In UDLD Normal mode, what happens when a frame is not acknowledged?

In UDLD (Unidirectional Link Detection) Normal mode, if a frame sent by a switch is not acknowledged, the behavior is that the port remains active and undetermined. In this mode, the switch does not immediately assume there is a problem but continues to operate the link while it awaits further checks.

This allows for the possibility that the absence of an acknowledgment may be a transient issue, rather than a definitive failure. The switch will continue to send UDLD packets to ascertain the status of the link without taking immediate disruptive actions, such as disabling the link or changing its operational state.

The other options imply immediate cutoffs or changes that do not align with the operational characteristics of Normal mode in UDLD, where the goal is to provide a grace period where conditions can be reassessed before declaring a link as faulty. In this context, maintaining the link allows for continued operation while ensuring the network remains resilient to minor issues.