JP2005130408A - Link aggregation method and switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a link aggregation method and a link aggregation switch for realizing an increase in communication band and redundancy at the occurrence of disorder, by connecting two or more links with a conventional switch having no link aggregation function, and transferring a frame after collecting the links to one logical port. <P>SOLUTION: The link aggregation switch 300 includes physical ports 310a to 310e used as an interface for transmitting and receiving a frame, a logical port unit 320a for correcting and managing the physical ports, a frame transfer processing unit 330 for transferring the received frame to the physical port or to the logical port, and a MAC address learning table 340 for matching the MAC address with the logical port or the physical port as a transfer destination to which the MAC address corresponds. In the logical port unit 320a, physical ports 310a, 310b, 310c, corresponding to each link 400a, 400b, 400c to be connected with another switch are collected and managed as one logical port. In this case, an example, in which three physical ports are treated as one logical port, is shown, but it is not restricted to this case, an arbitrary desired number of physical ports may be collected to one logical port. In this explanation, one logic port is adopted to make it easily understandable, but an arbitrary number of logical ports may be feasible in this constitution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a link aggregation method and a link aggregation switch for a layer 2 switch, and in particular, is connected to a switch having no link aggregation function through a plurality of links, and the plurality of links are aggregated into one logical port to transfer a frame. It is related with the link aggregation method and link aggregation switch which implement | achieve the redundancy at the time of the increase in a communication band and failure occurrence by performing.

  When designing a network using a layer 2 switch, when it is desired to increase the communication bandwidth between two switches or when a communication path between two switches is to be configured in a redundant configuration, a plurality of links are provided between the two switches. If a frame is provided, duplication or looping of a frame to be transferred occurs, so that such a configuration cannot be actually used.

  FIG. 13 is an operation overview (1) of the prior art switch. The operation steps in which the frame received at the physical port 110d of the switch 100 is transferred between the switch 100 and the switch 200 are indicated by dotted arrows S01 to S06. Yes. Tables 140 and 240 in FIG. 13 are MAC address learning tables that store the correspondence between MAC addresses and physical port identification information, and are provided for each switch. As an initial state, description will be made assuming that no MAC address has been registered in the MAC address learning table 140 of the switch 100 and the MAC address learning table 240 of the switch 200. In order to distinguish from the logical port of the present invention described later, a port having a conventional meaning different from the logical port is referred to as a physical port. A symbol DA (Destination Address) written in the frame F1 means a destination address included in the header of the frame, and SA (Source Address) means a source address included in the header of the frame. Hereinafter, the same meaning is used in the text and the drawings.

  S01. Upon receiving the frame F1 from the physical port 110d, the switch 100 searches the MAC address learning table 140 and checks whether or not the transmission source address “01” included in the frame F1 has been registered. Since the MAC address of the transmission source address “01” is not registered in the MAC address learning table 140, a pair of the transmission source address “01” of the received frame F1 and the identification information “p4” of the physical port that has received the frame F1. Is registered in the MAC address learning table 140.

  Next, it is checked whether or not the destination address (DA) “02” included in the received frame F1 is registered in the MAC address learning table 140. In this case, since the MAC address of “02” is not registered and the transfer destination port cannot be specified, it is transferred to all physical ports other than the physical port that received the frame F1. This is called flooding. Here, the frame F1 is transferred to the physical ports 110a, 110b, 110c, and 110e. In FIG. 13, flooding is expressed in a form in which a plurality of dotted arrows are branched. Symbols p1 to p5 and q1 to q5 written in a frame indicating the physical port indicate identification information of each physical port.

  S02. The frame F1 transferred to the physical port 110a by the flooding in step S01 is transmitted to the physical port 210a of the switch 200.

  S03. Similarly to the switch 100, the MAC address learning table 240 of the switch 200 receives the source address “01” and the frame F1 of the received frame F1 because the source address “01” of the frame F1 is not registered. The pair of physical port identification information “q1” is registered in the MAC address learning table 240.

  Next, when it is checked whether or not the destination address “02” of the frame F1 is registered in the MAC address learning table 240, it is not registered in the MAC address learning table 240, so the frame F1 is other than the received physical port 210a. Are duplicated and transferred to all physical ports. In FIG. 13, among the duplicated and transferred frames, the frames transferred to the physical port 210d are emphasized, but actually, the frames are also transferred to the physical ports 210b, 210c, and 210e. Is transferred to the physical port 210d.

  S04. On the other hand, the frame F1 transferred to the physical port 110b of the switch 100 by the flooding in step S01 is transmitted to the physical port 210b of the switch 200.

  S05. Upon receiving the frame F1, the switch 200 checks whether or not the transmission source address “01” of the frame F1 has been registered in the MAC address learning table 240. In this case, since the MAC address “01” has already been registered in step S03, the registered port identification information “q1” is rewritten to the identification information “q2” of the physical port 210b that received the frame F1 this time. Here, this step S05 is described as being executed after step S03, but the reverse is true when step S03 is executed after step S05, and the information registered in step S05 is added to the information registered in step S05. In step S03, information is overwritten.

  Next, the reception MAC address learning table 240 is checked to check whether the destination address “02” of the frame F1 is already registered. Here, since the destination address “02” of the frame F1 is not yet registered in the MAC address learning table 240, the frame F1 is copied to all physical ports other than the received physical port 210b, as in step S03. Then transferred. In FIG. 13, the frame F1 transferred to the physical port 210d is emphasized.

  As described above, one frame F1 received by the switch 100 is transferred via the respective links to the step 200 which is oppositely connected by the two links, and these two frames F1 are transferred. Is transferred to the physical port 210d of the switch 200. Similarly, the two duplicated frames F1 are transferred to the other physical ports 210c and 210e of the switch 200.

  FIG. 12 is an operation outline (2) of the prior art switch. Operation steps in which a frame received at the physical port 110d of the switch 100 is transferred between the switch 100 and the switch 200 are indicated by dotted arrows S01 to S06. Yes. Here, it is assumed that the MAC address is not yet registered in the MAC address learning tables 140 and 240 of the switches 100 and 200 as an initial state. The expression of flooding and the expression of identification information of the physical port used in FIG. 12 are the same as those in FIG.

