Why cannot debugging messages be displayed on S series switches

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For S series switches (except the S1700), the debugging message display function is disabled by default. To display the debugging messages, run the following commands in the user view:
- terminal monitor: enables the terminal or console to display messages sent from the information center.
- terminal debugging: enables the debugging message display function on the terminal or console.

Other related questions:
Why cannot the OSPF MIB configuration on an S series switch be displayed in a MIB browser
Question: After MIB parameters are configured on a MIB browser and a device, the device fails to connect to the MIB browser and the OSPF MIB configuration cannot be displayed in the browser. What should I do? Answer: Perform the following operations on the S series switch to solve the problem. Check whether the connection between the Ethernet interface on the switch and the device where the MIB browser is installed is proper. Check whether IP address conflict occurs on the network. If the network is busy, set the interval at which packets are retransmitted to the MIB browser and the retransmission time to smaller values. Check whether the ospf mib-binding command is executed in the OSPF instance. Check whether the IP address specified by trap in the snmp-agent target-host trap command is the same as the interface IP address of the MIB browser. For example, check whether configurations of the following commands are correct. If the configurations are correct and the device where the MIB browser is installed is properly connected to the Ethernet interface on the switch, the browser can correctly display the MIB information. [HUAWEI] ospf mib-binding process-id [HUAWEI] snmp-agent sys-info version all [HUAWEI] snmp-agent community read public_huawei [HUAWEI] snmp-agent community write private_huawei

Why does the NMS display an error message when it uses SNMPv2c to connect to an S series switch
When an NMS uses SNMPv2c to connect to an S series switch (except the S1700), error message "another nms was polling the switch with wrong community" is displayed. The reason is that the community name configured on the NMS is different from that configured on the switch. Run the display snmp-agent community command on the switch to check the configured community name.

Why the Picture in the Email Message I Received Cannot Be Displayed?

Some email clients disable automatic picture download from the Internet by default for the sake of privacy protection. If the picture cannot be displayed in the email, you need to enable automatic picture download.


Reason why S series switch cannot learn ARP entries
When an S series switch, except S1700, works at Layer 2, the switch does not have ARP entries and cannot learn ARP entries. When an S series switch, except S1700, works at Layer 3 and cannot learn ARP entries, rectify the fault as follows: (1) Possible cause: The link between the switch and connected device fails. Solution: Perform ping operations to check whether the link fails. If so, rectify the link failure. (2) Possible cause: ARP strict learning is enabled on the switch. (After this function is enabled, the switch learns only the ARP reply packets in response to the ARP request packets sent by itself.) Solution: Run the undo arp learning strict command in the system or interface view to disable ARP strict learning. (3) Possible cause: The switch has too many ARP entries and may suffer an ARP attack. Solution: Configure static ARP entries for key servers or users and enable attack defense policies. Note: (1) By default, ARP strict learning is enabled on some models among fixed switches and disabled on modular switches. When a fixed switch connected to a modular switch receives a gratuitous ARP packet, the fixed switch does not learn ARP entries. Therefore, some fixed switches cannot learn ARP entries. (2) After ARP strict learning is enabled on a switch, the switch actively sends ARP request packets to hosts. Some PCs with wireless network adapters installed do not respond to ARP requests, so the switch cannot learn the ARP entries of the connected PCs. The PCs respond only after the network adapters are restarted. In this situation, disable ARP strict learning.

In which situation can an S series switch send the option field in Request messages to a client
For S series switches excluding the S1700, the DHCP server returns the corresponding option field to a client only when the corresponding option field is encapsulated in the Request message.

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