The hub is called "Hub" in English."Hub" means "center". The main function of the hub is tosignalCarry out regeneration, shaping and amplification to expand the transmission distance of the network, andnodeFocus on the node centered on it.It works on OSI（Open system interconnectionReference model) The first layer of the reference model, namely“physical layer”。Hub andnetwork card、Network cableEqual transmissionmediumSame, belonging toLANBasic equipment in, usingCSMA/CD(i.e. carrier sense multiple access technology with conflict detection) media access control mechanism.Hub EachInterfaceSimple transmit and receive bits: receive 1 and forward 1, receive 0 and forward 0, without collision detection.
Hub（hub）Belongs to pureHardwareThe underlying network equipment basically does not have the ability of "intelligent memory" and "learning" similar to switches.It doesn't haveSwitchOwnedMAC address table, so when it sends data, it is not targeted, but broadcast.That is, when it wants to send data to a node, it does not send the data directly to the destination node, but sendsdata packetSend to all nodes connected to the hub, as shown in the figure, which is simple and clear.
HUB is aMultiportOfTransponderWhen HUB is the central device, a fault occurs on one line in the network, which does not affect the work of other lines.So HUBLANHas been widely used.Most of the time it is used for star andtree type networktopological structure Middle, RJ45 interface is used to connect with eachhostConnected (also availableBNC interface）HUB has many kinds according to different statements.
Hub(Hub) refers to the equipment that connects multiple Ethernet twisted pairs or optical fibers together under the same physical medium.The hub is the physical layer that operates in the OSI model.It can be regarded as a multi port repeater. If it detects a collision, it will submit a blocking signal.[1]
The hub usually attaches BNC and/or AUI adapters to connect to a traditional 10BASE2 or 10BASE5 network.[1]
Since the hub will regenerate or amplify any digital signal it receives, and then submit it from all ports of the hub, it will cause a great chance of collision between signals, and the signal may also be eavesdropped. This means that all devices connected to the hub belong to the same collision domain name and broadcast domain name, so most hubs have been replaced by switches.[1]
principle
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Hub Configuration Diagram
Signal forwarding principle
The hub works on the physical layer and thedata link layerMAC of（Media Access Control）Sublayer.The physical layer defineselectricalsignal, symbol, line status and clock requirements,Data encodingAnd connectors for data transmission.Because the hub onlysignalIt is reshaped, magnified and retransmitted without coding, so it is a physical layer device.The 10M hub has four standard interfaces available on the physical layer: 10BASE-5, 10BASE-210BASE-T、10BASE-F。10BASE-5 (AUI) for 10M hubportIt is used to connect layer 1 and layer 2.[1]
The hub adopts CSMA/CD（carrierFrame listening multiple access/Conflict detection）Protocol, CSMA/CD is MAC layer protocol, so the hub also contains data link layer content.[1]
10M hub as a specialMultiportRepeater, which should be followed in the network trunk expansion5-4-3 RulesThat is, a network segment can only be divided into 5 segments at mostSubnetSegment;A network segment can only have 4 repeaters at most;A network segment can only have three sub network segments containing PCs at most. As shown in Figure 19, sub network segment 2 and sub network segment 4 are used to extend the distance.[1]
The working process of the hub is very simple. It can be simply described as follows: first, the node sendssignalTo the line, the hub receives the signal. Since the signal is attenuated in cable transmission, the hub shapes and amplifies the attenuated signal after receiving the signal, and finally the hub forwards the amplified signal broadcast to all othersport。[1]
classification
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handle
Hub
HUB input according tosignalIn terms of processing mode, it can be divided into passive HUB, active HUB, intelligent HUB and other HUBs.
Passive HUB
It's the worst quality, nosignalDo anything, rightmediumThe transmission distance of is not extended, and has a certain impact on the signal.Each set connected to this HUBcomputer, can receive the data from all other computers on the same HUBsignal；[1]
Active HUB
Active HUB and passive HUBdifferenceIs that it cansignal amplificationOr regeneration, so it has two morehostEffective transmission distance between;[1]
Smart HUB
This guy must be better than those two when I hear this word!In addition to all the functions of the active HUB, the intelligent HUB also hasNetwork managementAnd routing function.In the intelligent HUB network, not every machine can receivesignal, only the same address as the signal destination addressportcomputerCan be received.Some intelligent HUBs can choose the best path by themselves, which is good for network management![1]
other
There are many other methods, such as 10M, 100M, 10/100M adaptive HUB, and so on.In a word, the market price is not expensive. Try to buy better ones.[1]
Structure function
According to the structure and function, hubs can be divided into three categories: unmanaged hubs, stacked hubs, and chassis hubs.
