JP2002335258A - Network repeater and ring network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a network repeater and a ring network system, with which a line fault can be recovered even when that fault occurs inside a bridge network. SOLUTION: This device is provided with a bridge repeating part 3 for performing bridge repeating processing by a layer 2 protocol, router repeating part 2 for performing router repeating processing by a layer 3 protocol, bridge control part 5 for transmitting a fault notice message onto a ring network 13 when a line fault occurs on the bridge network while the bridge repeating part 3 executes bridge repeating processing, and router control part 4 for starting router repeating processing by means of the router repeating part 2 on the basis of preset network information for the case of line fault when the bridge control part 5 transmits the fault notice message.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network relay device installed between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network, and a network relay device for the same. The present invention relates to a ring network system used.

[0002]

2. Description of the Related Art Conventionally, as a recovery method when a line failure occurs in a ring network, for example, IEEE
E (Institute of Electrical and Electronic Enginee
rs) Spanning Tree Protocol (STP) standardized in 802.1d, IETF (Internet Enginee
Generally, a network is reconfigured by a routing protocol such as OSPF (Open Shortest Path First) standardized as RFC2328 by a ring task force.

[0003] However, these protocols are not originally specialized in ring topology, and therefore have some disadvantages. For example, when a ring network is constructed using a bridge that is a layer 2 switch, the number of bridge connections is limited to a maximum of seven according to the rules of the spanning tree protocol. For this reason, a ring network system using eight or more bridges cannot be constructed. When a ring network is constructed using a router that is a layer 3 switch, TTL (Time to Live: packet lifetime) is used.
Is set to about 64 and there is a terminal that transmits a packet, so that a ring network system having 64 or more routers cannot be constructed.

[0004]

Therefore, as shown in FIG. 9, by constructing a ring network system in which routers A and E and bridges B, C and D are mixed,
The number of routers A and E on the ring network system is reduced, and the number of bridges B, C and D is reduced by 7
It is conceivable to solve the above problem by setting the number of units to be equal to or smaller than the number of units.

[0005] However, the above-mentioned ring network system may cause the following new problems. For example, as shown in FIG. 10, when a line failure occurs in a bridge network that is a part of a ring network, the same I
P subnetwork (10.20.0.0/16) is 2
In other words, the communication is impossible in these divided networks. Further, the IP sub-network (10.20.
0.0 / 16), when data is transmitted from the terminal connected to the branch line of the router A, the data is all relayed to the bridge B by the router A, and the bridge C or the bridge D is connected to the network relay device. May not be able to be transmitted to each branch network.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a network relay device and a ring network system capable of recovering from a line failure in a bridge network.

[0007]

In order to achieve the above object, a network relay device according to the present invention is provided between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network. A network relay device installed in a layer 2
A bridge relay unit that performs a bridge relay process by using a protocol, a router relay unit that performs a router relay process by using a layer 3 protocol, and a line failure has occurred in the bridge network while the bridge relay unit is performing the bridge relay process. A failure notification transmitting unit that transmits a failure notification message over the ring network in the case where the router notification unit transmits the failure notification message based on the network information for a line failure set in advance when the router notification unit transmits the failure notification message; A router relay processing control unit that starts router relay processing.

According to the present invention, when a line failure occurs in the bridge network, the router relay processing control unit starts the router relay processing by the router relay unit.

A ring network system according to the next invention is configured by installing a network relay device between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network. A ring network system, wherein the network relay device performs a bridge relay process using a layer 2 protocol, a router relay device performs a router relay process using a layer 3 protocol,
A failure notification transmission unit that transmits a failure notification message on the ring network when a line failure occurs in the bridge network while the bridge relay unit is performing the bridge relay process; A router relay processing control unit configured to start a router relay process by the router relay unit based on network information for a line failure set in advance when a notification message is transmitted.

According to the present invention, when a line failure occurs in the bridge network, the router relay processing control unit starts the router relay processing by the router relay unit.

