Which feature limits which MAC addresses can use a port and prevents unauthorized devices?

• A. Spanning Tree Protocol.
• B. VLAN tagging.
• C. Port-security.
• D. Link aggregation.

Answer: (C)

Controlling which devices can use a switch port is done with port-security. This feature lets you lock a port to specific MAC addresses or limit how many unique MACs can appear on that port. When a device with an unauthorized MAC tries to send frames on that port, the switch can take action—protect, restrict, or shut down the port—preventing access from that device. This directly blocks unauthorized hardware from accessing the network through that port.

Spanning Tree Protocol focuses on avoiding loops in a network with switches and redundant paths, not on who is allowed to connect to a port. VLAN tagging splits traffic by VLAN to keep segments separate, but it doesn't enforce which devices can originate traffic on a given port. Link aggregation combines multiple physical links into a single logical link for higher bandwidth and resilience, not for controlling device access per port.