General categories of switch faults and troubleshooting measures

Switch faults are still commonly used. So I have studied the general classification and troubleshooting methods of switch faults. I will share them with you here, hoping they will be useful to you. A software fault of a vswitch refers to a switch fault in the system and its configuration. It can be divided into the following categories.
 
1) system error:
 
A vswitch system is a combination of hardware and software. There is a refresh read-only memory in the switch, which stores the software system required by the switch. Such errors are the same as common Windows and Linux errors. Due to the design at the time, there are some vulnerabilities. when conditions are appropriate, this may cause full load, packet loss, and wrong packets on the switch. Therefore, the switch system provides methods such as Web and TFTP to download and update the system. Of course, errors may also occur during system upgrade. For such problems, we need to develop the habit of browsing device manufacturers' websites frequently. If there is a new system or new patch, please update it in time.
 
2) misconfiguration:
 
Beginners are not familiar with vswitches, or because the configurations of various vswitches are different, administrators often encounter configuration Errors When configuring vswitches. For example, the network is disconnected due to incorrect VLAN division, the ports are mistakenly disabled, and the switch and nic pattern configuration do not match. The failure of such vswitches is sometimes difficult to find and requires some experience. If you cannot ensure that your configuration is correct, first restore the default factory configuration and then configure it step by step. It is best to read the manual before configuration. This is also one of the habits of network management. Each vswitch has a detailed installation manual and user manual, which are explained in detail in each module. Because many vswitch manuals are written in English, users with poor English skills can consult the supplier's engineers for specific configuration.
 
3) lost password:
 
This may have happened to every administrator. Once you forget the password, you can use certain steps to restore or reset the system password. Some of them are relatively simple. Just press a button on the switch. However, some operations are required. This type of situation occurs only when data is lost due to human forgetting or switch failure.
 
4) external factors:
 
Due to viruses or hacker attacks, a host may send a large number of packets that do not comply with the encapsulation rules to the connected port. As a result, the vswitch processor is too busy to forward packets, the buffer overflow causes packet loss. Another scenario is the broadcast storm, which not only occupies a large amount of network bandwidth, but also occupies a large amount of CPU processing time. If the network is occupied by a large number of broadcast data packets for a long time, normal point-to-point communication will fail, and the network speed will be slow or paralyzed.
 
A failure of a network card or a port may lead to a broadcast storm. Because vswitches can only split conflicting domains, but cannot split broadcast domains without VLAN division), when the number of broadcast packets accounts for 30% of the total communication volume, the network transmission efficiency will be significantly reduced.
 
In general, software faults should be harder to find than hardware faults. When solving the problems, it may not take too much money, but much time. It is best to develop the habit of logging in your daily work. When a fault occurs, record the fault phenomenon, analyze the fault process, solve the fault, and summarize the fault categories in time to accumulate your own experience. For example, sometimes the network is not affected or the problem is not found due to various reasons during configuration, but the problem may gradually become apparent in a few days. If there is a log record, you can think of whether the configuration has been incorrect a few days ago. Because this is often ignored, I thought it was a problem in other aspects. After a lot of detours, I found the problem. Therefore, it is necessary to record logs and maintain information.

General troubleshooting steps for switch faults: 
 
Vswitch faults are diverse, and different faults have different forms. In case of failure analysis, you must use various phenomena to flexibly use troubleshooting methods, such as troubleshooting, comparison, and replacement methods.
 
1) exclusion:
 
When we face the fault and analyze the problem, we have learned to use the exclusion method to determine the direction of the fault. Based on the observed fault phenomenon, this method lists all possible faults as much as possible, and then analyzes and resolves them one by one. We should follow the principle of simplicity to complexity to improve efficiency. This method can be used to cope with various faults. However, maintenance personnel must have a strong logical thinking and have a thorough understanding of switch knowledge.
 
2) comparison method:
 
The comparison method is to use the existing vswitches of the same model that can run normally as the reference object and compare them with the faulty vswitch to find out the fault point. This method is simple and effective, especially for System Configuration faults. You only need to make a simple comparison to find out the configuration differences, however, it is not easy to find a vswitch with the same model and configuration.
 
3) replacement method:
 
This is our most commonly used method, and it is also a frequently used method in the maintenance of computers. Replacement refers to using normal switch components to replace faulty parts, so as to find the fault point. It is mainly used for the diagnosis of hardware faults, but it should be noted that the replaced parts must be the same type of switches of the same brand and model. Of course, we can analyze faults according to the following principles in order to make the troubleshooting work follow the rules below.
 
1. From far to near
 
Port module-> horizontal cable-> jumper-> vswitch-Check one by one to eliminate the possibility of remote failure.
 
2. From the outside
 
If the switch has a fault, we can first identify the various indicators from the outside, and then check whether the corresponding internal components are faulty according to the switch fault instructions. For example, if the power led is green, the POWER supply is normal. If the POWER is off, the POWER supply is unavailable. If the LINK LEDs is yellow, the connection is currently working at 10 Mb/s. If the LINK green is 100 Mb/s, the connection is unavailable, flashing indicates that the port is manually disabled by the Administrator; rdp led indicates redundant power supply; mgmt led indicates the Administrator module. Regardless of whether the fault is located from the outside, you must log on to the switch to determine the specific fault and take corresponding troubleshooting measures.
 
3. From soft to hard
 
In the event of a fault, no one wants to move, so the screwdrivers should first split the switch, so during the inspection, the system configuration or system software should always be used for troubleshooting. If the problem cannot be solved on the software, the hardware is faulty. For example, if a port is not easy to use, we can first check whether the user's connected port is not in the corresponding VLAN, whether the port is disabled by another administrator, or other reasons for configuration. If the system and configuration possibilities are eliminated, You can suspect that the real problem lies in hardware faults.
 
4. Easy and difficult
 
In case of complex fault analysis, you must start with simple operations or configuration. This can speed up troubleshooting and improve efficiency.
 
Summary:
 
Due to various switch failures, there are no fixed troubleshooting steps, and some faults are often clearly oriented and can be identified at a glance. Therefore, you can only analyze the problem based on the actual situation. Of course, no matter what kind of fault is difficult for a new network administrator. If you want to become a master of switch troubleshooting, we must accumulate experience in our daily work. Every time we get a problem, we carefully review the root cause of the problem and the solution. In this way, we can constantly improve ourselves and better fulfill the important responsibilities of network management.