In the ring network system according to the next invention, a first network relay device is installed between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network. A ring network system configured by installing a second network relay device on the ring network, wherein the first network relay device performs a bridge relay process using a layer 2 protocol; A bridge for transmitting a failure notification message on the ring network when a line failure occurs in the bridge network while the bridge relay unit is performing the bridge relay process, and for continuing the bridge relay process by the bridge relay unit Relay processing control unit The second network relay device includes a router relay unit that performs router relay processing according to a layer 3 protocol, and a bridge of the first network relay device while the router relay unit performs router relay processing. When the relay processing control unit transmits the failure notification message, a network failure corresponding to the failure notification message is selected from the preset network failure network information, and the line failure is determined based on the selected network failure network information. And a router relay processing control unit for multi-assigning the IP sub-network of the bridge network in which the problem has occurred and continuing the router relay processing by the router relay unit.

According to this invention, when the failure notification message is transmitted from the bridge relay processing control unit of the first network relay device, the router relay processing control unit of the second network relay device responds to the line failure. The IP subnetwork of the bridge network is multi-assigned based on the network information thus obtained, and the router relay processing by the router relay unit is continued.

A ring network system according to the next invention is characterized in that, in the above invention, the monitoring packet is a BPDU packet, and the presence or absence of a line failure is detected by a spanning tree function.

According to the present invention, the presence or absence of a line failure can be detected by the spanning tree function.

The ring network system according to the next invention is characterized in that the monitoring packet is an ICMP packet and the presence or absence of a line failure is detected by a ping function.

According to the present invention, the presence or absence of a line failure can be detected by the ping function.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a network relay device and a ring network system according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a block diagram showing a configuration of the network relay device according to the first embodiment of the present invention. In FIG. 1, 1 is a network relay device,
Reference numeral 2 denotes a router relay unit that performs a router relay process using a layer 3 protocol, 3 denotes a bridge relay unit that performs a bridge relay process using a layer 2 protocol, 4 denotes a router control unit that controls the operation of the router relay unit 2, and 5 denotes a bridge. A bridge control unit that controls the operation of the relay unit 3. Reference numerals 6 and 7 denote an interface for a trunk line, and reference numeral 8 denotes an interface for a branch line. In the first embodiment, one branch network is connected to the branch interface 8, but a plurality of branch networks may be used.

FIG. 2 is a configuration diagram of a ring network system configured using the network relay device 1 shown in FIG. In FIG. 2, (R) shows that the above-described network relay device 1 operates as a router, and (B) shows that the above-described network relay device 1 operates as a bridge. That is, in the network relay device 1- (R), the router relay unit 2 operates by the router control unit 4, and the router relay unit 2 performs the router relay process. The operation has stopped. Conversely, in the network relay device 1- (B), the bridge relay unit 3 is operated by the bridge control unit 5, and the bridge relay unit 3 performs the bridge relay process. Is stopped. In FIG. 2, 13 indicates a trunk ring network, and 14 indicates a branch line network. Each of the trunk ring network 13 and the branch network 14 is an Ethernet (registered trademark) (Ethernet), but may be another network.

FIG. 3 is a diagram in which an IP network is defined for the ring network system shown in FIG. Each IP subnetwork is defined by the IP network number / mask length. For example, the branch network 14 of the network relay device 1A- (R) operating as a router is defined as "10.10.0.0/16". In this case, the IP network number is 10.1
0.0.0.0 IP subnetwork with a mask length of 16
Indicates a bit. In the first embodiment, as shown in FIG. 3, four IP sub-networks “10.10.
0.0 / 16 "," 10.20.0.0/16 "," 1
0.30.0.0/16 "," 10.40.0.0/1
6 "is defined.

FIG. 4 is a diagram defining an IP sub-network when the IP sub-network "10.20.0.0/16" shown in FIG. 3 is further subdivided. In the first embodiment, each mask length is 24 bits. In a normal bridge network, it is not necessary to further subdivide the inside, but in the first embodiment, the network is operated in advance by subdividing so as to cope with a line failure that has occurred in the bridge network. .

The router control unit 4 of the network relay device 1A- (R) has an IP subnetwork "10.20.
"10.20.10 / 24" is registered as network information for line failure to be used when a line failure occurs in the "0.0 / 16" bridge network. Similarly, in the router control unit 4 of the network relay device 1E- (R), the network information at the time of line failure of “10.20.70.0/24” is registered, and the router of the network relay device 1B- (B) is registered. The control unit 4 includes “10.2
0.10.0 / 24 "," 10.20.20.0/2
4 "and" 10.20.30.0/24 "are registered, and the network relay device 1C
-The router control unit 4 of (B) has “10.20.30.
0/24 "," 10.20.40.0/24 "," 1
The network information at the time of line failure of “0.20.50.0/24” is registered, and “10.20.50.0/2” is stored in the router control unit 4 of the network relay device 1D- (B).
4, 10.20.60.0/24, 10.2
"0.70.0 / 24" is registered.