(1) Unmanaged Hub
The simplest hub through EthernetBusProvide central network connection, which is connected in the form of star.This is called an unmanaged hub. It is only used in very small networks with up to 12 nodes (in a few cases, more can be used).Unmanaged hubs have no management software or protocol to provideNetwork management function, such hubs can be passive or active, and active hubs are used more frequently.[1]
(2) Stackable Hub
stackable hub
Stacked hubs are slightly more complex hubs.The most prominent feature of the stack hub is 8TransponderThey can be directly connected to each other.In this way, you can simply add hubs and connect them to the installed hubs to expand the network. This method is not only low-cost, but also simple and easy to operate.[1]
(3) Chassis hub
Chassis hub is a kind of modularized equipment, and various types of modules can be inserted on its backplane circuit board.Some hubs haveredundancyBackplane and power supply.At the same time, some modules allow users to replace failed modules without shutting down the entire hub.The backplane of the hub provides multiple buses for plug-in modules, which can adapt to different segments, such as EthernetFast Ethernet、Fiber distributed data interface(Fiber Distributed Data Interface, FDDl) andAsynchronous transmission mode(Asynchronous Transfer Mode, ATM).Some hubs also containbridge 、RouterOr exchange module.The active chassis hub may also have a retiming module for communicating with the amplified datasignalrelation.[1]
Hub (HUB) belongs toData communication systemThe basic equipment in, with flow monitoring function.It andTwisted pairetc.Transmission mediumSimilarly, it requires no software support or little management software managementHardwareEquipment.It is widely used in various occasions.Hub works inLAN(LAN) environment, called physical layer device.Electrical interconnection is adopted in the hub. When the LAN maintenance environment is logicalBusorAnnular structureThe hub can be used to create a physical star ortree type networkStructure.In this respect, the hub plays the role ofMultiportOfRepeater。In fact, the hub is actuallyRepeaterOne of thedifferenceOnly the hub can provide moreportService, so the hub is also calledMulti port repeater。[1]
The broadcast data transmission mode of this device has three shortcomings: (1) Usersdata packetSending to all nodes is likely to cause insecurity in data communication, and some people with ulterior motives can easily illegally intercept other people's data packets.(2) Since all data packets are sent to all nodes at the same time, plus their sharingbandwidthMode (if two devices share a 10M hub, each device has only 5M bandwidth), which is more likely to cause network congestion and further reduce network execution efficiency.(3) Non duplex transmission,Network CommunicationsLow efficiency.Each hub at the same timeportData communication can only be carried out in one direction, not likeSwitchIn that way, two-way duplex transmission is carried out, and the network execution efficiency is low, which cannot meet the requirements of largeNetwork CommunicationsDemand.[1]
structure
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The external board structure of a common hub is very simple.For example, the simplest 10BASE~T EthernetHub hub of D-Link is a cuboid, with an AC power socket and switch, an AUI interface and a BNC interface on the back, and a row of 17 RJ-45 interfaces distributed in most positions on the front.On the right side of the front, there are LED interface indicators and LEDs corresponding to each RJ-45 interfacestateindicator light.From the appearance, high-end hubs are different from modern hubsRouterOr switched routerdifference。Especially modern two speed adaptiveEthernetThe hub is generally built-in with a switching module that can realize mutual communication between internal 10Mb/s and 100Mb/s network segments, so this type of hub can completely realize communication exchange between nodes in the network segment with the hub as the node. Sometimes people also use this type of hubswitching hub Simply calledSwitch, which makes it difficult for users who use hubs for the first time to identify them correctly.However, it is a relatively simple method to judge the hub according to the type of backplane interface.[1]
