Coaxial cable

  • differentPC computerBetween, can be usedCoaxial cableIs connected, as shown in the following figure

1. Half duplex communication

  • Coaxial cable is half-duplex communication, that is, only one communication can pass through the cable at a time, and one computer sends the communication, all the computers will receive the communication, and do different processing of the communication
  • As follows, the second computer sends the communication, all the other computers receive the communication, and there is only one communication in the line

  • Suppose it goes from the second computer to the fourth computer, and the other three computers receive the communication and discard it without processing it

  • The fourth computer sends a response communication to the second computer, and all computers receive the communication from the fourth computer

  • Each computer does different things based on the communication it receives
  • The second computer receives the communication and processes it, while the other three computers receive the communication and discard it without processing it

2, easy to conflict

  • Only one signal can exist in the coaxial cable at a time, such as from a second computer to a third
  • If a fourth computer sends a signal to a third computer at this point, a signal collision occurs

3. Unsafe

  • When the second computer sends a message to the fourth computer, the other computers can also receive the message. If the other computers have a packet capture tool installed, the second computer will receive the message

There was a break in the middle and the whole thing was paralyzed

  • The communication travels through the cable, and the coaxial cable has terminal resistors at both ends that absorb the incoming communication
  • If there is no termination resistor, when a communication arrives, it will backtrack and travel throughout the line, causing a collision

  • As in the case above, without the termination resistor, the communication will bounce back
  • When a cable is broken at one point, the communication may not be reached, and the communication will bounce back at the break point
  • As shown in the figure below, there is a break between the second computer and the third computer. The third computer sends communication to the first computer. As a result, communication cannot be sent to the first computer

5. Conflict domains

  • The number of computers connected to each other that conflict is also known as a conflict domain

Two, the hub

1. Application of the hub

  • Hubs are basically the same as coaxial cables, tooHalf duplex communication,Easy to conflictandunsafe

  • However, if the connection between the hub and one computer is broken, it does not affect the communication between other computers
  • The following figure,Computer 1andHubs 0Between,Computer 3andComputer 2Communication is still normal

2. Packet Tracer uses a hub to communicate

  • Let’s add threePC computer

  • Put one in the middleA hub

  • Using the line will bePC computerandA hubConnect. If you don’t know what line to use, choose the first lightning bolt, okay

  • Click on theComputer 0.Configure IP

  • The inputThe IP addressLater, clicktabKey, automatically generatedSubnet mask

  • You can usenotesFunction, annotationComputer 0theThe IP address

  • Same thingComputer 1andComputer 2, the configurationThe IP addresswithnotesmarkThe IP address

  • Click on the bottom right cornerThe simulationAnd then usemail, fromComputer 0Sent to theComputer 2, you can see two generated in the simulation panelThe event

  • The first isICMP EventYou can see that there areComputer 0theThe source IP addressandComputer 2theDestination IP address

  • The second isARP eventYou can see that there areComputer 0theThe source MAC addressandDestination MAC address FF.FFff.ffffI don’t know at this pointComputer 2theThe MAC address, so needARP protocolTo obtainComputer 2theThe MAC address

  • Click on theThe next step.Computer 0toA hubsendARP protocolCommunicate and generate aThe event

  • Click on theThe event, you can see that the hub does not do data processing

  • Click on theThe next step.A hubWill send toComputer 1andComputer 2Send one eachARP protocolCommunicate and claim two events

  • Click on the first oneThe eventAs you can seeComputer 2forARP communicationThe processing of
    • contrastDestination IP addressWith his ownThe source IP addressIs it consistent? Is it consistent
    • toComputer 0Send your ownThe MAC address
    • Information carrying:Computer 2theThe source IP address,Source MACThe address andComputer 0theThe source IP address,The source MAC address

  • Click the second oneThe event.Computer 1receivedARP protocolCommunication, contrastDestination IP addressWith his ownThe source IP addressInconsistent, discarding information without processing

