In industrial network environments, the logs of industrial switches are an important basis for troubleshooting network issues. By analyzing logs, various network faults can be quickly located to ensure the stable operation of industrial networks. The following will provide a detailed introduction to common network issues, their causes, and corresponding solutions in industrial switch logs.
1、 Common network problems and analysis
（1） Port link status abnormal
In industrial switch logs, it is common to see frequent changes in port link status, such as ports constantly switching between UP/DOWN. This issue can lead to unstable network connections and affect the continuity of data transmission.
（2） Broadcast Storm
A large number of broadcast packets may be recorded in the log, causing a significant occupation of network bandwidth, decreased device processing capabilities, serious impact on normal business data transmission, and even network paralysis.
（3） MAC address drift
The log shows that the same MAC address is frequently registered on different ports, which can cause confusion in the switch's MAC address table, prevent data frames from being forwarded correctly, and lead to network communication failures.
（4） Link congestion
When the data traffic in the network exceeds the link carrying capacity, logs will show packet loss, increased latency, and other records, affecting the real-time and reliability of industrial applications.
（5） Device authentication failed
If authentication mechanisms are deployed in industrial networks, device authentication failures may appear in the logs, causing devices to be unable to access the network and affecting normal production processes.
2、 Cause of occurrence
（1） Port link status abnormal
Physical layer issues: Network cable damage, poor contact of crystal heads, loss or interruption of fiber optic links, and other physical connection problems can cause unstable port link status.
Equipment hardware failure: Switch port hardware damage, module failure, etc., may cause abnormal port link status.
Configuration issues: Port speed, duplex mode, and other configurations that do not match the other end device can also cause frequent changes in port link status.
（2） Broadcast Storm
Unreasonable network topology design: There are loops (such as physical loops formed by improper configuration of redundant links), and broadcast packets are continuously forwarded in the loop, causing broadcast storms.
Network equipment failure: Network card failure continues to send broadcast packets, switch failure causes broadcast packet flooding, etc., which may lead to the generation of broadcast storms.
Application layer issues: Some application programs are poorly designed and generate a large number of broadcast messages, such as frequently interacting with improperly configured DHCP and ARP protocols.
（3） MAC address drift
There are duplicate MAC addresses in the network: Different devices are configured with the same MAC address, causing the switch to not correctly identify the device location and resulting in MAC address drift.
Link switching or failure: In redundant link scenarios, link switching may result in MAC addresses being registered on different ports; Or a link failure may cause the device to reconnect to another port, resulting in MAC address drift.
The aging time setting of the switch MAC address table is unreasonable: if the aging time is too short, the MAC address may be deleted in advance during normal communication of the device, and may appear on different ports during re registration, causing MAC address drift.
（4） Link congestion
Insufficient bandwidth: With an increase in the number of devices and business traffic in the network, the existing link bandwidth cannot meet the demand, resulting in link congestion.
Uneven traffic distribution: There is a single bottleneck in the network topology, such as a low bandwidth link between the core switch and the access layer switch, which causes congestion due to a large amount of data passing through the link.
Failure to properly configure QoS (Quality of Service): Critical business data competes with non critical business data for bandwidth, resulting in increased transmission latency and packet loss rate for critical business data.
（5） Device authentication failed
Authentication parameter error: The authentication username, password, key, and other parameters entered by the device do not match the configuration of the authentication server, resulting in authentication failure.
Authentication server failure: The authentication server is down, the service is not started, the database connection is abnormal, and the device cannot be authenticated.
Network connectivity issues: Network link interruption between devices and authentication servers, firewall policies blocking authentication communication, etc., resulting in authentication requests being unable to be transmitted normally.
3、 Solution method
（1） Port link status abnormal
Check physical connections: Use a cable tester to test the connectivity of network cables and optical fibers, replace damaged cables or remake crystal heads; Check if the fiber optic interface is clean, use an optical power meter to measure the fiber optic link loss, and ensure it is within the normal range.
Troubleshooting device hardware: Replace port modules or switches, test whether the port link status has been restored to normal, to determine if it is a hardware failure of the device.
Check configuration parameters: Check the switch port configuration to ensure that the speed, duplex mode, and other parameters are consistent with the peer device. You can try configuring the port to auto negotiation mode.
（2） Broadcast Storm
Eliminate network loops: Use loop detection tools (such as Spanning Tree Protocol STP, RSTP, MSTP, etc.) to detect loops in the network, adjust the network topology, remove redundant links or enable Spanning Tree Protocol to block redundant ports to avoid loop formation.
Troubleshooting devices: Disconnect each device in the network, observe changes in the number of broadcast packets, locate and replace faulty network cards or switches.
Optimize application layer configuration: Reasonably configure DHCP server scope, ARP cache timeout, etc., to reduce unnecessary broadcast messages; For applications that require broadcasting, consider using multicast or unicast as alternatives.
（3） MAC address drift
Check MAC address uniqueness: Use network management tools to scan devices in the network for duplicate MAC addresses, modify duplicate MAC addresses, and ensure that each device's MAC address is unique.
Optimize redundant link configuration: In redundant links, set reasonable link switching strategies, such as using Link Aggregation (LACP) technology, to ensure that the ports connected to the devices remain stable during link switching; Adjust the aging time of the switch MAC address table to avoid frequent MAC address drift caused by too short aging time.
Enable MAC address binding: Enable the binding function between MAC address and port on the switch, fix the device's MAC address to a specific port, and prevent MAC address drift.
（4） Link congestion
Upgrade link bandwidth: Upgrade link bandwidth according to business traffic requirements, such as upgrading a 100Mbps link to a 1G link, to increase network transmission capacity.
Optimize network topology: adjust the network topology structure, disperse traffic distribution, and avoid single point bottlenecks; Increase the number of links between the core layer and the access layer to achieve load balancing.
Configure QoS policy: Configure QoS policy on the switch to set higher priority for critical business data (such as industrial control data, real-time monitoring data, etc.), ensuring that it can be transmitted first in case of link congestion; Restrict the bandwidth usage of non critical business data, such as file transfer, video surveillance, etc.
（5） Device authentication failed
Verify authentication parameters: Check whether the authentication parameters input by the device end are correct, ensuring consistency with the configuration on the authentication server; If using certificate authentication, check if the certificate is valid and installed correctly.
Troubleshooting the authentication server: Check the running status of the authentication server to ensure that the service starts normally and the database connection is normal; View the authentication server logs to obtain detailed reasons for authentication failure, such as non-existent username, incorrect password, certificate expiration, etc., and take corresponding actions.
Check network connection: Test the network connectivity between the device and the authentication server, use tools such as ping and traceroute to check if the link is interrupted; Check the access control policies of network devices such as firewalls and routers to ensure that the ports required for authentication communication (such as 8080, 443, 1812, etc.) are not blocked.
Through in-depth analysis of industrial switch logs, problems in the network can be identified in a timely manner, and corresponding solutions can be taken based on the causes of the problems, thereby quickly locating and eliminating network failures and ensuring the stable and reliable operation of industrial networks. In practical operation, it is recommended to combine network management tools for real-time monitoring and log analysis to improve the efficiency and accuracy of troubleshooting.
The above provides common network problems and solutions from the perspective of log analysis. You can talk about whether you have encountered similar problems or have other specific needs based on actual scenarios, and I will further improve the content.