Next, the operation of the ring network system will be described with reference to FIG. Network relay device 1B- (B), network relay device 1C-
(B) In each bridge control unit 5 of the network relay device 1D- (B), the spanning tree protocol operates to monitor the state of the bridge network. That is, the network relay device 1
B- (B) and network relay device 1C- (B)
The bridge control unit 5 transmits a BPDU (Bridge Protocol Data Unit) packet, which is a network monitoring packet, to the ring network at fixed time intervals, and even if a predetermined time, for example, three times the fixed time, elapses,
If a BPDU packet cannot be received from the other party, it is recognized that a line failure has occurred in the corresponding bridge network.

First, the network relay device 1B- (B)
When the link between the network relay device 1C- (B) and the network relay device 1C- (B) is disconnected, the bridge control unit 5 of the network relay device 1B- (B) and the network relay device 1C- (B)
The bridge control unit 5 recognizes that a line failure has occurred between the network relay device 1B- (B) and the network relay device 1C- (B) by the above-described spanning tree protocol.

The bridge control unit 5 of the network switching device 1B- (B) and the bridge control unit 5 of the network switching device 1C- (B) that recognize that a line fault has occurred.
Transmits a failure notification message to the trunk ring network 13 where no failure has occurred. The failure notification message at this time is transmitted to the trunk ring network 1
3, by setting the destination MAC address to broadcast, the network relay device 1A- (R), the network relay device 1D- (B),
Each bridge control unit 5 of the network relay device 1E- (R) can receive it.

The network relay device 1B- (B)
Of the bridge control unit 5 and the network relay device 1C-
Each of the bridge control units 5 in (B) notifies its own router control unit 4 to operate as a router. Further, the bridge control unit 5 of the network relay device 1D- (B) notifies its own router control unit 4 to operate as a router. That is, the network relay device 1B-
(B) becomes the network relay device 1B- (R), the network relay device 1C- (B) becomes the network relay device 1C- (R), and the network relay device 1
D- (B) becomes the network relay device 1D- (R). As a result, the network relay device 1B-
(R), each router control unit 4 of the network relay device 1C- (R) and the network relay device 1D- (R)
The router relay process by each router relay unit 2 is started based on the pre-registered network information at the time of line failure.

On the other hand, the bridge control unit 5 of the network switching device 1A- (R) and the bridge control unit 5 of the network switching device 1E- (R) that have received the failure notification message transmit the IP sub-network “10.20.0. 0/1
6 ”, the respective router controllers 4 are notified that a line failure has occurred in the bridge network. As a result, the router control unit 4 of the network switching device 1A- (R) and the router control unit 4 of the network switching device 1E- (R) determine each individual based on the network information at the time of line failure registered in advance. The router relay unit 2 starts router relay processing.

With the above operation, the ring network system is configured as shown in FIG. 6, and the network information (“10.20.20”) of the branch network 14 is obtained by the routing protocol by the router control unit 4 of each network relay device. .0 / 24 "," 10.20.
40.0 / 24 "," 10.20.60.0/24 ")
And network information (“10.20.10.0/24”, which is included in the IP subnetwork “10.20.0.0/16” in the trunk ring network 13,
"10.20.30.0/24", "10.20.5
0.0 / 24 "and" 10.20.70.0/24 ") are notified to the entire trunk ring network 13, so that inconsistency due to a failure in the bridge network does not occur and the ring network system can be restored. it can.

Further, in the above ring network system, whether or not there is a line failure in the bridge network is detected by the spanning tree protocol, so that the branch networks 14 are interconnected to form a loop. However, it is possible to surely recover.

Embodiment 2 FIG. Next, a second embodiment of the present invention will be described. In the first embodiment described above,
Since the bridge network is monitored by the spanning tree protocol, the number of bridge connections is limited to a maximum of seven. However, if a loop is not generated in the branch network 14, that is, it is guaranteed that the branch networks 14 are not interconnected, it is not necessary to monitor the bridge network by the spanning tree protocol, and the number of bridge connections should be eight or more. Becomes possible.

