Which command allows the logging on the switch to show the time of the flap according to the clock on the device?

A network engineer is investigating a flapping (up/down) interface issue on a core switch that is synchronized to an NTP server. Log output currently does not show the time of the flap.

Which command allows the logging on the switch to show the time of the flap according to the clock on the device?
A . clock calendar-valid
B . service timestamps log datetime localtime show-timezone
C . service timestamps log uptime
D . clock summer-time mst recurring 2 Sunday mar 2:00 1 Sunday nov 2:00

View Answer

Answer: C

Explanation:

By default, Catalyst switches add a simple uptime timestamp to logging messages. This is a cumulative counter that shows the hours, minutes, and seconds since the switch has been booted up.

For example:

20w2d: %LINK-3-UPDOWN: Interface FastEthernet1/0/27, changed state to down

21w3d: %SYs-5-CONFIG_T: Configured from console by vty0 (172. 25. 15. 246)

At exactly what date and time did that occur? Who knows!

Instead, you can configure the switch to add accurate clock-like timestamps that are easily interpreted. you can use the following command to begin using the switch clock as an accurate timestamp for syslog messages:

Switch(config) # service timestamps log datetime [localtime] [show-timezone][msec][year]

Below is the output if we entered the command "service timestamps log datetime localtime show-timezone"(without "msec" keyword the output would not show time in milisecond)

*Mar 1 00:02:24 UTC:%LINEPROTO-5-OPDOWN: Line protocol on InterfaceLoopback4, changed state to up