destination address field 301 of the transmitted frame. Since the address of the station 41 is already registered and the corresponding port number is the port number 531 which is a value indicating the trunk LAN side, this frame received from the branch line LAN3 is relayed to the trunk line LAN1.

When the frame is sent from the station 31 to the station 32, the LAN interconnection device 53 searches the learning table 20 for the address of the station 32 set in the destination address field 301 of the received frame and sets the address of the station 32 as the address of the station 32. Since the value port number 532 indicating the branch LAN side is set in the correspondingly registered port number field, the LAN interconnection device 53 does not relay this frame to the trunk LAN.

A procedure for detecting duplicate addresses using these will be described. In FIG. 1, it is assumed that the same address (here, "A") is erroneously set in the station 31 and the station 21. The station 31 is already in operation, and its entry is registered in the learning table in each LAN interconnection device. That is, in the LAN interconnection device 53, in the learning table 20, the port number field corresponding to the address "A" has a port number 5 as a value indicating the branch line LAN side.
32 is set, and in the LAN interconnection devices 52 and 54, in the learning table 20, the port number field corresponding to the address "A" has port numbers 521 and 54 as values indicating the trunk LAN side.
1 is set.

It is now assumed that the station 21 is newly connected. In this case, if a frame is sent from station 21 to another station connected to branch line LAN3 or branch line LAN4 via trunk line LAN1, LA
The N interconnection device 52 retrieves the destination address from the learning table and relays it to the trunk LAN 1. Then, the operation of registering the source address is performed. However, the address "A" is already registered in the learning table, and the port number field 521 indicating the trunk LAN is set in the corresponding port number field. In this case, the address "A"
The registered entry of is updated, the port number field is changed to the port number 522 indicating the branch line side, and the time to live field is set to the specified initial value.

Here, in the LAN interconnection device 52, since the value of the port number field in the entry of the address “A” in the learning table has been changed, the station having the station address “A” has been relocated or the duplicate address has Know that it is either set. LAN interconnection device 5
Similarly, in 3, when the frame from the station 21 is received, the address “A” is registered in the learning table 20, but this entry is already registered and the port number field indicates the branch line LAN side. The port number 531 is changed from 532 to the value indicating the trunk LAN side. As a result, also in the LAN interconnection device 53, it is possible to know that the station having the station address “A” has been relocated or the duplicate address has been set. In this case, another LAN interconnection device cannot detect the entry of address "A" because the port number field is not changed.

In the LAN interconnection device 53, in order to check whether the station with the address "A" has been relocated from the branch LAN or has a duplicate address set, check the connection by setting "A" in the destination address field. The frame is sent to both the branch line LAN side 3 and the trunk line LAN1 side ports 532 and 531 respectively. After that, when the connection confirmation response frame is received from both LANs independently, it is found that the duplicate address is set. In this case, the LAN interconnection device 53 notifies the management station of the duplicate address, and prompts the administrator to recover. When the connection confirmation response frame is received from only one LAN, it is considered that the station has been relocated, and normal operation is continued.

If the LAN interconnection device 52 sends a connection confirmation frame to both the trunk line LAN1 and the branch line LAN2, the connection confirmation frame sent to the trunk line side may not reach the station 31. That is, in this frame received by the LAN interconnection device 53, the port number field corresponding to the station address “A” in the learning table 20 is set to the port number 531 meaning the main LAN side, Branch line LAN3
It is because it is not relayed to.

However, there is no problem because duplicate address detection can be performed by either one of the above processes by both LAN interconnection devices 52 and 53.

Duplicate address detection between a station connected on the trunk line LAN1 and a station connected on the branch line LAN is possible by the same procedure as above.

As described above, according to the LAN interconnection device of the present invention, between the stations connected to the branch LAN, or between the branch LAN and the trunk LA.
It is possible to detect duplicate addresses between stations connected to N.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is an explanatory diagram showing a connection relationship between a trunk LAN, a branch LAN and a LAN interconnection device, and FIG. FIG. 3 is an internal configuration diagram of the interconnection device, FIG. 3 is an explanatory diagram of a learning table, and FIG. 4 is an explanatory diagram of a frame format used for communication between stations. 1 …… Main line LAN, 2,3,4 …… Blank LAN, 52,53,54 …… LAN interconnection device.

Claims (1)

(57) [Claims] 1. A trunk LAN that enables access to a trunk LAN
Main line LAN and branch line LA with access control means and branch line LAN access control means to enable access to branch line LAN
A LAN interconnection device that relays frames between N, and records and updates the source address and the port number of the receiving side of the frame received from the main LAN or branch LAN every time the frame is received. A learning table is provided and a connection confirmation frame with the source address as the destination address is sent to each port when the port number previously learned for the same source address and the port number learned this time are different. However, the LAN interconnection device is characterized by comprising duplicate address detection means for determining that a duplicate address has been set when there are a plurality of responses.