purpose
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According to IEEE 802.3 protocol, the hub function is to randomly select aportAnd make it exclusivebandwidth, uplink device with hub（Switch、RouterOr server, etc.).It can be seen that the hub has the following two characteristics when working.[1]
First of all, Hub is just aMultiportOfsignal amplificationWhen a data signal is received by a port during operationSource PortThe signal has been attenuated during transmission to the Hub, so the Hub will shape and amplify the signal to make the attenuatedSignal regeneration(Restore) to the status at the time of sending, and then forward to all otherworking condition On the port.From the way the Hub works, it only plays a role in the networksignal amplificationAnd retransmission function, which aims to expand the transmission range of the network, but does not have the directional transmission capability of signals, is a standard shared equipment.Therefore, some people call the hub "dumb hub" or "dumb hub".[1]
However, with the development of technology and changes in requirements, many Hubs have broadened their functions and are no longer affected by this working mechanism.The network composed of Hub is a shared network, and Hub can onlyHalf duplexWork under.[1]
Hub is mainly used to build a shared network. It is used to solve the problem from the server directly to thedesktopmostEconomicsThe scheme of.In a switched network, the Hub directly communicates withSwitchConnect the switchportThe data of is sent to the desktop.The Hub is flexible in networking. It is located at a star node of the network and connects the nodesworkstationCentralized management is carried out so that the faulty workstation will not affect the normal operation of the whole network, and users are free to join and exit.[1]
LAN partition
fromLANThe hub can be divided into five different types.
From single relayNetwork segmentThe hub is directly derived from the hub and uses the hub backplane. This hub has multiple trunk network segments.Its main advantage is that users can be distributed to multiple relaysNetwork segmentTo reduce the information traffic load of each network segment, the information traffic between network segments is generally required to be independentbridge orRouter。[1]
Based on the multi segment hub, the integratorUser PortConnection with multiple backplane network segmentsprocess automation, and by adding portsCommutative matrix(PSM).PSM can provide an automated tool to integrate any external userportConnect to any trunk segment on the hub backplane.portswitching hub Its main advantage is that it can realize the automation of movement, addition and modification.[1]
portswitching hub Pay attention to port switching, while the network interconnection hub is located in multipleNetwork segmentSome types of integrated connections can be provided between thebridge 、RouterOr LANSwitchTo complete.This type of hub is usually in the form of a chassis.[1]
Hub andSwitchThe boundaries between them have become blurred.switching hub There is a core switched backplane, which uses a pure switching system to replace the traditionalShared MediarelayNetwork segment。Such products are already on the market, and hybrid (trunk/switch) hubs are likely to dominate this market in the next few years.It should be noted that such hubs andSwitchThere are almost no features betweendifference。[1]
With the development of technologyLANEspecially in some large and medium-sized LANs, hubs have been gradually withdrawn from application, andSwitchReplace.Hub is mainly applied to the edge of some small and medium-sized networks or large and medium-sized networks.Below inSmall LANThe selection method is introduced.[1]
speed
The selection of hub speed mainly depends on the following three factors.
