It is inevitable that a malfunction occurs during the operation of a switch, but it is the responsibility of network management personnel to promptly handle it, identify the fault point as soon as possible, and eliminate the fault. However, to achieve this, it is necessary to understand the types of switch faults and have the ability to analyze and handle them.

1、 Power failure

Due to unstable external power supply, aging power lines, or lightning strikes, the power supply may be damaged or the fan may stall, resulting in abnormal operation. Or damage to other internal components due to power supply can cause problems with the switch. If the POWER indicator light on the switch panel is green, it indicates that it is normal; If the indicator light is off, it indicates that the switch is not supplying power properly. This type of problem is easy to detect, easy to solve, and also the easiest to prevent.

In response to such faults, the first step is to provide external power supply. Generally, independent power lines are introduced to provide independent power supply, and voltage stabilizers are added to avoid transient high or low voltage phenomena. If conditions permit, UPS (Uninterruptible Power Supply) can be added to ensure the normal power supply of the switch. Some UPS provide voltage stabilization function, while others do not. When selecting, attention should be paid. Install professional lightning protection measures in the computer room to avoid damage to the switch caused by lightning. There are many professional companies doing lightning protection engineering now, which can be considered when implementing network wiring.

2、 Port failure

This is the most common hardware failure, whether it is a fiber optic port or a twisted pair RJ-45 port, be careful when plugging and unplugging connectors. If the fiber optic plug is accidentally dirty, it may cause contamination of the fiber optic port and prevent normal communication. We often see that many people like to plug and unplug connectors with power, which is theoretically possible, but it also unintentionally increases the incidence of port failures. Careless handling can also cause physical damage to the port. If the size of the purchased crystal head is too large, it is also easy to damage the port when inserting it into the switch. In addition, if a section of the twisted pair connected to the port is exposed outdoors, if this cable is hit by lightning, it will cause the connected switch port to be damaged or cause more unpredictable damage.

In general, a port failure is when one or more ports are damaged. So, after troubleshooting the computer connected to the port, you can determine whether it is damaged by replacing the connected port. When encountering such faults, the port can be cleaned with an alcohol cotton ball after the power is turned off. If the port is indeed damaged, then the port can only be replaced.

3、 Module fault

A switch is composed of many modules, such as stacking modules, management modules (also known as control modules), expansion modules, and so on. The probability of these modules malfunctioning is very low, but once problems occur, they will suffer huge economic losses. If you are not careful when plugging and unplugging modules, or if you encounter collisions when handling switches, or if the power supply is unstable, these types of faults may occur.

Of course, all three modules mentioned above have external interfaces, which are relatively easy to identify. Some can also be identified by the indicator lights on the modules to identify faults. For example, there is a flat trapezoidal port on the stacked module, or there is a USB like interface on some switches. There is a C * OLE port on the management module, which is used to establish a connection with the network management computer for easy management. If the expansion module is connected via fiber optic, there will be a pair of fiber optic interfaces.

When troubleshooting such faults, first ensure that the power supply to the switch and modules is normal, then check whether each module is plugged in the correct position, and finally check whether the cables connecting the modules are normal. When connecting to the management module, it is also necessary to consider factors such as whether it adopts the specified connection rate, whether there is parity, and whether there is data flow control. When connecting the expansion module, it is necessary to check whether it matches the communication mode, such as using full duplex mode or half duplex mode. Of course, if it is confirmed that the module is faulty, there is only one solution, which is to immediately contact the supplier for replacement.

4、 Backplane fault

Each module of the switch is plugged into the backplane. If the environment is humid, the circuit board is short circuited due to moisture, or components are damaged due to factors such as high temperature and lightning strikes, it can cause the circuit board to not function properly. For example, poor heat dissipation performance or high ambient temperature can lead to an increase in internal temperature, resulting in component burnout. Under normal external power supply, if all internal modules of the switch cannot function properly, it is possible that the backplane is damaged. Even electrical maintenance engineers may not be able to do anything in this situation, and the only way is to replace the backplane.

5、 Cable fault

In fact, theoretically speaking, this type of fault does not belong to the fault of the switch itself, but in practical use, cable faults often cause the switch system or ports to not work properly. Therefore, this type of fault is also classified as a switch hardware fault. For example, the connectors are not tightly connected, the order of cable production is incorrect or non-standard, the cable connection should use a cross line but a straight line, the two optical fibers in the optical cable are connected in a staggered manner, and the wrong line connection leads to network loops.

From the above hardware faults, it can be seen that poor environment in the computer room can easily lead to various hardware faults. Therefore, when constructing the computer room, we must first establish a good environment for lightning protection, grounding, power supply, indoor temperature, indoor humidity, electromagnetic interference prevention, and static electricity prevention, in order to provide a good environment for the normal operation of network equipment.

6、 System error

A switch system is a combination of hardware and software. There is a refreshable read-only memory inside the switch that stores the necessary software systems for this switch. This type of error is also similar to our common Windows and Linux. Due to design reasons at the time, there are some vulnerabilities that, when conditions are suitable, can lead to the occurrence of switch full load, packet loss, packet error, and other situations. So the switch system provides methods such as Web and FTP to download and update the system. Of course, errors may also occur when upgrading the system. For such issues, we need to develop the habit of frequently browsing the device manufacturer's website. If there are new system releases or patches, please update them in a timely manner.

7、 Improper configuration

Beginners are not familiar with switches, or administrators often make configuration errors when configuring switches due to different configurations. For example, incorrect VLAN partitioning leads to network connectivity, ports being mistakenly closed, and mismatched mode configurations between switches and network cards. This type of fault is sometimes difficult to detect and requires some experience accumulation. If there are no issues with the user's configuration, please restore the factory default configuration first, and then configure step by step. It is best to read the manual before configuring, as this is also one of the habits that network management should cultivate. Each switch has a detailed installation manual, user manual, and detailed explanations for each type of module. Due to the fact that many switch manuals are written in English, users with poor English proficiency can consult with the supplier's engineers before making specific configurations.

8、 External factors

Due to the existence of virus or hacker attacks, it is possible that a host sends a large number of packets that do not conform to the encapsulation rules to the connected ports, causing the switch processor to be too busy, resulting in the packets not being forwarded in time, thus causing buffer overflow and packet loss. Another scenario is a broadcast storm, which not only consumes a large amount of network bandwidth, but also consumes 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 peer-to-peer communication cannot proceed normally, and the network speed will slow down or become paralyzed.

If a network card or a port fails, it may trigger a broadcast storm. Due to the fact that switches can only split conflict domains and cannot split broadcast domains (without dividing VLANs), when the number of broadcast packets accounts for 30% of the total communication volume, the transmission efficiency of the network will significantly decrease.

Summary: Due to the diverse phenomena of switch faults, there are no fixed troubleshooting steps, and some faults often have clear directionality and can be identified at a glance. So we can only analyze it based on the specific situation. Of course, no matter what kind of fault it is, it is difficult for a new network administrator. Therefore, if you want to become a master at troubleshooting switch faults, you must accumulate experience in daily work and carefully review the root cause and solutions of each problem. Only in this way can we better complete the work of network management.