  • Click on theThe next step.Computer 2toA hubsendARP protocolCommunication, generating an event

  • Click on theThe event.A hubNo communication is processed

  • Click on theThe next step.A hubwillARP protocolCommunication sent toComputer 0And computer1And produces threeThe event

  • Click on the first oneThe event.Computer 0To receiveARP protocolCommunication, comparison of information, further processing
    • Destination MAC AddresswithComputer 0theThe source MAC addressconsistent
    • Destination IP addresswithComputer 0theThe source IP addressconsistent
    • The cacheComputer 2theThe MAC address

  • Click the second oneThe event.Computer 1To receiveARP protocolCommunication, comparison of information, further processing
    • Destination MAC AddresswithComputer 1theThe source MAC addressDon’t agree
    • Information is discarded without processing

  • Click on the third oneThe event.Computer 0Access to theComputer 2theThe MAC addressGet under wayThe ICMP protocolcommunication

  • Click on theThe next step.Computer 0Began toA hubsendThe ICMP protocolCommunicate and generate aThe event

  • Click on theThe event.A hubCommunication data is not processed

  • Click on theThe next step.A hubTo theComputer 1andComputer 2sendThe ICMP protocolcommunication

  • Click on the first oneThe event.Computer 2receivedComputer 0theThe ICMP protocolCommunication to process and compare data
    • contrastDestination MAC Address, with their ownThe MAC addressconsistent
    • contrastDestination IP address, with their ownThe IP addressconsistent
    • Processing data toComputer 0Sending response data

  • Click the second oneThe event.Computer 1receivedComputer 0theThe ICMP protocolCommunication to process and compare data
    • contrastDestination MAC Address, with their ownThe MAC addressDon’t agree
    • Discard data without processing

  • Click on theThe next step.Computer 2toA hubsendThe ICMP protocolCommunicate and generate aThe event

  • Click on theThe event.A hubIncoming communications are not processed

  • Click on theThe next step, the hub toComputer 0andComputer 1Send one eachThe ICMP protocolCommunicate and generate twoThe event

  • Click on the first oneThe event.Computer 0Received fromComputer 2theThe ICMP protocolCommunicate, compare data
    • purposeThe MAC addressWith his ownThe source MAC addressconsistent
    • purposeThe IP addressWith his ownThe source IP addressconsistent
    • Process the data, pass it up

  • Click the second oneThe event.Computer 1Received fromComputer 2theThe ICMP protocolCommunicate, compare data
    • purposeThe MAC addressWith his ownThe source MAC addressDon’t agree
    • Discard data without processing

Note: This is the complete process of computer 0 sending data to computer 2 through the hub. As you can see, the hub does not have any “intelligence” during the whole process. It does not further process the received data and only sends the received traffic separately to all other connected computers

3. View the target MAC address of computer 0 cache

  • Click on theComputer 0, the choice ofCommand prompt

  • The inputarp -aTo view the cacheComputer 2theThe IP addressandThe MAC address

4. Computers communicate through multiple hubs

  • Before adding aHub 1andComputer 3, use the one in the lower right cornerThe simulation, by email fromComputer 3Sent to theComputer 1The events of the whole process are shown in the figure below

