Command for Showing Time of Flap in Switch Logs

C.

The command that allows the logging on the switch to show the time of the flap according to the clock on the device is option C: service timestamps log datetime localtime show-timezone.

Explanation: When a network interface is flapping, it means that it is going up and down continuously. This can be due to a hardware or a software issue, and it can cause instability in the network. To investigate this issue, network engineers usually rely on log messages generated by the switch.

By default, Cisco switches log messages using the system uptime (i.e., the time since the switch was last rebooted) as the timestamp. However, in the case of interface flapping, the uptime timestamp may not be very useful, as it does not provide information about the actual time of the event. Therefore, it is important to configure the switch to log messages using the local time of the device.

The command service timestamps log datetime enables logging with the date and time of the device. The localtime keyword specifies that the time should be logged in the local time zone of the device. Finally, the show-timezone keyword instructs the switch to display the time zone in the log messages, which can be useful if the device is located in a different time zone than the network engineer.

Option A (service timestamps log uptime) enables logging with the system uptime as the timestamp, which is the default behavior.

Option B (clock summer-time mst recurring 2 Sunday mar 2:00 1 Sunday nov 2:00) configures the device for daylight saving time in the Mountain Standard Time (MST) zone. This command is not relevant to the issue of interface flapping.

Option D (clock calendar-valid) is used to verify that the device's calendar is valid and that the device has a valid date and time. This command does not enable logging with the device's date and time.