  S01. When the switch 100 receives the frame F1 from the physical port 110d, the switch 100 searches the MAC address learning table 140 and checks whether or not the source address (SA) “01” included in the frame F1 has been registered. Since the MAC address of the transmission source address “01” is not registered in the MAC address learning table 140, a pair of the transmission source address “01” of the received frame F1 and the identification information “p4” of the physical port that has received the frame F1. Is registered in the MAC address learning table 140.

  Next, it is checked whether or not the destination address (DA) “02” included in the received frame F1 is registered in the MAC address learning table 140. In this case, since the MAC address of “02” is not registered and the transfer destination port cannot be specified, flooding is performed to all physical ports other than the physical port that received the frame F1. Here, the frame F1 is transferred to the physical ports 110a, 110b, 110c, and 110e.

  S02. The frame F1 transferred to the physical port 110a by the flooding in step S01 is transmitted to the physical port 210a of the switch 200.

  S03. Similarly to the switch 100, the MAC address learning table 240 of the switch 200 receives the source address “01” and the frame F1 of the received frame F1 because the source address “01” of the frame F1 is not registered. The pair of physical port identification information “q1” is registered in the MAC address learning table 240.

  Next, when it is checked whether or not the destination address “02” of the frame F1 has been registered in the MAC address learning table 240, since it is not registered in the MAC address learning table 240, the frame F1 is flooded and the received physical port It is duplicated and transferred to all physical ports except 210a. In FIG. 12, among the duplicated and transferred frames, the frame transferred to the physical port 210b is emphasized, but actually, it is also transferred to the physical ports 210c, 210d, and 210e.

  S04. The frame F1 duplicated from the physical port 210b of the switch 100 to the physical port 110b of the switch 100 by the flooding in step S03 is transmitted.

  S05. Upon receiving the frame F1 from the physical port 110b, the switch 100 checks whether or not the transmission source address “01” of the frame F1 is registered in the MAC address learning table 140. In the MAC address learning table 140, since the MAC address “01” has already been registered in step S01, the registered port identification information “p4” is used as the identification information of the physical port 110b that received the frame F1 this time. Rewrite to “p2”.

  Next, since the destination address “02” of the frame F1 is not registered in the MAC address learning table 140, the frame F1 is flooded and copied and transferred to all physical ports other than the received physical port 110b. One of them is transferred to the physical port 110a.

  S06. The frame F1 transferred to the physical port 110a by flooding is transmitted to the physical port 210a of the switch 200.

  Thereafter, the same operation steps as in steps S02 to S05 are repeated, and the frame F1 continues to be transferred in a loop between the switches 100 and 200.

As mentioned above, if you try to increase communication bandwidth by connecting multiple switches between switches that do not incorporate the conventional link aggregation function, the same frame is duplicated and two or more identical frames are transmitted from the switch. Or the frame continues to be transferred in a loop between the switches. In order to solve this, there is a method of replacing one link between two switches with a high-speed one, or incorporating a link aggregation function in both switches. The link aggregation function is standardized by the IEEE802.3ad task force, and a method with further improvements has been proposed (for example, see Patent Document 1).
Japanese translation of PCT publication No. 2003-526263 (pages 8-12, FIGS. 1A and 1B)

  As described above, in order to increase the communication bandwidth between switches and make the communication path redundant, it is necessary to replace both switches with switches having high-speed interfaces, or to incorporate a link aggregation function in both switches. In either case, it was difficult to respond at low cost using existing switches.

  Therefore, the present invention connects a conventional switch that does not have a link aggregation function with a plurality of links, aggregates the plurality of links into one logical port, and transfers frames, thereby increasing communication bandwidth and failure. An object of the present invention is to provide a link aggregation method and a link aggregation switch that realize redundancy at the time of occurrence.

  In the first invention, a plurality of physical ports that transmit and receive frames are aggregated into a logical port. When a frame is transmitted from the logical port, the logical port is aggregated to the logical port based on a source address included in the frame. One of the physical ports is selected as a transmission physical port, a frame is transmitted to the selected transmission physical port, and when a frame is received at the physical port aggregated to the logical port, the frame is received. Based on the destination address included in the frame, select one of the physical ports aggregated in the logical port as a receiving physical port, and the physical port that received the frame matches the selected receiving physical port The received frame is an effective received frame, and the MAC address is paired with port identification information indicating the transfer destination port of the frame. In the entry of the MAC address learning table storing the relationship, the identification information of the logical port is registered as port identification information for a plurality of physical ports aggregated in the logical port, and for the physical port not aggregated in the logical port The physical port identification information is registered as port identification information, and for the valid received frame received by the logical port or the frame received by the physical port that is not aggregated to the logical port, the destination address included in the frame is a key. The MAC address learning table is searched to acquire an entry including a MAC address that matches the destination address, and a frame is transferred to a logical port or a physical port indicated by the port identification information included in the acquired entry. It was configured as follows.

  According to the first aspect of the present invention, the link aggregation switch of the present invention and the prior art switch are connected by a plurality of links, and the link aggregation switch of the present invention uses a single physical port connected to the plurality of links. When aggregated to one logical port, based on the source address included in the frame to be transferred, one physical port is selected from the physical ports aggregated to the logical port, and the frame is transmitted. The same frame is not transmitted from a plurality of physical ports, and the frame is not duplicated by the opposed prior art switch. Even when a frame transferred from a link aggregation switch of the present invention to a prior art switch via one link is flooded by the prior art switch and transferred to another link again, the same logical port Since only one of the frames received by the plurality of physical ports aggregated in the network is accepted and the frame is not flooded to the physical port aggregated in the logical port, the prior art switch again. The frame is not transferred to the frame, and the frame loop transfer can be prevented.

  In a second aspect based on the first aspect, for the effective reception frame received at the logical port or the frame received at a physical port not aggregated to the logical port, a source address included in the frame is used as a key. The MAC address learning table is searched to acquire an entry including a MAC address that matches the source address, and the port identification information included in the acquired entry is used to identify the logical port or physical port that received the frame. If it is different from the information, the received frame is discarded.

  According to the second invention, when the link aggregation switch of the present invention and the prior art switch are connected by a plurality of links, the link aggregation switch of the present invention passes through one of the links in which the frames are aggregated. When the frame is forwarded to a prior art switch, the frame will not be flooded if it is received again via another link in the aggregated link that was flooded by the prior art switch. Since it is discarded, not only the loop transfer of frames to and from the prior art switch can be prevented, but also the transfer of unnecessary frames due to flooding can be prevented.