  • The generatedThe eventIn, the time of each step is different, the same stepThe eventAt the same time
    • 0.000The first:Computer 3Prepare data to send toComputer 1But it’s not clearComputer 1theThe MAC address
    • 0.000Article 2:Computer 3Ready to useARP broadcast protocolTo obtainComputer 1theThe MAC address
      • Carrying information:Source IP address (IP address of Computer 3).Destination IP address(The IP address of computer 1), The source MAC address(MAC address of computer 3), Destination MAC Address(FFFF.FFFF.FFFF)
    • 0.001: Computer 3willARP communicationSent to theHubs 0
    • 0.002The first:Hubs 0willARP communicationSent to theComputer 0
      • Computer 0contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressOtherwise, the communication is discarded without processing
    • 0.002Article 2:Hubs 0willARP communicationSent to theHub 1
    • 0.003The first:Hub 1willARP communicationSent to theComputer 2
      • Computer 2contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressOtherwise, the communication is discarded without processing
    • 0.003The first:Hub 1willARP communicationSent to theComputer 1
      • Computer 1contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressSame, processing data, ready to passARP communicationtoComputer 3Send your ownThe MAC address
      • Carrying information:The source IP address(The IP address of computer 1), Destination IP address(The IP address of computer 3), The source MAC address(MAC address of computer 1), Destination MAC Address(MAC address of computer 3)
    • 0.004: Computer 1willARP communicationSent to theHub 1
    • 0.005The first:Hub 1willARP communicationSent to theHubs 0
    • 0.005Article 2:Hub 1willARP communicationSent to theComputer 2
      • Computer 2contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressOtherwise, the communication is discarded without processing
    • 0.006The first:Hubs 0willARP communicationSent to theComputer 0
      • Computer 0contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressOtherwise, the communication is discarded without processing
    • 0.006Article 2:Hubs 0willARP communicationSent to theComputer 3
      • Computer 3contrastARP communicationIn theDestination IP addressWith his ownThe source IP addressThe same,Destination MAC AddressWith his ownThe source MAC addressAgain, processing data
    • 0.006Article 3:Computer 3receivedComputer 1theThe MAC addressAfter, ready toComputer 1sendICMP communication
      • Carrying information:The source IP address(The IP address of computer 3),Destination IP address(The IP address of computer 1),The source MAC address(MAC address of computer 3),Destination MAC Address(MAC address of computer 1)
    • 0.007: Computer 3willThe ICMP communicationsSent to theHubs 0
    • 0.008The first:Hubs 0willThe ICMP communicationsSent to theComputer 0
      • Computer 0contrastDestination MAC AddressWith his ownThe source MAC addressOtherwise, the communication is discarded without processing
    • 0.008Article 2:Hubs 0willThe ICMP communicationsSent to theHub 1
    • 0.009The first:Hub 1willThe ICMP communicationsSent to theComputer 2
      • Computer 2contrastDestination MAC AddressWith his ownThe source MAC addressOtherwise, the communication is discarded without processing
    • 0.009Article 2:Hub 1willThe ICMP communications hairSent to theComputer 1
      • Computer 1contrastDestination MAC AddressWith his ownThe source MAC addressIdentical, contrastDestination IP addressWith his ownThe source IP addressSame, process data, prepare willResponse data after processingBack to theComputer 3
      • Carrying information:The source IP address(The IP address of computer 1),Destination IP address(The IP address of computer 3),The source MAC address(MAC address of computer 1),Destination MAC Address(MAC address of computer 3)
    • 0.010: Computer 1willThe ICMP communicationsSent to theHub 1
    • 0.011The first:Hub 1willThe ICMP communicationsSent to theHubs 0
    • 0.011Article 2:Hub 1willThe ICMP communicationsSent to theComputer 2
      • Computer 2contrastDestination MAC AddressWith his ownThe source MAC addressOtherwise, the communication is discarded without processing
    • 0.012The first:Hubs 0willThe ICMP communicationsSent to theComputer 3
      • Computer 3contrastDestination MAC AddressWith his ownThe source MAC addressThe same,Destination IP addressWith his ownThe source IP addressSimilarly, reading data in communication
    • 0.012Article 2:Hubs 0willThe ICMP communicationsSent to theComputer 0
      • Computer 0contrastDestination MAC AddressWith his ownThe source MAC addressOtherwise, the communication is discarded without processing

To sum up: the hub has no “IQ”, it can only receive and send communication, but cannot process and save communication, and has no “memory” function. When there are 1000 computers, it has to send messages to 999 computers, resulting in great waste. The more devices, the lower the efficiency

Third, the bridge

1, the application of network bridge

  • The bridge can learn the MAC address of each interface
  • Thus play the role of isolating the conflict domain

