Upcoming time change

ksarin123_2 · ‎10-30-2008

Hello folks -

I have a question about the upcoming Daylight Savings time change this weekend.

If I configure my routers to synchronize time using an external NTP Server, do I still need the following command configured:

clock summer-time CST recurring 2 Sun Mar 2:00 1 Sun Nov 2:00

I know I still need the following:

clock timezone CST -6

Also, I read somewhere that Cisco routers loose time and date information when rebooted? Is that correct?

Thanks for your help!!

Joseph W. Doherty · ‎10-30-2008

re: "Also, I read somewhere that Cisco routers loose time and date information when rebooted? Is that correct?"

Some do, the more powerful models and many of the newer models have on-board clocks. However, the on-board clocks can have inaccurate time, but you can have NTP update them too. (Command is something like "ntp update-calandar")

ksarin123_2 · ‎10-30-2008

What do you mean by "on-board clocks have inaccurate time?"

What if you set the time manually?

Joseph W. Doherty · ‎10-30-2008

Setting either clock manually is fine, but they often "drift". (I.e. gain or lose time each day. One reason for NTP.)

PS:

Also note, the on-board clock I have in mind is the calendar clock, not the since bootup running clock. Again, the former isn't available on all Cisco devices. (Commands, I recall, to see each are "show clock" vs. "show calendar".)

ksarin123_2 · ‎10-30-2008

Thanks for your reply.

Do you know why do the clocks drift if set manually?

Joseph W. Doherty · ‎10-30-2008

Manual setting doesn't have any thing to do with clock drift, they drift normally (something like NTP keeps reseting them).

As to why, this short Wiki article tries to explain: http://en.wikipedia.org/wiki/Clock_drift