If the uplink device is allowed to run 100Mbit/s, you can naturally purchase a 100Mbit/s hub;Otherwise, 10Mbit/s hub should be the ideal choice because it is used forNetwork connection deviceA 10Mbit/s hub can meet the application needs of a small number of networks with low communication traffic.[1]
Since all sites connected to the hub compete for the same uplink busNumber of portsThe more, the more likely it is to cause conflict.At the same time, send to any hubportThe data of will be sent to all ports connected to the hub. Too many ports will reduce the effective utilization of the device.According to practical experience, a 10Mbit/s hubcomputerThe number should not exceed 15, and the number of 100Mbit/s should not exceed 25.If more than, useSwitchTo replace the hub.[1]
(3) Application requirements
The content transmitted does not involve voiceimageWhen the transmission capacity is relatively small, select 10Mbit/s.If the transmission volume is large and may involveMulti-MediaApplication (note that hubs are not suitable for transmitting time sensitivitysignal, such as voice signal), 100Mbit/s or 10/100Mbit/s adaptive hub should be selected.The price of 10/100Mbit/s adaptive hub is generally higher than that of 100Mbit/s.[1]
Repeater
Hub is a specialRepeater, can be used as a switching device for multiple network segments, because several hubs can be cascaded.Intelligent hub, which can alsoNetwork management、routeNetwork functions such as selection are integrated into it.The hub is the smallest unit to manage the networkLANStar connection point for.It centralizes the management of workstations and does not let the problem section affect the normal operation of the whole network.Hub isLANThe most widely used connection equipment in the can be divided into independent hub, modular hub and stacked hub according to the configuration form. Its role can be simply understood as connecting some machines to form a LAN.[1]
For the most commonStar topologyStructurally, the hub (HUB) is the heart part. Once it fails, the whole network will not work, so its quality is very important for the whole network.[1]
Operation method
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Stacking mode
To make the hub meet the requirements of large network pairsportIn general, the stacking or cascading mode of hubs is adopted in larger networks to meet the quantity requirements of.However, the main applications of these two methods are different. Now let's introduce the stacking method.[1]
Stacking means that several hubs are connected by cablesstackportConnect them to expand the number of ports of a single hub. Note that onlyStacking HubOnly this port is available. A stackable hub usually has both "UP" and "DOWN" stacking ports, as shown in Figure 9.[1]
The hub stack is directly connected from the "UP" stack port of one hub to the "DOWN" stack port of another hub through a special connection cable provided by the manufacturer.All hubs in the stack can be regarded as a whole hub for management, that is, all hubs in the stack can be regarded as a hub from the topological structure.Figure 20 shows the stack connection diagram of a 3Com SuperStack II PS Hub 40/50 stack hub, while Figure 21 shows the stack connection diagram of Cisco FastHub 300/400 stack hub.This connection between hubs usually does not occupy the original commonport, and the stack port has intelligent recognition performance, so the hubs stacked together can be managed as a hub.HubStacked Die Special management module and stack connection cable are used to establish a wide bandwidth between hubslink , so that every actual userbandwidthIt is possible to be wider (only when not allportIn use).[1]
Stacked hubsportThe expansion mode is limited by the type and spacing distance of hubs. The first condition is that the hubs that realize stacking must be able tostackOf;The other kind of stack connection is generally the connection between the inbound hubs that are very close to each other (the stack connection cable provided by the manufacturer is generally 1m), so this hub port expansion connection mode is too limited by the distance.[1]
Key points of installation
Refer tocountryBuilding standard design atlas "Construction atlas of smart home control system 03X602" and international standard specification "EIA/TIA569 communication channel and space standard of business building".
Troubleshooting
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Hub (HUB) orSwitch(Switch) YesLANThe most popular equipment in China.Generally, they findNetwork failureProvide convenience, such as connecting with HUB (or Switch) through observationportTo determine whether the network connection is normal, check whether the indicator of is on.For 10/100Mb/s adaptive HUB (or switch), it can also be connected byportThe different colors of the indicator light can be used to determine whether the connected computer is working at 10Mb/s or 100Mb/s.Therefore, in most applications, the use of HUB (or Switch) is beneficial tonetwork maintenanceOf.However, the improper use of HUB (or switch) or its own damage will bring problems to the network connection.[1]
[Fault phenomenon]
After upgrading the network from 10Mb/s to 100Mb/s, the network cannot work normally.
