Why cannot the switch learn an MAC address

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The possible causes are:

The mac-limit command is used on an interface and the VLAN that the interface belongs to and the number of dynamic MAC address entries learned by the interface reaches the limit.

MAC address learning is disabled on the Ethernet interface and the VLAN that the interface belongs to by using the mac-address learning disable command.

A blackhole MAC entry or static MAC entry is created or the sticky MAC function is enabled.

Other related questions:
Why cannot a switch port learn MAC addresses
Failure of MAC address learning may be caused by configuration. If the switch port is in Up state, check whether the port, VLAN, and traffic policy is configured to allow MAC address learning and all VLANs, and check the status of the spanning tree.

Why are source MAC addresses not learned
The causes are as follows: -The device does not receive packets because the link is Down, the interface does not join the VLAN, the interface participates in spanning tree calculation and is blocked, and so on. -Loops cause MAC address flapping. -MAC address learning is disabled or corresponding Sticky MAC address entries already exist. -The number of learned MAC address entries has reached the maximum. -The static or blackhole route is configured.

Cause why an AR cannot learn correct MAC address entries
The possible causes are as follows: - The AR does not receive packets because the link is Down, the interface does not join the VLAN, the interface participates in spanning tree calculation and is blocked, or MAC address flapping detection is configured and the interface or MAC address is blocked. - Loops cause MAC address flapping. - The AR is disabled from learning MAC address entries or the sticky MAC function is enabled on the interface. - The number of learned MAC address entries has reached the maximum. - The static or blackhole route is configured.

Why Is one MAC address learned in multiple VLANs on S series switch
On S series switches (except S1700), MAC addresses are learned based on MAC addresses+VLANs. If multiple VLANs receive packets with the same MAC address, these VLANs will learn the same MAC address.

How can I configure the limit on MAC address learning on CE switches
Run the mac-address limit maximum max-num command in the interface or VLAN view to change the maximum number of MAC addresses learned by an interface or VLAN. By default, no limit on MAC address learning is configured. The value of max-num ranges from 0 to 32767. 0 indicates that the number of MAC addresses learned by an interface or VLAN is not limited. # Configure 10GE1/0/1 to learn a maximum of 30 MAC addresses.
system-view
[~HUAWEI] interface 10ge 1/0/1
[~HUAWEI-10GE1/0/1] mac-address limit maximum 30 [*HUAWEI-10GE1/0/1] commit
# Configure VLAN 10 to learn a maximum of 20 MAC addresses.
system-view [~HUAWEI] vlan 10
[*HUAWEI-vlan10] mac-address limit maximum 20 [*HUAWEI-vlan10] commit Description: After a limit on MAC address learning is configured on an interface of a CE12800 switch, the number of VLAN, VXLAN, and VSI packets received on the interface is limited by the number of learned MAC addresses. For CE8800&CE7800&CE6800&CE5800 series switches, only VXLAN packets received on an interface are not limited by the number of learned MAC addresses.

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