Coaxial cable

• different`PC computer`Between, can be used`Coaxial cable`Is 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, too`Half duplex communication`,`Easy to conflict`and`unsafe`

• 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 1`and`Hubs 0`Between,`Computer 3`and`Computer 2`Communication is still normal

2. Packet Tracer uses a hub to communicate

• Let’s add three`PC computer`

• Put one in the middle`A hub`

• Using the line will be`PC computer`and`A hub`Connect. If you don’t know what line to use, choose the first lightning bolt, okay

• Click on the`Computer 0`.`Configure IP`

• The input`The IP address`Later, click`tab`Key, automatically generated`Subnet mask`

• You can use`notes`Function, annotation`Computer 0`the`The IP address`

• Same thing`Computer 1`and`Computer 2`, the configuration`The IP address`with`notes`mark`The IP address`

• Click on the bottom right corner`The simulation`And then use`mail`, from`Computer 0`Sent to the`Computer 2`, you can see two generated in the simulation panel`The event`

• The first is`ICMP Event`You can see that there are`Computer 0`the`The source IP address`and`Computer 2`the`Destination IP address`

• The second is`ARP event`You can see that there are`Computer 0`the`The source MAC address`and`Destination MAC address FF.FFff.ffff`I don’t know at this point`Computer 2`the`The MAC address`, so need`ARP protocol`To obtain`Computer 2`the`The MAC address`

• Click on the`The next step`.`Computer 0`to`A hub`send`ARP protocol`Communicate and generate a`The event`

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

• Click on the`The next step`.`A hub`Will send to`Computer 1`and`Computer 2`Send one each`ARP protocol`Communicate and claim two events

• Click on the first one`The event`As you can see`Computer 2`for`ARP communication`The processing of
• contrast`Destination IP address`With his own`The source IP address`Is it consistent? Is it consistent
• to`Computer 0`Send your own`The MAC address`
• Information carrying:`Computer 2`the`The source IP address`,`Source MAC`The address and`Computer 0`the`The source IP address`,`The source MAC address`

• Click the second one`The event`.`Computer 1`received`ARP protocol`Communication, contrast`Destination IP address`With his own`The source IP address`Inconsistent, discarding information without processing

• Click on the`The next step`.`Computer 2`to`A hub`send`ARP protocol`Communication, generating an event

• Click on the`The event`.`A hub`No communication is processed

• Click on the`The next step`.`A hub`will`ARP protocol`Communication sent to`Computer 0`And computer`1`And produces three`The event`

• Click on the first one`The event`.`Computer 0`To receive`ARP protocol`Communication, comparison of information, further processing
• `Destination MAC Address`with`Computer 0`the`The source MAC address`consistent
• `Destination IP address`with`Computer 0`the`The source IP address`consistent
• The cache`Computer 2`the`The MAC address`

• Click the second one`The event`.`Computer 1`To receive`ARP protocol`Communication, comparison of information, further processing
• `Destination MAC Address`with`Computer 1`the`The source MAC address`Don’t agree
• Information is discarded without processing

• Click on the third one`The event`.`Computer 0`Access to the`Computer 2`the`The MAC address`Get under way`The ICMP protocol`communication

• Click on the`The next step`.`Computer 0`Began to`A hub`send`The ICMP protocol`Communicate and generate a`The event`

• Click on the`The event`.`A hub`Communication data is not processed

• Click on the`The next step`.`A hub`To the`Computer 1`and`Computer 2`send`The ICMP protocol`communication

• Click on the first one`The event`.`Computer 2`received`Computer 0`the`The ICMP protocol`Communication to process and compare data
• contrast`Destination MAC Address`, with their own`The MAC address`consistent
• contrast`Destination IP address`, with their own`The IP address`consistent
• Processing data to`Computer 0`Sending response data

• Click the second one`The event`.`Computer 1`received`Computer 0`the`The ICMP protocol`Communication to process and compare data
• contrast`Destination MAC Address`, with their own`The MAC address`Don’t agree

• Click on the`The next step`.`Computer 2`to`A hub`send`The ICMP protocol`Communicate and generate a`The event`