  • The bridge is intelligent, learning the MAC address of each interface and recording the computer as traffic comes inThe source IP addressandThe source MAC address
  • The following figure,Computer 6Send out a communication,The bridgeThe port on the left will recordComputer 6theThe IP addressandThe MAC address

  • When anotherComputer 7toComputer 6When sending a communication,The bridge on the left side of theIt has been recordedComputer 6theThe IP addressandThe MAC address, the communication will no longer be passed to the right

2. Network bridge is used in Packet Tracer

  • Place a bridge

  • Configuration of PCThe IP addressAnd then carry out the configurationattachment, as shown in the figure below

  • ifThe bridgeIf there is an orange part on the line, switch to the one in the lower right cornerreal-timeandThe simulation

  • usemailfromComputer 0Sent to theComputer 1And the wholeARP communicationThe flow is shown in the figure below
    • whenComputer 0Outgoing communication, throughHubs 0And send it toThe bridgeWhen,Port on the left of the bridgeWill first recordComputer 0theThe IP addressandThe MAC addressCheck the communicationDestination MAC AddressisFFFF.FFFF.FFFF, so the communication continues to the right
    • whenComputer 1After receiving the message, start returning your ownThe MAC address, will passHubs 0And send it toThe bridge
    • At this point,Port on the left of the bridgeRecord theComputer 0theThe IP addressandThe MAC address, compared with communicationDestination IP addressandDestination MAC Address, found consistent, interrupted communication, no longer passed to the right
    • Colleagues,The bridgerecordComputer 1theThe IP addressandThe MAC address

  • Use the one in the lower rightThe simulationFunction to use mail fromComputer 0Sent to theComputer 1, subdivision steps
  • As shown in the picture below,Computer 0useARP protocolCommunication, accessComputer 1theThe MAC address
    • Computer 0sendARP communicationarriveHubs 0
    • Hubs 0sendARP communicationarriveComputer 1
      • Computer 1Contrastive communicationDestination IP addressWith his ownThe IP addressHas been,The MAC addressisFFFF.FFFF.FFFF“, so ready toComputer 0Send your ownThe MAC address
    • Hubs 0sendARP communicationarriveThe bridge
      • The bridgeThe left interface is recording the communicationComputer 0theThe IP addressandThe MAC address

  • The bridgeThe left interface is recording the communicationComputer 0theThe IP addressandThe MAC addressAfter discovering communication inDestination MAC AddressisFFFF.FFFF.FFFF, and sends it to the rightARP protocol
    • The bridgewillARP communicationSent to theHub 1
    • Hub 1willARP communicationSent to theComputer 2
      • Computer 2Contrast communicationDestination IP addressWith his ownThe IP addressDifferent, not processed
    • Hub 1willARP communicationSent to theComputer 3
      • Computer 3Contrast communicationDestination IP addressWith his ownThe IP addressDifferent, not processed
  • Computer 1toComputer 0throughARP communicationSend your ownThe MAC address
    • Computer 1sendARP protocoltoHubs 0
    • Hubs 0toComputer 0sendARP communication
      • Computer 0Contrast communicationDestination IP address,Destination MAC AddressWith his ownThe IP address,The MAC addressThe same
      • soComputer 0Ready toComputer 1sendThe ICMP communications
    • Hubs 0toThe bridgesendARP communication
      • The bridgeAnd by comparison,On the left side of theThe interface has been loggedARP communicationIn theDestination IP addressandDestination MAC Address
      • soThe bridgeCommunication interrupted. No longer sending to the rightARP communication
      • At the same timeThe bridgerecordComputer 1theThe IP addressandThe MAC address

