If you are a maintenance engineer, read the following precautions before doing your work:

• Confirm whether the fault is an emergency fault. If it is an emergency fault, recover the faulty module by using the pre-defined troubleshooting methods immediately, and then restore services.

• Strictly conform to operation rules and industrial safety standards, ensuring human and device safety.

• Wear the ESD wrist strap when touching device components.

• Record original information about the problems occurring during troubleshooting.

• Record all the operations you have performed, especially the key operations such as restarting device and clearing database. Before performing the key operations, confirm the operation feasibility, back up data, and prepare the emergency and security measures. Only qualified personnel can perform key operations.

Some faults cause resource or money loss for customers. Therefore, maintenance engineers should focus on preventing faults and quickly restoring faults. Data backup helps you quickly locate and recover faults. After a network is set up and operates normally, you should back up important data as soon as possible.

Important data includes:

• Complete network topology, including device models, versions, and networking diagram

• Configuration files

• System software and patch files

• (Optional) Logs

Systematic troubleshooting is to find fault causes step by step, and finally recover the fault.

Generally, troubleshooting steps include observing fault symptom, collecting information, analyzing problem, and finding the root cause. The possible causes of all faults can be grouped into multiple cause sets, which make troubleshooting easier.