Why cannot fan information be displayed in the display device command output and why is the ALM indicator of AC power yellow when the S7700&S9700's fan is operating


The monitoring unit (MCU or CMU) fails to communicate with the fan or AC power supply.

If you need to buy the CMU, contact Huawei local office.

Other related questions:
Does the S7700&S9700 support the adjustment of fan speed
The S7700&S9700 series switches support the adjustment of fan speed. The speed of operating fans can be automatically adjusted based on the temperature inside the chassis. In addition, you can also manually change the fan speed using the set fan-speed command. You can run the display fan command to check the status of fans.

Different MTUs are displayed in the display isis interface command output on an S series switch
Q: In the display isis interface command output, why is the MTU on a broadcast network 1497 bytes whereas the MTU on a P2P network 1500 bytes? A: By default, the physical MTU of Ethernet interfaces are 1500 bytes. On a P2P network that has PPP enabled, the MTU is 1500 bytes in the display isis interface command output. On a broadcast network, a 3-byte Local Link Control (LLC) field is added to the data field according to the 802.3 link protocol encapsulation format, and the value of the LLC field is FEFE03. Therefore, in IS-IS, the actual length of the data to be transmitted is 1497 bytes, which is 3 bytes shorter than the physical MTU.

No information is displayed when IGMP snooping is enabled on an S series switch
For S series switches excluding the S1700, the display igmp-snooping command displays information about an IGMP snooping enabled VLAN. The command displays information only when the following conditions are met: - IGMP snooping has been enabled in the VLAN. - The VLAN is in Up state and at least one interface in the VLAN is Up.

Why the Fan Module Indicator is blinking red ?
An alarm has been generated and needs to be handled. Possible causes of the alarm include errors of dual in-line package (DIP) switches, short-circuit, fan blades blocked, and fault of the fan module.

Why are executed commands recorded in log files but cannot be displayed by the display logbuffer command
Information in the log buffer differs from information in log files because they use different channels of the information center. Log files record more information than the log buffer. The log buffer has a higher information level and records more important than log files. As logs have a lower information level, they are not saved in the log buffer. You can use the following command to set a lower level for the logs sent to the log buffer: [HUAWEI] info-center source SHELL channel logbuffer log level informationalRun some commands and use the display logbuffer command to check the logs in the log buffer. These commands will be displayed.

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