• Click on the`The event`.`A hub`Incoming communications are not processed

• Click on the`The next step`, the hub to`Computer 0`and`Computer 1`Send one each`The ICMP protocol`Communicate and generate two`The event`

• Click on the first one`The event`.`Computer 0`Received from`Computer 2`the`The ICMP protocol`Communicate, compare data
• purpose`The MAC address`With his own`The source MAC address`consistent
• purpose`The IP address`With his own`The source IP address`consistent
• Process the data, pass it up

• Click the second one`The event`.`Computer 1`Received from`Computer 2`the`The ICMP protocol`Communicate, compare data
• purpose`The MAC address`With his own`The source MAC address`Don’t agree

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 the`Computer 0`, the choice of`Command prompt`

• The input`arp -a`To view the cache`Computer 2`the`The IP address`and`The MAC address`

4. Computers communicate through multiple hubs

• Before adding a`Hub 1`and`Computer 3`, use the one in the lower right corner`The simulation`, by email from`Computer 3`Sent to the`Computer 1`The events of the whole process are shown in the figure below

• The generated`The event`In, the time of each step is different, the same step`The event`At the same time
• `0.000`The first:`Computer 3`Prepare data to send to`Computer 1`But it’s not clear`Computer 1`the`The MAC address`
• `0.000`Article 2:`Computer 3`Ready to use`ARP broadcast protocol`To obtain`Computer 1`the`The 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 3`will`ARP communication`Sent to the`Hubs 0`
• `0.002`The first:`Hubs 0`will`ARP communication`Sent to the`Computer 0`
• `Computer 0`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`Otherwise, the communication is discarded without processing
• `0.002`Article 2:`Hubs 0`will`ARP communication`Sent to the`Hub 1`
• `0.003`The first:`Hub 1`will`ARP communication`Sent to the`Computer 2`
• `Computer 2`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`Otherwise, the communication is discarded without processing
• `0.003`The first:`Hub 1`will`ARP communication`Sent to the`Computer 1`
• `Computer 1`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`Same, processing data, ready to pass`ARP communication`to`Computer 3`Send your own`The 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 1`will`ARP communication`Sent to the`Hub 1`
• `0.005`The first:`Hub 1`will`ARP communication`Sent to the`Hubs 0`
• `0.005`Article 2:`Hub 1`will`ARP communication`Sent to the`Computer 2`
• `Computer 2`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`Otherwise, the communication is discarded without processing
• `0.006`The first:`Hubs 0`will`ARP communication`Sent to the`Computer 0`
• `Computer 0`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`Otherwise, the communication is discarded without processing
• `0.006`Article 2:`Hubs 0`will`ARP communication`Sent to the`Computer 3`
• `Computer 3`contrast`ARP communication`In the`Destination IP address`With his own`The source IP address`The same,`Destination MAC Address`With his own`The source MAC address`Again, processing data
• `0.006`Article 3:`Computer 3`received`Computer 1`the`The MAC address`After, ready to`Computer 1`send`ICMP 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 3`will`The ICMP communications`Sent to the`Hubs 0`
• `0.008`The first:`Hubs 0`will`The ICMP communications`Sent to the`Computer 0`
• `Computer 0`contrast`Destination MAC Address`With his own`The source MAC address`Otherwise, the communication is discarded without processing
• `0.008`Article 2:`Hubs 0`will`The ICMP communications`Sent to the`Hub 1`
• `0.009`The first:`Hub 1`will`The ICMP communications`Sent to the`Computer 2`
• `Computer 2`contrast`Destination MAC Address`With his own`The source MAC address`Otherwise, the communication is discarded without processing
• `0.009`Article 2:`Hub 1`will`The ICMP communications hair`Sent to the`Computer 1`
• `Computer 1`contrast`Destination MAC Address`With his own`The source MAC address`Identical, contrast`Destination IP address`With his own`The source IP address`Same, process data, prepare will`Response data after processing`Back to the`Computer 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 1`will`The ICMP communications`Sent to the`Hub 1`
• `0.011`The first:`Hub 1`will`The ICMP communications`Sent to the`Hubs 0`
• `0.011`Article 2:`Hub 1`will`The ICMP communications`Sent to the`Computer 2`
• `Computer 2`contrast`Destination MAC Address`With his own`The source MAC address`Otherwise, the communication is discarded without processing
• `0.012`The first:`Hubs 0`will`The ICMP communications`Sent to the`Computer 3`
• `Computer 3`contrast`Destination MAC Address`With his own`The source MAC address`The same,`Destination IP address`With his own`The source IP address`Similarly, reading data in communication
• `0.012`Article 2:`Hubs 0`will`The ICMP communications`Sent to the`Computer 0`
• `Computer 0`contrast`Destination MAC Address`With his own`The source MAC address`Otherwise, 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 in`The source IP address`and`The source MAC address`
• The following figure,`Computer 6`Send out a communication,`The bridge`The port on the left will record`Computer 6`the`The IP address`and`The MAC address`