  • Computer 0Began toComputer 1sendThe ICMP communications
    • Computer 0toHubs 0sendThe ICMP communications
    • Hubs 0toComputer 1sendThe ICMP communications
      • Computer 1By comparing theThe ICMP communications,theDestination IP addressandDestination MACAddress with your ownThe IP addressandThe MAC addressThe same
      • As a result,Computer 1Process the data and prepare the dataComputer 0sendThe response data
    • Hubs 0toThe bridgesendThe ICMP communications
      • The bridgeAnd by comparison,The ICMP communications,theDestination IP addressandDestination MACAddress andOn the left side of the interfaceIn the recordComputer 1theThe IP addressandThe MAC addressThe same
      • As a result,The bridgeThe communication is interrupted and ICMP communication is not sent to the right side

  • Computer 1processedComputer 0Send theThe ICMP communicationsafterThe response datathroughICMPCommunications sent toComputer 0
    • Computer 1willThe ICMP communicationsSent to theHubs 0
    • Hubs 0willThe ICMP communicationsSent to theComputer 0
      • Computer 0By contrast, it is found thatThe ICMP communicationsIn theDestination IP addressAnd purposeThe MAC addressWith his ownThe IP addressandThe MAC addressThe same
      • As a result,Computer 0receiveThe response data
    • Hubs 0willThe ICMP communicationsSend to the bridge
      • The bridgeBy contrast, it is found thatThe ICMP communicationsIn theDestination IP addressAnd purposeThe MAC addresswithPort on the left of the bridgeRecorded in theComputer 0theThe IP addressandThe MAC addressThe same
      • As a result,The bridgeCommunication interrupted. No longer sending to the rightThe ICMP communications

This is the computers 0 and 1 at the same network segment in the communication process The bridge is “intelligence”, will record in communication sent from the source IP address and source MAC address contrast communication if the destination IP address and the destination MAC address has been recorded If the record, it will interrupt the communication, no longer send other interface communication

Iv. Switch

1. Switch application

  • switchesEquivalent to more interfacesThe bridge, can record each connected computerThe IP addressandThe MAC address

  • switchesIt is full duplex communication, all computers in the entire connection can send communication at the same time

  • switchesSafer than the hub, when the switch recordsComputer 2theThe IP addressandThe MAC addressAnd otherThe computergiveComputer 2Send the communication, the communication will not be sent to othersThe computer

2. Switch is used in Packet Tracer

  • As shown in the picture below, place four on the desktopPC computer.Configure IPAnd place another oneswitches

  • inPC computerandswitchesConnection between

  • usemail, fromComputer 0Sent to theComputer 3

  • The detailed steps are as follows
  • Computer 0sendARP communicationtoComputer 3To obtainComputer 3theThe MAC address
    • Computer 0toswitchessendARP communication
      • switchesrecordARP communicationIn theComputer 0theThe IP addressandThe MAC address
      • switchesPrepare to send to all three computersARP communication
    • switchestoComputer 1sendARP communication
      • Computer 1Through comparison, the communication is foundDestination IP addressWith his ownThe IP addressOtherwise, the communication is discarded without processing
    • switchestoComputer 2sendARP communication
      • Computer 2Through comparison, the communication is foundDestination IP addressWith his ownThe IP addressOtherwise, the communication is discarded without processing
    • switchestoComputer 3sendARP communication
      • Computer 3Through comparison, the communication is foundDestination IP addressWith his ownThe IP addressSame, ready forComputer 0Send your ownThe MAC address

  • Computer 3toComputer 0sendARP communicationCarry,MAC address of computer 3
    • Computer 3toswitchessendARP communication
      • switchesrecordARP communicationIn theComputer 3theThe IP addressandThe MAC address
      • switchesKnow by comparisonARP communicationSent to theIt has been recordedtheComputer 0
      • As a result,switchesOnly toComputer 0sendARP communication, not toComputer 1andComputer 2Send a communication
    • switchestoComputer 0sendARP protocol
      • Computer 0Through comparison, the communication is foundDestination IP addressandDestination MAC AddressWith his ownThe IP addressandThe MAC addressconsistent
      • So, receiveComputer 3theThe MAC address, ready toComputer 3sendICMP communication

