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New Member


Hello everyone,

I have a Windows server on the network acting as the time server and I would like to point the Switches to it to get the time. I've entered the command ntp server ( IP Address of server ). I also have the clock timezone EST -5 command set. Should I also have the clock summertime EST recurring command set? Could someone explain the clock summertime command. I have also seen on the network Clock summertime EDT recurring. The switches are 3524XL and 3550's. Should I have an access-list for NTP also?

Thank you for your help,




Check that the Windows server is really running NTP, because mostly they run a different, simpler, time protocol (TNTP?)

The NTP will synchronise your router to standtard UTC. You then set your timezine as an offset from that according to your winter time.

For the clock summer time, you specify what you want the timezone code to look like, and the dates and time that the offset should go forwards an hour. You can have it change automatically every year (recurring), and you can specify something like "last Sun Arp 02/00 last Sun Oct 03:00".

The most important thing is to synchronise with your NTP server, and you might have a problem with a Windows server.

Kevin Dorrell


New Member


Hello, Matt

What the clock summertime command does, it tells the switch to respect daylight savings time. When you look at your logs if you do not have the summertime recurring command, during daylight savings time the clock on the switch will be off by 1 hour. For example I have the follow configuration for the time-zone on my switches.

clock timezone EST -5

clock summer-time EDT recurring

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