[Fault analysis and handling]
stayLANWhen the network connection range is large, the network transmission can be expanded through the cascade between HUBsdistance。In a 10Mb/s network, up to four levels can be cascaded to make the maximum transmission distance of the network reach 600m.But when the network is upgraded from 10Mb/s to 100Mb/s or a new 100Mb/sLANIf the 100MHUB is connected by ordinary methodslocal area networkNot working properly.As we all know, only two 100Mb/s HUBs can be cascaded in a 100Mb/s network, and the connection distance between two 100Mb/s HUBs cannot be greater than 5m, so 100Mb/sLANThe maximum distance when HUB is used is 205m.If the actual connection distance does not meet the above requirements, the network will not be connected.This point should be paid enough attention, otherwise it is easy to cause serious errors when users plan the network.[1]
[Fault phenomenon]
A unit sets up aLAN, using two 16 ports (with a cascadeport）All computers are connected to the HUB of the main computer room through HUB.Wherein, HUBA passedcascadeportIt is connected to the 16th port of the HUBB, and the HUBB is connected to the HUB of the main computer room through the cascade port,Other portsConnect workstations separately.Used by the whole workstationStatic IP address, whose values are 192.168.0.2, 192.168.0.3, and so on. 192.168.0.1 is allocated to NT serversSubnet maskAll are 255.255.255.0.Ping is used for each workstation set before formal connection to the servercommandTest,resultAll are connected, and all workstations connected to HUB A can also be connected to the workstations connected to HUB B with the Ping command.However, when the server is connected, only the workstation connected to HUB B can log in to the server, while the workstation connected to HUBA cannot log in.[1]
[Fault analysis and handling]
By observing the computernetwork cardAnd each of the two HUBsportExcept the 16th HUBBportThe LEDs corresponding to the cascade port of HUB A are not lit, but the LEDs of all network cards and other ports are lit evenly, indicating that the connection between the computer and HUB is normal. Therefore, the problem is most likely due to the cascade port of HUBA and the 16th port of HUB B.In this case, the cascade in HUB A is suspectedportAt least one of the 16th ports of HUB B and HUB B is bad.In order to further confirm itsportIt is bad. You can change the positions of the two HUBs, but the result is still the same.Next, try to connect theTwisted pairIt is inserted into a common port elsewhere in HUB B, and the result isProblem solvingAll workstations in the network can be connected to the server, and the workstations connected to the two HUBs can respond to each other.It can be seen that some HUB cascadesportThe ports next to and are not independent but belong to the same port (although there are two independent physical ports).Many HUBs used a toggle switch in twoportBetweencascadeThe switch is omitted in the later products, but if one port is used as a cascade port, the other port will be invalid.[1]
[Fault phenomenon]
A HUB connecting two buildings often burns out, sometimes three or four times a month.
[Fault analysis and handling]
After testingPower supply systemIt is aging, the absolute voltage of the zero line is 30V, and the absolute voltage of the live line is 250V, but the voltage is still 220V when measured with a multimeter;From UB to HUB on Floor B, the two HUBs will bear a potential difference of 30V, which is likely to cause damage.The solution is very simple, just in the A buildingSwitchThe room can be connected to a ground wire.[1]
We know that there is only one ring networkPhysical signalTransmission channels are all transmitted through one transmission medium, so there arenodeScramblechannelThe contradiction of,transmission efficiency Lower.After the introduction of the hub, each station is connected to the hub with its own dedicated transmission medianodeThere is no longer only one transmission channel between nodessignalThrough the hub centralization, the hub will shape and amplify the signal and send it to all nodes, so that at least there will be no collision on the uplink channel.But the hub based network is still a sharemediumOfLAN"Sharing" here is actually a hubInternal busTherefore, when the uplink channel and downlink channel send data at the same time, it will still existsignalCollision phenomenon.When the hub willportCollision intensification occurs when collision is detectedsignal(Jam) Deliver to the destination port to which the hub is connected.At this time, all data cannot be sent successfully, forming a network "traffic jam".[1]
The emergence of this network phenomenon can be illustrated by a vivid reality, that is, there are two directions of cars coming at the same time on a single lane.
We know that only one direction of travel is allowed on a single lane, butSmall townsWith limited conditionsregulationsThe single lane is also likely to allow vehicles from two directions to pass, but it must pass at different times.The same is true in the hub. Although each node has its own independent channel to connect with the hub, there is only one common channel inside the hub. The uplink and downlink data must be sent and received through this shared channel. This may be like a single lane. When the uplink and downlink channels send data at the same time, traffic jams may occur.It's easy to understand, isn't it?[1]
Because of this shortcoming, the hub cannot be applied to a larger network alone (usually withSwitchAnd other equipment to share a small partNetwork Communicationsload）Just like there can't be a single lane in the center of a big city, because the larger the network, the greater the chance of network collision.Because of this, the hub'sdata transmissionThe efficiency is relatively low, because it can only transmit data in one direction at the same time, which is the so-called "simplex" mode.If the hub is to be selected as a single hub device in the network, the network size should be less than 10 sets, and the hubbandwidthIt should be more than 10/100Mbps.[1]
Hub except sharingbandwidthIn addition to this shortcoming, there is another aspect that must be considered when selecting a hub, that is, its broadcast mode.Because the hub is pureHardwareThe underlying network equipment basically does not have the ability of "intelligent memory", let alone the ability of "learning".It also does not have theMAC address table, as shown in Figure 2.[1]
This broadcast data transmission method has two shortcomings: plus the sharing described abovebandwidthIn this way, network congestion is more likely to occur and network execution efficiency is further reduced.[1]
Understand the hub'sworking principleThen, let's learn more about the hub inLANInstallation and connection methods in.
