When the user-defined error threshold on a per-port basis is reached, which switching method does the switch revert to?

In the context of switching methods used in network switches, the store-and-forward method is a technique where the switch receives the entire frame before forwarding it. This allows the switch to perform error checking on the frame using methods such as a cyclic redundancy check (CRC). When a user-defined error threshold on a per-port basis is reached, the switch will revert to the store-and-forward method. This serves an essential purpose: it ensures that any errors in the data can be detected and discarded before the data is forwarded to the destination. By doing so, it helps maintain the integrity and quality of the data being transmitted across the network.

While cut-through switching offers lower latency by forwarding frames after reading only the destination address, it does not include error checking, which can lead to data being forwarded even if it contains errors. Options such as fragile and VLAN tagging do not apply in this context of error handling. Therefore, reverting to store-and-forward ensures a reliable transfer of data by emphasizing error checking and correction, making it the most appropriate choice when a threshold of errors has been exceeded.