How does a switch react when it detects a link status change in STP?

When a switch detects a link status change in the Spanning Tree Protocol (STP), it sends a Topology Change Notification (TCN) Bridge Protocol Data Unit (BPDU). This event is critical for maintaining the topology of the network. The TCN BPDU informs other switches in the network that a change in the topology has occurred, allowing them to respond appropriately and potentially recalculate their spanning tree to ensure there are no looping conditions.

This process involves the switch that detected the change sending the TCN BPDU upstream to its root bridge. Upon receiving this notification, the root bridge will generate its own BPDUs indicating the topology change, which will propagate throughout the network. This mechanism helps the entire network stay synchronized with the current topology and aids in optimal path selection for data transmission, mitigating issues caused by changes in the network.

Knowing this process is vital for anyone working with STP, as it highlights how dynamic changes in the physical or logical structure of the network can be communicated and managed effectively to maintain network stability and performance. Other options do not accurately reflect the behavior of switches within STP concerning link status changes. The reaction to link status changes is not to simply enter the Learning state, forward traffic immediately, or block packets; rather