• When another`Computer 7`to`Computer 6`When sending a communication,`The bridge on the left side of the`It has been recorded`Computer 6`the`The IP address`and`The 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 PC`The IP address`And then carry out the configuration`attachment`, as shown in the figure below

• if`The bridge`If there is an orange part on the line, switch to the one in the lower right corner`real-time`and`The simulation`

• use`mail`from`Computer 0`Sent to the`Computer 1`And the whole`ARP communication`The flow is shown in the figure below
• when`Computer 0`Outgoing communication, through`Hubs 0`And send it to`The bridge`When,`Port on the left of the bridge`Will first record`Computer 0`the`The IP address`and`The MAC address`Check the communication`Destination MAC Address`is`FFFF.FFFF.FFFF`, so the communication continues to the right
• when`Computer 1`After receiving the message, start returning your own`The MAC address`, will pass`Hubs 0`And send it to`The bridge`
• At this point,`Port on the left of the bridge`Record the`Computer 0`the`The IP address`and`The MAC address`, compared with communication`Destination IP address`and`Destination MAC Address`, found consistent, interrupted communication, no longer passed to the right
• Colleagues,`The bridge`record`Computer 1`the`The IP address`and`The MAC address`

• Use the one in the lower right`The simulation`Function to use mail from`Computer 0`Sent to the`Computer 1`, subdivision steps
• As shown in the picture below,`Computer 0`use`ARP protocol`Communication, access`Computer 1`the`The MAC address`
• `Computer 0`send`ARP communication`arrive`Hubs 0`
• `Hubs 0`send`ARP communication`arrive`Computer 1`
• `Computer 1`Contrastive communication`Destination IP address`With his own`The IP address`Has been,`The MAC address`is`FFFF.FFFF.FFFF`“, so ready to`Computer 0`Send your own`The MAC address`
• `Hubs 0`send`ARP communication`arrive`The bridge`
• `The bridge`The left interface is recording the communication`Computer 0`the`The IP address`and`The MAC address`

• `The bridge`The left interface is recording the communication`Computer 0`the`The IP address`and`The MAC address`After discovering communication in`Destination MAC Address`is`FFFF.FFFF.FFFF`, and sends it to the right`ARP protocol`
• `The bridge`will`ARP communication`Sent to the`Hub 1`
• `Hub 1`will`ARP communication`Sent to the`Computer 2`
• `Computer 2`Contrast communication`Destination IP address`With his own`The IP address`Different, not processed
• `Hub 1`will`ARP communication`Sent to the`Computer 3`
• `Computer 3`Contrast communication`Destination IP address`With his own`The IP address`Different, not processed
• `Computer 1`to`Computer 0`through`ARP communication`Send your own`The MAC address`
• `Computer 1`send`ARP protocol`to`Hubs 0`
• `Hubs 0`to`Computer 0`send`ARP communication`
• `Computer 0`Contrast communication`Destination IP address`,`Destination MAC Address`With his own`The IP address`,`The MAC address`The same
• so`Computer 0`Ready to`Computer 1`send`The ICMP communications`
• `Hubs 0`to`The bridge`send`ARP communication`
• `The bridge`And by comparison,`On the left side of the`The interface has been logged`ARP communication`In the`Destination IP address`and`Destination MAC Address`
• so`The bridge`Communication interrupted. No longer sending to the right`ARP communication`
• At the same time`The bridge`record`Computer 1`the`The IP address`and`The MAC address`

