Several reasons for the network broadcast storm from the perspective of the switch principle

The competition in the internet cafe industry has intensified and some large Internet cafes have emerged. At present, more than Internet cafes are everywhere in the internet cafe industry. Due to the lack of professional network technical support during the network construction of Internet cafes, the network faults of Internet cafes occur frequently. Among the network faults in Internet cafes, network faults caused by the network broadcast storm account for more than of network faults in Internet cafes. How is the network broadcast storm formed?

To correctly understand the meaning of a broadcast storm, we must understand the working principles of network devices working on the network. Currently, network devices that work in Internet cafes are basically switches. No one really understands the working principle of vswitches.

I. Basic vswitch knowledge

1. Definition of a vswitch: A vswitch is a network device that can complete Packet encapsulation and Forwarding Based on the hardware address of the MAC Nic. The switch can "Learn" the MAC address and store it in the internal address table. By creating a temporary exchange path between the initiator of the data frame and the Target receiver, the data frame can directly reach the destination address from the source address.

Now, the switch has replaced the Hub, also known as the Hub, which is a familiar network device. However, this does not mean that we do not need to understand the basic knowledge of the Hub.

2. Definition of a HUB: a hub is a basic device in a data communication system. It is the same as twisted pair wires and other transmission media, A hardware device that does not require any software support or requires little management of software management. It is widely used in various scenarios. A hub works in a LAN environment and is applied to the first layer of the OSI reference model like a NIC. Therefore, it is also called a physical layer device. The Hub is interconnected with electrical appliances. When the LAN environment is maintained in a logical bus or ring structure, you can use the hub to establish a physical star or tree network structure. In this regard, the role of a hub is equivalent to a multi-port repeater. In fact, a hub is actually a type of repeater. The difference is that a hub can provide more port services, so a hub is also called a multi-port repeater.

Ii. Differences between vswitches and hubs

At present, we often have such a technical misunderstanding. We use switches and all data is forwarded point-to-point. Why is there a broadcast storm? After fully understanding the functional differences between a vswitch and a hub, we will understand why a broadcast storm occurs when a vswitch is used as a network device.

1. essential differences between a vswitch and a hub: a network composed of a hub is called a shared network, and a network composed of a vswitch is called a switched network. The main problem with shared Ethernet is that all users share bandwidth. The actual available bandwidth of each user decreases with the increase of the number of users. This is because when the information is busy, multiple users may "compete" for one channel at the same time, and one channel can only be occupied by one user at a certain time, therefore, a large number of users are often in monitoring waiting status, resulting in jitter, stagnation or distortion during signal transmission, seriously affecting network performance.

2. In switched Ethernet, the switch provides a dedicated information channel for each user, unless two source ports attempt to send information to the same destination port at the same time, otherwise, multiple source ports and destination ports can communicate simultaneously without conflict. According to the experiment, in a multi-server LAN, the actual maximum transmission speed of the switched Ethernet in half duplex mode is 1.7 times that of the shared network, the actual maximum transmission speed of switched Ethernet in full duplex mode can be 3.8 times that of shared network. Vswitches work in different ways than hubs. Other switches, such as the connection mode and speed selection, are basically the same as hubs. Currently, vswitches are also divided into 10 M, M, and M in terms of speed, the number of ports provided is 8, 16, and 24. Vswitches are mainly used to connect workstations, hubs, servers, or distributed backbone networks in LAN.

Iii. Causes of broadcast storm

By understanding the above network devices, we can simply analyze the reasons for the broadcast storm on the network. Generally, there are several reasons for a network broadcast storm:

1. network equipment reason: we often have such a misunderstanding that the switch is point-to-point forwarding and will not produce broadcast storms. When we purchase network settings, the purchased switch is usually an intelligent Hub, but it is sold as a switch by a profiteer. In this way, when the network is a little busy, a broadcast storm will certainly occur.

2. Network Card damage: if the network card of the network machine is damaged, a broadcast storm will also occur. The damaged Nic keeps sending a large number of data packets to the switch, resulting in a large number of useless data packets and a broadcast storm. Due to the broadcast storm caused by physical damage to the network card, it is difficult to troubleshoot the fault. Because the damaged network card can still access the Internet, we generally use the Sniffer LAN management software to view network data traffic, to determine the location of the fault point.

3. network loop: a ridiculous error was found in a network troubleshooting. A pair of twisted wires are inserted on different ports of the same switch, as a result, the network performance decreases rapidly and it is very difficult to open the web page. Such a fault is a typical network loop. The generation of a network loop is generally because the two ends of a physical network line are connected to a network device at the same time.

4. Network Viruses: Currently, some popular network viruses, such as Funlove, shock wave, and RPC, are spread over the network immediately after computer viruses are detected. The spread of Network viruses will consume a large amount of network bandwidth and cause network congestion and broadcast storms.

5. Use of hacker software: at present, some netusers often use hacker software such as cyber law enforcement officers and network scissors to attack the internal network of Internet cafes. Due to the use of these software, the network may also cause a broadcast storm.

It is essential to have a sound and solid basic knowledge to quickly identify faults. Therefore, in the future study, do not ignore the basic knowledge!

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