Access equipmentThe most important thing is itsInterface technologyDifferent interfaces apply to different application environments, and different applications correspond to corresponding interfaces, not only hubs, but also the followingSwitch、RouterWaiting is the same.The interface of the hub is relatively simple. In order to make you master the connection of various applications of the hub, it is necessary for us to understand some of the main interfaces of the hub.[1]
Hub usually provides three types ofport, i.eRJ-45 port, BNC ports and AUI ports to be suitable for connecting networks built with different types of cables.Some high-end hubs also provideOptical fiberportAnd other types of ports.[1]
RJ-45 interface can be used for connectionRJ-45 connector, for use byTwisted pairBuilt network, thisportIt is the most common port. Generally, Ethernet hubs provide this port.What we usually talk about is how many RJ-45 hubsport。As shown in Figure 3.
RJ-45 of hubportDirect connectioncomputer、Network printeretc.terminal equipment, can also be compared with otherSwitch, hub and other hub equipment andRouterConnect.It should be noted that when connecting to different devices, theTwisted pair cableOfJumperThe methods are different.For details, please refer to the introduction of network cable production.[1]
BNCportIt is used forCoaxial cableThe connected interface is usually connected through the BNC T-connector. Figure 4 shows the schematic diagram of a hub BNC port connected through the BNC connector.[1]
Most 10Mbit/s hubs have a BNCport。When the hub has both BNC and RJ-45portBecause the RJ-45 port can be connected with theTwisted pairNetwork connection can also be connected to the thin cable network through the BNC interface, so twisted pair and thin cableCoaxial cableTwo use different communicationTransmission mediumThe connection between the networks of.This dual interface feature is compatible with the originalCoaxial cableNetwork (10Base-2), and can gradually become mainstreamTwisted pairThe transition of the network (10Base-T), of course, can also realize the connection with the remote thin coaxial cable network (less than 185 meters). The following figure 5 shows two different connections through the BNC interface provided by the hub and the twisted pair RJ-45 interfaceTransmission mediumNetwork connection diagram of the network.[1]
Similarly, if the distance between two networks is greater than 100 meters, useTwisted pairWhen the connection between two networks cannot be realized, you can also use the BNC port of the hub toCoaxial cable transmissionConnect two transmission networks, and both networks can still use twisted pair, which is a cheap and common transmissionmedium, as shown in Figure 6.However, it should be noted that the distance between the two networks cannot be greater than 185m.[1]
AUIportCan be used to connect thickCoaxial cableAUI connector, so this interface is used forCoaxial cableThe schematic diagram of network connection is shown in Figure 7. There are few hubs with such interfaces, which are mainly available in some backbone hubs.[1]
Due to the use of coarseCoaxial cableAsTransmission mediumThe network cost is high, and the wiring is relativelydifficultyTherefore, in practice, it is very rare that it is really used for thick coaxial cable wiring.However, because the single segment is thickCoaxial cableThe transmission distance supported by 10Base-5 is up to 500 meters. Therefore, thick coaxial cable can be used as the communication cable between long-distance networks.Therefore, it can also be used as a cheapRemote connectionSolution.The connection diagram is shown in Figure 6 above, which differs from the network connection used heremediumIt is a thick coaxial cable.[1]
With the help of transceivers, AUIportIt can also realize the connection with RJ-45 interface, BNC interface and even optical fiber interface.Figure 8 below shows the AUI to RJ-45 transceiver from left to right (used to realize AUIportConnection with RJ-45 interface), AUI to BNC transceiver (used to realize the connection between AUI port and BNC interface), AUI to ST transceiver (used to realize the connection between AUI port and optical fiber interface).Of course, there are many kinds of transceivers, such as RJ-45 toRS-232RJ-45 to BNC, etc.But don't underestimate this small thing. Guess its price. I think you will underestimate it in most cases. I couldn't figure out the price when I bought it for the first time. But after asking a lot of people (it's hard to find), I realized that I had to accept this price.Generally speaking, this kind of product costs about 130 yuan for authentic products. Is it unexpected?The main brands of such transceivers are D-Link, HP, etc.This kind of product plays a role of interface type conversion (of course, it is not as simple as cable connection and needs to be completed through a certain circuit), so it is usually called "adapter".[1]
suchportOf course, only stackable hubs are available. Its function is to connect two stackable hubs, just like its name.Generally speaking, a stackable hub has two similarport: One is marked as "UP" and the other is marked as "DOWN". When connecting, the cable is used to connect from the "UP" port of one hub to the "DOWN" port of another stackable hub, all of which are "female" heads. Therefore, the connecting line ends must be "male". However, this kind of connecting line is provided by the manufacturer when purchasing stackable hubs. If it is damaged or lost, it can also be directly connected to theComputer CityJust explain the purpose to the merchant, and the port diagram is shown in Figure 9 below.[1]