• `Computer 0`Began to`Computer 1`send`The ICMP communications`
• `Computer 0`to`Hubs 0`send`The ICMP communications`
• `Hubs 0`to`Computer 1`send`The ICMP communications`
• `Computer 1`By comparing the`The ICMP communications,`the`Destination IP address`and`Destination MAC`Address with your own`The IP address`and`The MAC address`The same
• As a result,`Computer 1`Process the data and prepare the data`Computer 0`send`The response data`
• `Hubs 0`to`The bridge`send`The ICMP communications`
• `The bridge`And by comparison,`The ICMP communications,`the`Destination IP address`and`Destination MAC`Address and`On the left side of the interface`In the record`Computer 1`the`The IP address`and`The MAC address`The same
• As a result,`The bridge`The communication is interrupted and ICMP communication is not sent to the right side

• `Computer 1`processed`Computer 0`Send the`The ICMP communications`after`The response data`through`ICMP`Communications sent to`Computer 0`
• `Computer 1`will`The ICMP communications`Sent to the`Hubs 0`
• `Hubs 0`will`The ICMP communications`Sent to the`Computer 0`
• `Computer 0`By contrast, it is found that`The ICMP communications`In the`Destination IP address`And purpose`The MAC address`With his own`The IP address`and`The MAC address`The same
• As a result,`Computer 0`receive`The response data`
• `Hubs 0`will`The ICMP communications`Send to the bridge
• `The bridge`By contrast, it is found that`The ICMP communications`In the`Destination IP address`And purpose`The MAC address`with`Port on the left of the bridge`Recorded in the`Computer 0`the`The IP address`and`The MAC address`The same
• As a result,`The bridge`Communication interrupted. No longer sending to the right`The 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

• `switches`Equivalent to more interfaces`The bridge`, can record each connected computer`The IP address`and`The MAC address`

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

• `switches`Safer than the hub, when the switch records`Computer 2`the`The IP address`and`The MAC address`And other`The computer`give`Computer 2`Send the communication, the communication will not be sent to others`The computer`

2. Switch is used in Packet Tracer

• As shown in the picture below, place four on the desktop`PC computer`.`Configure IP`And place another one`switches`

• in`PC computer`and`switches`Connection between

• use`mail`, from`Computer 0`Sent to the`Computer 3`

• The detailed steps are as follows
• `Computer 0`send`ARP communication`to`Computer 3`To obtain`Computer 3`the`The MAC address`
• `Computer 0`to`switches`send`ARP communication`
• `switches`record`ARP communication`In the`Computer 0`the`The IP address`and`The MAC address`
• `switches`Prepare to send to all three computers`ARP communication`
• `switches`to`Computer 1`send`ARP communication`
• `Computer 1`Through comparison, the communication is found`Destination IP address`With his own`The IP address`Otherwise, the communication is discarded without processing
• `switches`to`Computer 2`send`ARP communication`
• `Computer 2`Through comparison, the communication is found`Destination IP address`With his own`The IP address`Otherwise, the communication is discarded without processing
• `switches`to`Computer 3`send`ARP communication`
• `Computer 3`Through comparison, the communication is found`Destination IP address`With his own`The IP address`Same, ready for`Computer 0`Send your own`The MAC address`

• `Computer 3`to`Computer 0`send`ARP communication`Carry,`MAC address of computer 3`
• `Computer 3`to`switches`send`ARP communication`
• `switches`record`ARP communication`In the`Computer 3`the`The IP address`and`The MAC address`
• `switches`Know by comparison`ARP communication`Sent to the`It has been recorded`the`Computer 0`
• As a result,`switches`Only to`Computer 0`send`ARP communication`, not to`Computer 1`and`Computer 2`Send a communication
• `switches`to`Computer 0`send`ARP protocol`
• `Computer 0`Through comparison, the communication is found`Destination IP address`and`Destination MAC Address`With his own`The IP address`and`The MAC address`consistent
• So, receive`Computer 3`the`The MAC address`, ready to`Computer 3`send`ICMP communication`

