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In UDLD (Unidirectional Link Detection) normal mode, if the configured miss count is reached and messages are not received from the neighboring device, the port transitions to an undetermined state. This state indicates that the switch cannot confirm whether the link is functioning properly or is operating in a unidirectional manner.

When UDLD is in normal mode and it detects that it has not received messages from the corresponding device after a number of misses that exceeds the configured threshold, it does not disable the port or put it into an errdisable state. Instead, the undetermined state signifies a potential problem that requires attention. Network administrators can investigate the link to determine the cause of the communication issue, ensuring connectivity is restored or identifying any physical connection problems.

This mechanism helps in identifying misconfigurations or failures in the link without immediately taking drastic measures such as disabling the port, which could lead to service outages. The other options either imply that the port is disabled or that UDLD is turned off globally, which is not the case in normal mode's handling of missed messages.