  According to a third invention, in the first invention, when a failure is detected in the physical port aggregated in the logical port, the physical port in which the failure is detected is excluded from the aggregation target of the logical port, and the transmission physical When the physical port that detected the failure is recovered by redefining the selection method of the port and the reception physical port, the recovered physical port is incorporated as an aggregation target of the logical port, and the redefined transmission physical The method for selecting the port and the receiving physical port is set back to the method before the redefinition.

  According to the third invention, the physical port in which the failure is detected is disconnected, the frame transfer is continued with the remaining physical port suppressing the communication bandwidth, and the original bandwidth is restored when the failure is recovered. The frame can be transferred back to the width.

  In a fourth aspect based on the first aspect, the selection of the transmission physical port and the reception physical port in the logical port is performed by using a MAC address as an input value and identifying one physical port corresponding to the input value. This is configured to be performed by a hash function that outputs information.

  According to the fourth invention, the MAC address can be used as an input value, the port identification information as an output value can be randomly distributed, and the frames can be distributed in a form with less bias to the physical ports to be aggregated into logical ports. Can be used to effectively utilize the communication bandwidth.

  According to the present invention, it is possible to increase the communication bandwidth of frame transfer between switches in a form in which a plurality of links are connected to a conventional switch that does not have a link aggregation function, and a failure occurs in the link. Even in this case, the frame transfer can be continued through another normal link, and an efficient network can be constructed at a low cost.

  FIG. 1 shows the configuration of the link aggregation switch of the present invention.

  The link aggregation switch 300 of the present invention includes physical ports 310a to 310e serving as interfaces for transmitting and receiving frames, a logical port unit 320a that aggregates and manages a plurality of physical ports, and a frame that transfers received frames to physical ports or logical ports. It includes a transfer processing unit 330 and a MAC address learning table 340 for associating a MAC address with a corresponding logical port or physical port as a transfer destination.

  The logical port unit 320a aggregates and manages the physical ports 310a, 310b, and 310c corresponding to the plurality of links 400a, 400b, and 400c for connecting to other switches as one logical port. Here, an example is shown in which three physical ports are handled as one logical port, but the present invention is not limited to this, and a plurality of arbitrary physical ports can be aggregated into one logical port. In addition, here, in order to make the explanation easy to understand, only one logical port is configured. However, the configuration is not limited to this, and an arbitrary number of logical ports can be configured.

  When a frame is delivered from a frame transfer unit 330 (to be described later), the logical port 320a selects a physical port from a plurality of aggregated physical ports by a predetermined method based on a transmission source address included in the frame. One is selected and the frame is transmitted to the selected physical port. In addition, when a frame is received from any of the aggregated physical ports, the frame should be received from the aggregated physical ports based on the destination address included in the frame. One physical port is selected by a predetermined method, and only when the physical port from which the frame has been received matches the selected physical port, the frame is accepted and delivered to the frame transfer physical port 330 described later.

  The physical ports 310d and 310e are physical ports that are not aggregated as logical ports, and transmission / reception of frames to / from physical ports that are not aggregated into these logical ports is performed in the same manner as before.

  The MAC address learning table 340 is accessed during frame transfer processing performed by the frame transfer unit 330 described later, and stores MAC addresses and identification information of ports serving as frame transfer destinations in association with each other. The port here is used in the meaning including both the logical port and the physical port not aggregated into the logical port. When transferring a frame, the MAC address learning table 330 is searched using the destination address (DA) included in the frame as a key, and the port identification information stored in the entry having the MAC address that matches the destination address is obtained. Then, the frame is transferred to the logical port indicated by the port identification information or the physical port not aggregated into the logical port. In the prior art switch, only the physical port identification information is registered as the port identification information. However, in the MAC address learning table 340 of the present invention, the port identification information is stored for a plurality of physical ports aggregated in the logical port. They are not registered, but are different in that logical port identification information is registered as a representative of those physical ports instead.

  The frame transfer unit 330 associates the source address (SA) of the received frame delivered from the physical port 310d, 310e or the logical port unit 320a with the port identification number of the delivered port in the MAC address learning table 340. register. The MAC address registered in the MAC address learning table 340 is collated with the destination address in the received and delivered frame, and if they match, the logical port indicated by the port identification information corresponding to the MAC address or not aggregated Forwarded to physical port. Here, a frame is transferred between the logical port 320a, the physical port 310d, and the physical port 310e.

  FIG. 2 shows the operation of the transmission physical port selection unit of the logical port of the present invention.

  When the transmission physical port selection unit 321a included in the logical port 320a receives the frame Fs from the frame transfer unit 330, the logical port 320a aggregates the transmission source address input value included in the frame by a predetermined method. One physical port is selected from the physical port group, and the frame Fs is transmitted to the selected physical port. As a predetermined method for selecting a physical port, a known hash function can be used, and for example, a method used in a method related to link aggregation standardized by IEEE 802.3ad can be used.

  In the example of FIG. 2, the transmission source address of the frame Fs is “01”, the transmission physical port selection unit 321a selects the physical port 310a, and the frame Fs is transmitted to the selected physical port 310a. Yes. The correspondence relationship between the transmission source address and the selected physical port remains unchanged until the physical port aggregation unit 232a described later changes the configuration of the group of physical ports to be aggregated in the logical port 320a.

  As described above, the frame Fs delivered from the frame transfer unit 330 using the logical port 320a as the transfer destination is not duplicated and transmitted to the plurality of physical ports 310a, 310b, 310c, but to one physical port. Only sent. Accordingly, the same frame is not received by two or more physical ports in the oppositely connected switches, and duplication of a frame in which two or more identical frames are transferred to the same physical port can be prevented.

  FIG. 3 shows the operation of the reception physical port selection unit of the logical port of the present invention.

  When the received physical port selection unit 322a included in the logical port 320a is handed over the frame Fr received by any of the physical ports 310a, 310b, and 310c, the destination address included in the frame Fr is used as an input value in a predetermined method, Frame Fr received only when one physical port is selected from the group of physical ports aggregated by logical port 320a, and the selected physical port matches the physical port that received the delivered frame Fr. Is transferred to the frame transfer unit 330. A frame Fr including the same destination address delivered from a physical port other than the selected physical port is discarded.

  The example of FIG. 3 shows a case where the same frame Fr is received by three physical ports aggregated by the logical port 320a, and the physical port 310a is selected as the physical port corresponding to the destination address “01”. Only the frame Fr received at the physical port 310a is delivered to the frame transfer unit 330, and the frame Fr received at the physical ports 310b and 310c is discarded.

