Message 'Native VLAN mismatch discovered'

Do you need to mix traffic between different VLANs without any limits and configuration settings? The best way is to inject a hub between access ports on switch and customers.

This is actually a joke. But, unfortunately, this is possible, and there is no way to hope for the STP. The first thing that should alert you is the repeated messages "%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on…" if CDP is enabled. A hundred percent confirmation is the duplication of mac addresses for all VLAN interfaces.

By the way, for a while you are searching problem it will be useful disable CDP.

command for global disable CDP: no cdp run

command for disable CDP for the current interface (in interface configuration mode): no cdp enable