Hereinafter, a second embodiment to which a bridge network monitoring method not based on the spanning tree protocol is applied will be described. FIG. 7 is a block diagram showing a configuration of the network relay device according to the second embodiment of the present invention. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 9 denotes a network monitoring unit 9 that monitors the state of the bridge network. The network monitoring unit 9 periodically sends an ICM message to the network relay device 1 adjacent to the bridge network.
While transmitting a P (Internet Control Message Protocol) packet, this part receives the ping response. If the ping response cannot be received a specified number of times or more, it is recognized that a line failure has occurred. When the network monitoring unit 9 recognizes that a line failure has occurred, the network monitoring unit 9 notifies its own bridge control unit 5 and router control unit 4 that the line failure has occurred so as to operate as a router. The failure notification message is transmitted to another network relay device installed in the network switching device 13.

For example, as shown in FIG. 5, when the link between the network relay device 1B- (B) and the network relay device 1C- (B) is disconnected, the network relay device 1B- (B) The network monitoring unit 9 and the network monitoring unit 9 of the network switching device 1C- (B) use the ping function described above to perform the network switching devices 1B- (B) and 1C- (B).
Recognizing that a line failure has occurred with (B), the network relay devices 1A- (R) and 1D-
(B), a failure notification message is transmitted to each network monitoring unit 9 of the network relay device 1E- (R).

The network relay device 1B- (B)
Each network monitoring unit 9 of the network relay device 1C- (B) notifies its own router control unit 4 to operate as a router. Further, the network monitoring unit 9 of the network relay device 1D- (B) notifies its own router control unit 4 to operate as a router. That is, the network relay device 1B- (B) becomes the network relay device 1B- (R), and the network relay device 1C- (B) becomes the network relay device 1C- (B).
(R), and further, the network relay device 1D-
(B) becomes the network relay device 1D- (R).
As a result, each of the router control units 4 of the network relay device 1B- (R), the network relay device 1C- (R), and the network relay device 1D- (R) registers the network information for line failure in advance registered. , The router relay process by each router relay unit 2 is started.

On the other hand, the network monitoring unit 9 of the network relay device 1A- (R) that has received the failure notification message
And the network monitoring unit 9 of the network relay device 1E- (R) transmits the IP subnetwork “10.20.
The respective router controllers 4 are notified that a line failure has occurred in the "0.0 / 16" bridge network. As a result, the router control unit 4 of the network relay device 1A- (R) and the network relay device 1E- (R)
The router control unit 4 starts the router relay processing by the individual router relay units 2 based on the network information for line faults registered in advance.

With the above operation, the ring network system has a configuration as shown in FIG. 6, and the network information of the branch network 14 and the IP in the trunk ring network 13 are determined by the routing protocol by the router control unit 4 of each network relay device. Since the network information included in the subnetwork “10.20.0.0/16” is notified to the entire trunk ring network 13, inconsistency due to a failure in the bridge network does not occur, and the ring network system can be restored. .

Further, in the above ring network system, since the spanning tree protocol is not used, the number of bridge connections in the bridge network is eight.
The number can be more than one, and a larger-scale system can be configured.

Embodiment 3 Next, a third embodiment of the present invention will be described. In the first and second embodiments, when a line failure occurs, the network relay device operating as a bridge on the ring network is operated as a router.
On the other hand, in a third embodiment, a ring network system will be described in which a network relay device operating as a bridge is operated as a bridge even when a line failure occurs.

The network relay device applied in the third embodiment may be the one shown in the first embodiment or the one shown in the second embodiment. The configurations of the ring network and the bridge network are the same as those shown in FIGS. However, in the router control unit 4 of the network relay device 1A- (R), network information for a line failure used when a failure notification message is received is registered for each transmission source of the failure notification message. For example, when the failure notification message is transmitted from the network relay device 1B- (B), "10.20.10 / 2"
4 "and" 10.20.20.0/24 "are registered, and" 10.20.10 "is used as network information for line failure when a failure notification message is transmitted from the network relay device 1C- (B). .0 / 24 "and" 10.20.
20.0 / 24 "," 10.20.30.0/24 ", and" 10.20.40.0/24 "are registered, and a failure notification message is transmitted from the network relay device 1D- (B). "10.20.10.0/24" and "10.20.2"
0.0 / 24 "," 10.20.30.0/24 "," 10.20.40.0/24 ", and" 10.20.5 "
0.0 / 24 "and" 10.20.60.0/24 "are registered. Similarly, the network relay device 1E-
The network information for a line failure is also registered in the router control unit 4 of (R) for each transmission source of the failure notification message.