  As a predetermined method for selecting a physical port, the same method as that shown in the operation of the transmission physical port selection unit of the logical port of the present invention in FIG. 2 is used. Therefore, when the logical port 320a receives a frame including a destination address having the same MAC address as the transmission source address at the time of frame transmission, the same physical port as the physical port selected at the time of frame transmission is selected.

  As in the case of the frame transmission shown in FIG. 2, the correspondence relationship between the destination address in the received frame and the selected physical port is determined by the physical port aggregating unit 323a (to be described later) It remains unchanged until the port group configuration is changed.

  As described above, even when the same frame is received from a plurality of physical ports 310a, 310b, 310c, only one of them is selected and subjected to frame transfer processing. The duplicated frames sent from the technology switch can be narrowed down to one.

  FIG. 4 shows the operation of the physical port aggregation unit of the logical port of the present invention.

  The physical port aggregation unit 323a included in the logical port processing unit 320a monitors the status of the aggregated physical ports 310a, 310b, and 310c, and when a failure is detected, aggregates the physical ports that detected the failure separately. Regroup the physical port groups to be targeted. At this time, the correspondence between the physical port selection performed by the transmission physical port selection unit 321a and the reception physical port selection unit 322a shown in FIGS. 2 and 3, that is, the correspondence between the MAC address and the selected physical port identification information Change the attachment at the same time. In the embodiment of FIG. 4, since a failure is detected in the physical port 310c, the physical port 310c is disconnected from the physical port group G1 configured by the physical ports 310a, 310b, 310c, and the physical configured by the physical ports 310a, 310b. The port group G2 is reconfigured, and the correspondence between the MAC address for selecting the physical port and the physical ports 310a and 310b is also changed.

  When the failure detected in the physical port 310c is recovered, the physical port 310c is again incorporated into the aggregation target physical port group of the logical port 320a, and the correspondence relationship between the MAC address and the physical port is also restored to the original state.

  As described above, even when a failure occurs in a physical port aggregated in a logical port, frame transfer can be continued by another physical port.

  FIG. 5 is an operation flowchart of the logical port of the present invention. When a frame is transferred from the frame transfer unit 330, a physical port aggregated by the logical port receives a frame, or a physical port aggregated by the logical port Is triggered when a failure and recovery is detected.

  S01. The content of the event that has occurred is determined. If the frame transmission request is from the frame transfer unit 330, the process proceeds to step S02. If the frame is received at a physical port aggregated by the logical port 320a, the process proceeds to step S04. The process proceeds to step S08 when a failure is detected in the physical ports aggregated by the logical port 320a, and to step S10 when the failure is recovered.

  S02. Based on the transmission source address (SA) of the frame delivered from the frame transfer unit 330, one physical port for transmitting the frame is selected using a predetermined hash function.

  S03. The frame is transmitted to the physical port selected in step S02, and the process ends.

  As a result, it is possible to prevent the delivered frame from being copied to a plurality of physical ports and transmitted to the prior art switch.

  S04. Based on the destination address (DA) in the received frame delivered from the physical port aggregated in the logical port 320a, one corresponding physical port is selected using a predetermined hash function.

  S05. It is determined whether or not the identification information of the physical port selected in step S04 matches the identification information of the physical port that actually received the received frame, and if they match (YES), go to step S06. If they do not match (NO), the process proceeds to step S07.

  S06. Deliver the frame to the frame transfer unit 330 to request transfer of the frame, and the process ends.

  S07. Discard the frame and end the process. As a result, even when a duplicated frame is received by a plurality of physical ports from a counter-connected prior art switch, only one of the frames is received and transferred, so that the duplicated frame Unnecessary transfer can be prevented.

  S08. When a failure of a physical port aggregated by logical port 320a is detected, the correspondence between the input and output values of the hash function for selecting the physical port from the physical port group to be aggregated of logical port 320a The definition is changed so that the range of the output value does not include the identification information of the physical port in which the failure is detected.

  S09. The physical port in which the failure is detected is separated from the group of physical ports to be aggregated by the logical port processing unit 320a, and the process ends.

  As a result, even if some of the physical ports in the physical port group aggregated by the logical port 320a do not operate normally, it is possible to transfer frames by reassembling the logical ports with other normally operating physical ports. Thus, a redundant configuration of the links between switches can be realized.

  S10. When recovering from a failure of a physical port aggregated by logical port 320a, the definition of the correspondence relationship between the input and output values of the hash function changed in step 08 above is used, and the range of output values is the physical that detected the failure recovery. Change to include port identification information.

  S11. The physical port in which failure recovery has been detected is incorporated into the group of physical ports to be aggregated by the logical port processing unit 320a, and the process ends.

  FIG. 6 is an operation flowchart of the frame transfer unit of the present invention, which is activated when a frame received from a logical port or a physical port that is not aggregated into a logical port is delivered.

  S01. It is determined whether or not the source address (SA) included in the logical port or the frame delivered from the physical port that is not aggregated to the logical port is registered in the MAC address learning table 340. ) Acquire corresponding entry data and proceed to the next step S02. If not registered (NO), proceed to step S05.

  S02. Determine whether the identification information of the port that delivered the frame, that is, the logical port or the physical port that is not aggregated to the logical port, matches the port identification information included in the entry data acquired in step S01. If they match, the process proceeds to (YES) the next step S03, and if they do not match (NO), the process proceeds to step S06.

  S03. It is determined whether or not the destination address (DA) included in the frame has been registered in the MAC address learning table 340. If it has been registered (YES), the corresponding entry data is acquired and the process proceeds to the next step S04. If not registered (NO), the process proceeds to step S07.

  S04. The frame is transferred to the port indicated by the port identification information included in the entry data acquired in step S03, that is, the logical port or the physical port not aggregated into the logical port, and the process is terminated.

  S05. A pair of the source address (SA) included in the frame and the identification information of the port that delivered the frame, that is, the identification information of the physical port that is not aggregated to the logical port, is entered in the MAC learning table 340 as entry data. Register and move to step S03.

  S06. The frame is discarded and the process is terminated. As a result, when a frame transferred from the link aggregation switch 300 of the present invention to the oppositely linked switch is received by the flooding process of the oppositely linked switch, the frame is discarded. Frame loop transfer and unnecessary frame transfer can be prevented.