• `Computer 0`to`Computer 3`send`ICMP communication`
• `Computer 0`to`switches`send`ICMP communication`
• `switches`By contrast, it is found that`The ICMP communications`In the`Destination IP address`with`Destination MAC Address`And already recorded`Computer 3`the`The IP address`and`The MAC address`The same
• As a result,`switches`Only to`Computer 3`send`The ICMP communications`
• `switches`to`Computer 3`send`ICMP communication`
• `Computer 3`Contrast, in communication`Destination IP address`and`Destination MAC Address`With his own`The IP address`and`The MAC address`The same
• `Computer 3`Handle the traffic. Get ready for`Computer 0`send`The response data`

• `Computer 3`to`Computer 0`send`ICMP communication`To return to`The response data`
• `Computer 3`to`switches`send`ICMP communication`
• `switches`By contrast, it is found that`The ICMP communications`In the`Destination IP address`with`Destination MAC Address`And already recorded`Computer 0`the`The IP address`and`The MAC address`The same
• As a result,`switches`Only to`Computer 0`send`The ICMP communications`
• `switches`to`Computer 0`send`ICMP communication`
• `Computer 0`Contrast, in communication`Destination IP address`and`Destination MAC Address`With his own`The IP address`and`The MAC address`The same
• As a result,`Computer 0`Receive and process`Computer 3`From the`The response data`

5. Router

1. Router application

• In the same network segment, it can be used`Cable directly connected`,`Coaxial cable`,`A hub`,`The bridge`,`switches`Transmit data
• This parameter is required in different network segments`The router`Transmit data

• Cable direct connection, coaxial cable, hub, bridge, switch
• The connected devices must be on the same network segment
• For example,`192.168.1.10`and`192.168.1.11`, including`The IP address`In front of`192.168.1`You can think of it as a network segment`10`and`11`It’s computer`Id no.`Both network segment`192.168.1`In the`Id10 computer`and`Id11 computer`
• The connected devices are in the same broadcast domain
• Devices connected to the same network segment, for example`192.168.1.10`,`192.168.1.11`,`192.168.1.12`,`192.168.1.13`, the four devices in the same network segment are connected

• The router
• Data can be forwarded between different network segments
• As shown below, the network segment on the left is`192.168.1`The network segment on the right is`192.168.2`

• 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 figure`Computer 0`the`The IP address`and`The default gateway`
• Default gateway: 192.168.1.1

• configuration`Computer 1`the`The IP address`and`The default gateway`
• Default gateway: 192.168.1.1

• configuration`Computer 2`the`The IP address`and`The default gateway`
• Default gateway: 192.168.2.1

• configuration`Computer 3`the`The IP address`and`The default gateway`
• 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 the`The toolbar`On the`options`, the choice of`Preferences...`

• Check the`Port labels are always displayed in logical workspaces`

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

• configuration`The router`Left side interface`Network segment`for`192.168.1.1`And open the`Port state`

• configuration`The router`Right-side interface`Network segment`for`192.168.2.1`And open the`Port state`

• The line is now connected

(2) Communication between computer 0 and computer 1
• Click on the bottom right corner`The simulation`And then use email from`Computer 0`Sent to the`Computer 1`

• when`Computer 0`Ready to send`ARP broadcast`To obtain`Computer 1`the`The MAC address`“, will judge first`Destination IP address`(`The IP address of computer 1`) and`The source IP address`(`The IP address of computer 0`(Is it in`Same network segment`, if the`Same network segment`.`Computer 0`through`ARP broadcast`To obtain`Computer 1`the`The MAC address`