Next, the operation of the ring network system will be described with reference to FIG. The monitoring of the network state is performed by the network relay device according to the first embodiment.
In the case where the one shown in the above is applied, the spanning tree protocol is applied, and in the case where the network relay device of the second embodiment is applied, the ping function may be applied.

First, the network relay device 1B- (B)
When the link between the network relay device 1C- (B) and the network relay device 1C- (B) is disconnected, the bridge control unit 5 of the network relay device 1B- (B) and the network relay device 1C- (B)
The bridge controller 5 of the network relay device 1B- (B) and the network relay device 1C-
Recognize that a line failure has occurred between (B).

The bridge control unit 5 of the network relay device 1B- (B) and the bridge control unit 5 of the network relay device 1C- (B) that recognize that a line failure has occurred.
Transmits a failure notification message to the trunk ring network 13 where no failure has occurred, as in the first embodiment, but continues the bridge relay processing by the bridge relay unit 3 as it is. Further, the bridge control unit 5 of the network relay device 1D- (B) also continues the bridge relay processing by the bridge relay unit 3.
In other words, even after a line failure occurs, the network relay device 1B- (B) and the network relay device 1C-
(B), the network relay device 1D- (B) maintains the state as it is.

On the other hand, the bridge control unit 5 of the network relay device 1A- (R) and the bridge control unit 5 of the network relay device 1E- (R) that have received the failure notification message are connected to the IP subnetwork "10.20.0. 0/1
6 ”, the router controller 4 is notified that a line failure has occurred. Router controller 4 notified of line failure
Selects from the pre-registered network information at the time of circuit failure according to the source of the failure notification message,
Based on the selected network information at the time of line failure, the router relay processing by each router relay unit 2 is started. For example, when the router control unit 4 of the network relay device 1A- (R) receives the failure notification message from the network relay device 1B- (B), the router control unit 4 selects “10.20.10” from the above-described network information for line failure. .0
/ 24 "and" 10.20.20.0/24 "to operate as a router in which these two IP subnetworks are multi-assigned to one trunk ring interface 6,7. Similarly, the network relay device 1E
-(R) router control unit 4
When the failure notification message is received from C- (B), "1"
0.20.40.0/24 "and" 10.20.50.0
/ 24 "," 10.20.60.0/24 ", and" 10.
20.70.0 / 24 "and select these four IPs
It operates as a router in which the subnetwork is multi-assigned to one trunk ring interface 6,7.

With the above operation, the ring network system has a configuration as shown in FIG. Also in this case, the branch line network 1 is controlled by the routing protocol by each router control unit 4 of the network relay device 1A- (R) and the network relay device 1E- (R).
4 and the IP network "10.20.0.
Since the network information included in “0/16” is notified to the entire trunk ring network 13, inconsistency due to a failure in the bridge network does not occur, and the ring network system can be restored. Note that, in the third embodiment, the network relay devices 1A- (R) and 1E- (R) do not necessarily need to include the bridge relay unit 3 and the bridge control unit 5. 1B- (B), the network relay device 1C- (B), and the network relay device 1D- (B) do not necessarily need to include the router relay unit 2 and the router control unit 4.

[0044]

As described above, according to the present invention, when a line failure occurs in the bridge network, the router relay processing control unit starts the router relay processing by the router relay unit. The network information of the failed bridge network is notified to the entire ring network, and the network can be restored.

According to the next invention, when a line failure occurs in the bridge network, the router relay processing by the router relay unit is started by the router relay processing control unit. The network information is notified to the entire ring network, and recovery becomes possible.

According to the next invention, when a failure notification message is transmitted from the bridge relay processing control unit of the first network relay device, the router relay processing control unit of the second network relay device causes the router relay processing control unit to resolve the line failure. Bridge network IP based on corresponding network information
Since the subnetwork is multi-assigned and the router relay processing by the router relay unit is continued, the network information of the bridge network in which the line failure has occurred is notified to the entire ring network by the routing protocol, and the ring network can be recovered.

