When would a switch record multiple entries for a single switch port in its MAC address table?

Question:
When would a switch record multiple entries for a single switch port in its MAC address table?

• when a router is connected to the switch port
• when multiple ARP broadcasts have been forwarded
• when another switch is connected to the switch port
• when the switch is configured for Layer 3 switching

Explanation: When another switch or a hub is connected to a switch port then frames could be received from the multiple nodes connected to the other switch or the hub. This will result in the MAC address for each of those multiple nodes to be recorded in the MAC address table against that one port. When a router is connected to a switch port, only the MAC address of the router interface would be recorded against the switch port. ARP broadcasts are used to associate MAC addresses with IP addresses and such broadcasts would not directly result in multiple MAC addresses being recorded against a single switch port. Configuring the switch to perform Layer 3 switching will not result in multiple MAC addresses being recorded against a single switch port. The ARP table associated with the Layer 3 switch port may contain multiple IP address to MAC address mappings but this is to enable the correct framing of Layer 3 packets, not the Layer 2 frame switching function.

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