How to solve MAC address flapping on S series switch

1

Firstly, check whether a loop occurs on the network.
Secondly, use one of the following methods to prevent MAC address flapping:
1. Run the mac-address static mac-address command in the system view to configure static MAC addresses on an interface.
2. Configure the MAC address learning priority on an interface. That is, run the mac-learning priority priority-id command in the interface view on modular switches or S5720HI, S6720EI, and S5720EI fixed switches or run the mac-spoofing-defend enable command in the interface view on S5700LI, S5700S-LI, S5710-X-LI, S2750EI, S5720S-SI, and S5720SI fixed switches.
After different MAC address learning priorities are configured for interfaces, only the MAC address entry learned by a high-priority interface can overwrite that learned by a low-priority interface if different interfaces have learned the same MAC address entry. This prevents MAC address flapping.
Note that SA cards of modular switches do not support the MAC address learning priority configuration. You can run the undo mac-learning priority priority-id allow-flapping command in the system view to prohibit MAC address flapping between interfaces with the same priority.

Other related questions:
Meaning of MAC address flapping on S series switches
For S series switches (except the S1700), MAC address flapping occurs when a MAC address is learned by two interfaces in the same VLAN and the MAC address entry learned later overrides the earlier one. For example, in the MAC address entry with the MAC address 0011-0022-0034 and VLAN 2, the outbound interface is changed from Port1 to Port2. In this case, MAC address flapping occurs. MAC address flapping can cause an increase in the CPU usage on the switch. Generally, MAC address flapping occurs when a loop exists on the network. S series switches support MAC address flapping detection and take configured actions after detecting MAC address flapping.

Query MAC address flapping records on S series switch
When loops occur on S series switches (except S1700), MAC address flapping often occurs. You can check whether MAC address flapping occurs on a switch to determine whether a loop occurs on the switch. Methods to check MAC address flapping vary depending on the system version. 1. In versions earlier than V200R001 on S series switches: Run the display trapbuffer command. If the command output displays MAC move detected, MAC address flapping occurred on the switch. 2. E series switches and S series switches running V200R001 and later versions: - Run the display trapbuffer command. If the command output displays MAC move detected, MAC address flapping occurred on the switch. - Run the display mac-address flapping record command. If information is displayed, MAC address flapping occurred on the switch.

In which situation does MAC address flapping occur on CE switches
MAC address flapping occurs when a MAC address is learned by two interfaces in the same VLAN and the MAC address entry learned later replaces the earlier one. MAC address flapping is usually caused by Layer 2 loops.

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