  S07. Flood the frame. In other words, the frame is transferred to all ports other than the port that delivered the frame, and the process ends. The port here means a logical port or a physical port that is not aggregated into a logical port. Therefore, when the port that delivered the frame is a logical port, the frame is not transferred to the physical port that the logical port aggregates, and the conventional port linked through the logical port is not used. It is possible to prevent a loop transfer of frames from occurring to the switch.

  7 to 11 show the operation sequence of the link aggregation method of the present invention according to conditions. Here, in the switch 300 of the present invention, an embodiment is shown in which a plurality of links are aggregated with the switch 200 of the prior art. The operation sequence will be described along the frame flow indicated by the dotted arrow. Dotted arrows outside the frame of the MAC address learning tables 340 and 240 indicate that the table is updated with the operation sequence of the sequence number described there. Moreover, the symbol described in the frame which shows the logical port 320a and the physical ports 310a-310e, 210a-210e has shown the identification information of each port.

  FIG. 7 is an operation sequence (1) of the link aggregation method of the present invention. In the switch 300 of the present invention, a frame having a MAC address not registered in the MAC address learning table 340 as a transmission source address (SA) is received. The operation sequence is shown. Here, it is assumed that the physical ports 310a to 310c of the switch 300 are aggregated by the logical port 320a, and the physical ports 310d to 310e are not aggregated by the logical port.

  S01. In the switch 300 of the present invention, when the frame F1 is received from the physical port 310d, the frame F1 is delivered to the frame transfer unit 330. Here, it is assumed that the source address (SA) included in the frame F1 is “01” and the destination address (DA) is “02”.

  S02. Since the transmission source address “01” included in the delivered frame F1 is not registered in the MAC address learning table 340, the frame transfer unit 330 determines that the transmission source address “01” of the frame F1 and the frame F1 are The entry data storing the received physical port identification information “p4” is registered in the MAC address learning table 340.

  Next, since the destination address “02” included in the frame F1 is not registered in the MAC address learning table 340 and the transfer destination port of the frame F1 cannot be specified, the frame F1 is flooded. That is, the frame F1 is transferred to all the logical ports L1 other than the received physical port 310d and the physical port 320e that is not aggregated. Here, since the physical ports 310a, 310b, and 310c are link-aggregated to the logical port 320a, the frame forwarding unit 330 does not directly transfer the frame F1 to the physical ports 310a, 310b, and 310c. Transferred to the representative logical port 320a.

  S03. The logical port 320a selects a physical port 310a as a transmission destination using a predetermined hash function based on the transmission source address “01” included in the frame F1 delivered from the frame transfer unit 330, and transmits the frame F1. Is transmitted to the physical port 310a.

  S04. The switch 200 delivers the frame F1 received at the physical port 210a to the frame transfer unit 230. The frame transfer unit 230 stores the transmission source address “01” and the identification information “q1” of the received physical port 210a because the transmission source address “01” of the frame F1 is not registered in the MAC address learning table 240. The registered entry data is registered in the MAC address learning table 240.

  S05. Further, since the destination address “02” of the frame F1 is not registered in the MAC address learning table 240, the frame transfer unit 230 sends the frame to all the physical ports 210b, 210c, 210d, 210e other than the received physical port 210a. Flood F1. As a result, the frame F1 is also transmitted to the links 400b and 400c connected to the physical ports 210b and 210c, and the duplicated frame F1 is delivered to the physical ports 310b and 310c of the link aggregation switch 300. Then, the frame F1 received by the physical ports 310b and 310c is delivered to the logical port 320a that aggregates the physical ports 310b and 310c.

  S06. The logical port 320a selects a corresponding physical port using a predetermined hash function with the destination address of the delivered frame F1 as an input value, and sends only the frame received from the selected physical port to the frame transfer unit 330. Deliver and discard frames received from other physical ports. Here, if the physical port identification information “p2” corresponds to the destination address “02” of the frame F1, the physical port 310b of the identification information “p2” is selected, and the frame F1 received from the physical port 310b is frame-transferred. The frame F1 delivered to the unit 330 and received at the physical port 310c is discarded. As a result, a plurality of frames copied and transferred by flooding from the switch 200 can be narrowed down to one.

  The frame transfer unit 330 checks whether or not entry data including the transmission source address “01” of the frame F1 delivered from the logical port 320a is registered in the MAC address learning table 340. Here, since the entry data in which the MAC address “01” is associated with the port identification information “p4” has already been registered, the identification information “L1” of the port that delivered the frame F1, that is, the logical port 320a However, since it does not match the port identification information “p4” stored in the entry data, the delivered frame F1 is discarded. As a result, even when the frame F1 transmitted from the link aggregation switch 300 to the switch 200 is received again by the link aggregation switch 300 via the switch 200, the frame F1 is not transmitted to the switch 200 again. F1 loop transfer can be prevented. In addition, by distributing frames to the physical ports 310a, 310b, and 310c aggregated in the logical port 320a, the maximum number of frames is 3 compared to when the link aggregation switch 300 and the switch 200 are connected by a single link. Double bandwidth can be obtained.

  In the above operation sequence, the case where the frame having the source address “01” and the destination address “02” is transferred has been described. However, even if the addresses are different, only the physical port selected by the logical port 320a is changed. It operates in the same way. The same applies when the number of physical ports to be aggregated by the logical port 320a is other than three.

  FIG. 8 shows an operation sequence (2) of the link aggregation method according to the present invention, in which a frame including a MAC address that is not registered in the MAC address learning tables 240 and 340 as a source address (SA) is used. The operation sequence in the case of receiving by is shown. Assume that the states of the MAC address learning tables 340 and 240 inherit the state described with reference to FIG.

  S01. In the conventional switch 200, when the frame F2 is received from the physical port 210d, the frame F2 is delivered to the frame transfer unit 230. Here, it is assumed that the source address (SA) included in the frame F2 is “03” and the destination address (DA) is “04”.

  S02. Since the transmission source address “03” included in the delivered frame F2 is not registered in the MAC address learning table 240, the frame transfer unit 230 uses the transmission source address “03” of the frame F2 and the frame F2. The received identification information “q4” of the physical port 210d is registered in the MAC address learning table 240.

