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Does NTPD of Juniper EX switches respond to the "leap-second calculations"



Article ID: KB12981 KB Last Updated: 05 Mar 2017Version: 3.0

Does NTPD of Juniper EX switches respond to the "leap-second calculations"?


Juniper EX switches support "leap-second" adjustment.

A leap second is a one-second adjustment that keeps broadcast standards for time of day close to mean solar time. The standard way to count UTC time across a leap second is:

2008-12-31 23.59.57
2008-12-31 23.59.58
2008-12-31 23.59.59
2008-12-31 23.59.60 <-- leap second
2009-01-01 00.00.00
2009-01-01 00.00.01
2009-01-01 00.00.02

After UTC 23:59:59, a positive leap second at 23:59:60 would be counted, before the clock indicates 00:00:00 of the next day.

The Junos OS software provides support in the Network Time Protocol (NTP) for the IERS leap second, with no risk of service impact. The root NTP servers are configured to inject the leap second, and send a flag in the client updates that a leap second is pending.

However, the additional second is not observable, and thus cannot be viewed in any of the system log files.

If the NTP server is aware of the leap-second calculations,then our switch will also add the 1-second delay by default. We don't need to do anything specific on the switch. NTP automatic time synchronization works only if the times on the two systems are very close. Very close means between 128 milliseconds and 128 seconds apart.  Between 128 seconds and 1000 seconds, the time is not changed at all. If the time is more than 1000 seconds off, NTP records a system log message:

Mar 16 16:41:41  xntpd[28243]: time error 4217 over 1000 seconds; set clock manually

If the time is this far off or if you need to syncronize the clock manually, use the following command:

user@switch1# set date ntp

This command uses the NTP servers that you have configured.

To learn more about leap seconds, see "".

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