How can I check whether a loop exists on an S series switch


The simplest way to check the existence of a loop on an S series switch (except the S1700) is to check whether a MAC address flapping alarm exists on the switch. If the alarm exists, you can quickly locate the loop based on the information in the alarm. Run the display mac-address flapping record command to check whether MAC address flapping exists, or run the display trapbuffer command to check whether the alarm contains The mac-address has flap value or MAC move detected.
For more information, visit Layer 2 Loop Troubleshooting.

Other related questions:
Does STP need to be enabled if no loop exists on an S series switch
For S (except the S1700) series switches, STP is used to prevent loops on a network. If no loop exists, STP can be disabled.

Whether the router port always exists during checking of Layer 2 multicast entries on an S series switch
During entry generation, the router port is added. You can run the display l2-multicast forwarding-table command to check the router port. The display igmp-snooping port-info command checks member port information.

How to to check whether a valid management exists the AP
Log in to the AP and run the display system-information command. If a management VLAN is incorrectly configured for the AP, run the undo management-vlan command on the AC to delete the management VLAN, and restart the AP.

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