  Furthermore, since the destination address “04” included in the frame F2 is not registered in the MAC address learning table 240 and the forwarding port of the frame F2 cannot be specified, all physical ports other than the physical port 210d that received the frame F2 Flood to 210a, 210b, 210c, 210e. As a result, the frame F2 is delivered to the physical ports 310a, 310b, 310c of the link aggregation switch 300 connected via the links 400a, 400b, 400c, respectively.

  S03. The logical port 320a selects the corresponding physical port identification information using the predetermined hash function with the destination address “04” of the frame F2 delivered from the physical ports 310a, 310b, 310c to be aggregated as an input value. Here, assuming that the physical port identification information “p1” corresponds to the destination address “04”, only the frame received from the physical port 310a indicated by the selected identification information “p1” is delivered to the frame transfer unit 330. Frames received from other physical ports 310b and 310c are discarded. Thereby, the frame F2 duplicated by the switch 200 can be narrowed down to one.

  Next, the frame transfer unit 330 checks whether or not the source address “03” of the frame F2 delivered from the logical port 320a is registered in the MAC address learning table 340, and the MAC address “03” is still registered. Therefore, the stored entry data of the identification information “L1” and the MAC address “03” of the logical port 320a that is the port that has delivered the frame F2 is registered in the MAC address learning table 340.

  S04. Further, the frame transfer unit 330 does not register the destination address “04” of the frame F2 in the MAC address learning table 340 and cannot specify the transfer destination port. The frame F2 is flooded to all logical ports other than the logical port 320a and physical ports that are not aggregated. Here, the frame F2 is duplicated and transmitted to the physical ports 310d and 310e. In this way, even when a frame whose destination address is not yet registered in the MAC address learning table is transmitted from the switch 200 via a plurality of links, the frame is flooded to the link with the switch 200. Therefore, it is possible to prevent frames from being transferred in a loop between the link aggregation switch 300 and the switch 200.

  FIG. 9 is an operation sequence (3) of the link aggregation method of the present invention. In the link aggregation switch 300 of the present invention, a frame including a MAC address registered in the MAC address learning table 340 as a destination address (DA) is received. The operation sequence in the case of having been performed is shown. Assume that the states of the MAC address learning tables 340 and 240 inherit the state described with reference to FIG.

  S01. In the switch 300 of the present invention, when the frame F3 is received from the physical port 310e, the frame F3 is delivered to the frame transfer unit 330. Here, it is assumed that the source address (SA) included in the frame F3 is “05” and the destination address (DA) is “03”.

  Since the source address “05” included in the delivered frame F3 is not registered in the MAC address learning table 340, the frame transfer unit 330 delivers the source address “05” and the frame F3 of the frame F3. The physical port identification information “p5” is registered in the MAC address learning table 340.

  S02. Furthermore, since the destination address “03” included in the frame F3 has already been registered in the MAC address learning table 340, the frame transfer unit 330 stores the port identification information “L1” included in the registered entry data. Forward to indicated port. Here, since the port identification information “L1” indicates the logical port 320a, the frame F3 is transferred to the logical port 320a.

  S03. The logical port 320a selects a physical port as a transmission destination using a predetermined hash function based on the transmission source address “05” included in the frame F3 delivered from the frame transfer unit 330, and selects the frame F3. Send to selected physical port. Here, assuming that the identification information “p3” of the physical port corresponds to the MAC address “05”, the frame F3 is transmitted to the physical port 310c corresponding to the selected identification information “p3”.

  S04. The frame F3 received at the physical port 210c of the switch 200 is delivered to the frame transfer unit 230. The frame transfer unit 230 stores the transmission source address “05” and the received identification information “q3” of the physical port 210c because the transmission source address “05” of the frame F3 is not registered in the MAC address learning table 240. The registered entry data is registered in the MAC address learning table 240.

  S05. Next, since the destination address “03” of the frame F3 has already been registered in the MAC address learning table 240, the frame transfer unit 230 stores the port identification information “q4” included in the registered entry data. The frame F3 is transmitted to the physical port 210d shown.

  As described above, when a frame is transmitted from the link aggregation switch 300 of the present invention to the conventional switch 200, a plurality of links 400a, 400b, and 400c provided between the link aggregation switch 300 and the switch 200 are used. From this, one link is selected, and the frame is transferred only to the selected link. That is, the frame transfer from the link aggregation switch 300 of the present invention to the conventional switch 200 can be distributed and transferred to a plurality of links.

  FIG. 10 is an operation sequence (4) of the link aggregation method of the present invention, and a frame including a MAC address registered in the MAC address learning tables 240 and 340 as a destination address (DA) is received by the prior art switch 200. The operation sequence is shown. Assume that the states of the MAC address learning tables 340 and 240 inherit the state described with reference to FIG.

  S01. When the switch 200 receives the frame F4 from the physical port 210e, the frame F4 is delivered to the frame transfer unit 230. Here, it is assumed that the source address (SA) included in the frame F4 is “06” and the destination address (DA) is “05”.

  The frame transfer unit 230 to which the frame F4 has been delivered has the transmission source address “06” of the frame F4 and the corresponding physical port identification information “q5” because the transmission source address “06” of the frame F4 is not registered in the MAC address learning table 240. "Is stored in the MAC address learning table 240.

  S02. Next, since the destination address “05” included in the delivered frame F4 has already been registered in the MAC address learning table 240, the frame transfer unit 230 includes the frame F4 in the registered entry data. Transfer to the physical port 210c indicated by the identification information "q3". As a result, the frame F4 is delivered to the physical port 310c of the link aggregation switch 300 via the link 400c.

  S03. The logical port 320a of the link aggregation switch 300 selects the corresponding physical port identification information using a predetermined hash function with the destination address “05” of the frame F4 delivered from the physical port 310c as an input value. Here, assuming that the physical port identification information “p3” corresponds to the MAC address “05”, the identification information “p3” of the physical port 310c from which the frame F4 has been received and the selected physical port identification information. Since “p3” matches, the frame F4 is received and delivered to the frame transfer unit 330.

  The frame transfer unit 330 identifies the logical port 320a that is the port that delivered the frame F4 because the transmission source address “06” of the frame F4 delivered from the logical port 320a is not yet registered in the MAC address learning table 340. The entry data storing the information “L1” and the MAC address “06” is registered in the MAC address learning table 340.

  S04. Next, since the destination address “05” of the frame F4 has already been registered in the MAC address learning table 340, the frame transfer unit 330 has the port identification information “p5 included in the registered entry data of the frame F4. "To the physical port 310e indicated by".

