Fault Description

After a terminal connected to a switch starts, it cannot display anything or displays garbled characters.

Possible Cause

• The power module of the switch is faulty or the switch is not powered on.

• The serial interface connected to the switch is incorrectly configured.

• The cable between the terminal and switch is faulty or not firmly connected to the serial interface.

Troubleshooting Procedure

1. Check the power indicator on the switch's front panel. If the RUN/ALM indicator is On, the power module is working properly. If the power indicator is Off, rectify the fault according to Power Module Failures.

2. Check whether the parameters of the serial interface are correctly configured.

   # Verify that the connection interfaces are configured correctly. Some PCs have multiple numbered serial interfaces. When configuring connection interfaces, you must select the correct connection interface number, as shown in Figure 5-1.

   Figure 5-1  Setting a connection port 
   

   # Verify that the physical attributes of the serial interface on the PC are the same as those of the console interface on the device, as shown in Figure 5-2. The default attributes of the console interface are as follows:

   • Baud rate: 9600

   • Data bit: 8

   • Stop bit: 1

   • Parity check: None

   • Flow control: None

   Figure 5-2  Setting the parameters of the serial interface on the PC 
   

3. Ensure that the cable is firmly connected to the serial interface. You can replace it with a new cable to verify whether the cable is faulty. If the fault persists, contact technical support personnel.

Fault Description

The command line interface of the device does not respond to input from the keyboard.

Possible Cause

• The device is processing other services and the high CPU usage results in no response to the input from the keyboard.

• Another user restarts the device or the device restarts at the scheduled time.

• The device hardware is damaged or a software bug occurs.

Procedure

1. Check whether any users are running save or display diagnostic-information command. The execution of these commands results in high CPU usage for a short period during which the device cannot respond to input from the keyboard. Wait for a while and check whether the fault is rectified. If the fault persists, go to the next step.

2. Check whether any users restart the device.

   Only users of level 3 and higher levels can run the reboot command to restart the device. Check whether any authorized users restart the device.

   Log in to the device through the console interface to check whether frequently changing information is displayed and whether the device starts normally based on the information. If the device starts normally, the fault will be rectified after a while. If the device starts abnormally, rectify the fault by referring to 5.3 The Device Repeatedly Restarts. If no information is displayed or illegible characters are displayed, go to the next step.

3. If the fault persists, the device hardware may be damaged or a software bug has occurred. Contact technical support personnel to rectify the fault.

Fault Description

The device restarts unexpectedly or repeatedly.

Possible Causes

• The device hardware is faulty or the BootROM is damaged.
• When the device is reading or writing data, the device encounters abnormal voltage, surge voltage, or electrostatic discharge (ESD).

Troubleshooting Procedure

BIOS LOADING...                                                          
BIOS LOADING...                                                          
BIOS LOADING...                                                          

1. If the device always fails to enter the BootROM menu (that is, the device stops at the BIOS LOADING state or BIOS LOADING information is incomplete), collect the following information:

   • The device reboot record
   • The onsite environment information, including ambient temperature, humidity, and cabling
   • The voltage of the power supply (maximum AC voltage supported by the device: 90 V AC to 264 V AC, maximum DC voltage supported by the device -36 V DC to -72 V DC)

   After collecting the preceding information, send the device to Huawei for repair. Pack the device with the standard packaging to prevent damages.

2. If the device occasionally fails to enter the BootROM menu or other information is displayed, contact technical support personnel.

Fault Description

The device can be powered on, but the system cannot start and no information is displayed on the serial port.

Possible Causes

The device is damaged by lightning.

Troubleshooting Procedure

1. Check whether any port or connector on the device becomes yellow. If any RJ45 connector becomes yellow, the device may encounter lightning or surge voltage. Send the device to Huawei for repair.

2. If no port or connector becomes yellow, contact technical support personnel.

 NOTE:

If the device is prone to lightning or surge voltage, it is recommended that a surge protection device or a voltage regulator be used for the device.

Fault Description

The device starts only after the optical module is removed.

Possible Causes

A non-Huawei certified optical module is used.

Troubleshooting Procedure

 NOTE:

To obtain the list of Huawei certified optical modules, see S1720&S2700&S5700&S6720 Series Ethernet Switches Hardware Description or contact technical support personnel.