Network Communication fails due to cascade of 3 MB hubs

Fault symptom

Don't look at my friends, Mr. Wang, who knows little about computers and networks, but he sees a huge reward for training and reemployment. A computer school will be jointly run with the community service center. Initially, we plan to purchase 60 computers and then expand them as appropriate. As a result, candle king found me, known as "taixia", and asked me to provide him with a purchase list. Considering the needs of multimedia transmission, I have selected a 10/100 Mbit/s adaptive switch for the cabling device. A week later, I was in a meeting, and my cell phone shook up, quietly watching it was called by John. Are you sure you want to invite me? It's still early. Now it's only 10: 30. As Mr. Wang struggled to make endless calls over and over again, he had to go out to answer the phone call. In the past, a problem occurred during device installation, and computers could not communicate with each other.

This is a simple question! I asked him to call the technician to power over and ask him: What is the connection between switches? He said it was a crossover line. That's okay. It seems like you have to take a look.

Diagnosis Process　

When he came to John's computer school, he was waiting for my big drive at the door. Seeing me is like seeing a savior. The reason is very simple. It will start school tomorrow. Today, the Internet is not connected. Can he be impatient!

Come to the data center: I first pulled out the lines connecting to the three slave machines and tested them with a network cable tester. No problem. The cables are crossed and each one is connected. After inserting the wire, I tried to Ping the computer again. As a result, the nephew played the lantern-as usual!

When inserting a network cable, I noticed a UP-Link port on the switch. Can I only use the UP-Link port to connect through a straight line, but not a cross line? I tried to perform two direct connections. After the test was successful, I connected the UP-Link port of one vswitch to the normal port of another vswitch and sat in front of the computer for testing, yes! Connect to another instance and Ping the instance again. Another cascade port is changed. connect two tests first! Connect to the third server and test again!

What brand of switch is this! Let me see, I ......, I shouted, "Mr. Wang, which vswitch did you buy! "Mr. Wang hurried over." Didn't you say it was 100 Mb/s? You see, isn't it? "He pointed to the 100Base-TX and showed it to me. "Hi, I said you should wear a pair of glasses. Do you think this is a Switch? This is clearly the HUB, which is clearly written above. This is what the HUB understands! "I was so angry with the master of this hub and switch. "People say it is almost the same, but it is cheaper than that. "John is still talking. "Too bad. You cannot connect these three hubs at all. You can only connect two hubs at most. "John is dumb." No, you can say that. It makes sense. "I have to stare at it and say," You can help me find a solution. Otherwise, so much money will be spent ".

Is there any way to think about it? We had to give Mr. Smith an idle 16-port switch for the time being, so that he could buy another 8-port or 16-port switch. In this case, the hub does not need to be bought when the computer is added in the future.

Tips　

Now, the price of the 100Base-TX hub and the 10/100 Mbit/s switch is not much different, but the performance of the two is much different, especially when the network traffic is large. We know that the hub is a shared bandwidth, that is, all the computers in the network share the 100 Mbit/s bandwidth, and the switch is an exclusive bandwidth, that is, communication between any two vswitches in the network is 100 Mb/s. In addition, in a shared network, only two computers can communicate with each other at the same time. In a switched network, all computers can communicate with each other at the same time. In fact, the biggest difference is that the 100 Mbit/s hub and the 10 Mbit/s hub also have topology rules, which have strict requirements on the network topology structure.

100 Mb/s hubs are classified into two categories: I-type hubs and II-type hubs. All the shared 100Base-TX Ethernet networks built on the 100 Mbit/S hub must comply with the fast Ethernet rules.

100Base-TX Fast Ethernet rules are as follows:

◆ The length of all twisted pair wires cannot exceed 100 meters, including Category 5, category 4, and category 3 twisted pair wires.

◆ A separate Fast Ethernet can have one or two class II hubs. In other words, interconnection between three or more types of II hubs is not allowed.

◆ The length of the uplink cable connecting to a Type II hub must be less than 5 meters.

◆ A single fast Ethernet can only have one I-type hub.

◆ Class I and II hubs cannot be used simultaneously in the same Fast Ethernet.

Because the stacked hub stack can be viewed as a hub, you can stack the stack to solve this problem if you need to provide multiple ports. Of course, the best way is to use a vswitch as the central node and connect each hub to a vswitch, so that each CIDR block has only one hub, which greatly improves the network communication efficiency.

After a vswitch is added to the network as a set-line device, the rule is only applicable to each CIDR block because the original CIDR blocks are separated: instead of the entire network. In this case, each vswitch port is a network segment. All hubs that are connected to the same port are in the same network segment. The topology of these hubs must follow the rules of Fast Ethernet. Similarly, all the hubs that are uplinked to the other port are in the other two network segments, and the topology of those hubs must also follow the rules of Fast Ethernet. For hubs connected to different ports of a vswitch, the rule does not need to be followed.

1. Differences and connections between switches, routers, hubs, network cards, and other network devices
2. Fundamental differences between routers, hubs, and switches