  As described above, a plurality of links 400a, 400b, and 400c provided between the link aggregation switch 300 and the switch 200 are also transmitted from the conventional switch 200 to the link aggregation switch 300 of the present invention. One link is selected from among the frames, and the frame is transferred only to the selected link. That is, the frame transfer from the conventional switch 200 to the link aggregation switch 300 of the present invention can be distributed and transferred to a plurality of links.

  FIG. 11 shows an operation sequence when a failure occurs in the link between the link aggregation switch 300 and the switch 200 in the operation sequence (5) of the link aggregation method of the present invention. Assume that the states of the MAC address learning tables 340 and 240 inherit the state described in FIG.

  S01. When a failure occurs in the link 400c, it is detected by the physical port 310c of the link aggregation switch 300 and notified to the logical port 320a.

  S02. The logical port 320a separates the physical port 310c that detected the failure from the group of physical ports to be aggregated (physical ports 310a, 310b, 310c), and makes the group consisting of the physical ports 310a, 310b aggregate Change the configuration. At this time, the correspondence relationship between the MAC address used in the transmission physical port selection unit and the reception physical port selection unit of the logical port 320a and the selected physical port is redefined. As a result, the frame passing link between the link aggregation switch 300 and the switch 200 is changed from the link group G1 composed of three links to the link group G2 composed of two links. Although the total bandwidth is reduced, frame passing continues in a distributed manner across the two links.

  Here, the frame transfer from the switch 200 to the link aggregation switch 300 includes the correspondence between the MAC address registered in the MAC address learning table 240 on the switch 200 side and the transfer destination port identification information, and the logic of the link aggregation switch 300. There is a possibility of mismatch between the correspondence between the MAC address redefined at the port 320a and the physical port identification information. In this case, there is a possibility that the frame transmitted from the switch 200 to the link aggregation switch 300 may be temporarily discarded. However, in this state, the mismatched entry is deleted from the MAC address learning table 240 due to the aging time of the switch 200. Or the frame address transmitted from the link aggregation switch 300 to the switch 200 after redefinition of the logical port 320a is received by the switch 200. The

  S03. When the failure detected in the sequence S01 is recovered, the logical port 320a of the link aggregation switch 300 incorporates the separated physical port 310c into the aggregation-target physical port group, and transmits the physical port selection unit. The correspondence relationship between the MAC address and the physical port used in the reception physical port selection unit is returned to the original state definition before the failure detection.

  In this way, even if a failure occurs in the link with the prior art switch, it is possible to continue the frame transfer by distributing and transferring the frame to the remaining links. Configuration is possible.

  In the embodiment of the present invention described in detail above, the case where the link aggregation switch 300 has one logical port has been described. However, the present invention is not limited to this, and an arbitrary number is possible. Further, the number of physical ports aggregated in the logical port is not limited to three.

  A method for selecting one physical port aggregated in a logical port when transmitting and receiving a frame is not limited to the hash function, and other methods are possible.

The embodiment of the present invention described above is as follows.
(Appendix 1) Aggregating multiple physical ports that transmit and receive frames into a logical port
When transmitting a frame from the logical port, the selected transmission physical is selected as a transmission physical port by selecting one of the physical ports aggregated in the logical port based on a transmission source address included in the frame. Send a frame to the port
When receiving a frame in a physical port aggregated in the logical port, select one of the physical ports aggregated in the logical port based on a destination address included in the received frame and receive physical port As the received frame is a valid received frame when the physical port that received the frame and the selected received physical port match,
The MAC address learning table entry that stores the correspondence between the MAC address and the port identification information indicating the transfer destination port of the frame contains the identification information of the logical port for a plurality of physical ports aggregated in the logical port. Register as port identification information, register physical port identification information as port identification information for physical ports that are not aggregated into the logical port,
For the valid received frame received at the logical port or the frame received at the physical port that is not aggregated to the logical port, the MAC address learning table is searched using the destination address included in the frame as a key and the destination address Acquiring an entry including a matching MAC address, and transferring a frame to a logical port or a physical port indicated by the port identification information included in the acquired entry;
A link aggregation method characterized by the above.
(Supplementary Note 2) In the link aggregation method described in Supplementary Note 1,
For the valid received frame received at the logical port or the frame received at the physical port not aggregated to the logical port, the MAC address learning table is searched as a key for the transmission address included in the frame, and the transmission is performed. An entry including a MAC address that matches the original address is acquired, and if the port identification information included in the acquired entry is different from the identification information of the logical port or physical port that received the frame, the received frame is discarded.
A link aggregation method characterized by the above.
(Supplementary Note 3) In the link aggregation method described in Supplementary Note 1,
When a failure is detected in a physical port aggregated in the logical port, the selection method of the transmission physical port and the reception physical port is redefined by excluding the physical port in which the failure is detected from the aggregation target of the logical port. ,
When the physical port that detected the failure is recovered, the recovered physical port is incorporated as an aggregation target of the logical port, and a method for selecting the redefined transmission physical port and reception physical port is a method before redefinition. Back to
A link aggregation method characterized by the above.
(Supplementary note 4) In the link aggregation method described in supplementary note 1,
The selection of the transmission physical port and the reception physical port in the logical port is performed by a hash function that takes a MAC address as an input value and outputs identification information of one physical port corresponding to the input value.
A link aggregation method characterized by the above.
(Supplementary Note 5) A physical port aggregation unit that aggregates a plurality of physical ports that transmit and receive frames into a logical port;
When a frame is transmitted from the logical port, one physical port belonging to the logical port is selected as a transmission physical port based on a transmission source address included in the frame, and a frame is transmitted to the selected transmission physical port. A transmission physical port selection unit for transmission;
When receiving a frame at a physical port aggregated in the logical port, select one of the physical ports aggregated in the logical port as a reception physical port based on the destination address included in the received frame. A reception physical port selection unit that sets the received frame as an effective reception frame when the physical port that received the frame matches the selected reception physical port;
An entry indicating a correspondence relationship between the MAC address and port identification information indicating a frame transfer destination port is held, and the port identification information in the entry includes the logical port for a plurality of physical ports aggregated in the logical port. A MAC address learning table that stores port identification information, and stores physical port identification information for physical ports that are not aggregated into the logical port;
For the valid received frame received at the logical port or the frame received at the physical port that is not aggregated to the logical port, the MAC address learning table is searched using the destination address included in the frame as a key and the destination address Means for acquiring an entry including a matching MAC address and transferring a frame to a logical port or a physical port indicated by port identification information included in the acquired entry.
A link aggregation switch characterized by that.
(Appendix 6) In the link aggregation switch described in Appendix 5,
For the valid received frame received at the logical port or the frame received at the physical port not aggregated to the logical port, the MAC address learning table is searched as a key for the transmission address included in the frame, and the transmission is performed. Means for acquiring an entry including a MAC address that matches the original address, and discarding the received frame if the port identification information included in the acquired entry is different from the identification information of the logical port or physical port that received the frame Comprising
A link aggregation switch characterized by that.
(Appendix 7) In the link aggregation switch described in Appendix 5,
When a failure is detected in a physical port aggregated in the logical port, the physical port in which the failure is detected is excluded from the aggregation target of the logical port, and the selection method of the transmission physical port and the reception physical port is redefined. Means,
When the physical port that detected the failure is recovered, the recovered physical port is incorporated as an aggregation target of the logical port, and a method for selecting the redefined transmission physical port and reception physical port is a method before redefinition. Comprising means for returning to
A link aggregation switch characterized by that.
(Appendix 8) In the link aggregation switch described in Appendix 5,
The selection of the transmission physical port and the reception physical port in the logical port includes means for performing a hash function that takes a MAC address as an input value and outputs identification information of one physical port corresponding to the input value.
A link aggregation switch characterized by that.