The installation of the hub is relatively simple, especially the fool hub, as long as it is fixed in the distribution cabinet and plugged in the power cord.Which one needs to be connectedTwisted pairInsert the RJ-45 head of which twisted pair into the hubportOK.Although the intelligent hub can be used after being fixed, if you want to achieve remote management, you must make the necessary configuration to specify the IP address information for the hub.In addition, rack mounted hubs are generally used in some large networks, which involves the rack installation of hubs.[1]
In terms of structure, there are two types of hubs: rack type and desktop type. The hub used by general departments is desktop type;Enterprise computer rooms are usually rack mounted.The rack type hub is convenient to be fixed in a fixed place, usually with other hubsSwitchOthers are installed in the same cabinet as the server, which is convenient for network connection and management, and also saves the space occupied by the devices.If you choose to purchase a rack mounted hub, you can select a hub rack (usually provided by the manufacturer).Now let's take a look at the installation of rack hub.
Rack mounted hubs are generally installed in cabinets together with other equipment. Of course, these cabinets have corresponding structural standards in the industry, especially strict regulations on dimensions (such as width, 1U (unit) height, etc.), so that all equipment can be installed together easily and aesthetically. This is why the hub is empty,The reason why we have to do it as big as it is, of course, there is another advantage of large chassis, which is better heat dissipation.[1]
In terms of width, international standard cabinets can be roughly divided into three categories: 19 inches, 23 inches and 24 inches. This is mainly based onServer cabinetAccording to the requirements of.Depending on the number of installed equipment, cabinets with different heights can also be selected.The height of the cabinet is usually measured in "U". "U" actually means "Unit". In Chinese, it means "one unit". 1U=1.75 inches.This kind of cabinet is usually installed in the following steps.[1]
Step 1: Fix the mounting bracket
Before installing the hub to the cabinet, the fixed bracket should be installed at the specified position of the hub (refer to the operation manual), which is to prepare for installing the hub on the rack in the future.Different hubs have different brackets, but the installation principle is basically the same.Figure 10 shows a mounting bracket provided with Cisco hub.[1]
Cisconetwork equipment The size of 19 inch is mostly 19 inch (because 19 inch is the most popular cabinet standard in the world). When 19 inch network equipment is installed in a 19 inch cabinet, the mounting bracket is fixed as shown in Figure 11.When the size of the cabinet is 23 or 24 inches, the network equipment needs to be installed in the 23 or 24 inch cabinet. The fixing method of the mounting bracket is shown in Figure 12.[1]
Step 2: Fix the equipment
Mounting bracketfixedAfter that, the next thing to do is to put the hub equipment installed with the bracket into the corresponding position of the cabinet and fix it in the cabinet.In fact, this installation method is very easy. In fact, only a few screws can be fixed. Refer to Figure 13 for the installation method.[1]
Step 3: Fix conductor
After the hub is installed in the cabinet, it is necessary to connect the network cables. Generally speaking, there are several network devices in a cabinet from the ground, so many network cables are concentrated in the cabinet. If these network cables are not clearNetwork managementIt will bring great inconvenience, so we need to bundle, install and tidy the network cables.At this time, it is generally necessary to install conductors for the network cables, so that the bundled ground network cables become neat and beautiful, and easy to manage.The installation method of conductor is shown in Figure 14.[1]
Above, we introduced the method of installing the rack hub in the cabinet, which is generally applicable to large networks, and for smallofficeThere is usually no cabinet, and the hub can only be installed on the desktop or wall.[1]
For the installation of the hub on the desktop, the mounting bracket can be fixed on the desktop first. In this installation mode, there are two different installation directions: one is the horizontal installation mode that allows the hub to be placed horizontally, as shown in Figure 15;The other is to place the hub vertically, and its bracket is fixed as shown in Figure 16.[1]
There are two ways to install the hub on the wall: one is to fix the hub horizontally on the wall, and the installation method shown in Figure 17 can be used;The other is to install the hub vertically on the wall as shown in Figure 18.[1]
Although the connection of the hub is simple and basically requires no configuration, through understanding its connection principle, the hub can be better used to meet the needs of small and medium-sized network applications.Before formally introducing the connection method of the hub, let's learn about thesignalForwarding principle.[1]
Emergency methods
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When a hub providesportIf not, there are generally two ways to expand the number of users.