  • Computer 0toComputer 3sendICMP communication
    • Computer 0toswitchessendICMP communication
      • switchesBy contrast, it is found thatThe ICMP communicationsIn theDestination IP addresswithDestination MAC AddressAnd already recordedComputer 3theThe IP addressandThe MAC addressThe same
      • As a result,switchesOnly toComputer 3sendThe ICMP communications
    • switchestoComputer 3sendICMP communication
      • Computer 3Contrast, in communicationDestination IP addressandDestination MAC AddressWith his ownThe IP addressandThe MAC addressThe same
      • Computer 3Handle the traffic. Get ready forComputer 0sendThe response data

  • Computer 3toComputer 0sendICMP communicationTo return toThe response data
    • Computer 3toswitchessendICMP communication
      • switchesBy contrast, it is found thatThe ICMP communicationsIn theDestination IP addresswithDestination MAC AddressAnd already recordedComputer 0theThe IP addressandThe MAC addressThe same
      • As a result,switchesOnly toComputer 0sendThe ICMP communications
    • switchestoComputer 0sendICMP communication
      • Computer 0Contrast, in communicationDestination IP addressandDestination MAC AddressWith his ownThe IP addressandThe MAC addressThe same
      • As a result,Computer 0Receive and processComputer 3From theThe response data

5. Router

1. Router application

  • In the same network segment, it can be usedCable directly connected,Coaxial cable,A hub,The bridge,switchesTransmit data
  • This parameter is required in different network segmentsThe routerTransmit data

  • Cable direct connection, coaxial cable, hub, bridge, switch
    • The connected devices must be on the same network segment
      • For example,192.168.1.10and192.168.1.11, includingThe IP addressIn front of192.168.1You can think of it as a network segment10and11It’s computerId no.Both network segment192.168.1In theId10 computerandId11 computer
    • The connected devices are in the same broadcast domain
      • Devices connected to the same network segment, for example192.168.1.10,192.168.1.11,192.168.1.12,192.168.1.13, the four devices in the same network segment are connected
      • The broadcast will propagate in the same broadcast domain

  • The router
    • Data can be forwarded between different network segments
    • Isolated broadcast domain
  • As shown below, the network segment on the left is192.168.1The network segment on the right is192.168.2

  • When computer 0 sends a message to computer 1, the ARP broadcast is blocked from reaching the router and does not travel to the right

2. Use the router in Packet Tracer

(1) Configure the device
  • As shown in the picture below, place four computers, two switches, and one router, and connect them with wires

  • The configuration is shown in the following figureComputer 0theThe IP addressandThe default gateway
    • IP address: 192.168.1.10
    • Default gateway: 192.168.1.1

  • configurationComputer 1theThe IP addressandThe default gateway
    • IP address: 192.168.1.11
    • Default gateway: 192.168.1.1

  • configurationComputer 2theThe IP addressandThe default gateway
    • IP address: 192.168.2.10
    • Default gateway: 192.168.2.1

  • configurationComputer 3theThe IP addressandThe default gateway
    • IP address: 192.168.2.11
    • Default gateway: 192.168.2.1

  • In this case, the lines on both sides of the route are red, indicating that the route is not connected

  • Click on theThe toolbarOn theoptions, the choice ofPreferences...

  • Check thePort labels are always displayed in logical workspaces

  • In this way, you can see the port name that each device uses when it is connected

  • configurationThe routerLeft side interfaceNetwork segmentfor192.168.1.1And open thePort state

  • configurationThe routerRight-side interfaceNetwork segmentfor192.168.2.1And open thePort state

  • The line is now connected

(2) Communication between computer 0 and computer 1
  • Click on the bottom right cornerThe simulationAnd then use email fromComputer 0Sent to theComputer 1

  • whenComputer 0Ready to sendARP broadcastTo obtainComputer 1theThe MAC address“, will judge firstDestination IP address(The IP address of computer 1) andThe source IP address(The IP address of computer 0(Is it inSame network segment, if theSame network segment.Computer 0throughARP broadcastTo obtainComputer 1theThe MAC address

