switch timezone off

[jcounsell1222]

some of my switches (3750s) are on the right time and some are not. i have them all pointed to the same DC for NTP and they all say they are syncronized. is it possiable to have the switches pole the DC for the right time and update?

[Marvin Rhoads]

Some probably have the default (UTC) and others have a timezone command. Look for something like:

clock timezone EST -5

clock summer-time EDT recurring

...and correct it according to what standard you wish to adopt. "no clock timezone" will set it back to UTC. (And add "no clock summer-time" to disable Daylight Savings Time adjustments.)

[jcounsell1222]

will this sync the switches so that they update to the correct time?

[Marvin Rhoads]

The clock synchronization is determined by your ntp status. If "show ntp association" reports that you are synchronized to an accurate clock on your ntp server, the switch will have a synchronized clock.

What it displays as the time ("show clock") or on log messages (if you have service logging timestamps enabled) will be adjusted per the configured timezone offset (e.g. the "EST -5" in my example above) and summer-time settings.

[Richard Burts]

I sense that there is some confusion about how NTP works and how routers and switches display the time that they have learned from NTP. So I offer this clarification. NTP always advertises time using UTC. When a router or switch learns time from NTP it learns it in UTC. If the router or switch indicates that it is in sync with its server then it has learned it in UTC.

Having learned time then how the router or switch will use it depends on how it is configured. If the router or switch is configured with clock timezone commands then it will display the time in the local timezone. But what it learns from NTP or what it might advertise in NTP is always in UTC.

HTH

Rick

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