Setting Time On A Cisco Device (Manually) - Part 2
Setting Time On A Cisco Device (Manually) - Part 2 of 2
NOTE: This lesson will not cover Network Time Protocol (NTP).
Probably the biggest reason to set the time on your Cisco devices is to be able to correlate events, especially log messages, across a network. If your customers tell you that the network dropped at 5 pm on Tuesday, you're going to want to be able to check your devices for any events that happened around that time. If your devices don't maintain a consistent time, then this task becomes difficult to nearly impossible. This lesson shows you how to set, view, and maniupulate the clock on a Cisco device. While the best way to do this is to use Network Time Protocol (NTP), this lesson does not cover NTP, but rather concentrates on manually setting the time.
Cisco devices have a software clock that tracks the time. You'll want to have your devices keep accurate time across your network so that you can correlate events, especially log messages, across a network. If your devices don't maintain a consistent time, then this task becomes difficult to nearly impossible. The preferred method of maintaining consistent time across a network is with the Network Time Protocol (NTP). That method is not discussed in this lesson as it concentrates on "manual" time configuration.
Older Cisco platforms only maintain a software clock, which will not persist device reloads. The clock save interval global configuration command mitigates this liability to some extent by saving the clock to NVRAM (every 8 -- 24 hours depending on your configuration) and prior to user reload requests. Your software clock will still lose accuracy during downtime and especially during unplanned (e.g. power outage) downtime, but will not reset to epoch start (typically midnight (UTC) March 1, 1993 or 2002) as it will without this command.
Newer Cisco platforms have a hardware clock that survives reloads and power outages.
To manually set the time, use the clock set privileged EXEC command. To view the time, use the show clock privileged EXEC command.