  • Computer 0toComputer 1sendARP broadcastTo obtainComputer 1theThe MAC address
    • 1.Computer 0toSwitches 0Send broadcast
      • Switches 0recordComputer 0theThe IP addressandThe MAC address
    • 2.1,Switches 0toComputer 1Send broadcast
      • Computer 1By contrast, the broadcast was foundDestination IP addressWith his ownThe IP addressThe same,Destination MAC AddressisFFFF.FFFF.FFFF
      • As a result,Computer 1Ready toComputer 0Send your ownThe MAC address
    • 2.2,Switches 0toThe router 0Send broadcast
      • The router 0By contrast, the broadcast was foundNetwork segmentis192.168.1.1And on the leftNetwork segmentThe same
      • As a result,The router 0Block the broadcast. It doesn’t go right

  • Computer 1toComputer 0sendARP broadcast, sendComputer 1theThe MAC address
    • 3,Computer 1toSwitches 0sendARP broadcast
      • Switches 0By contrast, the broadcast was foundDestination IP addressandDestination MAC AddressWith the record ofComputer 0theThe IP addressandThe MAC addressThe same
      • As a result,Switches 0Ready toComputer 0sendARP broadcastDo not broadcast to other devices
      • At the same time,Switches 0recordComputer 1theThe IP addressandThe MAC address
    • 4,Switches 0toComputer 0sendARP broadcast
      • Computer 0Access to theComputer 1theThe MAC address, ready toComputer 1sendICMP communication

  • Computer 0toComputer 1sendICMP communication
    • 5,Computer 0toSwitches 0sendICMP communication
      • Switches 0By contrast, it is found thatcommunicationIn theDestination IP addressandDestination MAC AddressWith the record ofComputer 1theThe IP addressandThe MAC addressThe same
      • As a result,Switches 0Ready toComputer 1Send a communication
    • 6,Switches 0toComputer 1sendICMP communication
      • Computer 1By contrast, it is found thatcommunicationIn theDestination IP addressandDestination MAC AddressWith the record ofComputer 1theThe IP addressandThe MAC addressThe same
      • As a result,Computer 1Process the data and prepare the dataComputer 0sendThe response data

  • Computer 1toComputer 0sendICMP communication
    • 7,Computer 1toSwitches 0sendICMP communication
      • Switches 0By contrast, it is found thatcommunicationIn theDestination IP addressandDestination MAC AddressWith the record ofComputer 0theThe IP addressandThe MAC addressThe same
      • As a result,Switches 0Ready toComputer 0Send a communication
    • Eight,Switches 0toComputer 0sendICMP communication
      • Computer 0By contrast, it is found thatcommunicationIn theDestination IP addressandDestination MAC AddressWith the record ofComputer 0theThe IP addressandThe MAC addressThe same
      • As a result,Computer 0To deal withThe response data

(2) Communication between computer 0 and computer 3
  • Computer 0toComputer 3The data is sent, first checkedComputer 0andComputer 3Check whether they are on the same network segment
  • whenComputer 0andComputer 3If the routes are in different network segments, the routes are in different network segmentsThe routerSo,Computer 0To pass theThe routerForwarding data sumComputer 3communication
  • First of all,Computer 0To obtain aThe routerThe network cardThe MAC address

  • Computer 0toThe router 0sendARP broadcastTo obtainThe routerThe gatewayThe MAC address
    • 1.Computer 0toSwitches 0sendARP broadcast
      • Switches 0recordComputer 0theThe IP addressandThe MAC address
      • Switches 0Prepared to giveComputer 1andThe router 0sendARP broadcast
    • 2.1,Switches 0toComputer 1sendARP broadcast
      • Computer 1Received broadcast by contrast broadcastDestination IP addressAnd his ownThe IP addressDifferent, not processed
    • 2.2,Switches 0toThe router 0sendARP broadcast
      • The routerReceived broadcast by contrast broadcastDestination IP addressAnd his ownThe IP addressSame, return gatewayThe MAC address