• `Computer 0`to`Computer 1`send`ARP broadcast`To obtain`Computer 1`the`The MAC address`
• 1.`Computer 0`to`Switches 0`Send broadcast
• `Switches 0`record`Computer 0`the`The IP address`and`The MAC address`
• 2.1,`Switches 0`to`Computer 1`Send broadcast
• `Computer 1`By contrast, the broadcast was found`Destination IP address`With his own`The IP address`The same,`Destination MAC Address`is`FFFF.FFFF.FFFF`
• As a result,`Computer 1`Ready to`Computer 0`Send your own`The MAC address`
• 2.2,`Switches 0`to`The router 0`Send broadcast
• `The router 0`By contrast, the broadcast was found`Network segment`is`192.168.1.1`And on the left`Network segment`The same
• As a result,`The router 0`Block the broadcast. It doesn’t go right

• `Computer 1`to`Computer 0`send`ARP broadcast`, send`Computer 1`the`The MAC address`
• 3,`Computer 1`to`Switches 0`send`ARP broadcast`
• `Switches 0`By contrast, the broadcast was found`Destination IP address`and`Destination MAC Address`With the record of`Computer 0`the`The IP address`and`The MAC address`The same
• As a result,`Switches 0`Ready to`Computer 0`send`ARP broadcast`Do not broadcast to other devices
• At the same time,`Switches 0`record`Computer 1`the`The IP address`and`The MAC address`
• 4,`Switches 0`to`Computer 0`send`ARP broadcast`
• `Computer 0`Access to the`Computer 1`the`The MAC address`, ready to`Computer 1`send`ICMP communication`

• `Computer 0`to`Computer 1`send`ICMP communication`
• 5,`Computer 0`to`Switches 0`send`ICMP communication`
• `Switches 0`By contrast, it is found that`communication`In the`Destination IP address`and`Destination MAC Address`With the record of`Computer 1`the`The IP address`and`The MAC address`The same
• As a result,`Switches 0`Ready to`Computer 1`Send a communication
• 6,`Switches 0`to`Computer 1`send`ICMP communication`
• `Computer 1`By contrast, it is found that`communication`In the`Destination IP address`and`Destination MAC Address`With the record of`Computer 1`the`The IP address`and`The MAC address`The same
• As a result,`Computer 1`Process the data and prepare the data`Computer 0`send`The response data`

• `Computer 1`to`Computer 0`send`ICMP communication`
• 7,`Computer 1`to`Switches 0`send`ICMP communication`
• `Switches 0`By contrast, it is found that`communication`In the`Destination IP address`and`Destination MAC Address`With the record of`Computer 0`the`The IP address`and`The MAC address`The same
• As a result,`Switches 0`Ready to`Computer 0`Send a communication
• Eight,`Switches 0`to`Computer 0`send`ICMP communication`
• `Computer 0`By contrast, it is found that`communication`In the`Destination IP address`and`Destination MAC Address`With the record of`Computer 0`the`The IP address`and`The MAC address`The same
• As a result,`Computer 0`To deal with`The response data`

(2) Communication between computer 0 and computer 3
• `Computer 0`to`Computer 3`The data is sent, first checked`Computer 0`and`Computer 3`Check whether they are on the same network segment
• when`Computer 0`and`Computer 3`If the routes are in different network segments, the routes are in different network segments`The router`So,`Computer 0`To pass the`The router`Forwarding data sum`Computer 3`communication
• First of all,`Computer 0`To obtain a`The router`The network card`The MAC address`

• `Computer 0`to`The router 0`send`ARP broadcast`To obtain`The router`The gateway`The MAC address`
• 1.`Computer 0`to`Switches 0`send`ARP broadcast`
• `Switches 0`record`Computer 0`the`The IP address`and`The MAC address`
• `Switches 0`Prepared to give`Computer 1`and`The router 0`send`ARP broadcast`
• 2.1,`Switches 0`to`Computer 1`send`ARP broadcast`
• `Computer 1`Received broadcast by contrast broadcast`Destination IP address`And his own`The IP address`Different, not processed
• 2.2,`Switches 0`to`The router 0`send`ARP broadcast`
• `The router`Received broadcast by contrast broadcast`Destination IP address`And his own`The IP address`Same, return gateway`The MAC address`