According to the present invention, the presence or absence of a line failure can be detected by the spanning tree function, which is suitable when the bridge network is a ring network.

According to the present invention, the presence or absence of a line failure can be detected by the ping function, which is suitable when the bridge network is not a ring network. In this case, the number of bridge connections in the bridge network can be eight or more, and a large-scale ring network system can be constructed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a network relay device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a ring network system configured using the network relay device 1 shown in FIG.

FIG. 3 is a diagram in which an IP network is defined for the ring network system shown in FIG. 2;

FIG. 4 is a diagram defining an IP sub-network when the IP sub-network shown in FIG. 3 is further subdivided.

FIG. 5 is a diagram illustrating the operation of the ring network system.

FIG. 6 is a diagram showing a ring network system after a line failure occurs in the first embodiment.

FIG. 7 is a block diagram illustrating a configuration of a network relay device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a ring network system after a line failure has occurred in a third embodiment.

FIG. 9 is a diagram showing a conventional ring network system.

10 is a diagram showing a state where a line failure has occurred in the ring network system of FIG. 9;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Network relay device, 2 router relay unit, 3 bridge relay unit, 4 router control unit, 5 bridge control unit, 6, 7 trunk ring interface, 8 branch line interface, 9 network monitoring unit, 13 trunk ring network, 14 branch line network.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Hiroshi Nakamura, 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Teruko Fujii 2-3-2, Marunouchi, Chiyoda-ku, Tokyo Inside Ryo Denki Co., Ltd. (72) Inventor Tetsuo Sadahaku 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) within Sanishi Electric Co., Ltd. 5K030 GA12 HA08 HC01 HC14 HD03 JA05 JA10 KA05 LB08 MA01 MB01 MD01 5K031 AA08 CB12 CB13 DA05 DB04 DB14 EA01 EA04 EA12 EB06

Claims (5)

[Claims] 1. A network relay device installed between a bridge network capable of detecting the presence / absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network, wherein a bridge relay process is performed by a layer 2 protocol. A bridge relay unit for performing a router relay process according to a layer 3 protocol; and a router relay unit for performing a router relay process according to a layer 3 protocol. A failure notification transmitting unit that transmits a failure notification message to the router, and when the failure notification transmitting unit transmits the failure notification message, starts router relay processing by the router relay unit based on network information for a line failure that is set in advance. And a router relay processing control unit. Network relay device. 2. A ring network system comprising a network relay device installed between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network, A bridge relay unit that performs a bridge relay process using a layer 2 protocol; a router relay unit that performs a router relay process using a layer 3 protocol; and the bridge relay unit while the bridge relay unit performs the bridge relay process. A failure notification transmitting unit that transmits a failure notification message on the ring network when a line failure occurs in the network; and a network information for a predetermined line failure when the failure notification transmission unit transmits the failure notification message. Based on the router Ring network system comprising: the router relay processing control unit for starting the data relay processing, the. 3. A first network relay device is installed between a bridge network capable of detecting the presence or absence of a line failure based on transmission / reception of a monitoring packet and a predetermined ring network, and a second network relay device is provided on the ring network. A ring network system configured by installing the network relay device of (1), wherein the first network relay device performs a bridge relay process using a layer 2 protocol; and the bridge relay unit performs a bridge relay process. When a line failure has occurred in the bridge network during execution, a failure notification message is transmitted on the ring network, and a bridge relay processing control unit that continues bridge relay processing by the bridge relay unit, The second network relay device A router relay unit that performs a router relay process according to a layer 3 protocol; and a bridge relay process control unit of the first network relay device transmits a failure notification message while the router relay unit is performing the router relay process. In this case, a network failure corresponding to the failure notification message is selected from the preset network failure network information, and based on the selected network failure network information, the IP subnetwork of the bridge network in which the network failure has occurred is multiplied. A router relay processing control unit for assigning and continuing router relay processing by the router relay unit. 4. The ring network system according to claim 2, wherein the monitoring packet is a BPDU packet, and the presence or absence of a line failure is detected by a spanning tree function. 5. The ring network system according to claim 2, wherein the monitoring packet is an ICMP packet, and the presence or absence of a line failure is detected by a ping function.