  • The router 0toComputer 0sendARP broadcast, sendThe router 0theThe MAC address
    • 3,The router 0toSwitches 0sendARP broadcast
      • Switches 0Has been recordedComputer 0theThe IP addressandThe MAC addressBy contrast, prepare itemsComputer 0sendARP broadcast
      • Switches 0recordThe routerThe network cardThe IP addressandThe MAC address
      • 4,Switches 0toComputer 0sendARP broadcast
      • Computer 0Access to theThe router 0theThe MAC address, ready toThe router 0sendThe ICMP communications

  • Computer 0toThe router 0sendThe ICMP communications, the ultimate goal is toComputer 3sendThe ICMP communications
    • 5. Computer 0 sends ICMP communication to switch 0
      • Switches 0Has been recordedThe router 0The network cardThe IP addressandThe MAC address, ready toThe router 0sendThe ICMP communications
    • 6,Switches 0toThe router 0sendThe ICMP communications
      • The router 0Received the communication, through comparison, found that there is no recordComputer 3theThe IP addressandThe MAC address, so ready to the network segment192.168.2.1The direction to sendARP broadcastTo obtainComputer 3theThe MAC address

  • The router 0toComputer 3sendARP broadcastTo obtainComputer 3theThe MAC address
    • 7,The router 0toSwitches 0Sending ARP Broadcasts
      • Switches 0There is no recordComputer 3theThe IP addressandThe MAC address
      • As a result,Switches 0Ready toComputer 2andComputer 3Send separatelyARP broadcast
      • At the same time,Switches 0recordThe router 0theThe IP addressandThe MAC address
    • 8.1,Switch 1toComputer 2sendARP broadcast
      • Computer 2After receiving the broadcast, compare the broadcastDestination IP addressWith his ownThe IP addressDifferent, not processed
    • 8.2,Switch 1toComputer 3sendARP broadcast
      • Computer 3After receiving the broadcast, compare the broadcastDestination IP addressWith his ownThe IP addressSame, ready forThe router 0Return one’s ownThe MAC address

  • Computer 3toThe router 0sendARP broadcast, sendComputer 3theThe MAC address
    • 9,Computer 3toSwitch 1sendARP broadcast
      • Switch 1Record theThe router 0theThe IP addressandThe MAC address, ready toThe router 0sendARP broadcast
      • At the same time,Switch 1recordComputer 3theThe IP addressandThe MAC address
    • 10,Switch 1toThe router 0sendARP broadcast
      • The router 0receivedComputer 3theThe MAC address, ready toComputer 3sendICMP communication

  • The router 0toComputer 3sendICMP communication
    • 11,The router 0toSwitch 1sendICMP communication
      • Switch 1Record theComputer 3theThe IP addressandThe MAC address
    • 12,Switch 1toComputer 3sendICMP communication
      • Computer 3Received message, compareDestination IP addressandDestination MAC AddressWith his ownThe IP addressandThe MAC addressThe same
      • As a result,Computer 3Process the data and prepare it forComputer 0sendThe response data

  • Computer 3toThe router 0sendICMP communicationCarry,The response data
    • Computer 3toSwitch 1sendICMP communication
      • Switch 1recordedThe routing path 0theThe IP addressandThe MAC address, ready toThe router 0Send a communication
    • Switch 1toThe router 0sendICMP communication
      • The router 0To the network segment192.168.1.1Directionally transmitted communication

  • The router 0toComputer 0sendThe ICMP communicationsCarry,Computer 3theThe response data
    • The router 0toSwitches 0sendThe ICMP communications
      • Switches 0Record theComputer 0theThe IP addressandThe MAC address, ready toComputer 0Send a communication
    • Switches 0toComputer 0sendThe ICMP communications
      • Computer 0According to the correspondenceDestination IP addressandDestination MAC AddressWith his ownThe IP addressandThe MAC addressSame, receiveThe response data

In the whole communication process, the router serves as a transit role, connecting two different network segments and transmitting the communication of computers in different network segments