(1) Stacking
Stacking is a solution for a single hubportIt is a method when there is not enough. However, since multiple hubs stacked together still work in the same environment, the number of layers stacked cannot be too many.However, many hubs on the market have more stack layers than other brands as selling points. If this happensdifferenceTreatment: on the one hand, the more stackable layers, the higher the stability of the hub;On the other hand, the more stackable layers, the morebandwidthThe smaller.[1]
Cascading is another way to increase the number of users in the network, but the use of this function is generally conditional, that is, the Hub must provide a stackableportThis port is usually marked with "Uplink" or "MDI", and is used to cascade with other Hubs.If no specialportWhen cascade connection is necessary, connect theTwisted pairMisalignment must be carried out during fabrication.[1]
The early Hub was a low-end product and could not be managed.With the development of technology, some hubs have introducedSwitchBy addingNetwork managementThe module implements simple management of the hub (SNMP) for ease of use.However, it should be noted that although the same support is provided for SNMP, it is differentmanufacturerModules of different products of the same manufacturer are different.The price of the Hub with SNMP function is higher. For example, the price of the DEl824 non intelligent 24 port 10Base-T from D-Link is about 1000 yuan cheaper than that of the DEl8241 with network management module.[1]
If the network system is simple, there is noGeneric cablingIn addition, there are fewer users in the network, such as a home, one or several adjacent offices, so it is unnecessary to consider the overall dimensions of the Hub.However, sometimes this is not the case. For example, in order to facilitate the centralized management of multiple Hubs, they have already purchased Hubs before purchasing themcabinetAt this time, the overall dimensions of the Hub must be considered when purchasing it, otherwise the Hub cannot be installed on the rack.The cabinets on the market are generally designed according to the 19 inch industrial specifications, and can be installed with most 5-port, 8-port, 16 port and 24 port Hubs.However, in order to prevent accidents, be sure to pay attention to whether it conforms to the 19 inch working specification when purchasing, so as to ensure safe and centralized management in the cabinet.[1]
imagenetwork cardSimilarly, the Hub on the market is basically composed ofU.S.ABrand and ChinaTaiwanBrand occupied, and several mainland companies have also launched hub products.Among them, the high-end Hubs are mainly occupied by American brands, such as 3COM, Intel, Bay, etc., which are unique in designportConfigure oneprocessorOf course, the price is also high.D-Link and Accton in Taiwan of China occupy the main share of the low-end hub. Lenovo, Stark, TPLink and other companies in the mainland have launched their own products to the market with strong strength.These middle and low-end products all use single processor technology, and their peripheral circuit design ideas are much the same, and the welding process means to realize these ideas are basically the same, with little difference in price. The mainland products are relatively cheaper, and are increasingly occupying a larger market share.along withSwitchThe price of the product is declining day by day, and the hub market is shrinking day by day. However, in specific occasions, the hub can bring higher efficiency with lower investment because of its low latency.SwitchIt is impossible to completely replace the hub.[1]
