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.

Other related questions:
Can multicast packet source MAC addresses be learned
Yes, multicast packet source MAC addresses can be learned.

Does an AR learn the source MAC address of multicast packets
The AR learns MAC addresses of received multicast packets.

Why cannot the switch learn an MAC address
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.

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 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.

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