Configuration of the link aggregation switch of the present invention Operation of transmission physical port selection unit of logical port of the present invention Operation of receiving physical port selection unit of logical port of the present invention Operation of the physical port aggregation unit of the logical port of the present invention Operation flow chart of logical port of the present invention Operation flow chart of frame transfer unit of the present invention Operation sequence (1) of the link aggregation method of the present invention Operation sequence (2) of the link aggregation method of the present invention Operation sequence (3) of the link aggregation method of the present invention Operation sequence (4) of the link aggregation method of the present invention Operation sequence (5) of the link aggregation method of the present invention Overview of switch operation in the prior art (2) Overview of switch operation in the prior art (1)

Explanation of symbols

100,200 Prior art switch
110a, 110b, 110c, 110d, 110e Conventional physical port
140,240 Conventional MAC address learning table
210a, 210b, 210c, 210d, 210e Physical port of the prior art
230 Conventional frame transfer unit
300 link aggregation switch
310a, 310b, 310c, 310d, 310e Physical port
320a logical port
321a Transmission physical port selector
322a Receive physical port selector
323a Physical port aggregation unit
400a, 400b, 400c link
p1, p2, p3, p4, p5 Physical port identification information of link aggregation switch
q1, q2, q3, q4, q5 Physical port identification information of prior art switch
DA frame destination address
Fs transmission frame
Fr received frame
F1, F2, F3, F4 frame
G1, G2 link group
Logical port identification information of L1 link aggregation switch
SA frame source address

Claims (5)

Aggregate multiple physical ports that transmit and receive frames into a logical port,
When transmitting a frame from the logical port, the selected transmission physical is selected as a transmission physical port by selecting one of the physical ports aggregated in the logical port based on a transmission source address included in the frame. Send a frame to the port
When receiving a frame in a physical port aggregated in the logical port, select one of the physical ports aggregated in the logical port based on a destination address included in the received frame and receive physical port As the received frame is a valid received frame when the physical port that received the frame and the selected received physical port match,
The MAC address learning table entry that stores the correspondence between the MAC address and the port identification information indicating the transfer destination port of the frame contains the identification information of the logical port for a plurality of physical ports aggregated in the logical port. Register as port identification information, register physical port identification information as port identification information for physical ports that are not aggregated into the logical port,
For the valid received frame received at the logical port or the frame received at the physical port that is not aggregated to the logical port, the MAC address learning table is searched using the destination address included in the frame as a key and the destination address Acquiring an entry including a matching MAC address, and transferring a frame to a logical port or a physical port indicated by the port identification information included in the acquired entry;
A link aggregation method characterized by the above. The link aggregation method according to claim 1,
For the valid received frame received at the logical port or the frame received at the physical port not aggregated to the logical port, the MAC address learning table is searched as a key for the transmission address included in the frame, and the transmission is performed. An entry including a MAC address that matches the original address is acquired, and if the port identification information included in the acquired entry is different from the identification information of the logical port or physical port that received the frame, the received frame is discarded.
A link aggregation method characterized by the above. The link aggregation method according to claim 1,
When a failure is detected in a physical port aggregated in the logical port, the selection method of the transmission physical port and the reception physical port is redefined by excluding the physical port in which the failure is detected from the aggregation target of the logical port. ,
When the physical port that detected the failure is recovered, the recovered physical port is incorporated as an aggregation target of the logical port, and a method for selecting the redefined transmission physical port and reception physical port is a method before redefinition. Back to
A link aggregation method characterized by the above. The link aggregation method according to claim 1,
The selection of the transmission physical port and the reception physical port in the logical port is performed by a hash function that takes a MAC address as an input value and outputs identification information of one physical port corresponding to the input value.
A link aggregation method characterized by the above. A physical port aggregating unit that aggregates multiple physical ports that transmit and receive frames into a logical port;
When a frame is transmitted from the logical port, one physical port belonging to the logical port is selected as a transmission physical port based on a transmission source address included in the frame, and a frame is transmitted to the selected transmission physical port. A transmission physical port selection unit for transmission;
When receiving a frame at a physical port aggregated in the logical port, select one of the physical ports aggregated in the logical port as a reception physical port based on the destination address included in the received frame. A reception physical port selection unit that sets the received frame as an effective reception frame when the physical port that received the frame matches the selected reception physical port;
An entry indicating a correspondence relationship between the MAC address and port identification information indicating a frame transfer destination port is held, and the port identification information in the entry includes the logical port for a plurality of physical ports aggregated in the logical port. A MAC address learning table that stores port identification information, and stores physical port identification information for physical ports that are not aggregated into the logical port;
For the valid received frame received at the logical port or the frame received at the physical port that is not aggregated to the logical port, the MAC address learning table is searched using the destination address included in the frame as a key and the destination address Means for acquiring an entry including a matching MAC address and transferring a frame to a logical port or a physical port indicated by port identification information included in the acquired entry.
A link aggregation switch characterized by that.

Images