A switch may record multiple entries for a single switch port in its MAC address table in the following scenarios:
Multiple devices are connected to the same switch port: If a hub or switch is connected to a switch port, and multiple devices are connected to that hub or switch, then the switch will learn the MAC addresses of all those devices and record them against the same switch port in its MAC address table.
Virtual local area network (VLAN) tagging: If VLAN tagging is enabled on the switch port, then the switch may learn multiple MAC addresses associated with different VLANs on the same switch port.
Port channeling or link aggregation: If multiple physical links are aggregated into a single logical link using link aggregation or port channeling, then the switch may learn multiple MAC addresses associated with that logical link, and record them against the same switch port in its MAC address table.
In all these cases, the switch maintains separate entries for each MAC address learned on the same switch port, and uses this information to forward traffic to the appropriate destination.