• `The router 0`to`Computer 0`send`ARP broadcast`, send`The router 0`the`The MAC address`
• 3,`The router 0`to`Switches 0`send`ARP broadcast`
• `Switches 0`Has been recorded`Computer 0`the`The IP address`and`The MAC address`By contrast, prepare items`Computer 0`send`ARP broadcast`
• `Switches 0`record`The router`The network card`The IP address`and`The MAC address`
• 4,`Switches 0`to`Computer 0`send`ARP broadcast`
• `Computer 0`Access to the`The router 0`the`The MAC address`, ready to`The router 0`send`The ICMP communications`

• `Computer 0`to`The router 0`send`The ICMP communications`, the ultimate goal is to`Computer 3`send`The ICMP communications`
• 5. Computer 0 sends ICMP communication to switch 0
• `Switches 0`Has been recorded`The router 0`The network card`The IP address`and`The MAC address`, ready to`The router 0`send`The ICMP communications`
• 6,`Switches 0`to`The router 0`send`The ICMP communications`
• `The router 0`Received the communication, through comparison, found that there is no record`Computer 3`the`The IP address`and`The MAC address`, so ready to the network segment`192.168.2.1`The direction to send`ARP broadcast`To obtain`Computer 3`the`The MAC address`

• `The router 0`to`Computer 3`send`ARP broadcast`To obtain`Computer 3`the`The MAC address`
• 7,`The router 0`to`Switches 0`Sending ARP Broadcasts
• `Switches 0`There is no record`Computer 3`the`The IP address`and`The MAC address`
• As a result,`Switches 0`Ready to`Computer 2`and`Computer 3`Send separately`ARP broadcast`
• At the same time,`Switches 0`record`The router 0`the`The IP address`and`The MAC address`
• 8.1,`Switch 1`to`Computer 2`send`ARP broadcast`
• `Computer 2`After receiving the broadcast, compare the broadcast`Destination IP address`With his own`The IP address`Different, not processed
• 8.2,`Switch 1`to`Computer 3`send`ARP broadcast`
• `Computer 3`After receiving the broadcast, compare the broadcast`Destination IP address`With his own`The IP address`Same, ready for`The router 0`Return one’s own`The MAC address`

• `Computer 3`to`The router 0`send`ARP broadcast`, send`Computer 3`the`The MAC address`
• 9,`Computer 3`to`Switch 1`send`ARP broadcast`
• `Switch 1`Record the`The router 0`the`The IP address`and`The MAC address`, ready to`The router 0`send`ARP broadcast`
• At the same time,`Switch 1`record`Computer 3`the`The IP address`and`The MAC address`
• 10,`Switch 1`to`The router 0`send`ARP broadcast`
• `The router 0`received`Computer 3`the`The MAC address`, ready to`Computer 3`send`ICMP communication`

• `The router 0`to`Computer 3`send`ICMP communication`
• 11,`The router 0`to`Switch 1`send`ICMP communication`
• `Switch 1`Record the`Computer 3`the`The IP address`and`The MAC address`
• 12,`Switch 1`to`Computer 3`send`ICMP communication`
• `Computer 3`Received message, compare`Destination IP address`and`Destination MAC Address`With his own`The IP address`and`The MAC address`The same
• As a result,`Computer 3`Process the data and prepare it for`Computer 0`send`The response data`

• `Computer 3`to`The router 0`send`ICMP communication`Carry,`The response data`
• `Computer 3`to`Switch 1`send`ICMP communication`
• `Switch 1`recorded`The routing path 0`the`The IP address`and`The MAC address`, ready to`The router 0`Send a communication
• `Switch 1`to`The router 0`send`ICMP communication`
• `The router 0`To the network segment`192.168.1.1`Directionally transmitted communication

• `The router 0`to`Computer 0`send`The ICMP communications`Carry,`Computer 3`the`The response data`
• `The router 0`to`Switches 0`send`The ICMP communications`
• `Switches 0`Record the`Computer 0`the`The IP address`and`The MAC address`, ready to`Computer 0`Send a communication
• `Switches 0`to`Computer 0`send`The ICMP communications`
• `Computer 0`According to the correspondence`Destination IP address`and`Destination MAC Address`With his own`The IP address`and`The MAC address`Same, receive`The 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